CSP-H-2 BASIC HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369H HELICOPTERS

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

The engine−to−firewall seal ring is a stamped

(1). Remove engine.

steel assembly incorporating three flat springs

for mounting on the inlet bell mounting flange.

(2). Pull engine air inlet to firewall seal

The engine inlet−to−firewall seal is a high

from firewall.

temperature, all synthetic seal. The seal

provides a pliable surface for the rim of steel to

(3). Carefully scrape firewall as necessary

press against when the engine is installed.

to remove seal particles. Remove

residue from firewall with methyl−

10. Engine Air Inlet Bell and Engine-to-

ethyl−ketone (MEK) (22, Table 2−4).

Firewall Seal Ring Replacement

(4). Using adhesive (19), bond replacement

(Ref. Figure 16−1)

engine air inlet−to−firewall seal so that

it is centered on firewall opening.

(1). Remove engine.

(2). Remove five screws, washers and nuts;

(5). Reinstall engine.

remove engine air inlet bell.

11. Air Induction System Drains

(3). Pull engine to firewall seal ring from

bell.

Air induction system drains are provided for

the plenum chamber, the transmission cooling

(4). Attach replacement engine−to−firewall

shroud, and the oil cooler blower shroud. The

seal ring to engine air inlet bell by

drains are located at the low points

lifting the leaf springs on the ring and

repositioning them over bell flange.

of these components to prevent accumulations

(5). Position engine air inlet bell and

of moisture that may have been entrained with

firewall seal ring on compressor inlet

the inducted air. The drain tubes are generally

mounting flange; secure with five

of clear plastic material which is attached to

screws, washers and nuts.

metal drain fittings with lockwire.

(6). Reinstall engine.

12. Air Induction System Drain Tubing

Replacement

A. Engine Air Inlet Bell and Engine-to-

Firewall Seal Ring Repair

Replace the drain tubing using standard shop

(1). To repair engine−to−firewall seal ring,

procedures. See Figure 16−3 for routing and

replace any damaged or broken springs.

installation details for tubing located on the

aft side of the firewall. See a similar figure in

(2). There is no authorized repair for the

Section 9 for tubing located on the forward

inlet bell.

side of the firewall.

B. Engine Air Inlet-to-Firewall Seal

NOTE: When replacing drain tubing, the rout−

Replacement

ing should be as direct as possible. Avoid

(Ref. Figure 16−1)

creating loops that can become liquid traps.

Page 16-5

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

TABLE OF CONTENTS

Para/Figure/Table

Title

Page

Section 17 Instrument Panel and Indicating System .

17−1

Instrument Panel

17−1

A. Instrument Panel Maintenance

17−1

B. Instrument Panel Removal

17−1

Figure 17−1. Arrangement of Instruments and Indicators (Instrument

Panel Type A)

17−2

Figure 17−2. Arrangement of Instruments and Indicators (Instrument

Panel Type B)

17−3

C. Instrument Panel Installation

17−4

Figure 17−3. Component Locations (Instrument Panel Type A) .

17−5

Figure 17−4. Component Location (Instrument Panel Type B) (Sheet 1 of 2) .

17−6

Instrument Panel Type B Hood

17−7

Instrument Indicating System

17−7

A. Instrument Indicating System Troubleshooting

17−8

Table 17−1. Troubleshooting the Instrument Indicating System

17−8

B. Indicating System Instrument Replacement

17−11

C. Indicating System Instrument Inspection

17−11

D. Indicating System Instrument Repair

17−11

Pitot−Static System

17−11

A. Pitot−Static System Inspection

17−12

B. Pitot Tube Assembly Replacement

17−12

C. Static Pressure Tubing Replacement

17−12

Figure 17−5. Pitot Static System

17−13

D. Static Pressure Tube Aft End Protective Screen Installation .

17−14

Figure 17−6. Installation of Static Pressure Tube Bug Screen .

17−14

Altimeter

17−14

A. Altimeter Maintenance

17−14

Airspeed Indicator

17−14

A. Airspeed Indicator Maintenance

17−15

N1, N2 and Rotor Tachometer Indicating System

17−15

A. N1, N2 and NR Tachometer Indicator Maintenance

17−15

B. Tachometer Generator Replacement

17−15

C. Tachometer Generator Testing

17−15

Turbine Outlet Temperature (TOT) Indicating System

17−16

A. TOT Indicator Maintenance

17−16

B. Thermocouple Harness Maintenance

17−16

C. TOT Indicating System Calibration

17−16

Page 17−i

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

Figure 17−7. Indicating System Electrical Senders (Sheet 1 of 3) .

17−17

Figure 17−8. Test Hookup For Tachometer Generator

17−20

Engine Torque Indicating System

17−20

A. Torque Gage Maintenance

17−20

B. Torque Gage Pressure Line Removal

17−21

C. Torque Gage Pressure Lines Installation

17−21

Figure 17−9. Torque Gage and Direct Reading Engine Oil Pressure Gage

(Sheet 1 of 2)

17−22

10. Direct Reading Oil Pressure Indicating System

17−24

A. Engine Oil Pressure Gage Tubing Replacement

17−24

B. Torque or Direct Reading Engine Oil Pressure Line Bleeding and Servicing .

17−24

11. Instrument Cluster Three−Pack or Four−Pack Indicating System .

17−24

A. Instrument Cluster Three−Pack or Four−Pack Maintenance .

17−25

B. Instrument Cluster Three−Pack or Four−Pack Calibration Check .

17−25

Figure 17−10. Instrument Cluster Three−Pack with Wiring Harness

(Instrument Panel Type B) (Sheet 1 of 2)

17−26

Figure 17−11. Instrument Cluster Four−Pack with Wiring Harness .

17−28

12. Engine Oil Temperature Sender

17−29

A. Engine Oil Temperature Sender Replacement

17−29

13. Engine Electrical Oil Pressure System

17−30

A. Engine Electrical Oil Pressure Sender Replacement

17−30

B. Electrical Oil Pressure Gage Calibration

17−30

14. Fuel Quantity System

17−31

A. Fuel Quantity Transmitter (Tank Unit) Replacement

17−31

B. Fuel Quantity Transmitter and Indicator Operational Check .

17−32

C. Fuel Tank Sending Unit and Fuel Low Warning Light Indicating System

Inspection

17−33

Figure 17−12. Bench Test and Potting of Fuel Tank Sending Unit .

17−34

D. Tank Unit Testing

17−35

15. Outside Air Temperature Indicator

17−35

A. Outside Air Temperature Indicator Replacement

17−35

16. Magnetic Compass

17−36

A. Magnetic Compass Maintenance

17−36

17. Caution and Warning Lights Indicating System

17−36

A. Caution and Warning Lights Indicating System Troubleshooting .

17−37

Figure 17−13. Testing of Tank Unit

17−38

Figure 17−14. Outside Air Temperature Indicator and Magnetic Compass .

17−39

Table 17−2. Caution and Warning Lights Troubleshooting Data .

17−40

Page 17−ii

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

Table 17−3. Troubleshooting the Caution and Warning Lights Indicating

System

17−41

18. Instrument Panel Type A Caution and Warning Indicator Lights .

17−45

A. Instrument Panel Type A Indicator Lights Replacement .

17−46

19. Instrument Panel Type B Caution and Warning Indicator Lights .

17−46

A. Panel Type B Indicator Lights Replacement

17−47

20. Engine Out Warning System

17−47

A. N1 Sensing Equipment

17−47

B. N1/NR Sensing Equipment

17−48

C. Engine Out Warning System Functioning

17−48

21. Vapair 26530332M Engine Power Out (EPO) Warning Control Unit .

17−49

A. Engine Power Out Warning Unit Circuit

17−49

B. Engine Out Frequency Sensor and Light Flasher Circuits .

17−49

C. Dc Voltage Regulator Circuit

17−49

D. Audio Tone Signal Generators

17−49

Figure 17−15. N1/NR Engine Power Out Warning System Combined Simplified

Block and Schematic Diagram (Panel Type B) (Sheet 1 of 2) .

17−50

E. Transmission Oil and Temperature Light Flasher

17−52

F. Vapair 26530332M EPO Warning Unit Frequency Sensing Adjustment .

17−52

Figure 17−16. Vapair 26530332M Engine Power Out Warning Control Unit

Schematic Diagram

17−53

Figure 17−17. Vapair 26530332M Warning Audio and Light Flashing Control

Circuit (Sheet 1 of 2)

17−54

G. Vapair 26530332M EPO Warning Unit Repair

17−56

H. Vapair 26530332M EPO Warning Control Unit Replacement .

17−56

22. Autronics 2146−5 Engine Power Out (EPO) Warning Control Unit .

17−56

A. Engine Power Out Warning Circuits

17−56

B. Engine Out Frequency Sensing Circuits

17−56

C. Engine Out and Transmission Lights Flasher Circuits .

17−57

D. Audio Tone Circuits

17−57

E. Audio Tone Output Level Adjustment − Autronics 2146−5 EPO Warning

Control Unit

17−57

Figure 17−18. Autronics 2146−5 Engine Power Out Warning Control Unit

Schematic Diagram

17−58

F. Autronics 2146−5 EPO Warning Control Unit Repair

17−59

G. Autronics 2146−5 EPO Warning Control Unit Replacement .

17−59

Figure 17−19. Autronics 2146−5 Warning Audio and Lights Flashing Control

Circuit (Sheet 1 of 2)

17−60

23. Autronics 2200−3 EPO Warning Control Unit

17−61

Page 17−iii

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

A. Autronics 2200−3 EPO Warning Control Unit Maintenance .

17−61

24. Grimes 70−0054−1 Indicator Lights Dimmer Assembly (Panel Type A) .

17−62

A. Indicator Lights Dimming Assembly Circuits

17−62

B. Negative (Ground) Input Fault Dimming Circuits

17−62

C. Positive (+28 Vdc) Input Fault and Function Dimming Circuits .

17−62

D. Panel Lights Dimming Circuit

17−63

E. Grimes 70−0054−1 Indicator Lights Dimmer Assembly Repair .

17−63

F. Grimes 70−0054−1 Indicator Lights Dimmer Assembly Replacement .

17−63

25. Autronics 2245−1 Indicator Lights Dimmer Assembly (Panel Type B) .

17−63

A. Dimmer Assembly Associated Circuits

17−63

Table 17−4. Input/Output Signals − Autronics 2200−3 EPO Unit .

17−64

Figure 17−20. Grimes 70−0054−1 Indicator Dimming Assembly Schematic

Diagram

17−65

Figure 17−21. Caution and Warning Indicating Light System Dimming Circuits

(Instrument Panel Type A)

17−66

B. Negative (Ground) Input Fault Caution Light Indicator Circuits .

17−67

C. Negative (Ground) Input Fault Warning Light Indicator Circuits .

17−67

D. Positive (+28 Vdc) Input Start Pump Warning Light Circuit .

17−67

E. Engine Out warning Light and Horn Circuit

17−67

F. Panel and Instrument Lights Dimming Circuit

17−67

G. Caution and Warning Lights Press−To−Test Circuits

17−67

H. Autronics 2245−1 Dimmer Assembly Test and Repair . .

17−68

Autronics 2245−1 Dimmer Assembly Replacement

17−68

26. Engine Power Out (EPO) Audio Amplifier (Used with Vapair EPO Warning

Control Unit)

17−68

A. EPO Audio Amplifier Replacement

17−68

Figure 17−22. Autronics 2245−1 Dimmer Schematic Diagram (Instrument

Panel Type B)

17−69

Figure 17−23. Caution and Warning Indicating Lights System Circuits

(Instrument Panel Type B) (Sheet 1 of 2)

17−70

Figure 17−24. Audio Amplifier (Dual and Single Channel) Schematic

Diagram

17−72

27. Engine Power Out (EPO) Audible Warning Horn

17−73

A. Edwards Audible Warning Horn Replacement

17−73

28. NR Disable Switch

17−73

A. NR Disable Switch Replacement

17−73

Figure 17−25. NR Disable Switch Installation (Sheet 1 of 2) .

17−74

B. NR Disable Switch Adjustment

17−76

29. Chip Detector Circuits Operational Check

17−76

Page 17−iv

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

SECTION 17

INSTRUMENT PANEL AND INDICATING SYSTEM

1. Instrument Panel

warning lights indicating system to provide

visual and audible signals for the pilot during

The instrument panel is an assembly of

certain conditions. The caution and warning

aluminum alloy angles and a 0.040 inch (1.016

lights indicating system and engine out

mm) thick aluminum alloy panel. The panel

warning equipment are described in this

assembly is riveted to an aluminum alloy

section.

structural framework called the upper

instrument panel support assembly.

Provisions are incorporated in the panel face

for installation of night−lighting, vhf/uhf

This instrument panel and upper support

communication equipment, navigational aid

assembly is fabricated so that it is removable

equipment and miscellaneous instrumenta−

from the lower structural framework, called

tion.

the lower instrument panel support assembly,

that is attached to the pilot’s compartment

Information on instruments, controls and

floor.

equipment other than those shown in

Figure 17−1 and Figure 17−2 is provided in

Contour−molded thermoplastic fairings and a

CSP−H−3.

hood enclose the instrument panel structure,

shield the instruments and equipment from

A. Instrument Panel Maintenance

direct sunlight and prevent instrument glare.

Perform maintenance on the instrument panel

All standard flight, navigation and engine

and supporting structure according to the

instrument, except the canopy−located outside

Cleaning, Corrosion Control and Paint Finish

air temperature gage, are mounted in the

in Section 2, the Fuselage Sheet Metal Repair

instrument panel.

in CSP−H−6 and Maintenance of Electric

Bonding Connections in Section 19.

Two different types of instrument face panels

are provided; panel type A (Figure 17−1) and

B. Instrument Panel Removal

type B (Figure 17−2). The major differences

are that panel type B provides integral

The instrument panel and upper support

provisions for the addition of optional equip−

assembly, along with installed instruments

ment and panel type B instruments are

and most of the electrical wiring, is remove−

recessed in a thermoplastic hood covering the

able as an assembled unit. Follow the basic

face of the panel. See Figure 17−3 and

requirements outlined below to accomplish

Figure 17−4 for structure details and location

removal.

of indicating system components.

The main electrical power

The switches, circuit breakers and other

WARNING

supply wiring is discon−

manually operated controls on the panel face

nected for removal of the panel assem−

that are parts of the fuel supply system

bly. External power and the battery

(Section 12), heating and ventilating system

must remain disconnected at all times

(Section 18) and electrical system (Section 19)

during this procedure.

are discussed as part of the system in which

they function.

(1). Remove the instrument panel side

fairings.

Caution and warning lights indicators are

mounted in a row horizontally across the top of

(2). Disconnect the torque gage, engine oil

the panel face.

pressure gage (panel type B), and the

pitot and static pressure lines to the

Engine out warning equipment functions with

altimeter and airspeed indicator. Cap

an audible warning horn and the caution and

the lines and fittings.

Page 17-1

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

ENGINE OUT AUDIBLE WARNING HORN

MAGNETIC COMPASS

(NOTE 1)

ANTIVIBRATION BRACKET

CAUTION AND WARNING LIGHTS

AIRSPEED INDICATOR

N2 AND NR (ROTOR)

TACHOMETER INDICATOR

ALTIMETER

BLANK PLATES

(5 PLCS)

TORQUE GAUGE

TURBINE OUTLET TEMPERATURE

FAIRING AND

(TOT) INDICATOR

HOOD

(NOTE 2)

START PUMP LIGHT

INSTRUMENT

N1 TACHOMETER

CLUSTER (4−PACK)

INDICATOR

NOTES:

ORIGINAL CONFIGURATION SHOWN; EITHER

RIGHT OR LEFT SIDE (MODEL DIFFERENCE).

MODIFICATION OF ORIGINAL CONFIGURATION

IS REQUIRED FOR INCORPORATION OF BATTERY

TEMPERATURE SENSING EQUIPMENT (REF.

SEC 19). MODIFIED CONFIGURATION IS

IDENTICAL TO THAT SHOWN IN FIGURE FOR

ARRANGEMENT OF INSTRUMENTS AND

INDICATORS (FRONT PANEL OF INSTRUMENT

PANEL TYPE B).

RESISTOR BOARD ASSY TB9 AND THERMOCOUPLE

LEAD RESISTOR R4 MOUNTED ON INDICATOR

TERMINALS.

30-1 15A

Figure 17-1. Arrangement of Instruments and Indicators (Instrument Panel Type A)

Page 17-2

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

BATTERY TEMPERATURE SENSING

CAUTION AND WARNING LIGHTS

(NOTE 6)

HOUSING

(NOTES 1, 6)

CLOCK

(NOTE 5)

ENGINE OUT AUDIBLE

WARNING HORN

CAUTION AND

WARNING LIGHTS

AIRSPEED INDICATOR

FAIRING AND HOOD

ALTIMETER

BLANK PLATES (4 OR 5 PLCS)

N2 AND NR (ROTOR)

(NOTE 3)

TACHOMETER INDICATORS

TORQUE GAUGE

(8 PLCS)

TURBINE OUTLET

TEMPERATURE

(TOT) INDICATOR

BOLT LIGHT (14 PLCS)

(NOTE 2)

N1 TACHOMETER

INDICATOR

INSTRUMENT CLUSTER (3−PACK)

ENGINE OIL PRESSURE

INDICATOR

NOTES:

EITHER RIGHT OR LEFT SIDE (MODEL

DIFFERENCE).

RESISTOR BOARD ASSY TB9 AND

THERMOCOUPLE LEAD RESISTOR R4

MOUNTED ON INDICATOR TERMINALS.

VARIES WITH EQUIPMENT INSTALLED.

ASTERISK ( * ) INDICATES SCREW

SECURING FRONT OF HOOD TO

INSTRUMENT PANEL FACE. (SEE FIGURE

SHOWING INSTRUMENT PANEL TYPE B

COMPONENT LOCATIONS FOR

LOCATIONS OF SCREWS SECURING

SIDE OF HOOD TO INSTRUMENT

CONSOLE.)

MAGNETIC COMPASS ON EARLY PANEL.

ADDITION REQUIRED ON EARLY PANEL.

30-1 183C

Figure 17-2. Arrangement of Instruments and Indicators (Instrument Panel Type B)

Page 17-3

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(3).

Disconnect thermocouple leads from

(1). Mount the instrument panel and

terminal board TB9 on the TOT

support assembly on the supporting

indicator.

structure and secure the base in place

with screws and washers (Figure 17−3).

(4).

Remove the fuel shutoff valve control

cable. Disconnect the wire end of the

NOTE: If upper support does not align with

ventilating valve control cable. (Remov−

canopy structure, use special shim washers,

ing the fuel shutoff cable will also

0.120 inch (3.048 mm) thickness, under both

release a clamp holding the pitot

forward or both aft console−to−support at−

pressure line; leave the line detached.)

tachment points. Use one− half the shim

thickness at both middle attachment screws

(5).

Disconnect the electrical plugs from the

and vary screw length accordingly.

connector support bracket under the

upper support assembly.

(2).

Attach the Z−brace to the upper

structure.

(6).

Disconnect coaxial antenna cables if

radio equipment is installed.

(3).

Route all lines and wiring into position

for connection. Check that there is

(7).

Disconnect the wiring (three wire

sufficient slack for proper connection

bundles) from the power selector switch

without straining the lines or wiring.

and insulate the wiring terminals.

Remove clamps that secure the three

(4).

Connect power supply wiring (three−

wire bundles to the panel structure.

wire bundles) to the power selector

switch and reinstall wiring support

(8).

Check the entire instrument panel and

clamps and straps where previously

upper support assembly for clamps or

removed.

nylon straps that would restrict

separation from the lower support

(5).

Connect coaxial antenna cables if radio

assembly. Disconnect any such items.

equipment is installed.

(9).

Remove the two screws, washers and

(6).

Connect the electrical plugs under the

nuts that attach the upper support (Z

upper support assembly.

brace) to the panel structure.

(7).

Connect the ventilating valve control

(10).

Remove the screws and washers that

cable and perform an operational check.

attach the base of the panel assembly to

the lower support (Figure 17−3 or

(8).

Install the fuel shutoff valve control

Figure 17−4).

cable and perform an operational check.

Reattach the pitot pressure line clamp

NOTE: Make notes of the routing of all lines,

with the hardware used to attach the

cables and wiring before removing the panel

cable under the upper support assem−

assembly to aid reinstallation.

bly.

(11). Obtain assistance and carefully lift out

(9).

Connect the thermocouple leads to

the panel and support assembly.

terminal board TB9 on the TOT

indicator. Check for correct thermocou−

C. Instrument Panel Installation

ple circuit resistance.

Before and during placement of the instru−

(10).

Connect the torque gage, engine oil

ment panel and upper support assembly into

pressure gage (panel type B), and the

position on the supporting structure, check all

pitot and static pressure lines to the

cables, wiring and lines are routed properly.

altimeter and airspeed indicator

Incorrect routing can result in lines or wiring

(Figure 17−5).

not being long enough to reach the connection

point, or in lines or wiring being subjected to

(11).

Check that all lines and wiring are

unnecessary strain and possible damage from

connected and secure; then reconnect

chafing.

the battery.

Page 17-4

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

ENGINE OUT AUDIBLE WARNING HORN

(NOTE 1)

HORN RING

ELECTRICAL WIRING

SUPPORT BRACKET

GASKET

INSTRUMENT PANEL

AUDIBLE WARNING

CENTER FAIRING

INSTRUMENT PANEL

HORN INSTALLATION

(NOTE 4)

UPPER SUPPORT

TERMINAL

BLOCK TB501

R303, OIL PRESSURE GAUGE

ADJUSTMENT RESISTOR ASSY

(NOTE 2)

AUDIO AMPLIFIER

(NOTE 3)

ENGINE POWER OUT

SADDLE CLAMP

(EPO) WARNING UNIT

TERMINAL

BLOCK TB6

INDICATOR LIGHTS

DIMMING ASSEMBLY

LOWER SUPPORT

ASSEMBLY

LIGHTS INDICATOR

(TYP)

LEGEND CAP

NOTES:

EITHER RIGHT OR LEFT SIDE INSTALLATION (MODEL DIFFERENCE).

SUPPORT BRACKET IS PART OF KIT M50436.

PART OF OIL PRESSURE GAGE CIRCUIT (KIT M50438).

USED WITH VAPAIR EPO UNIT ONLY.

30−117E

MODIFICATIONS OF ORIGINAL CONFIGURATION SHOWN IS REQUIRED.

Figure 17-3. Component Locations (Instrument Panel Type A)

Page 17-5

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

RED 160°F WARING

AMBER 140°F CAUTION

LIGHT / SWITCH

CAUTION AND WARNING

LIGHT ASSEMBLY

(TYP)

MOUNTING SLEEVE

ENGINE OUT AUDIBLE

WANING HORN

WIRING HARNESS

(NOTE 2)

SWITCH HOUSING

LAMP

(4 PLCS)

LIGHT / SWITCH AND

HORN HOUSING

LOCKING

CAM

LOCKING CAM

SCREW (2)

INSTRUMENT PANEL

FWD

CENTER FAIRING

PANEL

LIGHT / SWITCH AND HORN HOUSING

MOUNTED ON HOOD

SWITCH ACTUATOR

LEGEND FACE

INDICATOR MODULE

30-185-2

Figure 17-4. Component Location (Instrument Panel Type B) (Sheet 2 of 2)

(12). Connect an external power supply, if

To remove the hood, remove nine attaching

available, and perform a power−on

screws and washers at sides of hood

check of all systems. If there is a

(Figure 17−4), eight screws at front of hood

malfunction, correct the trouble as

(Figure 17−2) and pull hood away from panel

necessary.

far enough to disconnect two panel light wiring

splices.

(13). Perform a ground run−up of the

Use tetrahydrofuran (46, Table 2−4), or

helicopter according to the Owner’s

equivalent, to bond and repair cracks and

Manual to check operation of all

tears in the hood.

systems. Bleed the torque gage and

engine oil pressure gage (panel type B)

3. Instrument Indicating System

pressure lines as necessary.

Three basic types of instrument indicating

(14). Shut down helicopter and reinstall the

system are installed in the helicopter.

instrument panel side fairings.

The first group includes indicators that are

actuated by other than electrical power input

2. Instrument Panel Type B Hood

these are the airspeed indicator, altimeter,

outside air temperature indicator, torque gage,

The panel type B hood, formed of 0.063 inch

engine oil pressure gage (panel type B) and the

(1.6002 mm) thick thermoplastic, covers the

magnetic compass.

upper portion of the instrument panel face and

The second group of indicators are intercon−

is secured to the instrument console with nine

nected with electrical sending units that

screw and washers at side and top edges of the

self−generate the power source necessary for

hood.

indicator operation once they are mechanically

or thermally actuated; indicators in this are N₁

Built−in panel bolt lights on the hood provide

and N₂ rotor tachometer indicators and the

illumination for all standard instruments and

TOT indicator.

indicators, except the magnetic compass and

optional clock. The panel lights are part of the

The third group includes those indicators and

night lighting system that is standard equip−

sending units that rely on power from the

ment on the helicopter with panel type B.

helicopter electrical system for functional

Page 17-7

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

capability; such indicators include the caution

ic helicopter instrument limit markings.

and warning lights and the instrument cluster

Instrument markings used with the Model

3−pack or 4−pack.

250− C20 Engine Conversion Kit M50031

are also described in CSP−H−3.

NOTE: Instrument limit markings shown in

A. Instrument Indicating System

this section may differ depending on heli−

Troubleshooting

copter configuration and engine installa−

tion. Refer to the Owner’s Manual for specif−

(Ref. Table 17−1)

Table 17-1. Troubleshooting the Instrument Indicating System

Symptom

Probable Trouble

Corrective Action

NOTE: Ref. Table 17-3 for Troubleshooting the Caution and Warning Lights Indicating System.

Pitot-Static System

No reading on airspeed indicator

Ice or water in pitot lines or static

Thaw out; clean and dry lines and

pressure tube

tube.

Erratic readings on airspeed

Leak in pressure lines

Tighten line connections.

indicator or altimeter

Ice or water in pitot lines and static

Thaw out; clean and dry lines.

pressure tube

Defective interconnecting lines

Check pitot static system using test

set. Repair leaks by tightening

connections and replacing lines as

required.

Pointer of altimeter or airspeed

Obstruction in pressure source

Clear static and pitot lines.

indicator does not move

Defective altimeter or airspeed

Replace defective indicator.

indicator

Disconnected line

Check for disconnected line and

make necessary connections.

Altimeter or airspeed indicator

Loose static connections

Tighten static source line

pointer oscillates

connections.

Moisture in lines

Clear line.

Defective indicator

Replace defective indicator.

Altimeter pointer will not adjust to

Moisture in static pressure lines

Clear static source and

airport altitude within 70 feet (21 M)

interconnecting lines.

on ground with proper barometric

Altimeter instrument case leaking

Replace altimeter.

scale setting

Barometric scale out of adjustment

Replace altimeter or remove for

adjustment by an authorized

instrument repair agency.

High reading

Improper venting

Clear lines.

Altimeter adjustment knob binds

Defective altimeter

Replace altimeter.

Airspeed indicator pointer does not

Defective indicator

Replace indicator.

align with 0 ±1/16 inch (0 ±1.6 mm)

Moisture in lines

Clear lines.

on ground

N₁, N₂ and Rotor Tachometer Indicators

Excessive scale error (low reading) Weak magnet in tachometer

Replace indicator.

indicator

Page 17-8

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-1. Troubleshooting the Instrument Indicating System (Cont.)

Symptom

Probable Trouble

Corrective Action

Excessive scale error (high reading Weak restraining spring in

Replace indicator.

tachometer indicator

Pointer off zero position with

Pointer shifted

Replace indicator.

engine inoperative

No reading or intermittent reading

Loose wiring, disconnected

Check continuity through wiring and

connector or bad ground terminal

connectors. Repair as necessary.

connection

Defective tachometer indicator or

Replace defective indicator or

generator

generator.

Poor ground connection on

Check for good bond between

tachometer generator

tachometer generator mounting

flange and engine pad stud.

Turbine Outlet Temperature Indicator

No reading on indicator

Loose connection

Check and tighten all connections.

Defective airframe thermocouple

Replace or repair thermocouple

harness

harness.

Defective engine thermocouple

Replace engine thermocouple

harness

harness. (Refer to engine operational

and maintenance manual.)

Defective indicator

Replace indicator.

Open adjustable resistor R4

Replace resistor.

Erratic reading on indicator

Defective indicator

Replace indicator.

Defective connections or resistor

Repair connections or replace

R4 on TB9 at back of instrument

resistor.

Torque Gage and Direct Reading Engine Oil Pressure Gage

Pointer fails to respond

Pressure line kinked or bent

Check entire length of line; replace if

necessary.

Pointer indications sluggish

Torquemeter oil pressure snubber

Remove torquemeter oil pressure

inoperative due to cold weather

snubber. (Reinstall snubber when

weather conditions improve.)

Obstruction in line

Clear the line.

Defective gage

Replace gage.

Pointer indicates incorrectly

Line or line connectors leaking

Check for damaged ring gasket

under fitting hex and tighten

connections; if leak persists, replace

line.

Air trapped in line

Check for air bubbles and bleed if

necessary.

Page 17-9

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-1. Troubleshooting the Instrument Indicating System (Cont.)

Symptom

Probable Trouble

Corrective Action

Instrument Cluster 3-Pack and 4-Pack

Engine oil temperature pointer or

Open or short circuit in indicator

Replace instrument cluster.

oil pressure pointer (4-pack) off

Open or short circuit in wiring

Replace sender.

either end of scale or does not

harness

respond

Defective sender

Replace sender.

No reading or erratic ammeter

Malfunctioning voltage regulator

Replace voltage regulator.

rereading

Shunt leads open or intermittent or

Check security of shunt leads;

defective resistor R3

tighten if loose. Replace defective

resistor R3.

Open or short circuit in ammeter

Replace instrument cluster.

Dirty or worn mechanism in

Replace instrument cluster.

ammeter

Fuel quantity indicator inaccurate,

Wire loose, shorted or open

Check tank unit electrical

erratic or inoperative

connections; repair as necessary.

NOTE: The top of a later type tank

Check electrical wires between tank

unit is potted with sealant (3,

unit and instrument cluster. Repair as

Table 2-4) to prevent shorting

necessary.

due to moisture accumulation

Fuel indicator or tank unit defective

Perform operational check. Replace

instrument cluster or tank unit.

Calibrate fuel system.

Magnetic Compass

Excessive error

External magnetic interference

Locate and eliminate magnetic

interference.

Defective bearings

Replace magnetic compass.

Improper compensation

Compensate compass as required.

(Refer to FAA AC 43.13-1A.)

Excessive oscillation

Insufficient liquid in bowl

Replace compass.

Rotating element not level

Leaking float chamber

Replace compass.

Magnets detached from rotating

Replace compass.

element

Sluggish operation

Dirty jewels or pivots

Replace compass.

Weak cards magnets

Replace compass.

Liquid leakage or bubbles visible

Defective gasket or float chamber

Replace compass.

under normal flight conditions

Page 17-10

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

B. Indicating System Instrument

(7). Reinstall panel fairings. Install hood on

Replacement

instrument panel type B.

(8). Perform engine run−up and flight test

The following instructions are typical and

to check instrument operation.

apply to all instruments installed in the

instrument panel.

C. Indicating System Instrument Inspection

(1). Check that all electrical power is OFF

(1). Inspect instrument case for dents and

to avoid the possibility of electrical

cover glass for slippage and cracks.

shorts while working in the area of the

(2). Inspect fitting or electrical receptacle at

instrument panel.

back of instrument for damaged

threads that might prevent proper

(2). Remove instrument panel fairings. For

connection of the tube nut or electrical

instrument panel type B, remove hood

plug.

attaching screws and move hood aft far

enough for access to instrument

(3). Inspect index markings and numerals

mounting screws.

on dial face for discoloration and

legibility. Inspect pointers for cracked

(3). Disconnect electrical plug, wiring or

or peeling fluorescent paint.

tubing, as applicable, from back of the

instrument. Install suitable covers over

(4). Inspect for presence of all required

tube fittings, instrument fittings and

range markings and white slippage

loose wire terminals.

mark at bottom of glass.

D. Indicating System Instrument Repair

(4). At the face of the panel, remove the

screws (usually two or four) that attach

Refer to FAA AC 43.13−lA, Aircraft Inspection

instrument to panel and remove

and Repair, when repair or overhaul of

instrument from back side of panel.

instruments becomes necessary.

NOTE: The N₁ tachometer and TOT indicators

4. Pitot-Static System

are mounted to the panel with clamps that

only have to be loosened to remove the

CAUTION

instrument. Always loosen the cinching

screws in the upper left corner of the clamp

D Do not blow air through the pitot−static

first to release the clamp adjusting mecha−

system lines without disconnecting the al−

nism; then loosen the lower right, or holding

timeter and airspeed indicator. Instanta−

screw and slide the instrument outward,

neous air pressure may result in distor−

away from the panel face and out of the

tion or rupture of the instrument

clamp.

diaphragm.

D Before performing maintenance near the

(5). Position replacement instrument into

engine air inlet, covers of cardboard or

panel cutout from back side of panel

other suitable material should be taped in

and secure with mounting screws.

place over the engine inlet screen and oil

cooler air inlets to prevent entry of foreign

NOTE: When installing either the N₁ tachome−

objects into the engine compressor. Cov−

ter or TOT indicator, slide the instrument

ers should not be removed until work is

into the face side of the panel and through

completed and debris is thoroughly

the supporting clamp. Align the instrument,

cleaned out of the area. After removing

tighten the lower right (holding) screw and

covers, verify that area around base of

then tighten the upper left (cinching) screw

mast, inlet to plenum and entire plenum

to tighten the clamp and secure the case.

chamber is free of foreign material.

(6). Connect tubing, electrical plug or

(Ref. Figure 17−5) The pitot−static system

wiring to the back of the instrument.

consists of a pitot tube assembly, a static

Use care to avoid reversing connections

pressure port installation and interconnecting

for the pitot and static lines.

tubing and fittings.

Page 17-11

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

The pitot tube, in the lower center of the

panel grommet and connect pitot line to

canopy panel, is connected to the airspeed

elbow at back of airspeed indicator.

indicator by a nylon pitot line.

(5). Secure tube to structure with the

The static pressure port may be either a single

removed hardware.

or dual type.

(6). Check that pitot tube head is aligned

parallel to the longitudinal centerline of

The dual type has interconnected ports in each

the helicopter.

side of the engine air intake fairing while the

single type has one port in the aft end of the

(7). Check pitot pressure system for leaks;

fairing. The port(s) are connected to a pressure

repair leaks as necessary.

line routed between the port(s) and the

altimeter.

(8). Reinstall instrument panel fairings and

cover panel.

On current configuration helicopters, spring

C. Static Pressure Tubing Replacement

loaded drain valves are provided at the static

line low points aft of Sta. 127.00 and forward

(Ref. Figure 17−4)

of the instrument panel.

(1).

Remove the instrument panel fairings,

A static source crossover line interconnects the

forward right side fairing of engine air

altimeter and airspeed indicator.

intake and plenum chamber access

door.

A. Pitot-Static System Inspection

(2).

Remove tube(s) from single or dual

(1). Inspect system lines for damage that

pressure ports in engine air intake

could prevent an airtight connection.

fairing by breaking the bondline or

disconnecting coupling nuts at the tee

(2). Inspect pitot tube opening, drain hole

fitting.

and line for foreign matter. Clear and

clean the pressure line, as necessary.

(3).

Remove nylon straps attaching the

main tube (detail B) and drain valve, if

(3). Inspect static pressure tube port(s) for

installed, to the canopy structure.

foreign matter. Clear and clean the

port(s) and pressure lines, as necessary.

(4).

Remove nylon straps attaching the

main tube to air intake fairing longer−

(4). Inspect pitot tube for lateral misalign−

on, aft section strut and structure

ment. The pitot tube should be parallel

(detail A and C).

to the longitudinal centerline of the

helicopter.

(5).

Disconnect aft end of tube from tee

fitting.

B. Pitot Tube Assembly Replacement

(6).

Disconnect the main tube from altime−

(Ref. Figure 17−5)

ter and cover instrument opening.

(1). Remove the instrument panel fairings

(7).

Withdraw the main tube through

and the cover panel from the left side of

canted bulkhead grommet.

the lower instrument panel support

(8).

Remove crossover tube from altimeter

assembly.

and airspeed indicator.

(2). Remove the clamps, screws, washers

(9).

Route replacement static pressure tube

and nuts that attach pitot tube assem−

through the grommet in canted bulk−

bly to structure.

head and locate aft end of the tube at

pressure port tee fitting.

(3). Disconnect pitot tube from back of

airspeed indicator, slide aluminum

(10).

Secure the main tube to the canopy

head end of tube from canopy panel

structure with nylon straps (detail B).

grommet and remove the assembly.

(11).

Attach the main tube to the air intake

(4). Insert the replacement pitot tube

fairing longeron, aft section strut and

assembly head into place in canopy

structure (details A and C).

Page 17-12

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

SINGLE STATIC

PRESSURE PORT

LEFT STATIC

(NOTE 2)

PRESSURE PORT

(NOTE 2)

STATIC PRESSURE TUBE

RIGHT STATIC

PRESSURE PORT

GROMMET

(NOTE 2)

DRAIN VALVE

(NOTE 3)

STA. 127.00 DRAIN VALVE

(NOTE 3)

AIRSPEED

INDICATOR

ALTIMETER

COVER PANEL

CANOPY FRAME

NYLON CROSSOVER TUBE

STATIC PRESSURE

(NOTE 1)

TUBE

DRAIN VALVE

(NOTE 3)

TORQUE GAUGE

PRESSURE LINE

PITOT PRESSURE

NYLON STRAP

NYLON TUBE

TYPICAL

INSTRUMENT PANEL LOWER

SUPPORT STRUCTURE

NOTES:

GROMMET

MAINTAIN MINIMUM BEND RADIUS OF

1.00 IN. (2.54 CM) FOR ALL TUBES.

BOND TUBES TO FAIRING WITH ADHESIVE

(19, TABLE 2−4). TUBE ENDS MUST BE

DRAIN HOLE

FLUSH WITH OUTSIDE SURFACE.

NOT INSTALLED ON ALL HELICOPTERS.

AFT DRAIN VALVE ATTACHED WITH NYLON

PITOT TUBE ASSEMBLY

STRAPS AND FORWARD VALVE WITH

LACING CORD (37).

30−123E

Figure 17-5. Pitot Static System

Page 17-13

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(12). Secure static pressure tube and drain

AFT ENGINE AIR INLET FAIRING

valve, if installed, to canopy structure;

then connect tube to tee on altimeter.

(13). Using adhesive (19, Table 2−4), bond

STATIC PRESSURE TUBE

tube to static pressure port(s) in engine

VIEW A

air intake fairing. The outer end of the

STATIC PRESSURE PORT

tube must be flush with the fairing

surface. Connect lines of dual type to

BUG SCREEN

tee fitting.

(14). Connect crossover tube to altimeter and

airspeed indicator.

DETAIL B

30−224

Figure 17-6. Installation of Static Pressure

(15). Check that system tubing and fittings

Tube Bug Screen

are secure and air tight.

5. Altimeter

(Ref. Figure 17−1 and Figure 17−2) The

(16). Reinstall instrument panel fairings, air

altimeter presents helicopter altitude in feet

intake fairing and plenum chamber

above sea level under standard conditions of

access door.

atmospheric pressure and temperature.

The range of the internal mechanism is

0−50,000 feet. Three pointers, concentrically

D. Static Pressure Tube Aft End Protective

arranged, indicate altitude in increments of

Screen Installation

100, 1000 and 10,000 feet.

A small scale, located between the 2 and 3

index marking on the instrument face is

(Ref. Figure 17−6) Protective screen D3738 or

calibrated in inches of mercury. The scale is

D4272 may be installed at the aft end of the

rotated by a knob at the lower left of the

static pressure tube to preclude entry of

instrument for adjustment to the ambient

foreign material or objects and improve the

barometric pressure. After this adjustment is

maintainability of the pitot−static system.

accomplished, the reading of the altimeter will

indicate the actual height of the helicopter in

feet above sea level.

(1). Check static pressure tube aft port for

A. Altimeter Maintenance

foreign matter; clear and clean port, as

necessary.

Use the information in Instrument Indicating

System Troubleshooting thru Indicating

System Instrument Repair for troubleshooting,

(2). Clean faying surface of protective

inspection, replacement and repair of the

altimeter.

screen and coat with adhesive.

6. Airspeed Indicator

(3). Insert and seat protective screen in

(Ref. Figure 17−1 and Figure 17−2) The

airspeed indicator is a pressure−sensitive unit

static pressure tube.

actuated by the differential between impact

and static air pressures.

(4). Check installation of protective screen

The impact (pitot) pressure is connected from

for discrepancies.

the pitot tube to the inside of a pressure−sensi−

Page 17-14

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

tive diaphragm in the indicator case. Static air

B. Tachometer Generator Replacement

pressure, derived from the static port(s) in the

(Ref. Figure 17−7) The following instructions

engine air intake fairing, is connected to the

are typical and apply to all three tachometer

interior of the indicator case.

generators.

The pitot tube and airspeed indicator function

(1).

Gain access to the generators by

in forward flight only; the speed of rearward or

opening the engine access doors or the

sideward movement is not indicated.

air inlet and tail rotor drive shaft

access door, as applicable.

A. Airspeed Indicator Maintenance

(2).

Remove electrical connector from

Use the information in Instrument Indicating

tachometer generator and install

System Troubleshooting thru Indicating

protective cover on the generator

System Instrument Repair for troubleshooting,

receptacle.

inspection, replacement and repair of the

(3).

Remove four nuts and washers, remove

airspeed indicator.

bonding jumper and lift tachometer

generator straight off mounting pad.

7. N₁, N₂ and Rotor Tachometer Indicating

Discard gasket if unserviceable.

System

(4).

Check the grounding surface on nut

side of replacement generator case

(Ref. Figure 17−1 and Figure 17−2) The N₁

flange to be sure it will provide a good

tachometer indicator indicates the speed of the

electrical bond.

gas producer turbine in percent of rpm.

(5).

Position gasket and generator on

(Ref. Figure 17−1 and Figure 17−2) The N₂

mounting studs with shaft aligned so

and rotor tachometer indicator provides two

that it will mate with driving gear. If

indications: the actual rpm of the main rotor is

generator with side mounted electrical

indicated on the inner scale with the small (_R)

connector is used at the transmission,

pointer; the engine power turbine speed is

install with connector outboard. Rotate

indicated in percent of rpm on the outer scale

driven shaft as necessary to obtain

with the long pointer.

flush mounting.

Three 3−phase, 2−pole, synchronous tachome−

(6).

Secure generator with four washers and

ter generators produce the voltages that

nuts, with bonding jumper attached at

energize the power turbine rpm (N₂), gas

appropriate stud.

producer turbine rpm (N₁) and main rotor rpm

(7).

Remove protective cover and connect

(N_R) indicators.

electrical plug to generator receptacle.

The N₂ and N₁ tachometer generators are

C. Tachometer Generator Testing

located on the front of the engine accessories

gear case and the N_R tachometer generator is

(1). Connect the tachometer generator to

located by the tail rotor drive output shaft on

test harness and equipment shown in

the main transmission accessory section. The

Figure 17−8.

tachometer generators are connected through

individual wiring circuits to the indicators.

(2). Mount tachometer generator on test

stand. Check that the case grounding

surface has good contact.

A. N₁, N₂ and N_R Tachometer Indicator

Maintenance

(3). Start tachometer test stand. Set speed

control to zero rpm. Turn strobe light

Use the information in Instrument Indicating

switch to ON.

System Troubleshooting thru Indicating

System Instrument Repair for troubleshooting,

(4). Connect the tachometer generator to

inspection, replacement and repair of the N₁,

test setup for 20 ohm load test (test No.

N₂ and N_R tachometer indicators.

1).

Page 17-15

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(5).

Increase tachometer generator speed to

nals, is adjusted to establish and maintain an

1000 rpm. Check phase to phase

accurate circuit resistance of 8 ohms.

voltage; TP1 to TP2, TP1 to TP3 and

TP2 to TP3. Voltage should be 3.0−4.0

A. TOT Indicator Maintenance

Vac for each measurement.

Use the information in Instrument Indicating

(6).

Reduce tachometer generator speed to

System Troubleshooting thru Indicating

zero, disconnect 20 ohm test setup and

System Instrument Repair for troubleshooting,

connect 40 ohm load test setup.

inspection, replacement and repair of the TOT

indicator.

(7).

Increase tachometer generator speed to

3600 rpm. Check phase to phase

B. Thermocouple Harness Maintenance

voltage; TP1 to TP2, TP1 to TP3 and

TP2 to TP3. Voltage should be

The thermocouple harness that interconnects

17.5−18.5 Vac for each measurement.

the engine thermocouple harness from the

engine terminal block to the TOT indicator is a

(8).

Increase tachometer generator speed to

one−piece harness.

4200 rpm. Check phase to phase

voltage; TP1 to TP2, TP1 to TP3 and

(1). Replace the helicopter thermocouple

TP2 to TP3. Voltage should be

leads according to harness replacement

20.0−22.0 Vac for each measurement.

instructions in Section 19.

(9).

Reduce tachometer generator speed to

(2). Replace damaged harness lead termi−

zero, disconnect 40 ohm test setup and

nal; install new terminal with silver

prepare for open circuit test.

solder.

(10).

Increase tachometer generator speed to

(3). Adjust TOT circuit resistance after

3600 rpm. Check phase voltage; pin A

completion of any repair.

to ground, pin B to ground and pin A to

pin B. Voltage should be 25.0−31.0 Vac

(4). Maintain the engine thermocouple

for each measurement.

harness according to instructions in the

engine operation and maintenance

(11).

Replace generator if its output does not

manual.

meet test requirements.

C. TOT Indicating System Calibration

8. Turbine Outlet Temperature (TOT)

Indicating System

The following procedure is to be performed

periodically as specified in CSP−H−4 and when

(Ref. Figure 17−1 and Figure 17−2) The TOT

required due to system malfunction or

indicator indicates the temperature of the

suspected error in indications.

gases moving from the gas producer turbine to

the power turbine.

(1). Remove the left instrument panel

fairing.

The indicator is calibrated in major units from

0−12; reading is in degrees centigrade times

(2). Check that the engine thermocouple

one hundred (0−1200 degrees centigrade).

lead connections are tight and that

there are no signs of corrosion on the

The indicator is energized by electrical signals

terminals.

received from the 8 ohm thermocouple harness

mounted on the engine.

Do not connect test equipment

CAUTION

The thermocouple harness is chromel and

to the TOT indicating system

alumel and is self−generating; there is no

until the indicator is disconnected.

connection to the helicopter electrical system.

(3). Disconnect resistor board TB 9 from the

A variable resistor, mounted on a resistor

indicator terminal lugs and remove

board that is attached to the indicator termi−

indicator from instrument panel

Page 17-16

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

BEFORE FILTER

ENGINE FUEL

PORT (BF)

PUMP FILTER

AFTER FILTER

REDUCER

PORT (AF)

40−50 IN. LB

(4.52−5.65 NM)

MAIN TRANSMISSION OIL

PRESSURE SENDER

30−40 IN. LB (3.39−4.52 NM)

HOSE ASSEMBLY

20−25 IN. LB

(2.26−2.82 NM)

FITTING

40−50 IN. LB (4.52−5.65 NM)

FUEL FILTER PRESSURE SWITCH

40−50 IN. LB (4.52−5.65 NM)

(NOTE 2)

BUSHING

40−50 IN. LB (4.52−5.65 NM)

(NOTE 1)

ELBOW

20−25 IN. LB

(2.26−2.82 NM)

HOSE OR

TUBE

SINGLE ELEMENT PUMP

OIL TEMPERATURE SWITCH

12−25 IN. LB (1.36−2.82 NM)

FUEL FILTER

ENGINE FUEL

PRESSURE SWITCH

PUMP FILTER

40−50 IN. LB

(4.52−5.65 NM)

NOTES:

INSTALL PRESSURE SWITCH BEFORE INSTALLATION

OF BUSHING.

ENSURE THAT TWO HALVES OF THE SWITCH BODY ARE

NOT TWISTED RELATIVE TO EACH OTHER DURING

TORQUING, AS DIAPHRAGM DAMAGE CAN OCCUR.

DUAL ELEMENT PUMP

30−124−1G

Figure 17-7. Indicating System Electrical Senders (Sheet 1 of 3)

Page 17-17

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

GENERATOR

CONNECTOR 369A4599

GENERATOR

TP1

TP2

ALL RESISTORS

20 OHM 5W

TP3

CASE GND

TEST NO. 1 − 20 OHM LOAD TEST

TEST NO. 3 − OPEN CIRCUIT TEST

GENERATOR

ITEM

EQUIPMENT DESCRIPTION

NO.

TP1

TACHOMETER TEST STAND (IDEAL AEROSMITH , MODEL

17−23−3 O, OR EQUIVALENT).

TP2

ALL RESISTORS

VTVM (RCA MODEL WV−77C, OR EQUIVALENT) CALIBRATED

40 OHM 5W

TO 25 VAC ±2%.

20 OHM, 5 WATT RESISTORS (THREE REQUIRED).

40 OHM, 5 WATT RESISTORS (THREE REQUIRED).

TP3

369A4599 OR MS316E8−3P CONNECTORS AND WIRING

CASE GND

AS REQUIRED.

TEST NO. 2 − 40 OHM LOAD TEST

30−125A

Figure 17-8. Test Hookup For Tachometer Generator

(4).

Using tester (52, Table 2−2) or an

(8). Reconnect TB 9 to indicator terminal

equivalent precision ohmmeter, check

lugs and reinstall instrument panel

total circuit resistance through resistor

fairings.

R 4 and complete thermocouple system.

9. Engine Torque Indicating System

Resistance must be 8 +0.05, −0.0 ohms.

If adjustment is required, loosen screw

(Ref. Figure 17−1 and Figure 17−2) The torque

and retighten finger−tight in sliding

gage indicates engine torque supplied to the

contact on older type resistor R4 or by

engine output shaft.

turning rotating contact on resistor

currently being used, adjust contact

The torque gage is a reading instrument that

position to obtain specified resistance.

indicates a pound−per−square inch reading

Fully tighten screw on older type

equivalent to the amount of pressure (torque)

resistor. Recheck resistance and repeat

exerted on the accessory gear train by the

turbine output shaft.

adjustment, if necessary.

Oil pressure is routed from the torquemeter

(5).

Connect tester or an equivalent tester

pressure port of the engine through metal

to the indicator terminal lugs. Select

tubing and nylon tubing to the gage.

750°C (250−C18) or 790° (250−C20) on

the tester dial. The indicator must

A. Torque Gage Maintenance

indicate the selected temperature

Federal Aviation Adminis−

±5°C,. Adjust slotted adjustment screw

WARNING

tration rules CAR 6.606(b) &

on back of indicator if required.

6.613 require the installation of a re−

striction device at the pressure source

(6).

Select 1000°C on tester dial; the

of engine oil and torque sensing system

indicator must indicate 1000° ±20°C. If

to restrict oil flow in the event of sys−

this requirement is not met, recheck

tem failure. (Refer to HN−221).

adjustment of repeating step (5).

Use the information in Instrument Indicating

(7).

Seal the adjustment screw on the back

System Troubleshooting thru Indicating

of the indicator with a small amount of

System Instrument Repair for troubleshooting,

sealant (24, Table 2−4) and reinstall

inspection, replacement and repair of the

indicator in the instrument panel.

torque gauge.

Page 17-20

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

B. Torque Gage Pressure Line Removal

C. Torque Gage Pressure Lines Installation

NOTE: At replacement, use only a 3/16 inch di−

(Ref. Figure 17−9)

ameter nylon forward tube section line. The

3/16 inch diameter replacement line is long−

(1). Forward Tube Section (Nylon):

er and replaces both the 1/8 inch diameter

forward tube section and 1/8 inch aluminum

(a).

Check that all electrical power is

(or corrosion− resistant steel) center tube

OFF and remove left instrument

section on an early installation. After re−

panel fairing.

placement of any section of the pressure line

installation, pressure and leak test the as−

(b).

Disconnect pressure line from fitting

sembled lines between the engine and the

on torque gage (detail B).

gage at 200 psi (1379 kPa).

(c).

Cap the openings in torque gage and

(1). Forward Tube Section (Nylon):

pressure line.

(a). Remove covers from pressure line

(d).

Remove nylon pressure line by

and torque gage fitting.

releasing or cutting the three nylon

(b). Connect pressure line to torque gage.

straps along center canopy frame

Connect bleed valve at torquemeter

(detail C). If center tube section

on helicopters so equipped.

(aluminum alloy or corrosion−resis−

tant steel) is installed, disconnect the

(c). Route line along center canopy

pressure line nut at upper frame of

frame, and connect line to bulkhead

canted Sta. 78.50 (detail F). Cap end

at upper frame of canted Sta. 78.50.

of line

(d). If a fitting is installed at bulkhead

(e).

Remove left forward air inlet fairing

and a 1/8 inch diameter nylon line is

and left aft bulkhead access cover in

being reinstalled, connect the line to

cargo compartment.

the fitting. Or if a 3/16 inch diameter

line is being installed, remove any

(f).

Remove screws, clamps, nuts and

fitting at the bulkhead and route line

washers that secure line along left

aft through hole in bulkhead to

side of mast support structure and at

plenum chamber pan fitting. Use

left side of air inlet (plenum) cham−

grommet to secure line in bulkhead

ber (detail D).

hole.

1). Wrap duct tape around tube,

(g).

If center tube section (aluminum

approximately one inch in front of

alloy or corrosion−resistant steel) is

bulkhead fittings.

installed, disconnect pressure line

nuts at bulkhead fittings. Cap ends of

2). Tie a small loop in one end of a 2−3

line.

foot (0.6−0.9 m) length of cord. Tie

opposite end of cord to tube using a

(2). Aft Tube Section (Corrosion−Resistant

rolling hitch; slide rolling hitch

Steel):

down tube until it rests on duct

tape; tighten hitch.

(a). Open left engine compartment access

door.

3). Using a short body length spring

scale, capacity, 0 − 25 pounds(0 −

(b). Remove screw, clamp, nut and

12 kg), attach hook on scale to loop

washer (detail D).

in free end of cord. Apply 15 − 20

Lbs. (6.80 − 11.34 kg) straight

(c). Disconnect pressure line nuts at

pull, using cord. on oil pressure

plenum chamber pan fitting and at

tube for approximately 15 seconds.

engine torquemeter fitting (details E

If tube pulls partially or completely

and A).

out of fitting, replace fitting.

Page 17-21

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

CLAMPING

(TYP)

AT ENGINE

REDUCER

(TYP)

TORQUEMETER

OIL PRESSURE

SNUBBER

O−RING SNUBBER

O−RING

FITTING

(NOTE 1)

CHAFING TAPE OR PLASTIC

ENGINE BOSS

EDGING GROMMET

TYPICAL TORQUE OR

OIL PRESSURE GAUGE

O−RING

PLENUM CHAMBER

PAN

NYLON TUBE

OIL

(NOTE 4)

PRESSURE

TORQUE

PRESSURE

TORQUE PRESSURE GAUGE

WITH BLEED PROVISION

TEE

TORQUE GAUGE LINE

NYLON TUBE

(NOTE 3)

(NOTE 4)

ADAPTER

NYLON TUBE

(NOTE 4)

BLEED VALVE

ALUMINUM ALLOY OR CORROSION

(NOTE 5)

RESISTANT STEEL TUBE

(NOTE 4)

UNION AND NUT

ATTACH 1/4 IN.

BLEED HOSE

OIL PRESSURE LINE

(NOTE 2)

GROMMET

ENGINE OIL

PRESSURE LINE

(NOTE 2)

TORQUE GAUGE

PRESSURE LINE

CANOPY FRAME

TYING

NOTES:

(TYP)

USE ONLY AT 250 SERIES TORQUEMETER CONNECTION.

ENGINE OIL PRESSURE LINE USED WHEN DIRECT READING

STATIC PRESSURE

TYPE GAUGE IS INSTALLED.

NYLON TUBE

NYLON STRAP

LINE WITH FITTINGS APPLIES ONLY TO HELICOPTER WITH

INSTRUMENT PANEL A. SINGLE CONTINUOUS NYLON LINE

FOR PANEL TYPE B WITH GROMMET AS SHOWN FOR OIL

PRESSURE LINE (REF. NOTE 4).

AT REPLACEMENT, USE SINGLE CONTINUOUS 3/16 IN. O.D.

LINE. ORIGINAL LINES ARE 3/16 IN. O.D. FOR PANEL TYPE B

AND 1/8 IN. O.D. FOR PANEL TYPE B.

30−126−1B

AT INSTALLATION, WRAP VALVE THREADS WITH TEFLON

TAPE (79, TABLE 2−4).

Figure 17-9. Torque Gage and Direct Reading Engine Oil Pressure Gage (Sheet 1 of 2)

Page 17-22

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

ALUMINUM ALLOY, CORROSION

RESISTANT STEEL OR NYLON TUBE

(NOTE 4)

DUCT TAPE

(NOTE 6)

NYLON TUBING

ROLLING HITCH

(NOTES 6, 7)

FIREWALL FITTING,

FORWARD SIDE

NOTE 7

UNION AND NUT

FIREWALL FITTING,

AFT SIDE

CORROSION RESISTANT

STEEL TUBE

NOTES: (CONT.)

FIREWALL

(TYP)

WRAP TUBE AT LEAST ONCE WITH 2 IN. (5.08 CM)

WIDE DUCT TAPE APPROX. 1 IN. (2.54 CM) FROM FITTING.

SLIDE HITCH DOWN TUBE UNTIL IT RESTS ON DUCT TAPE.

30−126−2

Figure 17-9. Torque Gage and Direct Reading Engine Oil Pressure Gage (Sheet 2 of 2)

4). Remove cord, scale and duct tape

NOTE: Following procedure is for reinstalla−

from tube assembly.

tion of 1/8 inch OD center tube section. For

replacement, a single longer 3/16 inch OD

(e). Secure line in place along side static

nylon forward tube section replaces both the

pressure line, using the canopy frame

1/8 inch OD nylon forward tube section and

slots and nylon straps, or tying twine

1/8 inch OD center tube section.

(30, Table 2−4) if straps arc is not

available.

(a).

Locate pressure line in position,

connect to bulkhead fittings, and

(f). After pressure and leak test, reinstall

tighten.

instrument panel fairing.

(2). Aft Tube Section (Corrosion−Resistant

(b).

Wrap length of aluminum tubing

Steel):

where it is routed past aft corner of

mast support structure and into

(a). Locate pressure line in position,

plenum chamber, using tape and

connect to plenum chamber pan

activator (56, Table 2−4), to prevent

fitting and engine torquemeter

chafing between the tube and struc−

fitting, and tighten.

ture. Steel tubing has a plastic

edging grommet instead of tape.

(b). Secure pressure line to left side of

mast support structure and plenum

(c).

Secure line along left side of mast

chamber with screws, clamps,

support structure and at left side of

washers and nuts or stand−off (detail

plenum chamber with screws,

D).

clamps, nuts and washers (detail D).

(c). After pressure and leak test, secure

(d).

After pressure and leak test, install

engine compartment access door.

left forward air intake fairing and

(3). Center Tube Section (Aluminum Alloy

left aft bulkhead access cover in

or Corrosion−Resistant Steel):

cargo compartment.

Page 17-23

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

10. Direct Reading Oil Pressure Indicating

(5). Disconnect pressure line from fitting at

System

gage.

NOTE: During filling of line, do not introduce

The direct reading engine oil pressure indicat−

any air bubbles into the system. Use a suit−

ing system utilizes a pressure gage of 0−150

able pump with sufficient volume to fill the

psi (0−1035 kPa) capacity which is mounted

entire length of the pressure line.

near other engine instruments in instrument

panel type B (Figure 17−2). The gage is

(6). At gage end, pump the pressure line

connected to an oil pressure port on the front

full with new engine oil. Force oil

face of the engine accessory section by 1/8 inch

through the line until clean oil flows at

diameter corrosion resistant steel and nylon

the engine end.

tubing. The tubing is in two sections, with

(7). Tighten tube fitting at the engine and

corrosion resistant steel being used aft of the

continue to pump a small amount of oil

engine firewall and nylon tubing forward of

back into the engine.

the firewall. The tubing is routed adjacent to

the torque gage tubing from the firewall to the

(8). Install and tighten gage line fitting at

instrument panel and some tie straps and

back of instrument. Keep the line as

clamping arrangements are common to both

full as possible during connection.

(Figure 17−9).

(9). Start and operate engine at idle

according to the Owner’s Manual and

A. Engine Oil Pressure Gage Tubing

check for visible air bubbles in the

Replacement

forward nylon line.

Replace engine oil pressure gage tubing using,

(10). If air bubbles are present (introduced

in general, the instructions provided for

during connection at instrument),

replacement of torque gage tubing. After

momentarily loosen fitting at back of

replacement, service and bleed the system.

instrument and bleed system with

engine running.

B. Torque or Direct Reading Engine Oil

Pressure Line Bleeding and Servicing

NOTE: A higher power setting may be required

to obtain adequate pressure.

NOTE: On helicopters equipped with a plunger

11. Instrument Cluster Three-Pack or

actuated bleed valve at the torquemeter fit−

Four-Pack Indicating System

ting, gain access to the rear of the torqueme−

ter and attach a 1/4 inch diameter drain

(Ref. Figure 17−10 and Figure 17−11) The

hose at the bleed valve. For best access, re−

instrument cluster is an instrument assembly

move an adjacent instrument or avionics

built as a single unit with three or four

unit not necessary to ground operation of

indicators. The instrument clusters are

the helicopter. Proceed with bleeding and

identical except that the 3−pack does not

servicing described below; or service and

include an engine oil pressure indicator and is

bleed system with engine operating by de−

not internally illuminated.

pressing valve plunger until clear engine oil

Indicators register generator output in

flows through the drain hose into a contain−

amperes, engine oil pressure in pounds−per−

er.

square inch (4−pack), engine oil temperature

in degrees centigrade and operating fuel

(1). Remove left instrument panel fairing.

weight in pounds.

(2). Open engine compartment left access

The helicopter electrical system voltage of 28

door.

Vdc is reduced to a nominal 14.5 Vdc by

voltage dropping resistor R1, located on

(3). Wrap cloth around gage line under

terminal board TB8 mounted on the structure

fitting at engine and at the back of the

beneath the left side pilot’s compartment floor,

instrument.

for instrument circuit power.

(4). Loosen, but do not remove, pressure

The senders for the engine oil pressure

tube fitting at engine.

(4−pack), engine temperature and fuel

Page 17-24

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

quantity indicators each function as the

NOTE: The individual indicators of the instru−

variable resistance leg of the associated

ment cluster are not replaceable. If there is

instrument bridge circuit.

an indicator malfunction, the complete unit

should be replaced. Remove the wiring har−

As pressure, temperature or float arm position

ness for reinstallation of a replacement

change, the sender resistance changes and

instrument cluster (Figure 17−11 for 4−pack

causes an imbalance in current flow through

or Figure 17−10 for a 3−pack); resistor R112

the indicator windings to produce pointer

is supplied as part of a new 4−pack cluster

movement.

assembly.

B. Instrument Cluster Three-Pack or

Except for the ammeter, external, fixed value

Four-Pack Calibration Check

shunt resistors are mounted across the input

terminals of each of these instruments and

This calibration check is to be performed at a

furnished as part of the cluster (Figure 17−11).

qualified instrument calibration facility. The

following calibration information is supplied

for reference only, for convenience of the

An exception is the (4−pack) oil pressure

calibration facility. All calibration checks are

circuit which has a separate adjustable

to be made with precision equipment, carefully

potentiometer for indicator calibration. This

observing polarities and with face on instru−

potentiometer is used in conjunction with PN

ment cluster positioned approximately

6460013 pressure sender and is located on

vertically.

panel structure forward of and below the

4−pack cluster.

NOTE: Supply voltage is to be 14.5 ±0.3 Vdc for

all following checks. To measure and adjust

Ammeter pointer deflection is a result of

resistance of variable resistor in the checks,

current flow through resistor R3 which is

supply voltage source and variable resistor

located next to the reverse current relay in the

must be disconnected from circuits. For in−

engine compartment. The resistor, installed in

formation on the specific terminal studs

the low voltage output (ammeter) circuit of the

used for individual gages in the cluster, see

starter−generator , acts as a calibrating

Figure 17−10 for a 3−pack or Figure 17−11

resistance to cause ammeter pointer move−

for a 4−pack. Gages of the instrument clus−

ment that is proportional to the main power

ter should provide indications within the

output of the generator.

tolerances specified in following checks re−

gardless of cluster position. Vertical position

A plus scale reading on the ammeter indicates

is specified only to approximate the installa−

the current demand of the helicopter electrical

tion position in the helicopter. For a 3−pack,

system during normal generator operation.

scale error determined at any major gradua−

Minus amperage is indicated only during

tion that is checked should not exceed 5 per−

engine starting and shows the current demand

cent of the full scale value.

of the starter.

(1). Fuel Quantity Gage:

Resistor R112, mounted at terminal point 8 on

(a). Obtain a variable resistor that is

the back of a 4−pack cluster, is an input

continuously variable over a mini−

voltage dropping resistor for the instrument

mum range of 0−90 ohms, and adjust

lights circuit and functions only when night

it to provide 59 ohms resistance.

lighting is installed.

(b). Connect the 59 ohm resistance across

the terminal studs for the fuel

A. Instrument Cluster Three-Pack or

quantity gage and power input

Four-Pack Maintenance

ground.

Use the information in Instrument Indicating

(c). Apply supply voltage to instrument

System Troubleshooting thru Indicating

cluster. Note that the gage indicates

System Instrument Repair for troubleshooting,

approximately 200 pounds (2 mark)

inspection, replacement and repair of the

and keep supply voltage applied

instrument cluster.

approximately 5 minutes.

Page 17-25

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

WASHER

WIRE LEAD AND

LOCKWASHER

TERMINAL LUG

NUT

PRINTED CIRCUIT BOARD

(NOTE 1)

THREADED TERMINAL STUD

(NOTE 1)

NUT

NOTE 1

LOCKWASHER

WASHER

VIEW A−A

(TYP)

STOWED WIRES

(NOTE 7)

INSTRUMENT CLUSTER

WIRING HARNESS

E507A22

L534C22

FIXED SHUNT

(NOTE 4)

WIRE E540D22

RESISTOR (TYP)

(NOTES 1, 3)

AMP.

FUEL

OIL

FIXED SHUNT

RESISTOR (TYP)

(NOTES 1, 3)

INTERIOR LAMPS

INSTRUMENT CLUSTER

(NOTE 2)

3−PACK

WIRE L542E20N

REAR VIEW

NOTES:

PART OF AND FURNISHED WITH INSTRUMENT CLUSTER.

THREADED STUDS:

NOT USED.

NO.

ITEM

FOR ASSOCIATED INDICATOR INSIDE CLUSTER.

FUEL QUANTITY GAUGE

FOR INFORMATION ON HARNESS CONNECTION WIRING

OIL TEMPERATURE GAUGE

BETWEEN CONNECTOR J4 AND THREADED TERMINAL

AMMETER − (GND)

STUDS, SEE APPLICABLE ELECTRICAL SYSTEM WIRING

AMMETER +

DIAGRAM (REF. SEC. 20).

+14.5 VDC POWER INPUT

−POWER INPUT, COMMON GND (NOTE 6)

ALSO GND FOR FUEL QUANTITY AND TEMPERATURE GAUGES.

WIRE END INSULATED AND SECURED AT STOWED POSITION.

30−193−1

Figure 17-10. Instrument Cluster Three-Pack with Wiring Harness

(Instrument Panel Type B) (Sheet 1 of 2)

Page 17-26

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

E505A22

E506A22

(NOTE 7)

E507A22

(AMM BATT)

D501A20

(AMM GEN)

D505A20

10 E540D22 − (GEN)

E540C22

12 L542E20N

L535A20

ILLUMINATION 9

(NOTE 7)

L534C22

BLANK

KEY

INSTRUMENT CLUSTER

CLUSTER WIRING CONNECTIONS

WIRING HARNESS

(NOTE 4)

30−193−2

Figure 17-10. Instrument Cluster Three-pack with Wiring Harness

(Instrument Panel Type B) (Sheet 2 of 2)

(d). Remove supply voltage and adjust

(b). Connect the 139 ohm resistance

resistance to 88 ohms. Reapply

across the terminal studs for the

supply voltage and check that pointer

engine oil temperature gage and

ascends and indicates full (F).

power input ground.

Centerline of pointer should align

(c). Apply supply voltage to instrument

with ±4° of centerline of F mark.

cluster. Note that the gage indicates

approximately midrange (mid−range

NOTE: Checks, steps (e). and (f)., are to be per−

mark) and keep supply voltage

formed with descending pointer.

applied approximately 5 minutes.

(e). Remove supply voltage and adjust

NOTE: Checks, steps (d). thru (f)., are to be per−

resistance to 59 ohms. Reapply

formed with ascending pointer.

supply voltage and check that gage

(d).

Remove supply voltage and adjust

indicates 200 pounds (2 mark).

resistance to 734 ohms. Reapply

Centerline of pointer should align

supply voltage and check that pointer

with ±3° of centerline of 2 mark.

ascends and indicates 15°C. Center−

line of pointer should align with ±2°

(f). Remove supply voltage and adjust

of centerline of 15 mark.

resistance to 1 ohm. Reapply supply

voltage and check that gage indicates

(e).

Remove supply voltage and adjust

empty (E). Centerline of pointer

resistance to 139 ohms. Reapply

should align with −2° of centerline of

supply voltage and check that pointer

E mark.

indicates mid−range. Centerline of

pointer should align with ±3° of

(g). Disconnect supply voltage source and

centerline of mid−range mark.

variable resistor from terminals of

(f).

Remove supply voltage and adjust

the cluster.

resistance to 46.3 ohms. Reapply

supply voltage and check that gage

(2). Engine Oil Temperature Gage:

indicates 125°C. Centerline of pointer

should align within ±2° of centerline

(a). Obtain a variable resistor that is

of 125 mark.

continuously variable over a mini−

mum range of 0−750 ohms, and

(g).

Disconnect supply voltage source and

adjust it to provide 139 ohms resis−

variable resistor from terminal studs

tance.

of the cluster.

Page 17-27

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

E505A22

FUEL SENDER

E506A22

ENG TEMP SENDER

SP50

E507A22

E507B22

OIL PRESS SENDER

D501A20

AMMETER (BATTERY)

E507D22

D506A20

AMMETER (GEN)

R305

E540C22

POWER INPUT (R1)

L535A20

R304

GROUND

OIL PRESS. GAUGE

E532A22

E532B22

R303

CALIBRATION

R112

L542A22

L534C22

POTENTIOMETER

PANEL LIGHTS

(NOTE 1)

8W20Ω

CLUSTER WIRING CONNECTIONS

INSTRUMENT LIGHT

FUEL QUANTITY

INSTRUMENT CLUSTER 4−PACK

ENGINE OIL TEMPERATURE

ENGINE OIL PRESSURE

INSTRUMENT SHUNT

RESISTOR (TYP)

INPUT VOLTAGE DROPPING

RESISTOR R112 (LIGHTS)

FIBER WASHER (2 PLCS)

NOTE 2

AMMETER

CLUSTER WIRING HARNESS

NOTES:

OIL PRESSURE GAUGE CALIBRATION POTENTIOMETER AND

DASHED LINE CIRCUIT USED ON CURRENT CONFIGURATION.

FIXED RESISTOR (OIL PRESS. GAUGE SHUNT) USED IN THIS

LOCATION ONLY ON EARLY CONFIGURATION WITH 369A4534

OIL PRESSURE SENDER.

30−127A

Figure 17-11. Instrument Cluster Four-Pack with Wiring Harness

Page 17-28

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(3). Ammeter Gage:

(4). Engine Oil Pressure Gage (4−Pack):

Comply with applicable

(a). Obtain a variable resistor that is

WARNING

continuously variable over a mini−

electrical safety precautions

when checking the ammeter gage.

mum range of 0−90 ohms, and adjust

it to provide a resistance of 1 ohm.

(a). Connect a variable resistance load, a

(b). Connect the 1 ohm resistance across

test ammeter and the ammeter gage

the terminal studs for the engine oil

to be tested in a series circuit to a

pressure gage and power input

14.5 ±0.3 Vdc supply source that is

ground.

capable of supplying 1.38 amperes

through the circuit.

NOTE: Checks steps (c). thru (f). are to be per−

formed with ascending pointer.

NOTE: Variable resistance load must be adjust−

able to provide either a total current of 0.75

(c). Apply supply voltage to instrument

or 1.38 amperes through the combined resis−

cluster. Note that gage indicates

tance of the variable load, test ammeter and

approximately 0 pounds per square

ammeter gage being tested. Make resis−

inch (psi). Centerline of pointer

tance measurements and/or calculate re−

should align within ±2° of 0 psi mark.

quired values of load resistance for use with

the test ammeter in the series circuit as nec−

(d). Remove supply voltage and adjust

essary. A current flow of 0.75 ampere

resistance to 59 ohms. Reapply

through the ammeter gage being tested

supply voltage and check that pointer

should result in a 75 ampere indication on

ascends and indicates 90 psi. Center−

the gage.

line of pointer should align within

±3° of 90 psi mark.

(b).

Set variable load to correct resistance

and apply supply voltage with the

(e). Remove supply voltage and adjust

required polarity to provide a +0.75

resistance to 88 ohms. Reapply

ampere current reading on the test

supply voltage and check that pointer

ammeter and a +75 ampere indica−

ascends and indicates 125 psi.

tion on the ammeter gage being

Centerline of pointer should align

tested. Centerline of pointer should

within ±2° of 125 psi mark.

align within ±4° of centerline of +75

(f). Disconnect supply voltage source and

mark.

variable resistor from terminals of

the cluster.

(c).

Remove supply voltage from cluster.

(5). All Gages:

(d).

Set variable load to correct resistance

and apply supply voltage with the

Without supply voltage applied to cluster,

correct polarity to provide a −1.38

check that each pointer in the cluster returns

amperes current reading on the test

to a position at or below the lowest calibration

ammeter and a negative current

mark of its gage.

indication on the ammeter gage being

tested. Pointer on ammeter gage

12. Engine Oil Temperature Sender

being tested should indicate between

−75 and −150.

(Ref. Figure 17−7)

A. Engine Oil Temperature Sender

(e).

Remove supply voltage from cluster

Replacement

and check that ammeter gage being

tested indicates 0 (zero). Centerline

(1). Check that all electrical power is OFF.

of pointer should return to and align

with ±3° of centerline of 0 mark.

(2). Drain the engine oil tank.

(f).

Disconnect variable load resistor and

(3). Disconnect electrical wire from oil

test ammeter from ammeter gage

temperature sender, cut safetywire and

being tested.

remove sender from bushing in oil tank

Page 17-29

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

fitting; keep sender washer for rein−

(5). Tightly wrap two to three turns of

stallation if it is serviceable. (Plug tank

white teflon tape (79, Table 2−4) on

fitting and insulate wire terminals

sender pipe threads. Connect pressure

when replacement sender is not

line and check both ends of tube for

immediately available.

security.

(6). Tighten clamp bolts and connect

NOTE: 369A4533− BSC sensor is compatible

electrical wire.

with the 369D296305−21,

−23 and

−31

instrument clusters only. 369A4533−3 sen−

(7). Start the engine according to Owner’s

sor is compatible with the 369D296305−33,

Manual and check for oil leakage and

−35 and −37 instrument clusters only.

proper operation of the pressure system

indicator.

(4). Install replacement sender with

serviceable or new washer or gasket

B. Electrical Oil Pressure Gage Calibration

and tighten to 100 − 150 inch−pounds

Calibrate oil pressure gage systems having

(11.30 − 16.95 Nm). Lockwire the

adjustment potentiometer R303 and PN

sender to oil tank bushing. Connect

640013 pressure sender, using one of the

electrical wire.

following methods.

(5). Fill the engine oil tank.

(1). Method I:

(6). Start the engine according to Owner’s

The following equipment is required: A

Manual and check for oil leakage and

0−150 psi (0−1035 kPa) pressure gage

proper operation of the temperature

with 1 percent accuracy, high pressure

system indicator.

hose and tee fitting to connect into the

engine oil pressure sender inlet line.

(7). Reinstall aft bulkhead access cover.

(a).

Disconnect engine oil pressure inlet

13. Engine Electrical Oil Pressure System

line from sender (Figure 17−7) and

reconnect with the tee fitting in the

A. Engine Electrical Oil Pressure Sender

line.

Replacement

(b).

Connect master gage to high pres−

sure hose, fill the hose and gage with

(1). Check that all electrical power is OFF.

engine lubricating oil (Table 2−3);

then connect to the tee fitting.

(2). Disconnect electrical wire and pressure

line from oil pressure sender mounted

(c).

Locate potentiometer R303 on

on right engine mount; use suitable

instrument panel structure. Loosen

means to catch residual oil from line.

adjustment locknut and set poten−

(Cap pressure line and sender, and

tiometer at approximate mid−range.

insulate wire terminal when replace−

ment sender is not immediately

(d).

Start and operate the engine at idle

available).

in accordance with the Owner’s

Manual. Observe oil pressure indica−

(3). Observe locations of mounting clamps;

tion on the master gage. If indication

then remove clamps, bonding jumper

is erratic, bleed out air by loosening

and sender from mount.

hose fitting at the gage.

(4). Using the two removed support clamps,

(e).

Increase engine N₁ to 80 percent. The

install replacement sender on engine

stabilized oil pressure at this point

mount but do not tighten clamps.

should be in the 90−130 psi (621−896

kPa) range on the master gage. If oil

NOTE: The small clamp and bonding jumper

pressure is not in this range, the

provides the bonding path between the

engine oil pressure regulator will

sender and firewall. Be sure that sender

require adjustment according to

bonding is as specified in Maintenance of

engine operation and maintenance

Electrical Bonding Connections, Section 19.

manual.

Page 17-30

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(f). While maintaining 80 percent N₁,

(f). Connect engine oil pressure line to

adjust potentiometer R303 until

sender inlet. Start and operate

four−pack gage indicates the same

engine at idle in accordance with the

pressure as the master gage. Tighten

Owner’s Manual. Bleed engine oil

potentiometer locknut.

pressure line at the sender for a

stable indication on the four−pack

gage.

(g). Shut down engine and remove test

equipment. Reconnect oil pressure

(g). Perform a flight check to ensure that

line to sender. Check engine oil level

oil pressure regulation at high power

in tank and service if required.

settings is in the 120 ±10 psi (827 ±69

kPa) range.

(h). Perform a flight check to ensure that

14. Fuel Quantity System

oil pressure regulation at high power

settings is in the 120 ±10 psi (827 ±69

(Ref. Figure 17−7)

kPa) range.

A. Fuel Quantity Transmitter (Tank Unit)

Replacement

(2). Method II:

(1). Check that all electrical power is OFF

and that the helicopter is grounded.

The following equipment is required: A

0−150 psi (0−1035 kPa) gage of 1

Use all necessary precautions

CAUTION

percent accuracy, a source of regulated

consistent with safe practice

pressure (air, inert gas or hydraulic oil),

when working in or around the fuel cells. If

fittings, and necessary lines and hoses

a replacement tank unit is not available for

to connect gage and pressure source to

immediate installation,do not remove the

the oil pressure sender inlet.

installed unit.

(2). Remove left fuel cell access door.

(a).

Remove oil pressure line at pressure

sender (Figure 17−6) and connect

(3). Disconnect tank unit harness electrical

pressure source with master gage in

plug from mating connector at fuel

the line.

shutoff cable support bracket.

(4). Cut the lockwire, remove the five bolts

(b).

Locate potentiometer R303 on

and washers from tank unit and lift

instrument panel structure. Loosen

unit from fuel cell cover plate. Discard

adjustment locknut and set poten−

the gasket.

tiometer at approximate mid−range.

Connect 28 Vdc electrical power.

(5). Check the replacement tank unit for

the following:

(c).

Slowly pressurize the sender until

(a). Housing and pivot mechanism for

master gage indicates 130 psi (896

deformation or corrosion.

kPa). Adjust potentiometer until

(b). Float and arm for freedom of move−

four−pack gage also indicates 130 psi

ment between stops.

(896 kPa).

(c). Float arm for sufficient offset so that

(d).

Release pressure and then recheck.

the float will clear the edge of the cell

With pressure increased to 130 psi

sump and allow full travel of the

(896 kPa), the four−pack gage

arm.

tolerance is one needle width at the

(d). If shaft end play seems excessive,

tip.

install a washer and clip to limit play

to 0.015−0.025 inch (0.381−0.635

(e).

Tighten locknut on potentiometer,

mm) clearance between float arm and

release all pressure and remove test

bushing according to instructions in

equipment.

Hughes Notice HN−89.

Page 17-31

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(6). Install gasket, tank unit with float

(a). For the single unit type gage, cut the

inboard, washers and bolts. Torque

template circular to fit flat on the

bolts to 50 − 70 inch−pounds (5.65 −

instrument glass, inside the bezel.

7.91 Nm), and using lockwire (2,

Scribe two lines, pointer pivot shaft

Table 2−4), safety boltheads (three and

as the center.

two) together.

(b). For the 3−pack or 4−pack type gage,

(7). Reconnect electrical plug to mating

cut the template rectangular to fit

connector.

flat on the instrument glass, inside

the bezel and covering the fuel

quantity gage area. Tape the tem−

(8). Check fuel quantity indicator reading

plate in position and scribe lines on

against a known quantity of fuel in the

the template from center of pointer

cells.

pivot shaft through the center of

graduation marks at E, 2 and F.

(9). Fill cells to capacity and check for fuel

Scribe maximum tolerance, step

leakage; none is permissible.

(1).(b)., lines on each side of the

center lines.

(10). Reinstall fuel cell access cover.

NOTE: During defueling, the helicopter should

B. Fuel Quantity Transmitter and Indicator

be as near level as possible and battery or

Operational Check

external power voltage should be 24− 28.5

Vdc. Inaccurate readings may result if these

Perform the following checks to determine that

conditions are not met.

fuel quantity indicator readings are within

tolerance. Checks are made at empty, 200

(3). Defuel the helicopter. Refer to Section 2

pounds and full fuel loads.

for procedure and observe the following.

(1). Use the following tolerances when

(a). Stop defueling when the FUEL LOW

checking fuel quantity indications.

caution light goes on (Indicator

should be passing through the 35

(a). For the single unit type gage:

pound position).

E = +0 degrees from centerline of

marker (not above zero)

(b). Following caution light illumination,

2 = +6 degrees from centerline of

drain remaining fuel into a container.

marker

There should be approximately 5.4

F = +6 degrees from centerline of

gallons (20.5 L) of drained fuel.

marker

(c). If conditions in steps (a). and (b).

above are not met, check caution

(b). For the 3−pack or 4−pack type gage:

light circuitry and/or readjust tank

E = +0, −2 degrees from centerline

unit as required.

marker

2 = ±3 degrees from centerline of

(4). Turn electrical power ON. Check

marker

indicator reading. Pointer must be at E

F = +4, −0 degrees from centerline of

or below. Refer to tolerances, step

marker

(1).(a). and (b).

(c). Tank unit circuit resistance (gage

NOTE: If indications are not within tolerances,

disconnected) is as follows:

determine whether gage or tank unit is at

E = 1 ohm

fault by removing electrical power, discon−

2 = 59 ohms

necting gage wiring, and checking tank unit

F = 88 ohms

circuit resistance, step (1).(c).

(2). In order to check degrees of error,

(5). Start refueling slowly. Note that the

construct a template of thin clear

FUEL LOW caution light goes out

plastic as follows.

shortly after the indicator passes the

Page 17-32

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

35−pound position, approximately 5.4

NOTE: Sending units installed on early Model

gallons(20.5 L) of fuel in cells.

369H and 369HS helicopters may not have

potting compound applied on sending unit

mounting plate around terminals. If potting

(6). Continue to fill the cells to 200 pounds,

compound has not been applied, pot the

approximately 30.75 gal (116.5 L) of

tank sending unit as shown in

fuel.

Figure 17−12, detail A or detail C.

NOTE: Density of JP−4 fuel is 6.5 lb/gal (0.78

(3). Using flashlight and pointed probe

kg/L) on standard day 59°F (15°C), 29.92 in.

(wood or plastic), inspect interface of

Hg, dry air. Fuel density will vary under

potting compound and sending unit

other ambient conditions and should always

mounting plate for voids. Pay particular

be taken into account when indicator accu−

attention to area around terminal

racy is questionable.

screws (detail A, Figure 17−12). If any

voids are noted, perform steps (7). thru

(14).

(7). Check that indicator reading at 200

pounds is within scribed tolerance

NOTE: Troubleshooting is accomplished with

marks on template. For the single unit

electrical power ON, circuit breaker in (re−

type gage, rotate the template as

set) and caution and warning lights set at

required to check that pointer is within

BRT.

6 degrees of the center of the marker.

(4). If FUEL LOW warning light is on or

(8). Continue to refuel until the tanks are

glows when fuel level is above the low

full. Check that indication is within

level mark, perform steps (7). thru (14).;

tolerance in the same manner as in step

otherwise end inspection after step (6).

(7).

(5). Apply fault (ground) input to terminal

No. 2 on sending unit (Figure 17−12).

(9). Remove electrical power and secure the

Check that lamp illuminates properly

refueling operations. If fuel quantity

when fault input is applied. If lamp

indications were not within tolerances,

does not come on or does not illuminate

test the tank unit.

properly, check wiring between termi−

nal No. 2 and CB104−2 circuit breaker

C. Fuel Tank Sending Unit and Fuel Low

and make corrections.

Warning Light Indicating System

Inspection

(6). Reinstall fuel cell access door if steps

(7). thru (14). are not to be performed.

This inspection, checks for security and

When performing mainte−

condition of the fuel tank sending unit, and for

WARNING

nance of fuel system compo−

proper operation of the fuel low warning light

nents, comply with all applicable safe−

indicating system. Bench testing as well as

ty precautions to avoid possibility of

rework of the fuel tank sending unit may be

fuel vapor ignition and fire. Prior to

necessary if inspection reveals voids between

maintenance always turn off all electri−

potting compound and unit mounting plate or

cal power; make sure helicopter is

dimness/erroneous actuation of the fuel low

grounded; disconnect external pow−

level warning light.

ersource and disconnect battery.

(7). Remove fuel tank sending unit; refer to

(1). Remove left side fuel cell access door.

safety precautions noted above.

(2). Check fuel tank sending unit, electrical

(8). Dry top of sending unit with heat gun

terminals and wiring for security and

or oven for one hour at 100°F (38°C).

condition; check wiring harness

between tank unit and instrument

(9). Bench test sending unit (Ref. Tank Unit

cluster.

Testing); replace unit as required.

Page 17-33

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

FULL POSITION

NOTE 1

369A4245−3 BRACKET

NOTE 2

0.75 IN. (19.05 MM)

APPROX.

SPRING CONTACT POSITION

A − A

MODEL 369H AND 369HS ONLY

(SEE DETAIL C FOR MODEL 369HM)

EMPTY POSITION

0.04 IN. (1.016 MM)

TOPSIDE OF NUT

GS 6−5 EYELET

MS20364−632 NUT

MIN.

POTTING COMPOUND

TRANSISTOR

(RTV−732 SEALANT)

BOARD

B − B

(TYP) (2 PLCS)

TERMINAL NO. 1

NAS671−6 NUT

AN960−6L WASHER

COVER

MS35206−244 SCREW

AN960−8L WASHER

#46 TERMINAL LUG

NAS549−6 WASHER

NEOPRENE WASHER

NAS1598−C8Y STAT−O−SEAL

AN515−GR10 SCREW

−3 BRACKET

TERMINAL NO. 2

(NOTE 4)

MODEL 369H/369HS ONLY

1.75 IN. (4.445 CM)

MAX. DIA. SEALING ENVELOPE

NOTE 3

POTTING COMPOUND (PR1221)

369A4520 TANK UNIT

0.75 IN. (19.05 MM) MAX.

SEALING ENVELOPE

NOTES:

ORIENT ELECTRICAL HARNESS AS SHOWN.

APPLY POTTING COMPOUND AROUND TERMINALS

AS SHOWN; DO NOT EXTEND ABOVE NUT OR

MODEL 369HM ONLY

APPLY POTTING COMPOUNDS ON TOP SIDE OF NUT.

MINIMUM ENVELOPE OF POTTING COMPOUND

(0.60 IN. (15.24 MM) MIN. COVER OVER ELECTRICAL

COMPONENTS AND WIRING.

APPLY FAULT (GROUND) INPUT TO TERMINAL NO. 2.

30−225A

Figure 17-12. Bench Test and Potting of Fuel Tank Sending Unit

Page 17-34

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(10). For 369H and 369HS commercial

(22.835−23.140 cm). Bend the float full

helicopters only, perform the following

stop as required to obtain 88−95 ohms

(Figure 17−12, detail D and detail E):

(88 ohms desired) within these float

travel limits.

(a). Tighten NAS671−6 nut to hold

369A4245−3 bracket firmly in

(6). Disconnect the ohmmeter. Obtain a 24

position.

Vdc power supply or battery, a No. 328

lamp and the necessary wiring to make

(b). Disconnect and lift No. 46 ground

connections shown in Figure 17−13.

terminal lug away from mounting

(7). Apply 24 Vdc power and check that

plate flange; hold float arm at full

lamp illuminates when centerline of

position.

arm−to−float attachment is 1.25 inches

(c). Resistance measured from −3 bracket

(3.175 cm) above its empty position.

to flange shall be greater than 2

(8). Bend the spring attached to tank unit

megohms.

bracket if required and recheck that

(11). Apply potting compound to seal voids,

lamp is illuminated from the empty

as applicable.

(rest) position to the 1.25 inch (3.175

cm) raised position.

(12). Reinstall fuel tank sending unit; torque

(9). Disconnect 24 Vdc power and all test

screws to 12 − 15 inch−pounds (1.36 −

equipment.

1.69 Nm). Do not overtighten screws as

this may warp mounting plate flange.

(10). Seal all connections at top of tank unit

with sealant (3, Table 2−4).

(13). Recheck electrical circuitry per steps

(4). and (5).

15. Outside Air Temperature Indicator

(14). Reinstall fuel cell access door.

(Ref. Figure 17−14) The outside air tempera−

ture indicator consists of a bimetal element

D. Tank Unit Testing

(enclosed in a stainless steel thermometer

stem) attached through the stem to a dial−type

(Ref. Figure 17−13)

temperature indicator.

(1).

Set up tank unit on a level platform

The thermometer is installed through the right

approximately 9 inches (22.86 cm)

or left side canopy (as applicable) just forward

above a second level surface, such as a

of the instrument panel, and is secured by a

table top.

sunshield.

(2).

Obtain a sensitive ohmmeter and set on

0The temperature dial indicates outside air

low range resistance scale.

temperature in both Fahrenheit and centi−

grade.

(3).

Allow float arm to rest on the float

empty stop. If wiring harness is

NOTE: Left or right side installation de−

attached, measure resistance across

pendson model and configuration.

pins B to H of tank unit connector.

A. Outside Air Temperature Indicator

Resistance must be 0−3 ohms (1 ohm

Replacement

desired). Adjust (bend) the float empty

stop until this resistance is obtained.

(1). Hold indicator dial firmly and remove

sun shield from thermometer stem.

(4).

Raise the float until arm is in contact

Remove applicable hardware shown in

with the full stop and observe that

Figure 17−14 from stem; then remove

resistance increases to approximately

indicator from canopy.

88 ohms.

(2). Remove hardware from replacement

(5).

Measure from the centerline of arm

indicator and install indicator in canopy

attachment to float when in full

as shown.

position, to the same point when in

empty position! This measurement

(3). Rotate indicator dial for correct reading

should be 8.99−9.11 inches

position, install seal and spacer (if

Page 17-35

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

used), outer rubber washer, dished

power out warning unit or the indicator lights

washer and sun shield, and securely

dimming assembly or disable switch Sl99, if

hand−tighten the sun shield.

installed.

16. Magnetic Compass

17. Caution and Warning Lights Indicating

System

The magnetic compass is either installed in

the instrument console of type A panels or

The caution and warning light indicating

attached to the center canopy frame on

system includes the following components.

helicopters with a type B panel.

(1).

For instrument panel type A

Hughes Notice HN−77 provides optional

(Figure 17−1), six indicator lights

relocation instructions for canopy frame

mounted across the top of the panel.

mounting of a compass mounted in an A type

For instrument panel type B

panel.

(Figure 17−2), nine indicator lights

mounted in the same location. Early

The magnetic compass continuously indicates

type indicator lights on panel type B

the heading of the helicopter relative to the

are switched from bright to dim when

earth’s magnetic field.

the legend face of the indicator is

depressed and remain dim until

The compass consists of a liquid−filled case in

indicator is depressed a second time for

which a float assembly, incorporating a

bright illumination.

compass card and magnets, pivots on a jewel

post.

(2).

Senders, detectors and switches

associated with the indicators

The compass card is graduated in 5 degree

(Figure 17−7).

increments. The card is read against a fixed

vertical white line (lubber’s line) on the face of

(3).

An indicator light dimming assembly

the instrument.

for panel type A that automatically

dims the indicator lights when the

A compass correction card is located in the

instrument panel lights are on and

logbook holder.

furnishes light test circuits. The panel

type B dimmer assembly provides light

The compass face is tilted at a downward angle

test circuits and a switching regulator

so that the compass is level during normal

for panel and instrument light dim−

flight.

ming.

A wedge is used for this purpose in the type A

(4).

An engine power out (EPO) warning

panel installation.

control unit. EPO units manufactured

The compass is internally illuminated, using

by Autronics include an integral audio

dc electrical power, from the night lighting

amplifier (Figure 17−4) while an

system.

external audio amplifier is used with

Vapair EPO units (Figure 17−3).

A. Magnetic Compass Maintenance

(5).

Legend−type signal indicator lights

Use the information in Instrument Indicating

that are interconnected with the

System Troubleshooting thru Indicating

PRESS−TO−TEST light test pushbut−

System Instrument Repair for troubleshooting,

ton switch and EPO solidstate dimmer

inspection, replacement of the magnetic

assembly that isolates the light test

compass.

circuit from the operational circuits.

Operational Check. An operational check of

(6).

With power on, and the engine not

the caution and warning lights indicating

running, the red engine power out light

system must be performed after maintenance

and the red transmission oil pressure

on the caution and warning lights, engine

warning light flash alternately. None of

Page 17-36

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

the amber caution lights flash when

the indicator lights dimming assembly, are

they are on.

listed in Table 17−2.

NOTE:

(1). Operational Check. An operational

check of the caution and warning lights

D The early type indicator lights used in

indicating system must be performed

instrument panel type B may be individu−

after maintenance on the caution and

ally switched to dim illumination by

warning lights, engine power out

pressing the face of the indicator. The

warning unit or the indicator lights

light remains dim until the legend face of

dimming assembly or disable switch

the indicator is depressed a second time.

Sl99, if installed.

D The caution and warning lights indicat−

ing system on a current helicopter with

NOTE: Although the procedure outlined below

instrument panel type B functions with

reveals the functional state of only three of

N_l/N_R engine power out warning equip−

the fault input circuits, it will also show

ment.

whether or not the components common to

all circuits function correctly. A check of the

D Helicopters with an early instrument

other fault input circuits can be made in the

panel type B or panel type A use N_l engine

same way, when necessary, by bridging the

power out sensing equipment only. N_l/N_R

applicable switching device or sender.

sensing equipment senses both low en−

gine N_l and main rotor (N_R) speeds. N_l

sensing equipment functions only with

(a). Turn on electrical power. Check that

low engine N_l speed.

WARNING AND PANEL lights and

ENG out circuit breakers are in

D A helicopter with early panel type B or

(reset) and that the panel lights

type A may be modified to incorporate

dimming control is set at OFF (fully

N₁/N_R sensing equipment. For difference

counterclockwise) if installed.

information on a caution and warning

light system in which the N_l/N_R sensing

(b). Check that red warning lights

equipment was installed in this manner.

indicating engine out and low main

transmission oil pressure flash.

Caution and Warning Lights Indicating

System Troubleshooting

NOTE: These faults are supplied whenever the

engine is not operating.

When troubleshooting, perform an operational

check, step (1)., as necessary. Troubleshoot the

(c). Using a jumper lead, ground the

caution and warning lights indicating system,

terminal stud of the tail rotor trans−

using the data in Table 17−2 and Table 17−3.

mission chip detector to produce a

fault input.

Refer to Table 17−2 to determine the function−

al unit associated with each light indicator, the

input fault signal that activates each indicator,

(d). Check that the applicable CHIPS

and the connector pins used in each circuit.

lamps light.

Use Table 17−3 to assist in isolating trouble to

(e). If a panel lights dimming control is

a defective unit and component.

installed, check that the control can

control the panel instrument and

Apply the correct input signal to the connector

lamp illumination and select bright

pin(s) to provide a specific light indication, or

or dim indicator lamp illumination

check for presence of the correct fault input

(for panel type A).

signal for a light indication obtained.

(f). Check that early panel type B light

Light indications that are provided by the

indicators can be switched from

caution and warning lights, controlled by the

bright to dim illumination by de−

engine power out warning control unit and/or

pressing the indicator legend face.

Page 17-37

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

CONNECTOR

FUEL QUANTITY

369A4599

TRANSMITTER

NO. 328

LAMP

BLU

RED

24 VDC

POWER

G B

SUPPLY

BLK

−

BLK

TEST CONNECTIONS

FULL POSITION

FUEL QUANTITY

TRANSMITTER

FLOAT STOP (FULL)

SPRING

BRACKET

10.08 IN. (25.6032 CM)

FLOAT STOP

RADIUS

(EMPTY)

8.99−9.11 IN.

(22.8346−23.1394 CM)

FLOAT

SPRING CONTACT

POSITION

NOTE 3

1.25 IN.

GROUND TERMINAL

(3.175 CM)

EMPTY POSITION

TRANSISTOR SWITCH

(ON UNDERSIDE)

FLOAT POSITIONS

NOTES:

TRANSMITTER RESISTANCE (POINT A TO GROUND):

FLOAT POSITION

RESISTANCE

EMPTY

0−3 (1 NOMINAL OHMS

FULL

88−95 (88 NOMINAL) OHMS

REFER TO TEXT FOR INFORMATION ON CHECKING UNIT IN SYSTEM.

CONNECTIONS AT TOP TRANSMITTER ARE POTTED WITH

SEALANT (3, TABLE 2−4) ON LATER CONFIGURATION.

30−128C

Figure 17-13. Testing of Tank Unit

Page 17-38

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-2. Caution and Warning Lights Troubleshooting Data

Indicator Lights

Engine Power Out

Light Indicator

Fault Input Signal

Dimmer Assembly

Warning Unit

Connector Number and Pin Letter

Instrument Panel Type A

Caution Lights

Chips

Ground

Start Pump On (located near switch)

28 Vdc

Fuel Low

Ground

Fuel Filter

Ground

Generator Out

Ground

Warning Lights

{ Engine Out (N_l)

38.2 ±0.7 Hz

(at 13.0 ±2 Vac)

or less

{ Xmsn Oil Temp & Press

Ground

Miscellaneous

* Dim

** Ground

{{ Press-to-test

** 28 Vdc

{{ Press-to-test

** Ground

Instrument Panel Type B

P12

Pl9 P3 (4)

Caution Lights

Engine Chips

Ground

M/R Xmsn Chips

Ground

T/R Xmsn Chips

Ground

Fuel Low

Ground

Gen Out

Ground

Fuel Filter

Ground

Start Pump On (located near switch)

28 Vdc

Bat Temp Amber (140°F)

28 Vdc

P529

Warning Lights

{ Engine Out (N_l)

Frequency less than

A A

36.75 ±1.75 Hz

{ Engine Out (N_R)

Frequency less than

68.6 ±0.7Hz

BAT TEMP Red (160°F)

28 Vdc

P529C

{ Xmsn Oil Temp

Ground

{ Xmsn Oil Press

Ground

Miscellaneous

* N₁ disable (disables audible tone and

** Ground

J H

horn for N_l only)

Page 17-40

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-2. Caution and Warning Lights Troubleshooting Data (Cont.)

Indicator Lights

Engine Power Out

Light Indicator

Fault Input Signal

Dimmer Assembly

Warning Unit

Connector Number and Pin Letter

Instrument Panel Type B

P12

Pl9 P3 (4)

* N_R disable (disables N_R sensing and

** Ground

audible tone for N_R only)

* Dim to bright

** 0 to +28 Vdc

respectively

{{ Press-to-test

** 28 Vdc

{{ Press-to-test

** Ground

NOTE:

(1) Listed fault input signal causes the associated light indicator to illuminate when input is applied to listed

connector number and pin letter.

(2) For a helicopter with early instrument panel type B or A equipped with optional N₁/N_R sensing equipment,

for any necessary difference troubleshooting data refer to CSP-H-3.

(3) Wiring harness connectors listed are those that mate with connectors of units listed.

(4) Note that connector number and pin letters on mating connector for EPO warning unit differ according to

unit used (Pl9 for N₁/N_R EPO warning unit and P3 for N₁ EPO warning unit).

* Function (not an indicator) for instrument and panel lights.

* * Function input signal (not a fault input signal) for all lights.

{ Light indicator flashes with listed input applied; all other light indicators continuously illuminated with listed

inputs.

{{ Function (not an indicator) for caution and warning light indicators.

Table 17-3. Troubleshooting the Caution and Warning Lights Indicating System

CAUTION: Continuous flashing operation of the EPO warning unit is limited to 10 minutes. Excessive,

uninterrupted operation can result in damage to internal flasher circuits.

NOTE: Unless specified otherwise, troubleshooting is accomplished with the engine power out (EPO) warning

unit and indicator lights dimmer assembly installed, electrical power on, the WARNING AND PANEL LAMPS

and ENG OUT circuit breakers in (reset) and the panel lights dimming control set at BRT.

Symptom

Probable Trouble

Corrective Action

Caution and Warning Light Indicators

Indicator light erratic or inoperative

Circuit wiring loose, shorted, open, Inspect electrical connections; repair

when checked by PRESS-TO-

or improperly connected

as necessary.

TEST switch

Indicator defective

Replace defective lamp or indicator

socket.

One or more light indicators, but

Indicator lamp filaments open

Replace lamps.

not all, do not light when

Open diode in dimmer unit

Replace diode associated with

PRESS-T O-TEST switch is

unlighted indicator or replace dimmer

depressed

unit.

Light indicator on panel type B

Indicator lamp filaments open

Replace lamps.

extinguishes or does not dim or

brighten when legend face is

Defective switch in indicator

Replace indicator.

depressed, with PRESS-TO-TEST

switch held depressed

Page 17-41

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-3. Troubleshooting the Caution and Warning Lights Indicating System (Cont.)

Symptom

Probable Trouble

Corrective Action

NOTE: Indicator should alternately dim or brighten each time legend face is depressed for panel type B equipped

with N₁ sensing equipment. Light indicators do not dim on panel type B equipped with N₁/N_R sensing

equipment.

Indicator light on; associated

Short-circuit in light circuit

Check light circuit wiring; repair as

system functioning normally

necessary.

Sensor/sender unit defective

Replace sensor/sender.

Abnormal light indication(s)

Refer to corrective action column

Refer to caution light indicators

peculiar only to caution light

information below.

indicator(s)

Abnormal light indication(s)

Refer to corrective action column

Refer to warning light indicators

common to both caution and

information below.

warning light indicator(s)

Abnormal light indication(s)

Refer to corrective action column

Refer to warning light indicators

peculiar only to warning light

information below.

indicator(s) and/or audible warning

horn

Caution Light Indicators

NOTE: Panel lights dimming control affects dimming of light indicators only on panel type A. Dimming affects

dimming of light indicators on panel type B with N₁ sensing equipment is controlled by depressing legend face

of indicator.

One or more light indicators, but

One indicator lamp has open

Replace lamp.

not all, light dimly when panel type

filament

A light dimming control is set at

Defective diode in Grimes dimmer

Replace associated diode or dimmer

BRT and PRESS-TO-TEST switch

unit

unit.

is held depressed

All light indicators light brightly with

Open relay diode, relay winding or

Repair or replace dimmers unit.

panel type A panel lights dimming

shorted Zener diode in Grimes

control at DIM when PRESS-TO-

dimmer unit dimming circuit

TEST switch is held depressed

All light indicators do not light with

Open Zener diode in Grimes

Replace Zener diode or dimmer unit.

panel type A panel lights dimming

dimmer unit

control at DIM while PRESS-TO-

TEST switch is held depressed

Light indicator does not light with

Indicator lamp filaments open

Replace lamps.

fault input signal applied or when

Defective component in dimmer

Replace associated component in

PRESS-T O-TEST switch is

unit

dimmer unit or dimmer unit.

depressed

Defective switch in indicator on

Replace indicator.

panel type B

Lighted indicator without a fault

Defective component in dimmer

Replace associated component in

signal applied.

unit

dimmer unit or dimmer unit.

Page 17-42

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-3. Troubleshooting the Caution and Warning Lights Indicating System (Cont.)

Symptom

Probable Trouble

Corrective Action

Warning Light Indicators

No ENG OUT indication from either

Disconnected or defective wiring to

Reconnect or repair electrical wiring.

warning light indicator or audible

engine power out warning unit

warning horn with engine out fault

Misadjusted frequency sensing

For Vapair unit, adjust sensing

input signal applied (or low main

control in Vapair EPO warning

control. Replace defective EPO

rotor speed fault input signal

control unit, or defective sensing

warning unit.

applied with N₁/N_R sensing

circuit in any EPO unit

equipment)

Defective ENG OUT frequency

Repair or replace EPO warning unit.

sensor or flasher circuit in EPO

warning unit

No ENG OUT warning light

Indicator lamp filaments open

Replace lamps.

indication with engine out fault

input signal applied; sound from

Defective diode in dimmer unit

Repair or replace dimmer unit.

audible warning horn present (or

low main rotor speed fault input

Defective ENG OUT flasher in EPO

Repair or replace EPO warning unit.

signal applied with N₁/N_R sensing

unit

equipment)

Flashing ENG OUT light indicator

Defective audio amplifier or

Repair or replace EPO warning unit.

with fault input signal applied with

misadjusted tone level control in

sound from audible warning horn;

Autronics EPO warning unit

no audible warning tone in

Defective pilot’s audio tone

Repair or replace EPO warning unit,

headset(s)

generator in EPO warning unit

Defective audio amplifier (used

Replace audio amplifier.

with Vapair EPO warning unit)

No flashing XMSN OIL TEMP &

Defective xmsn oil and temp light

Repair or replace EPO warning unit.

OIL PRESS light indication with

flasher in EPO warning unit if

fault input applied; ENG OUT light

indicator lights when PRESS-TO-

indicator functions normally

TEST switch is depressed

Defective diode in dimmer unit if

Repair or replace dimmer unit.

indicator does not light when

PRESS-T O-TEST switch is

depressed

No flashing warning light indication

Defective voltage regulator in

Repair or replace EPO warning unit.

when any warning fault input signal

Vapair EPO warning unit

is applied; all indicators light when

PRESS-T O-TEST switch is

depressed

No flashing light indication or

Improperly adjusted or defective

Adjust position of or replace

audible warning with low main rotor

disable switch

defective switch.

speed fault input si

gnal, for N1/N

Defective EPO warning unit

Replace EPO warning unit.

sensing equipment

XMSN warning lights flash with

Defective voltage regulator in

Repair or replace EPO warning unit.

fault inputs; no audio tone in

Autronics EPO warning unit

headset, ENG OUT light does not

flash and audible warning horn

does not ‘‘beep” with engine off.

Page 17-43

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Table 17-3. Troubleshooting the Caution and Warning Lights Indicating System (Cont.)

Symptom

Probable Trouble

Corrective Action

Lighted or flashing light indicator

Defective component in EPO

Replace component in indicator

without fault input signal applied

warning unit

associated circuit in EPO warning

unit or replace EPO warning unit.

Defective component in dimmer

Replace component in indicator

unit

associated circuit in dimmer unit or

replace dimmer unit.

Light indicator on panel type A

Defective component in Grimes

Replace component associated with

does not dim when panel lights

dimmer unit

indicator dimming circuit in dimmer

dimming control is set from BRT to

unit or replace dimmer unit. (Refer to

DIM while PRESS-TO-TEST

information on caution light indicators

switch is held depressed

above.)

Audio Equipment

No warning tone in pilot’s headset;

Defective tone generator in EPO

Repair or replace EPO warning unit.

‘‘beeping” audible from audible

warning unit

warning horn and engine out light

Misadjusted or defective audio tone

For N_l sensing type EPO unit, adjust

indicator flashes

circuit in Autronics EPO warning

audio tone level control. Replace

unit

N_l/N_R sensing type EPO unit.

Defective audio amplifier in

Repair or replace Autronics EPO

Autronics EPO warning unit

warning unit.

Defective EPO audio amplifier

Replace EPO audio amplifier.

(used with Vapair EPO warning

unit)

No ‘‘beeping” from EPO audible

Defective EPO audible warning

Replace audible warning horn.

warning horn with engine off;

horn

engine out light indicator flashes

and warning tone is present in

pilot’s headset

No warning tone in pilot’s headset,

Defective engine out frequency

Repair or replace EPO warning unit.

flashing of engine out light indicator

sensor circuit in EPO warning unit

of ‘‘beeping” from audible warning

horn

Panel and Instrument Lights Dimming

One or more, but not all, panel or

Lamp filament(s) open

Replace lamp(s).

instrument lamps will not illuminate

All panel and instrument lamps will

Defective component in dimmer

Repair or replace dimmer unit.

not illuminate

unit

All panel and instrument lights

Defective component in dimmer

Repair or replace dimmer unit.

illuminate; panel lights dimming

unit

control does not vary brightness of

Defective or disconnected dimming

Replace or reconnect dimming

lights

control

control.

Page 17-44

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

18. Instrument Panel Type A Caution and

In case of a reduction or loss of trans−

Warning Indicator Lights

mission oil pressure, below approxi−

mately 15 psi, a pressure−sensing

(Ref. Figure 17−1) The caution and warning

sender (Figure 17−5) energizes the oil

indicator lights consist of two warning and

temperatures and pressure warning

four caution indicator lights across the top of

light flashing circuit of the EPO

the instrument panel and a start pump on

warning unit. If the transmission oil

light at the left of the instrument cluster.

supply reaches an abnormally high

temperature, a temperature−sensing

Each of the upper six indicators are separate

switch energizes the oil temperature

removable dual lamp light assemblies. The

and pressure warning light flashing

start pump on light assembly contains a single

circuit of the EPO warning unit. Early

lamp. The two upper left light indicators are

type senders actuate at 115°C while the

red warning lights. The four indicators at the

current type actuates at 121°C.

right of the warning lights are amber caution

(3).

Chip Detector Caution Light

lights.

The chip detector light will go on

Ground inputs, from caution fault sensors,

whenever loose ferrous metallic matter

applied directly to negative fault dimming

has been magnetically accumulated by

indicator circuits in the indicator lights

any one of five chip detectors; two are

dimmer assembly, control caution light

located in the engine oil system, two in

indicators illumination and dimming.

the main transmission, and one in the

tail rotor transmission.

Warning sensors supply inputs to and cause

the EPO warning unit to provide pulsating

(4).

Fuel Low Caution Light

positive output voltages. The pulsating

positive voltages are applied to positive fault

When the fuel supply has diminished to

input dimming circuits in the dimmer assem−

35 pounds, a spring wire contact is

bly to control flashing of warning light

made by the tank unit float arm at the

indicators.

warning level to complete a ground

circuit and energize the caution light.

The caution and warning lights function as

(5).

Fuel Filter Caution Light

follows:

When the engine fuel pump filter

NOTE: Hughes Notice HN−158 gives a proce−

becomes clogged, the caution light is

dure for rewiring the utility light circuit and

illuminated by a case−grounded

the transmission oil pressure and tempera−

differential pressure switch. The switch

ture warning light circuit. This wiring modi−

is installed across the fuel pump

fication is to eliminate deactuation of the

pressure drop ports to measure pres−

utility light and transmission warning light

sure differential increase across the

circuits should the engine power out (EPO)

filter.

circuit breaker be tripped, thus deactuating

the EPO unit.

(6).

Generator Out Caution Light

If generator output voltage should fall

(1). Engine Out Warning Light

below the battery voltage because of

engine shutdown, generator failure, or

The engine out warning light flashes

other cause, the reverse current relay

when engine speed decreases to

disconnects the generator from the 28

approximately 55% N₁ rpm or less.

Vdc bus and causes the generator out

With N₁/N_R sensing equipment (option−

caution light to illuminate.

al on panel type A) the light also

flashes when NR speed decreases to

(7).

Start Pump On Caution Light

approximately 98% N₁ rpm or less.

When the start pump circuit breaker is

(2). Main Transmission Oil Temperature

set to ON, the start pump is turned on

and Oil Pressure Warning Light

and +28 Vdc is applied to the start

Page 17-45

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

pump light circuit and the light illumi−

dimming unit and through an Autronics

nates.

engine power out (EPO) warning unit which

provides a pulsating source of 28 Vdc for light

A. Instrument Panel Type A Indicator Lights

flashing. The dimming unit used with this

Replacement

system provides the indicator lamps test

circuits and a dimming regulator for instru−

(Ref. Figure 17−3)

ment panel and instrument lighting.

(1).

Check that all electrical power is OFF.

Separate battery temperature caution and

warning light indicators are mounted in a

(2).

Remove instrument panel fairings, and

light−switch and horn housing on the side of

instruments as necessary, to gain access

the raised top center of the instrument panel

to defective indicator light.

center fairing. The amber caution BAT TEMP

(3).

Remove legend cap by using direct pull,

140°F light illuminates at a battery tempera−

and then remove the screw and saddle

ture of 140°F and the red BAT TEMP light at

clamp from light socket. Loosen light

160°F. Each light indicator incorporates a

wiring harness ties to release socket;

press−to−test switch for testing of internal

then unsolder wiring and tag for

lamps. (For circuit and other information on

identification.

the light indicators and battery temperature

sensing equipment, refer to Section 19.)

(4).

Using solder (48, Table 2−4), connect

wiring to replacement indicator light

The start pump is provided with an indicator

and remove tags.

light near the startpump switch on the lower

left side of the instrument panel. This light

(5).

Install indicator light in panel with

does not have a dimming feature and remains

saddle clamp and restore harness ties

on bright whenever the start pump is operat−

where removed.

ing.

(6).

Transfer old lamps to new indicator

For other than battery temperature light

light or install new lamps. Turn on

indicators, caution and warning light functions

power and check light circuit by the

are as described in Instrument Panel Type A

press−to−test switch.

Caution and Warning Indicator Lights, steps

18.(1). thru 18.(7)., except that separate chip

(7).

Reinstall removed instruments and

detector indicators are provided as well as

reinstall panel fairings.

separate main transmission oil pressure and

oil temperature warning indicators.

(8).

Reinstall legend cap.

Indicators provided are:

NOTE: Each light socket and legend cap is a

matched assembly. Legend caps cannot be

Engine Out Warning Light.

interchanged.

Main Transmission Oil Temperature

Warning Light.

19. Instrument Panel Type B Caution and

Warning Indicator Lights

Main Transmission Oil Pressure

Warning Light.

(Ref. Figure 17−2) The caution and warning

lights consist of nine modular units mounted

Battery Temperature Caution Light.

across the top of the instrument panel. The left

three indicators are red warning lights and the

Engine Chip Detector Caution Light.

remainder are yellow caution lights. The

Main Transmission Chip Detector

indicator assemblies contain places for four

Caution Light.

midget, flange base lamps (Figure 17−4).

Tail Rotor Transmission Chip Detector

The caution light circuits are completed to

Caution Light.

ground through their respective fault sensors.

Fuel Low Caution Light.

The warning light circuits are completed

through their fault sensors, an Autronics

Fuel Filter Caution Light.

Page 17-46

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Generator Out Caution Light.

(c).

Inside housing, locate two mounting

cam locking screws. Loosen the

Start Pump On Caution Light.

screws until cams are disengaged

from mounting sleeve.

Battery Temperature Warning Light.

(d).

Gain access to forward side of

NOTE:

instrument panel and slide mounting

sleeve from switch housing.

D For a helicopter equipped with N₁ sensing

equipment, each of the nine light indica−

(e).

Move switch housing assembly aft

tors across the top of the instrument pan−

from face of panel until wiring at

el contains a latching type switch. When

lamp terminals is accessible.

the legend face of the indicator is de−

pressed, the switch is actuated to dim the

(f).

Note wire and terminal numbers for

light. The indicator remains dim until the

reinstallation and then unsolder

legend face is depressed a second time

wires at the terminals. Remove

and then brightens. This feature is not in−

switch housing assembly.

corporated for light indicators used with

(g).

Install replacement indicator assem−

N₁/N_R sensing equipment.

bly by essentially reversing the

D Any helicopter not originally equipped

removal procedure above.

with battery temperature sensing equip−

(h).

Connect electrical power and check

ment requires addition of the equipment,

indicator operation with PRESS−TO−

including the battery temperature light

TEST switch. When N₁ sensing

indicators.

equipment is used, check that

indicator dims when legend face is

A. Panel Type B Indicator Lights

depressed and returns to bright when

Replacement

depressed again.

(Ref. Figure 17−4)

20. Engine Out Warning System

(1). Lamp Replacement

The engine out warning system consists of an

engine power out (EPO) warning control unit,

(a). Grasp edges of legend face and pull

an audible warning horn, interconnecting

lamp module out of housing.

electrical wiring and functions with the engine

out and transmission warning lights of the

(b). Allow lamp module to hinge down−

caution and warning lights system.

ward for access to base of midget

lamps.

One of two types of sensing equipment is used,

an early type that senses only engine N₁

low

(c). Replace faulty lamp and reinstall

speed and the current type that senses both N₁

lamp module in housing.

and main rotor (N_R) low speeds.

(d). Check lamp operation by depressing

Both provide a visual and audible indication of

PRESS−TO−TEST switch.

low speed(s) as follows:

A. N₁ Sensing Equipment

NOTE: If any light does not illuminate and N₁

sensing equipment is used, try pressing the

The EPO warning control unit monitors engine

indicator legend face to actuate the internal

N₁ speed, main transmission (low) oil pressure

switch.

and (high) oil temperature.

(2). Indicator Light Assembly Replacement

Engine low N₁ speed is sensed by the EPO

warning control unit monitoring the frequency

(a). Check that electrical power is OFF.

of the output ac voltage from the N₁ tachome−

ter generator.

(b). Grasp edges of legend face, pull lamp

module from switch housing and

When engine speed decreases to approximately

allow it to hinge downward.

55% N₁ rpm or less, the EPO warning control

Page 17-47

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

unit produces an output to flash the engine out

Low N_R rpm is sensed by the EPO warning

warning light and activates the EPO audible

control unit monitoring the frequency of the

warning horn which produces an audible

output ac voltage from the main rotor (N_R)

‘‘beeping" in the pilot’s compartment. Simulta−

tachometer generator; N_R sensing occurs at

neously, the EPO warning control unit

main rotor speed of approximately 98% N_R

provides separate audio tone warning signals

rpm, or less.

for headsets.

When the inboard collective pitch stick is full

down and the throttle is at idle or cutoff

The tone warning signals occur and the

position, the N_R disable switch activates to

audible warning horn ‘‘beeps" only when the

disable N_R sensing to prevent flashing the

generator (GEN) switch is ON and N_l speed is

engine out light and activation of both the

55% rpm or less; however, the engine−out

warning horn and audible tone during engine

warning light flashes regardless of GEN

idle and cutoff.

switch position.

A built−in time delay function keeps N_R

NOTE:

sensing disabled after N_R disable switch is

D On early N₁ sensing equipment using the

deactivated for sufficient time to permit N_R to

Vapair 26530332M EPO warning unit, a

be attained.

separate audio amplifier is also used.

N₁ sensing circuits remain operational (are not

When installed, the separate audio ampli−

disabled) while N_R sensing is disabled.

fier amplifies the audio tone warning sig−

nal before application to earphones of

The EPO warning control unit produces the

headsets.

output for flashing the engine out warning

light, "beeping" the warning horn and gener−

D The Autronics 2146−5 EPO warning con−

ates the audible warning tone if low N₁ rpm

trol unit on the later N₁ sensing equip−

occurs while N_R sensing is disabled.

ment contains an integral audio amplifier

used for the same purpose and the exter−

C. Engine Out Warning System Functioning

nal audio amplifier is not used. A helicop−

ter originally equipped with the N₁ sens−

Figure 17−15 is a combined simplified block

ing equipment may be modified with the

diagram and schematic diagram of the N₁/N_R

optional N₁/N_R engine sensing equipment

engine out warning system and shows signal

described below by installation of the N₁/

paths and flow for the system.

N_R Engine Out Warning System Kit

The EPO warning control unit senses low

M50033.

frequency ac output voltages from the N₁ and

N_R tachometer generators to actuate and

B. N₁/N_R Sensing Equipment

control warning light and audible indications.

The N₁/N_R sensing equipment uses an

When the GEN−OFF switch is ON, a ground is

Autronics 2200−3 EPO warning control unit,

supplied to a tone interrupt circuit in the EPO

NR disable switch S199 located on the base of

warning control unit to enable audio warning

the inboard collective pitch stick and resistor

tone circuits and to the audible warning horn

and diode board TB106.

for ‘beeping,’ when low N₁ rpm is sensed.

N₁/N_R sensing equipment has identical

When low N_l rpm is sensed, N_l speed sensing

capabilities and functions the same as the N1

circuits and flasher and tone control circuits

sensing equipment described above, except as

actuate engine out flashing light and audio

follows: The N₁/N_R sensing equipment has the

tone No. 1, 2 and 3 generation circuits. N_R

additional capabilities of sensing main rotor

sensing circuits, with the flasher and tone

(N_R) low speed, producing the output for

control circuits, actuate and control the

flashing of the engine out warning lights and

flashing light and audio tone generation

actuation of the audible warning horn,

circuits for operation at low N_R rpm. Audio

generating a separate additional audible

warning tone No. 1 is routed through the ICS

warning tone for headsets and providing

system to headsets. The higher amplitude

engine restart voltage when low N_R rpm is

audio warning tone No. 3 is applied directly to

sensed.

headsets so that audible warning is present in

Page 17-48

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

headsets in event of failure of ICS system

transmission oil and temperature light flasher,

equipment.

and dc voltage regulator circuits.

When either N₁ or N_R sensing occurs, the auto

Figure 17−17 is a breakdown of the EPO

reignition +28 Vdc control circuit supplies

warning unit overall schematic diagram and

steady state +28 Vdc for optional automatic

shows the circuits separately by functions. See

reignition equipment. N_R disable switch S199

the electrical system wiring diagram in Section

furnishes a ground to the EPO warning control

20 for interconnecting wiring information on

unit to disable N_R sensing and prevent engine

the lights indicating system.

out light flashing and audible warnings at

B. Engine Out Frequency Sensor and Light

engine idle and cutoff positions.

Flasher Circuits

Diodes in the indicator lights dimmer assem−

(Ref. Figure 17−17) The engine out frequency

bly provide directional paths for flashing light

sensor circuit functions when an N₁ tachome−

currents, and for test voltages and grounds

ter output ac voltage with a frequency of 28.2

during press−to−test check of lights.

±0.7 Hz (at approximately 13.0 ±2 Vac) or less

is applied to the EPO warning unit. Poten−

Resistor and diode board TB106 furnishes

tiometer R26 adjusts the frequency at which

isolation and correct termination impedance

the sensing circuit operates.

for audio warning tone No. 3.

The circuit controls conduction of transistors

NOTE: This information applies to the N₁/N_R

Q7 and Q6 which alternately open and close

engine out warning system. For an N₁ en−

the engine out lamp circuit current path

gine out warning system disregard informa−

through transistor Q5 and the indicator lights

tion on N_R sensing functions, since these

dimmer assembly and apply a pulsating dc

functions are not applicable.

voltage 150 ±30 times a minute to the engine

out lamps and the audible warning horn. The

21. Vapair 26530332M Engine Power Out

sensing circuit also provides a tone generator

(EPO) Warning Control Unit

control signal to the audio tone signal genera−

tors.

The Vapair 26530332M engine power out

(EPO) warning unit is a solid state device that

C. Dc Voltage Regulator Circuit

controls warning light indicators flashing and

provides drive for the audible warning horn

(Ref. Figure 17−17) A zener diode CR1

and tone signals for headsets in event of

develops a stable reference voltage for transis−

engine failure.

tor Q1. Transistor Q1 conducts with load

changes and voltage fluctuations as necessary

The EPO unit is installed at the lower right

to maintain a constant regulated positive dc

interior of the instrument panel console.

supply voltage across capacitor C8 for applica−

tion to and use of all other EPO warning unit

A removable cover permits access to interior

circuits.

components of the EPO unit for adjustment,

maintenance and repair.

D. Audio Tone Signal Generators

The unit provides pulsating dc voltage through

(Ref. Figure 17−17) Dual identical pilot’s and

indicator lights dimmer assembly warning

copilot’s tone signal generators are incorpo−

lights circuits to flash the warning lights.

rated into the EPO warning unit. Each tone

Figure 17−16 is a schematic diagram of the

generator utilizes a unijunction transistor.

EPO warning unit. The following information

Only the pilot’s tone generator is used.

describes EPO unit operation.

When the generator switch is set to on, the

A. Engine Power Out Warning Unit Circuit

tone generator control signal is present from

the engine out frequency sensor circuit at

(Ref. Figure 17−17) The EPO warning unit

engine rpm of less than approximately 55%

contains an engine out frequency sensor and

N₁, and the base of Q9 is biased to initiate

flasher circuit, two audio tone generators, a

conduction of Q9.

Page 17-49

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

Resistance capacitance (RC) charging and

connect the output to pins A and B of

discharging circuit components then alternate−

connector P2.

ly shut off and turn on Q9 to produce negative

NOTE: A driven tachometer generator, the

output pulses at an audio frequency of 680 to

equivalent of the N_l tachometer generator

1700 Hz for application to the external audio

and whose speed is variable and can be cor−

amplifier.

rectly regulated, may be used for the input

The generation of the output pulses is initiated

voltage source. Measuring equipment must

and interrupted at a rate of 150 ±30 times a

be sufficiently accurate.

minute by the tone generator control signal.

(6). Turn ON the helicopter electrical

Setting the generator switch to off, or an

system.

increase of engine rpm above 55% N_l, deactu−

(7). Set the ENG OUT circuit breaker to

ates the tone control signal and tone generator.

ON.

E. Transmission Oil and Temperature Light

Flasher circuits in the EPO

Flasher

CAUTION

warning unit should not be al−

(Ref. Figure 17−17) Transistors Q4, Q3, Q2

lowed to remain energized for more than 10

and associated components form the transmis−

minutes of uninterrupted operation to pre−

sion oil and temperature light flasher circuit.

vent possible internal EPO warning unit

damage.

Resistance−capacitance (RC) charging and

discharging circuit components cause Q2 and

NOTE: The engine out warning light should

Q3 to alternately turn on and turn off Q4. This

flash and the engine out audible warning

applies a pulsating dc voltage through the

horn should ‘‘beep".

dimmer unit to the lamps to make them flash

(8). Turn on the ac test voltage source and

150 ±30 times a minute, when the external

make sure that the test frequency of the

lamp circuit is closed to ground through the

ac voltage is set to the correct value (e

indicator lights dimmer assembly, lamps and

above).

fault sensor switch.

NOTE: The engine out indications, noted in

The flasher circuit continues to flash the lamps

step (7)., should cease when the correct test

until the input fault ground is removed.

frequency is applied. Any decrease of the in−

F. Vapair 26530332M EPO Warning Unit

put frequency should activate the indica−

Frequency Sensing Adjustment

tions. The indications should not be actu−

ated at any frequency above the input test

Use the following procedures to adjust sensing

frequency.

for the engine out warning light and EPO

audible warning horn ‘‘beeping".

(9). If necessary, adjust the variable

potentiometer in the EPO warning unit

(1). Turn OFF all electrical power.

to the position that the engine out

indicator light just goes out with the

(2). Remove the instrument panel right side

correct input test frequency, step (5).,

fairing for access to the EPO warning

applied.

unit.

(10). Turn OFF the ac test voltage source.

(3). Remove the cover from the installed

EPO warning unit (Figure 17−3).

(11). Set the ENG OUT circuit breaker to

OFF.

(4). Disconnect electrical wiring connector

P2 from the N_l tachometer generator.

(12). Turn off the helicopter electrical

system.

(5). With an ac voltage source, capable of

being set to provide an ac output

(13). Disconnect the ac test voltage source

voltage at a test frequency of 38.2 ±0.7

electrical leads from connector P2 and

Hz (at approximately 13.0 ±2 Vac),

reconnect P2 to the EPO warning unit.

Page 17-52

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

P/O P7

+28 VDC

(FROM EPO

DC VOLTAGE REGULATOR

AUDIO AMP)

P/O P7

CR1

NOTE 10

REGULATED

P/O P7

+DC VOLTAGE

(SHEET 2)

N1 TACH GEN V IN

CR3

(NOTES 2, 10)

R28

R29

CR6

ENGINE OUT

(NOTE 1)

FREQUENCY SENSOR

R21

N1 TACH

1.5K Ω

GEN

R27

R20

R22

R17

R24

FREQ

SENSE

ENGINE OUT

R26

FLASHER

R19

(NOTE 9)

CR2

PULSATING +DC

OUTPUT V TO

DIMMER UNIT (FOR

ENGINE OUT LIGHT

TONE GEN

AND AUDIBLE

CONTROL SIGNAL

(SHEET 2)

WARNING HORN)

(SHEET 2)

(NOTES 3, 10)

DC VOLTAGE REGULATOR AND ENGINE OUT FREQUENCY SENSOR

NOTES:

CR6 IS COMMON TO EMITTER CIRCUITS OF BOTH Q4 AND Q5.

DASHED LINES WITH ARROWHEAD ( − − − ) INDICATES INDICATOR

INPUT FREQUENCY OF 38.2 ±0.8 HZ (AT APPRO 13.0 ±2 VAC)

LAMPS CURRENT PATH.

OR LESS ACTIVATES CIRCUIT. THIS FREQUENCY REPRESENTS

ALL COMPONENTS WITH REFERENCE DESIGNATORS ARE PART

ENGINE SPEED OF 54.5 ±0.5% N1.

OF EPO UNIT UNLESS OTHERWISE INDICATED.

PULSATION RATE: 150 ±30/MINUTE.

REFERENCE DESIGNATORS ARE FOR REFERENCE ONLY AND MAY

NEGATIVE PULSES, 0.6V PEAK−TO−PEAK ACROSS 15−OHM

NOT BE ON COMPONENTS.

RESISTIVE LOAD OR 0.7 PEAK−TO−PEAK ACROSS 300−OHM

INTERNAL ADJUSTMENT. ADJUST SO THAT ENGINE OUT INDICATOR

LOAD (FREQUENCY OF 680 − 1700 HZ, INTERRUPTED 150 ±30

LIGHT JUST GOES OUT WITH INPUT SPECIFIED IN NOTE 2.

TIMES/MINUTE).

10. PATH COMPLETED BY STRAIGHT−THRU CIRCUITS IN EPO AUDIO

REFER TO ELECTRICAL SYSTEM WIRING DIAGRAMS (SECTION 20)

AMPLIFIER.

FOR FAULT INPUT SOURCES AND INTERCONNECTING WIRING

INFORMATION.

30−166−1

Figure 17-17. Vapair 26530332M Warning Audio and Light Flashing Control

Circuit (Sheet 1 of 2)

Page 17-54

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

NOTES: (CONT)

11. ABBREVIATIONS:

REGULATED

AMP − AMPLIFIER

+DC VOLTAGE

FREQ − FREQUENCY

(SHEET 1)

R10

R14

CR6

GEN − GENERATOR

(NOTE 1)

P/O − PART OF

XMSN − TRANSMISSION

R13

R15

X (SHEET 1)

R16

R11

PULSATING +DC VOLTAGE TO

DIMMER UNIT

R12

(FOR XMSN OIL AND TEMP LIGHT)

(NOTES 3, 10)

NOT USED

XMSN OIL AND TEMP LIGHT FLASHER

P/O

TONE GEN

CONTROL SIGNAL

(SHEET 1)

REGULATED

+DC VOLTAGE

(SHEET 1)

R35

R33

R34

R31

R38

CR5

CR4

COPILOT’S AUDIO

TONE GEN

PILOT’S AUDIO

TONE GEN

P/O

P/O GEN

P/O

SWITCH

R34

R37

R36

R30

OFF

GND IN

NOTE 10

(NOTE 10)

COPILOT’S AUDIO TONE

SIGNAL OUT (NOT USED)

PILOT’S AUDIO TONE SIGNAL OUT TO

EPO AUDIO AMP AND HEADSET(S)

(NOTE 4)

AUDIO TONE SIGNAL GENERATORS

30−166−2B

Figure 17-17. Vapair 26530332M Warning Audio and Light Flashing Control

Circuit (Sheet 2 of 2)

Page 17-55

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(14). Reinstall the cover on the EPO warning

Internal circuits are located on two circuit

unit.

boards inside a case under a removable cover.

The unit provides pulsating output dc voltage

(15). Install the instrument panel right side

for the engine out (ENG OUT) warning light

fairing.

indicator and audible warning horn, at engine

G. Vapair 26530332M EPO Warning Unit

speed of approximately 55% N_l rpm (with an

Repair

ac input frequency less than 36.75 ±1.75 Hz

from the N_l tachometer generator).

Replace defective circuit components as

The unit does not contain a frequency sensing

necessary in the EPO warning unit. Refer to

adjustment control.

the functional information and troubleshooting

data for the EPO warning unit to locate and

The pulsating output dc voltage for flashing

isolate defective internal components.

the ENG OUT warning lamps and sounding

the warning horn is rated at 0.20 ampere, 28

H. Vapair 26530332M EPO Warning Control

volts, 120−180 pulses per minute with an on

Unit Replacement

time of 50 ±15% of the period.

(1).

Check that all electrical power is OFF

The unit also furnishes separate pulsating

and remove right instrument panel

output dc voltages, identical to that for the

fairing.

ENG OUT warning lamps, to flash the main

transmission oil pressure and temperature

(2).

Disconnect electrical plug to control

(XMSN OIL PRESS and TEMP) warning

unit from audio amplifier and remove

lights when associated sensing switches are

amplifier from control unit case; then

actuated.

remove the four mounting screws and

washers, and lift out the control unit.

Audio tone generation and amplification

circuits provide an audio tone output level

(3).

Position replacement control unit and

sufficient for earphones of headsets without

install attaching hardware. Mount the

use of an external audio amplifier.

audio amplifier support clip with the

Internal adjustment controls permit setting

upper aft screw of the control unit case.

the level of the audio tone outputs.

(4).

Connect electrical plug to control unit,

Figure 17−18 is a schematic diagram of the

turn on power and check that the red

Autronics EPO warning unit.

warning lights flash. Turn on generator

switch and listen in headset for warn−

The following information describes differ−

ing signal beeping. When flashing and

ences in EPO operation from the Vapair unit.

audio signals are present, turn off

A. Engine Power Out Warning Circuits

switches and power. When control unit

does not function properly, check

The EPO warning unit contains engine out

warning circuits for continuity and

frequency sensing, warning lights flasher,

proper connection according to

audio tone generation and dc voltage regulator

Figure 17−16 and to the wiring dia−

circuits.

grams, Section 20.

Figure 17−19 is a breakdown of the Autronics

(5).

Reinstall instrument panel fairing.

EPO warning unit overall schematic diagram

and shows circuits separately by functions.

22. Autronics 2146-5 Engine Power Out

See the electrical system wiring diagram in

(EPO) Warning Control Unit

Section 20 for interconnection wiring informa−

tion on the warning lights indicating system.

The Autronics 2146−5 engine power out (EPO)

warning control unit is a solid state device

B. Engine Out Frequency Sensing Circuits

similar in function to the

(Ref. Figure 17−19) Engine out frequency

Vapair EPO warning control unit’s internal

sensing circuits consist of input gate and

circuit differences are as follows:

engine speed sensing circuits.

Page 17-56

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

In the input gate circuits, diode CR3 rectifies

When present, drive current from the under−

the positive portion of the input ac voltage

speed switch Q10 causes unijunction tone

from the N₁ tachometer generator for amplifi−

oscillator Q12 to provide a tone signal for

cation by series connected sense amplifiers Q7

amplification by tone oscillator amplifier Q13,

and Q8.

if a ground is applied to diode CR6 from the

external generator switch.

When the time interval of the rectified and

amplified input is longer than one−half the

Q10 drive current also causes tone interrupter

period of one cycle of the unijunction speed

Q14 to alternately enable and interrupt

sensing oscillator Q9, a pulsating output is

application of the amplified tone signal from

produced by Q9, is amplified by sensing

Q13 to audio #1 and #2 amplifiers Q15 and

oscillator amplifier Q11 and is applied to

Q16. Q15 and Q16 amplify the interrupted

underspeed switch Q10 of the engine speed

audio tone to a sufficient level for headsets

sensing circuits.

without additional external amplification.

Q10 drives the engine out and transmission

An internal audio tone level control in both the

lights flasher circuits and supplies dc power to

#1 and #2 audio amplifier circuits permits

the audio tone circuits.

adjustment of output tone audio level.

Sense oscillator and amplifier circuits are

supplied dc power from the dc voltage regula−

The amplified interrupted audio tone from Q15

tor circuit.

is applied to earphones of headsets.

C. Engine Out and Transmission Lights

Turning the generator switch off disables the

Flasher Circuits

audio tone circuits.

(Ref. Figure 17−19) Unijunction flasher

Output from Q16 is not used in the standard

oscillator Q1 operates continuously supplying

electrical system configuration.

a pulsating signal for amplification by flasher

oscillator amplifier Q3 to drive both engine out

and transmission lights flasher circuits.

E. Audio Tone Output Level Adjustment -

Autronics 2146-5 EPO Warning Control

Unit

Transmission light flasher driver Q2 applies

the pulsating signal to flasher amplifier Q4

that amplifies the pulsating signal to flash

When necessary, or after replacement of the

parallel connected main transmission oil

EPO warning control unit, adjust audio tone

pressure and temperature warning lights

output level for earphones of headsets as

indicators through associated sensing

follows.

switches.

(1). Be sure that a headset is connected to a

Engine out flasher driver Q5 and amplifier Q6

radio/intercom station and that any

function in the same manner to flash the

installed interphone equipment is

engine out warning lamps and drive the

functioning normally.

audible engine out warning horn, except Q5

drives Q6 to amplify the pulsating signal only

when drive is present from underspeed switch

(2). Check that all electrical power is OFF.

Q10.

(3). With right instrument panel fairing

D. Audio Tone Circuits

removed from instrument console,

remove cover from EPO warning

(Ref. Figure 17−19) Audio tone circuits consist

control unit and be sure that electrical

of audio generation, interrupter and amplifica−

wiring harness is connected to the

tion circuits.

warning control unit.

Page 17-57

Revision 19

MD Helicopters, Inc.

CSP−H−2

500 Series − Basic HMI

(4).

Turn electrical power ON. Check that

G. Autronics 2146-5 EPO Warning Control

WARNING AND PANEL lights and

Unit Replacement

ENG OUT circuit breakers are reset

(1). Check that all electrical power is OFF.

(in) and that generator switch is set to

GEN.

(2). Remove right instrument panel fairing

from instrument console.

(5).

Check that red warning light indicators

for ENG OUT and low XMSN OIL

(3). Disconnect electrical wiring harness

PRESS are flashing, that audible

connector from EPO warning unit that

warning horn is ‘‘beeping" and that

is mounted on inboard side of instru−

audible warning tone is present in

ment console.

headset. This should occur when engine

(4). Remove attaching hardware and EPO

is not operating.

warning unit from instrument console.

(6).

Set generator switch OFF to disable the

(5). Install replacement EPO warning unit

audible warning horn while completing

on right panel of instrument console in

the adjustment.

reverse order of removal.

(6). Turn on electrical power and check that

(7).

While listening with a headset, adjust

the red ENG OUT and OIL PRESS

#1 audio tone level control R32 inside

warning lights flash. Set generator

the EPO warning unit for adequate and

switch to GEN and listen to audible

desired warning tone audio level in

warning horn for audible ‘‘beeping" and

earphone. Be sure that the tone audio

headset for audible tone signal. When

level is present and adequate with

flashing and audio warning signals are

controls on any installed interphone

present, turn OFF switches and power.

audio equipment at normal operating

settings.

NOTE: If control unit does not function proper−

ly, check interconnection wiring for continu−

(8).

Set generator switch to GEN to enable

ity and proper connection according to wir−

the audible warning horn.

ing diagram in Section 20 and check

internal circuits according to Figure 17−18.

(9).

Set the generator switch OFF and

(7). If necessary, adjust #1 audio tone

verify that audible warning horn stops

output level from EPO warning unit for

‘‘beeping", audible warning tone is no

headsets.

longer present in the headset and that

ENG OUT and XMSN OIL PRESS

(8). Reinstall the right instrument panel

warning indicator lights continue to

fairing.

flash.

Application of a disable ground to the unit

(10).

Turn all electrical power OFF.

cause the disable circuits to deactivate N_R

sensing which prevents the warning indica−

(11).

Reinstall cover on EPO warning control

tions while the disable ground is applied.

unit, connect electrical connector to

The time delay keeps N_R sensing disabled for

warning control unit and install right

3.5 ±0.5 seconds after removal of the disable

instrument panel fairing on instrument

ground.

console.

Engine low N₁ speed sensing, and engine out

F. Autronics 2146-5 EPO Warning Control

flashing light and audible warning horn

Unit Repair

activation, control and generation circuits

function similarly for low N₁ rpm sensing

Replace defective circuit components as

similarly to those of the Autronics 2146−5;

necessary in the EPO warning unit. Refer to

except low N₁ speed sensing occurs at 55% N₁

the functional information and troubleshooting

rpm (equivalent to tachometer generator ac

data for the EPO warning unit to isolate

output voltage with a frequency of 36.75 ±1.75

defective internal components.

Hz) or less.

Page 17-59

Revision 19

CSP-H-2 BASIC HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369H HELICOPTERS - page 10