HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369D/E/FF-500/600N HELICOPTERS (ISSUED: 1990)

CSP−HMI−2

MD Helicopters, Inc.

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

A. Automatic Re-ignition Test Switch (S11) Replacement

401

B. Armed Light/Switch (XDS9) Assembly Replacement

401

C. Armed Light/Switch (XDS9) Lamps Replacement

401

D. Armed Lights/Switch (XDS9) Display Screen Replacement

401

E. K104/K304 Relay Replacement

401

F. CR1/CR2 Diode Replacement

402

Figure 401. Auto Re-ignition System Equipment (Sheet 1 of 3)

403

Figure 402. Auto Re-ignition Wiring Diagram (Sheet 1 of 6)

406

Figure 403. Auto Re-ignition Schematic (Sheet 1 of 3)

412

Inspection/Check

601

1. Automatic Re-ignition System Check (with Ground/Air Switch)

601

A. Normal Start

601

2. Automatic Re-ignition System Check (without Ground/Air Switch)

601

Repairs

801

1. Auto Re-ignition System Modification

801

A. Preparation for Modification

801

2. Instrument Panel Modification

801

3. Electrical System Modification

801

Figure 801. Relocation of Auto Re-ignition Controls (Sheet 1 of 2)

802

Figure 802. Auto Re-ignition Rewiring Diagram

804

Initial Installation

901

1. Auto Re-ignition Initial Installation

901

A. Reference Data

901

B. Preparation for Installation

901

C. Automatic Re-ignition System Installation

901

D. Diode Isolator Assembly Installation

901

E. Relay and Switch Assembly Installation

902

F. Relay and Switch Assembly Installation (T-Panel with Center Console)

903

G. Weight and Balance

905

Table 901. Weight and Balance Data

905

71-60-00 Engine Cooling System (250-C20B, 250-C20R/2, 250-C30 and 250-C47)

Maintenance Practices

201

1. Engine Cooling System Description and Operation

201

2. Engine Cooling System Inspection

201

3. Engine Cooling System Repair and Replacement

201

Figure 201. Engine Air Cooling System - 250-C20B and 250-C20R/2

(Sheet 1 of 2)

202

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71 Contents

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

POWER PLANT

DESCRIPTION AND OPERATION

Power Plant Description

consist of a combined four stage axial

and single stage centrifugal flow

(1).

MDHI 369D/E helicopters may be

compressor, an annular combustion

chamber and a four stage turbine

250-C20R/2 turboshaft engine man

system to extract power from the gas. A

ufactured by the Allison Engine

two-stage gas producer turbine drives

Company Inc.

the compressor, gas producer fuel

control, accessory gear train and N₁

(2).

MDHI 500N helicopter is powered by a

tachometer-generator. A two-stage

250-C20R/2 turboshaft engine man

power turbine drives the helicopter

ufactured by the Allison Engine

rotor system, governor control and N₂

Company Inc.

tachometer-generator. A start counter

is standard and part of the engine

(3).

The engine is secured in the helicopter

ignition system

by three mount assemblies and ac

cessed through two hinged, air-sealed

(2). Allison Engine Operation and Mainte

doors.

nance Manuals are the primary

(4).

A belt-driven blower provides external

information source for engine fault

cooling air through strategically

isolation and maintenance data (Ref.

positioned ducts that direct air onto

Sec. 01-00-00). Refer to these manuals

engine exterior surfaces and through

for specific engine maintenance proce

the engine and transmission oil cooler

dures.

heat exchangers. Spent blower air is

(3). Starter operational limitations are in

exhausted aft through an annular

the applicable Pilot's Flight Manual.

opening between the engine exhaust

pipes and fuselage.

3. Models 250−C20B and 250−C20R/2 Power

(5).

Engine intake air may be filtered

Plant Fault Isolation

through a standard screen or optional

air particle separator/mist eliminator

(Ref. Table 1)

assembly. Intake air is drawn through a

plenum chamber and into the engine

(1). Check engine support systems, i.e.; chip

detectors, instruments, fuel supply,

intake bell-mouth by the compressor.

electrical systems, etc., to ensure that

Engine compartment air is separated

helicopter equipment is functioning

from compressor intake air by a seal

correctly before disassembling engine

ring.

systems for an indicated fault.

Power Plant Operation

(2). Inspect and isolate engine problems per

(1). Allison turboshaft engines installed in

the applicable Allison Engine Operation

369D/E - 500N model helicopters

and Maintenance Manual.

Table 1. Power Plant Fault Isolation

Symptom

Probable Trouble

Corrective Action

High frequency vibration (1)

Loose engine mount bolts.

Retorque engine mount bolts to 100

− 140 inch−pounds (11.30 − 15.82

Nm).

NOTES:

(1) High frequency vibrations may be caused by other drive and rotor system components.

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CSP-HMI-2

MAINTENANCE MANUAL

POWER PLANT

REMOVAL/INSTALLATION

1. Engine Removal

(e). Disconnect ground jumper at center

firewall stud.

A. Engine Disconnecting for Removal

(f). Unclamp and remove electrical

(Ref. Figure 401 and Figure 402)

harness from right engine mount

After each opening, removal

(369D only).

WARNING

or replacement of any part

(5).

Remove combustion chamber drain line

of the engine and/or aircraft fuel sys

from burner drain valve.

tem between the aircraft fuel tank and

the engine fuel nozzle, the fuel system

(6).

Disconnect fuel inlet line from engine.

must be bled to remove trapped air.

Failure to comply with this procedure

(7).

Disconnect fuel pump seal drain line.

can result in engine flameout or power

loss.

(8).

Disconnect compressor cabin air bleed

outlet tube from tee fitting on engine

Cap fluid lines and fittings with

CAUTION

compressor scroll.

approved devices. Do not use

tape to cover fuel and oil openings. Tape

(9).

Loosen compressor cooling air ducts at

adhesives loosened by fuel or oil can con

firewall coupling and engine oil cooler

taminate systems.

deflector coupling (Ref. Sec. 71-60-00).

(1). Set all switches OFF. Disconnect

(10).

Disconnect duct support bracket at

external power. Disconnect battery.

hoisting eye. Remove ducts from engine

NOTE: Tag all hardware, wire terminals, fuel

compartment (Ref. Figure 401, view B).

and oil lines before removal to expedite en

(11).

Disconnect torque-meter oil line from

gine installation. Identify and bag loose

firewall.

parts to prevent loss or damage.

(2). Remove main transmission drive shaft

(12).

Disconnect oil pressure indicator line

(Ref. Sec. 63-10-00).

from firewall.

(3). Remove engine exhaust pipes (Ref. Sec.

(13).

Disconnect N₂ control rod from idler

78-20-00). Cover engine exhaust

bellcrank. Secure control rod to fire

outlet.

wall.

(4). Disconnect electrical wiring from

(14).

Disconnect anti-icing system as follows:

engine;

(a). Model 250-C20B;

(a). Disconnect engine electrical harness

Disconnect anti-ice control valve

ground lead and plug from recep

lever (Ref. Figure 401, view A).

tacle.

(b). Model 250-C20R/2:

(b). Disconnect thermocouple wire leads

Remove electrical connector from

from terminal studs on engine

anti-ice solenoid valve. Unclamp and

compartment door frame (Ref.

remove wiring harness from horizon

Figure 401, view C).

tal firewall shield.

(c). Remove thermocouple lead clamps

from door frame and exhaust pipe

(15). Disconnect N₁ control rod from gas

clamp.

producer lever. Secure control rod to

firewall.

(d). Disconnect terminals E, C, and B

from starter-generator.

(16). Disconnect accessory drive vent tube.

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MD Helicopters, Inc.

MAINTENANCE MANUAL

CONTROL CABLE

CONTROL VALVE

CLEVIS

LEVER

SCREW (5 PLCS)

AIR INLET BELL

(NOTE 1)

NUT (5 PLCS)

(NOTE 1)

ENGINE HOIST

NO. 1 BEARING

OIL RETURN

LINE

EXHAUST DUCT

ANTI-ICING VALVE

INSTALLATION

(NOTE 2)

CABIN AIR

THERMOCOUPLE LEAD

OUTLET TUBE

MOUNT FITTING

P307

(NOTE 3)

DRIVESHAFT

TORQUEMETER

OIL LINE

GROUND JUMPER

AIRFRAME HOIST

FITTING

N₂ CONTROL ROD

FUEL PUMP SEAL

FUEL CONTROL

BRACKET

DRAIN LINE

COMBUSTION CHAMBER

FUEL SUPPLY HOSE

DRAIN LINE

ROTATED

NOTES:

C20R/2 ENGINE (6 PLCS)

COMPRESSOR CASE

C20B ENGINES ONLY.

TURBINE CASE

COOLING AIR DUCT

C20R/2 ENGINES ONLY.

COOLING AIR DUCT

G71-0000-1

Figure 401. Allison 250−C20B and 250−C20R/2 Engine Removal and Installation (Sheet 1 of 2)

Page 402

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MD Helicopters, Inc.

MAINTENANCE MANUAL

(17). Disconnect fuel control drain line.

Do not use fuel or oil lines as

CAUTION

hand holds. Do not allow engine

The oil cooler is fragile. Unless

to strike airframe while maneuvering it out

CAUTION

otherwise required, disconnect

of the helicopter.

oil supply and return lines only at engine.

(5). Align engine stand (ST401) under

Support oil cooler port boss with a backup

engine with adjustable support shaft on

wrench when oil line removal is required.

left side (Ref. Figure 402).

Do not strain or bend unsupported tubes.

(6). Slowly lower engine out of helicopter.

(18). Disconnect and cap engine oil inlet,

Align engine side mount fittings

outlet and vent lines.

between fixed and adjustable support

shafts.

B. Removal of Disconnected Engine

(7). Screw in adjustable support shaft until

engine mount fittings are securely

(Ref. Figure 401 and Figure 402)

engaged with support shaft sockets.

(8). Insert detent pin through adjustable

Special Tools

support shaft.

(Ref. Section 91−00−00)

Item

Nomenclature

(9). Remove hoist from engine lift fitting.

ST401

Engine stand

(10). If engine is to be stored or transported,

ST402

Engine hoist

secure upper end of engine stand

transport and storage bar to engine

lifting eye fitting.

CAUTION

2. Engine Installation

A. Engine Installation in Mounts

D Do not remove engine mounts or disturb

engine mount adjustments to remove the

(Ref. Figure 401 and Figure 402)

engine (Ref. CSP-SRM-6).

D Engine-transmission alignment must be

Consumable Materials

inspected and realigned whenever one or

(Ref. Section 91−00−00)

more engine mount assemblies is re

Item

Nomenclature

placed or the existing engine-transmis

CM702

Lockwire CRES

sion alignment adjustment is disturbed.

Do not disturb adjustable engine mount

Special Tools

fittings unless an engine-transmission

(Ref. Section 91−00−00)

alignment check is planned.

Item

Nomenclature

(1). Install engine hoist apparatus (ST402)

ST402

Engine hoist

between airframe hoist fitting and

engine hoist eye.

(1). Open engine access doors.

(2). Have an assistant apply tension to

(2). Position engine to line up engine lifting

engine with hoist.

eye under airframe lift fitting.

(3). Remove detent pin from adjustable

(3). Maintain downward pressure on rear of

support shaft on engine stand. Detach

engine during mount bolt removal.

transport and storage bar from engine

Unbolt lower engine mount assembly

lift fitting.

from engine fitting.

(4). Install engine hoist (ST402) between

(4). Unbolt left and right engine mount

airframe fitting and engine hoist

assemblies from engine fittings.

fitting.

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CSP-HMI-2

MAINTENANCE MANUAL

(5). Have an assistant tension hoist to

Proper tightening of engine

WARNING

support engine. Unscrew engine stand

tubing connections is criti

adjustable support shaft.

cal to flight safety. Correct torque val

ues must be used at all times. Excessive

torque on fuel or pneumatic sensing

(6). Move engine to disengage fixed shaft.

system connections can result in crack

Roll stand away from engine.

ing of the flare causing an air leak

which can cause flameout, power loss,

or overspeed.

CAUTION

(1). Connect torque-meter oil line to

D Do not use tubes or hoses as hand holds.

firewall.

Do not allow engine to strike airframe.

Avoid damaging engine intake bell.

(2). Connect oil pressure gauge line to

firewall.

D Prevent FOD, ensure that no foreign ob

jects are trapped in firewall seal ring.

(3). Connect engine oil vent line. Torque

line nut to 120 - 140 inch-pounds

(7).

Have hoist operator raise engine while

(13.56 - 15.82 Nm) (Ref. Figure 401).

while pushing down to maintain correct

Do not bend oil return line.

helicopter and engine alignment.

CAUTION

Bending loads are transferred to

oil cooler port and may fracture cooler.

(8).

Align left and right engine mount

assemblies with engine mount fittings

(4).

Connect engine oil inlet and outlet

and install bolts and washers (Ref.

lines. Hand-tighten until snug.

Figure 403). Torque bolts to 100 - 140

Wrench-tighten approximately 1/4 turn

inch-pounds (11.30 - 15.82 Nm).

or until definite resistance is felt.

Safety bolts to engine mounts using

lockwire (CM702).

(5).

Position accessory drive vent elbow and

connect with vent tube. Torque elbow

jamnut to 150 - 250 inch-pounds

(9).

Align hole in lower engine mount

(16.95 - 28.25 Nm). Torque tube nut to

assembly with engine mount fitting and

20 - 30 inch-pounds (2.26 - 3.39 Nm)

install bolt and washer. Torque bolt to

(Ref. Figure 402, detail B).

100 - 140 inch-pounds (11.30 - 15.82

Nm). Safety bolt to engine mount using

(6).

Connect N_l control rod to lever with

lockwire (CM702).

bolt, two washers and nut. Install bolt

with head outboard, one standard OD

(10).

Ensure engine air inlet firewall seal

washer under nut and one large 0.80

ring contacts firewall seal around its

inch (20.32 mm) diameter washer

entire circumference.

under bolt head. Torque nut to 40 - 45

inch-pounds (4.52 - 5.08 Nm). Install

a new cotter pin.

(11).

Remove hoist from helicopter.

(7).

Connect short N₂

control rod to gover

B. Connecting an Installed Engine

nor lever with bolt head up, one

standard OD washer under head and

(Ref. Figure 401 and Figure 402)

one large 0.80 inch (20.32 mm) OD

washer under nut. Install a new cotter

pin. Connect long N₂ control rod with

Consumable Materials

bolt head forward, two washers and

(Ref. Section 91−00−00)

nut. Install a new cotter pin.

Item

Nomenclature

(8).

Connect engine fuel pump seal drain

CM702

Lockwire CRES

line. Torque tube nut to 20 - 30 inch-

pounds (2.26 - 3.39 Nm).

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

ENGINE MOUNT

SCREW (5 PLCS)

FITTING

(NOTE 2)

ENGINE AIR

INLET BELL

VENT ELBOW

ANGLE

(NOTE 1)

WASHER

(NOTE 2)

O-RING

JAM NUT

VENT ELBOW INSTALLATION

GROUND JUMPER

ACCESSORY DRIVE

(NOTE 1)

ENGINE MOUNT FITTING

INSTALLATION (TYP)

N₂ TACHOMETER

GENERATOR

NUT (5 PLCS)

(NOTE 2)

N₁ TACHOMETER

GENERATOR

IGNITION EXCITER

OIL INLET COUPLING

LEAD

OIL OUTLET COUPLING

START COUNTER

KNIFE SPLICE

ELECTRICAL

HARNESS

CHIP DETECTOR

CONNECTORS

FUEL INLET REDUCER

FUEL FILTER SWITCH

KNIFE SPLICE

”D” WIRE LEAD

STARTER-GENERATOR

REDUCER

”A” WIRE LEAD

O-RING

OIL PRESSURE

SNUBBER

ENGINE STAND

O-RING

NOTES:

APPLIES ONLY TO LOWER MOUNT.

OIL PRESSURE REDUCER

C20R/2 ENGINES (6 PLCS).

FITTING INSTALLATION

C20B ENGINES ONLY.

REMOVE CLUTCH ASSEMBLY WITH SEAL, COUPLING

AND ASSOCIATED HARDWARE INTACT.

G71-0001-1B

Figure 402. Model 250−C20B and 250−C20R/2 Engine Stripping and Buildup (Sheet 1 of 2)

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CSP-HMI-2

MAINTENANCE MANUAL

AIR INLET

HOSE

BELL

FIREWALL SEAL RING

FUEL PUMP SEAL ELBOW NUT AND O-RING

SPECIAL TEE FITTING

BEFORE FILTER PORT (BF)

SCREW

JAM NUT

(5 PLCS)

O-RING

REDUCER

O-RING

NUT

(5 PLCS)

CABIN AIR FITTING

ANTI-ICE VALVE

INSTALLATION

(NOTE 3)

O-RING

FIREWALL SEAL

AFTER FILTER

PORT (AF)

OVERRUNNING

FITTING

CLUTCH

(NOTE 4)

PRESSURE SWITCH

SPARK IGNITER

BUSHING

LEAD

HOSE ASSEMBLY

FUEL CONTROL

HOSE

FUEL PRESSURE SWITCH

DRAIN UNION

INSTALLATION

3/8 IN. (9.525 MM)

DETENT PIN

DIA. BOLT

LIFT FITTING

5/16 IN. (7.9375 MM)

DIA. BOLT (2)

ENGINE LIFT FITTING

INSTALLATION

GOVERNOR CONTROL IDLER

SUPPORT, BELLCRANK AND

REDUCER

N₂ CONTROL ROD ASSEMBLY

O-RING

SNUBBER

O-RING

ACCUMULATOR

TORQUE OIL PRESSURE FITTING

INSTALLATION

G71-0001-2

Figure 402. Model 250−C20B and 250−C20R/2 Engine Stripping and Buildup (Sheet 2 of 2)

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MAINTENANCE MANUAL

(9). Connect fuel inlet line to fuel pump.

located on right upper engine door

Torque hose nut to 230 - 260 inch-

frame with chromel and alumel nuts.

pounds (25.99 - 29.38 Nm).

(17). Install main transmission drive shaft

NOTE: Ensure burner drain valve and plug are

(Ref. Sec. 63-10-00).

installed in combustion chamber with an O-

(18). Remove all identifying tags from wires

ring on each part. Ensure drain valve is in

and hardware.

the aft (lowest) position.

Misrigging of throttle controls

(10). Install combustion chamber drain line

CAUTION

can cause inadvertent flameout

on drain valve.

when throttle is rapidly closed to the idle po

sition.

(11). Connect fuel control drain line. Torque

drain line nut to 20 - 30 inch-pounds

(19). Rig gas producer (N₁) and power

(2.26 - 3.39 Nm) (Ref. Figure 401).

turbine (N₂) controls (Ref. Chap. 76).

(12). Connect anti-ice system as follows:

After each opening, removal

WARNING

or replacement of any part

(a). Model 250-C20B:

of the engine and/or aircraft fuel sys

Connect anti-icing control cable to

tem between the aircraft fuel tank and

anti-icing control valve lever with

the engine fuel nozzle, the fuel system

clevis pin and washer. Secure with

must be bled to remove trapped air.

cotter pin (Ref. Figure 401, detail A).

Failure to comply with this procedure

can result in engine flameout or power

(b). Model 250-C20R/2:

loss.

Install connector P307 to anti-ice

solenoid valve and secure anti-icing

(20). Perform fuel system bleed.

wiring harness with clamps.

(21). Perform an engine deceleration check

(13). Install cooling air ducts and air duct

per the Pilot's Flight Manual.

support bracket on hoisting eye above

NOTE: Make engine adjustments per the Alli

engine. Connect and tighten ducts on

son Engine Operation and Maintenance

firewall coupling and oil cooler deflec

Manual.

tor.

(22). Perform an anti-icing system opera

(14). Secure engine electrical harness to

tional check (Ref. Sec. 75-10-00).

engine mount with cushioned loop

clamp. Connect harness plug to recep

(23). Inspect engine installation and connec

tacle and safety with lockwire (CM702).

tions for proper routing and security.

(a). Install engine harness ground lead.

3. Engine Stripping

(Ref. Figure 402)

(b). Install E, C, and B generator leads on

starter-generator terminal block

with washers and nuts.

Special Tools

(Ref. Section 91−00−00)

(c). At lower engine mount fitting; install

Item

Nomenclature

bonding jumper on engine compart

ST401

Engine stand

ment firewall stud. Torque bolt to 100

ST402

Engine hoist

- 140 inch-pounds (11.30 - 15.82

Nm). Safety bolt to engine mount

using lockwire (CM702).

(1). Install engine in engine stand (ST401).

(15). Install engine exhaust pipes and

(2). Disconnect wire leads from generator A

thermocouple clamp support.

and D terminals.

(16). Attach thermocouple clamps in frame

(a). Loosen mounting clamp and remove

and leads to terminal block studs

starter-generator.

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MAINTENANCE MANUAL

(b). Remove mounting flange and gasket.

(a). Remove hose, reducer and O-ring

from before filter (BF) port (Ref.

(c). Install cover on generator mounting

Figure 402, view D).

pad.

(b). Remove bushing, fuel pressure

(3). Disconnect electrical connectors from:

switch, fitting and O-rings from after

(a). Chip detectors.

filter (AF) port.

(b). Tachometer generators.

(12).

Remove engine air inlet bell and

firewall seal.

(c). Ignition exciter.

(13).

Model 250-C20B Only:

(d). Start counter.

Remove anti-icing valve lever assembly

(e). Fuel filter pressure switch.

from poppet guide (Ref. Figure 401,

view A).

(f). Unclamp and remove electrical

harness from overrunning clutch and

(14).

Remove fuel pump seal drain port

lower engine mount fitting.

elbow and jamnut.

(g). Remove entire engine electrical

(15).

Remove governor control idler support,

harness.

bellcrank and short N₂ control rod as

an assembly. Install vacuum/hydraulic

NOTE: Discard all used O-ring packings.

pump pad cover.

(4). Remove fuel supply and return reduc

(16).

Remove overrunning clutch and

ers/unions.

firewall seal. Install cover on engine

(5). Remove oil supply and return reducers/

pad.

unions.

(17).

Remove fuel control drain fitting.

(6). Remove accessories drive vent elbow

and jamnut.

(18).

Remove pneumatic line accumulator

per Allison installation bulletin (Ref.

(7). Remove compressor bleed air hose, tee

Sec. 01-00-00).

and jamnut (Ref. Figure 402. view C).

(19).

Hoist (ST402) engine out of engine

(8). Remove oil pressure reducer/snubber.

stand.

(9). Remove torque-meter reducer/snubber.

(20).

Unbolt and remove engine mount

(10). Remove N₁ and N₂ tachometer genera

fittings.

tors and gaskets.

(21).

Install engine in shipping container.

(11). Remove fuel pressure switch installa

tion as follows:

(22).

Remove engine hoist fitting.

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MAINTENANCE MANUAL

4. Engine Buildup

(3). Hoist engine clear of shipping contain

er.

(Ref. Figure 402 and Figure 403)

(4). Inspect engine as follows:

Proper tightening of engine

WARNING

tubing connections is criti

(a). If shipping container moisture

cal to flight safety. Correct torque val

indicator was other than a light blue

ues must be used at all times. Excessive

color, examine engine for corrosion.

torque on fuel or pneumatic sensing

Perform corrosion corrective mainte

system connections can result in crack

nance per Allison Operation and

ing of the flare causing an air leak

Maintenance Manual as required.

which can cause flameout, power loss,

(b). Inspect inlet guide vanes for damage.

or overspeed.

(c). Exhaust and inlet openings for FOD.

Consumable Materials

(d). Turbine blades for damage.

(Ref. Section 91−00−00)

Item

Nomenclature

(e). Install covers over intake and

CM113

Anti-seize compound low temperature

exhaust ports.

CM114

Petrolatum

(f). All fasteners for security, slippage

CM118

Grease

marks for alignment, potting com

CM502

Sleeving, fiberglass

pound and, or correctly installed

lockwire where applicable.

CM702

Lockwire CRES

CM808

Lacing cord

(g). Tubes and hoses for damage.

(5). Record engine serial number and

Special Tools

start-counter reading in appropriate

(Ref. Section 91−00−00)

log.

Item

Nomenclature

ST401

Engine stand

Prevent damage to machined

CAUTION

surfaces and contamination. Re

move covers from engine one at a time as re

(1). Review Allison instructions for remov

quired by the installation sequence.

ing engine from shipping container in

Allison Operation and Maintenance

(6). Install lower engine mount fitting with

Manual.

angle and ground wire under aft bolt

head. Install side engine mount fittings,

Prevent FOD Inspect and clean

bolts and washers. Torque bolts to 140 -

CAUTION

all accessories and hardware

160 inch-pounds (15.82 - 18.08 Nm).

prior to installing parts on engine.

Install lockwire (CM702).

NOTE: Replace O-rings and gaskets with new

(7). Install engine in engine stand (ST401).

parts. Lubricate fuel line packings with

(8). Install accumulator in pneumatic line

clean jet fuel or petrolatum (CM114) prior to

per Allison installation bulletin (Ref.

installation. Lubricate oil line packings with

Sec. 01-00-00).

clean engine oil prior to installation. Apply a

thin coating of anti-seize compound

(9). Install fuel control drain fitting and

(CM113) to the male threads of unions and

O-ring.

fittings before torquing.

(10). Remove overrunning clutch pad cover.

(2). Install engine hoist lift fitting and bolts.

Install overrunning clutch, firewall seal

Torque 3/8 inch-diameter bolt to 160 -

and engine electrical harness angle and

190 inch-pounds (18.08 - 21.47 Nm).

clamp (Ref. Sec. 63-10-00).

Torque 5/16 inch-diameter bolts to 140

- 160 inch-pounds (15.82 - 18.08

(11). Install oil pressure gauge reducer/snub

Nm).

ber and O-ring.

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MAINTENANCE MANUAL

(12). Install torque-meter reducer/snubber

(c). Install reducer and O-ring in BF

and O-ring.

port.

(d). Install hose assembly between AF

Engine spark igniter wire lead

CAUTION

and BF fittings.

may obstruct governor arm on a

new or overhauled engine.

(20). Lubricate splines with grease (CM118)

and install N₁ and N₂ tachometer

(13). Reroute engine spark igniter lead below

generators. Install washers and nuts.

governor as shown (Ref. Figure 402).

Torque nuts to 70 - 90 inch-pounds

Support igniter lead only with cush

(7.91 - 10.17 Nm).

ioned clamps and existing fasteners.

Replace and, or add clamps as required.

(21). Install special tee, jamnut and O-ring

in compressor scroll bleed air port. Do

(14). Remove vacuum/hydraulic pump pad

not torque at this time.

cover from gear case.

(22). Install hose between special tee and

(15). Install governor control idler support,

compressor bleed air elbow. Torque tee

bellcrank and short N₂ control rod as

jamnut. Torque hose nuts to 150 - 250

an assembly. Do not connect control rod

inch-pounds (16.95 - 28.25 Nm).

to governor lever.

(23). Install accessory gear case vent elbow,

jamnut and O-ring. Do not torque at

Only high temperature all met

CAUTION

this time.

al self locking nuts shall be used

to fasten governor control idler support

(24). Install oil inlet and outlet couplings and

bracket to engine accessory pad.

O-rings.

(16). Install elbow with O-ring and jamnut

(25). Install fuel inlet reducer and O-ring.

in fuel pump seal drain port.

(26). Install starter/generator.

(17). Model 250-C20B Only:

Always support the weight of

Install anti-icing valve lever with

CAUTION

the starter/generator during re

attaching hardware on poppet guide.

moval/installation. Damage can occur if

Position poppet guide so that lever is

weight is supported by the shear shaft.

parallel with top of engine.

(a). Remove starter/generator pad cover.

(18). Install engine air inlet bell and firewall

Install starter/generator mount with

seal.

gasket, washers and nuts. Torque

nuts to 100 - 140 inch-pounds

(19). Install fuel pressure switch fitting and

(11.29 - 15.81 Nm).

O-ring in fuel pump AF port (Ref. Sec.

28-00-00).

(b). Install starter/generator with V-

clamp. Torque clamp nut to 50

Ensure both halves of the fuel

inch-pounds (5.64 Nm).

CAUTION

filter pressure switch are

(c). Tap around clamp with a rawhide

gripped by wrench when torquing the in

mallet to seat clamp on flange.

stallation. An asymmetrical wrench grip

Retorque clamp nut to 50 inch-

may cause shearing motion between assem

pounds (5.64 Nm).

bly halves. Such damage may result in leak

age or failure to operate FUEL FILTER

(d). Continue tapping around clamp and

caution/warning light, or both.

retorquing clamp nut until nut no

longer turns when specified torque is

(a). Install fuel filter pressure switch and

applied.

O-ring.

(27). Clamp engine electrical harness to

(b). Install bushing and O-ring on

lower engine mount and starter-gener

switch.

ator.

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MAINTENANCE MANUAL

(28). Connect ignition exciter wire lead and

(1). Disconnect accessory drive overboard

starter-generator A and D wire leads.

vent tube from elbow on engine accesso

ry case; remove vent tube from helicop

(29). Attach electrical connectors to both chip

ter.

detectors and safety with lockwire

(CM702).

(2). Install extension tube to existing vent

(30). Connect N₁ and N₂ tachometer genera

tube as follows:

tors connectors.

(31). Connect start counter lead and fuel

(a). Position extension tube over vent

pressure switch wire lead splices.

tube. Drill rivet holes in line thru

Install fiberglass sleeving (CM502) over

tubing.

splices and secure with high tempera

ture lacing cord (CM808).

(b). Apply sealant (CM425) between

tubes. Install two NAS1738B4-2

5. Modification of Accessory Drive Gearbox

rivets. Fillet seal around circumfer

Overboard Vent Tube (SN 0004D − 0519D)

ence of tubes.

(Ref. Figure 404) The following procedure adds

a four inch extension tube to the existing

(3). Remove existing grommet at lower

engine accessory drive gearbox vent tube to

fuselage Sta. 127.00 and install new

reduce oil spattering onto the lower fuselage.

MS35489-22 grommet.

Consumable Materials

(4). Insert extension tube thru grommet

(Ref. Section 91−00−00)

and connect vent tube to elbow on

Item

Nomenclature

engine accessory case. Torque line nut

CM425

Sealing compound

to 120 - 140 inch-pounds (13.56 -

15.82 Nm).

FUSELAGE SKIN

NAS1738B4-2 RIVET

STA. 127.00

(2 REQD.)

MS35489-22 GROMMET

NOTE

EXTENSION TUBE

369A8010-615

TUBE ASSY.

0.250 IN.

(6.35 MM)

0.84 IN.

(21.34 MM)

4.85 IN.

NOTE: SEAL BETWEEN TUBES

(12.319 CM)

BEFORE ASSEMBLY AND FILLET

88-295A

SEAL ABOUT CIRCUMFERENCE.

Figure 404. Extension of Engine Accessory Drive Overboard Vent Tube

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MAINTENANCE MANUAL

POWER PLANT

DESCRIPTION AND OPERATION

Power Plant Description

sor, N₁ tachometer-generator and

accessory gear train, and a two-stage

(1).

MDHI 369FF helicopter is powered by a

power turbine driving the spare

250-C30 turboshaft engine manufac

accessory pad, governor, N₂ tachome

tured by the Allison Engine Company

ter-generator and helicopter rotor

Inc.

system. An overrunning clutch, drive

shaft, starter generator, fuel, oil, drain

(2).

The engine is secured in the helicopter

and bleed air lines, exhaust ducting,

by three mount assemblies and ac

mounting and hoist fittings and control

cessed through two hinged, air-sealed

levers adapt the engine to the helicop

doors.

ter.

(3).

A belt-driven blower forces external

(2). Allison Engine Operation and Mainte

cooling air through strategically

positioned ducts that direct the air onto

nance Manuals are the primary

engine exterior surfaces and through

information source for engine fault

the engine and transmission oil cooler

isolation and maintenance data (Ref.

heat exchangers. Spent cooling air is

Sec. 01-00-00). Refer to these manuals

exhausted aft through an annular

for specific engine maintenance proce

opening between the engine exhaust

dures.

duct and fuselage.

(3). Starter operational limitations are in

(4).

Engine intake air may be filtered

the applicable Pilot's Flight Manual.

through a standard screen or optional

air particle separator/mist eliminator

3. Model 250−C30 Power Plant Fault

assembly. Intake air is drawn through a

Isolation

plenum chamber and into the engine

intake bell-mouth by the compressor.

(Ref. Table 1)

Engine compartment air is separated

(1). Check engine support systems, i.e.; chip

from compressor intake air by a seal

detectors, instruments, fuel supply,

ring.

electrical systems, etc., to ensure that

Power Plant Operation

helicopter equipment is functioning

correctly before disassembling engine

(1). The Allison 250-C30 turboshaft engine

systems for an indicated fault.

consists of a single stage centrifugal

flow compressor, a can-annular

(2). Inspect and isolate engine problems per

combustion chamber, a two-stage gas

the applicable Allison Engine Operation

producer turbine driving the compres

and Maintenance Manual.

Table 1. Power Plant Fault Isolation

Symptom

Probable trouble

Corrective action

High frequency vibration (1)

Loose engine mount bolts

Retorque engine mount bolts to 100

− 140 inch−pounds (11.30 − 15.82

Nm).

NOTES:

(1) High frequency vibrations may be caused by other drive and rotor system components.

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CSP-HMI-2

MAINTENANCE MANUAL

POWER PLANT

REMOVAL/INSTALLATION

1. Engine Removal

(7).

Loosen and remove remaining engine

cooling air ducts from engine compart

A. Engine Disconnecting for Removal

ment (Ref. Figure 402, views A and D).

(Ref. Figure 401 and Figure 402)

(8).

Remove combustion chamber drain line

from burner drain valve.

After each opening, removal

WARNING

or replacement of any part

(9).

Disconnect fuel inlet line at engine-

of the engine and/or aircraft fuel sys

mounted fuel pump and cap line.

tem between the aircraft fuel tank and

the engine fuel nozzle, the fuel system

(10).

Disconnect and remove fuel pump seal

must be bled to remove trapped air.

drain line.

Failure to comply with this procedure

(11).

Disconnect and remove fireshield drain

can result in engine flameout or power

line.

loss.

(12).

Disconnect fuel control vent line and

Cap fluid lines and fittings with

CAUTION

cap line.

approved devices. Do not use

tape to cover fuel and oil openings. Tape

(13).

Disconnect customer bleed line at

adhesives loosened by fuel or oil can con

firewall.

taminate systems.

(14).

Disconnect torque-meter oil line from

(1). Set all switches OFF. Disconnect

firewall.

external power. Disconnect battery.

(15).

Disconnect oil pressure indicator line

NOTE: Tag all hardware, wire terminals, fuel

from firewall.

and oil lines before removal to expedite in

stallation. Identify and bag loose parts to

(16).

Disconnect N₂ control rod from idler

prevent loss or damage.

bellcrank. Secure control rod to fire

wall.

(2). Remove main transmission drive shaft

(Ref. Sec. 63-10-00).

(17).

Disconnect N₁ control rod from gas

producer lever. Secure control rod to

(3). Remove engine exhaust duct (Ref. Sec.

firewall.

78-30-00). Cover engine exhaust

(18).

Disconnect and remove starter-genera

outlet.

tor cooling air duct from starter and

(4). On left engine compartment door

fuselage bracket.

frame; unclamp and disconnect thermo

The oil cooler is fragile. Unless

couple wire leads from terminal studs

CAUTION

otherwise required, disconnect

(Ref. Figure 401, view B).

oil supply and return lines only at engine.

(5). Unplug engine-airframe electrical

Support oil cooler port boss with a backup

harness connector from engine recep

wrench when oil line removal is required.

tacle.

Do not strain or bend unsupported tubes.

(6). Disconnect thermal switch plug from

(19). Disconnect and cap engine oil inlet,

firewall.

outlet and vent lines.

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MAINTENANCE MANUAL

B. Removal of Disconnected Engine

between fixed and adjustable support

shafts.

(Ref. Figure 401 and Figure 402)

(7). Screw in adjustable support shaft until

engine mount fittings are securely

Special Tools

engaged with support shaft sockets.

(Ref. Section 91−00−00)

Item

Nomenclature

(8). Insert detent pin through adjustable

support shaft.

ST401

Engine stand

ST402

Engine hoist

(9). Remove hoist from engine lift fitting.

(10). If engine is to be stored or transported,

secure upper end of engine stand

CAUTION

transport and storage bar to engine

lifting eye fitting.

D Do not remove engine mounts or disturb

engine mount adjustments to remove en

2. Engine Installation

gine.

D Engine-transmission alignment shall be

A. Engine Installation in Mounts

inspected whenever one or more engine

mount assemblies is replaced or the exist

(Ref. Figure 401 and Figure 402)

ing alignment is disturbed. Do not disturb

adjustable engine mount fittings unless

Consumable Materials

an engine-transmission alignment check

(Ref. Section 91−00−00)

is planned.

Item

Nomenclature

CM702

Lockwire CRES

(1). Install engine hoist apparatus (ST402)

between engine hoist eye and airframe

hoist fitting.

Special Tools

(Ref. Section 91−00−00)

(2). Have an assistant apply tension to

Item

Nomenclature

engine with hoist.

ST402

Engine hoist

(3). Maintain downward pressure on rear of

engine during mount bolt removal.

(1).

Open engine access doors.

Unbolt engine at lower engine mount

fitting. Take care not to damage rod end

(2).

Position engine to line up engine lifting

bearings.

eye under airframe lift fitting.

(3).

Remove detent pin from adjustable

(4). Unbolt left and right engine mount

support shaft on engine stand. Detach

assemblies from engine fittings.

transport and storage bar from engine

lift fitting.

Do not use fuel or oil lines as

CAUTION

hand holds. Do not allow engine

(4).

Install engine hoist (ST402) between

to strike airframe while maneuvering it out

airframe fitting and engine hoist

of the helicopter.

fitting.

(5). Align engine stand (ST401) under

(5).

Have an assistant tension hoist to

engine with adjustable support shaft on

support engine. Unscrew engine stand

left side.

adjustable support shaft.

(6). Slowly lower engine out of helicopter.

(6).

Move engine to disengage fixed shaft.

Align engine side mount fittings

Roll stand away from engine.

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MAINTENANCE MANUAL

(2). Connect oil pressure gauge line to

CAUTION

firewall.

D Do not use tubes or hoses as hand holds.

(3). Connect engine oil vent line. Torque

Do not allow engine to strike airframe or

line nut to 120 - 140 inch-pounds

components. Avoid damaging engine in

(13.56 - 15.82 Nm).

take bell.

D Prevent FOD ensure that no foreign ob

Do not bend oil return line.

CAUTION

jects are trapped in firewall seal ring.

Bending loads are transferred to

oil cooler port and may fracture cooler.

(7). Have hoist operator slowly raise engine

while pushing engine down to maintain

(4).

Connect engine oil outlet and inlet

correct engine and transmission

lines. Hand-tighten until snug.

alignment.

Wrench-tighten approximately 1/4 turn

or until definite resistance is felt.

(8). Align left and right engine mount

assemblies with engine fittings. Install

(5).

Position accessory drive vent elbow and

bolts and washers (Ref. Figure 403).

connect with vent tube. Torque elbow

Torque bolts to 220 - 360 inch-pounds

jamnut to 150 - 250 inch-pounds

(24.86 - 40.67 Nm); Safety bolts to

(16.95 - 28.25 Nm). Torque tube nut to

engine mounts using lockwire (CM702).

20 - 30 inch-pounds (2.26 - 3.39

Nm).

(9). Align hole in lower engine mount

assembly with engine fitting. Install

(6).

Connect N₁ control rod to lever with

bolt, washers and nut. Torque nut to 95

bolt, two washers and nut. Install bolt

- 110 inch-pounds (10.73 - 12.43

with head outboard, one standard OD

Nm); install cotter pin as required.

washer under nut and one large 0.8

inch diameter washer under head.

(10). Ensure engine air inlet firewall seal

Torque nut to 40 - 45 inch-pounds

ring contacts firewall seal around its

(4.52 - 5.08 Nm). Install a new cotter

entire circumference.

pin.

(11). Remove hoist from helicopter.

(7).

Connect short N₂ control rod to gover

nor lever with bolt head up, one

B. Connecting an Installed Engine

standard OD washer under head, one

(Ref. Figure 401 and Figure 402)

large 0.80 inch (20.32 mm) OD washer

under nut and a new cotter pin.

Connect long N₂

control rod with bolt

Consumable Materials

head forward, two washers, nut and a

(Ref. Section 91−00−00)

new cotter pin.

Item

Nomenclature

CM702

Lockwire CRES

(8).

Connect engine fuel pump seal drain

line. Torque tube nut to 50 - 65 inch-

pounds (5.65 - 7.34 Nm).

Proper tightening of engine

WARNING

tubing connections is criti

(9).

Connect fuel inlet line to fuel pump.

cal to flight safety. Correct torque val

Torque hose nut to 230 - 260 inch-

ues must be used at all times. Excessive

pounds (25.99 - 29.38 Nm).

torque on fuel or pneumatic sensing

system connections can result in crack

NOTE: Ensure burner drain valve and plug are

ing of the flare causing an air leak

installed in combustion chamber with an O-

which can cause flameout, power loss,

ring on each part. Ensure drain valve is in

or overspeed.

the aft (lowest) position.

(1). Connect torque-meter oil line to

(10). Install combustion chamber drain line

firewall.

on drain valve.

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MAINTENANCE MANUAL

(11). Secure engine electrical harness to

(19). Perform an anti-icing system opera

engine mount with cushioned loop

tional check (Ref. Sec. 75-10-00).

clamp. Connect harness plug to recep

(20). Inspect engine installation and connec

tacle and safety with lockwire (CM702).

tions for proper routing and security.

(a). Install engine harness ground lead.

3. Engine Stripping

(b). Install E, C, and B generator leads on

(Ref. Figure 403)

starter-generator terminal block

with washers and nuts.

Special Tools

(c). Attach thermocouple leads to termi

(Ref. Section 91−00−00)

nal block studs located on right upper

Item

Nomenclature

engine door frame with chromel and

ST401

Engine stand

alumel nuts.

ST402

Engine hoist

(12). Install cooling air ducts and air duct

support bracket on airframe hoist

(1). Install engine in engine stand (ST401).

fitting. Connect and tighten ducts on

firewall coupling and oil cooler deflec

(2). Disconnect wire leads from generator A,

tor.

E and D terminals.

(3). Loosen mounting clamp and remove

(13). Install main transmission drive shaft

starter-generator.

(Ref. Sec. 63-10-00).

(4). Remove mounting flange and gasket.

(14). Install exhaust duct (Ref. Sec.

78-30-00).

(5). Install cover on generator mounting

pad.

(15). Remove all identifying tags from wires

and hardware.

(6). Disconnect electrical connectors from:

Improper rigging of throttle con

(a). Chip detectors.

CAUTION

trols can cause inadvertent

(b). Tachometer generators.

flameout when throttle is rapidly closed to

the idle position.

(c). Fuel filter pressure switch.

(16). Rig gas producer (N₁) and power

(d). Unplug electrical harness connector

turbine (N₂) controls (Ref. Chap. 76).

from front of engine.

After each opening, removal

(e). Unclamp and remove engine electri

WARNING

or replacement of any part

cal harness.

of the engine and/or aircraft fuel sys

NOTE: Discard all used O-ring packings.

tem between the aircraft fuel tank and

the engine fuel nozzle, the fuel system

(7). Remove oil vent line and associated

must be bled to remove trapped air.

hardware.

Failure to comply with this procedure

can result in engine flameout or power

(8). Remove fuel inlet fitting.

loss.

(9). Remove oil supply, return and vent

reducers/unions.

(17). Perform fuel system bleed.

(10). Remove oil pressure reducer/snubber.

(18). Perform an engine deceleration check

per the Pilot's Flight Manual.

(11). Remove torquemeter reducer/snubber.

NOTE: Make engine adjustments per the Alli

(12). Unclamp and remove compressor bleed

son Engine Operation and Maintenance

service line, fitting and associated

Manual.

clamps.

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MD Helicopters, Inc.

MAINTENANCE MANUAL

(13).

Remove compressor bleed duct from

(1). Review Allison instructions for remov

bleed valve.

ing engine from shipping container in

Allison Operation and Maintenance

(14).

Unfasten and remove N₁ and N₂

Manual.

tachometer generators and gaskets.

Prevent FOD Inspect and clean

(15).

Remove hose and reducer from fuel

CAUTION

all accessories and hardware

pump after filter (AF) port.

prior to installing parts on engine.

(16).

Remove fuel pressure switch and fitting

NOTE: Replace O-rings and gaskets with new

from fuel pump before filter (BF) port

parts. Lubricate fuel line packings with

(Ref. Figure 403).

clean jet fuel or petrolatum (CM114) prior to

(17).

Remove engine air inlet bell and

installation. Lubricate oil line packings with

firewall seal. Cover engine inlet.

clean engine oil prior to installation. Apply a

thin coating of anti-seize compound

(18).

Remove fuel pump seal drain port

(CM113) to the male threads of unions and

union/reducer.

fittings before torquing.

(19).

Remove governor control idler support

(2). Install engine hoist fitting and bolts.

complete with bellcrank, short N₂

Torque 3/8 inch diameter bolt to 160 -

control rod and lever. Do not dismantle

190 inch-pounds (18.08 - 21.47 Nm).

assembly.

Torque 5/16 inch-diameter bolts to 140

- 160 inch-pounds (15.82 - 18.08

(20).

Remove overrunning clutch and clutch

Nm).

firewall seal. Install cover on gear case.

(21).

Hoist (ST402) engine out of engine

(3). Hoist engine clear of shipping contain

stand.

er.

(22).

Unbolt and remove engine mount

(4). Inspect engine as follows:

fittings.

(a). If shipping container moisture

(23).

Install engine in shipping container.

indicator was other than a light blue

color, examine engine for corrosion.

(24).

Unbolt and remove hoist fitting.

Perform corrosion corrective mainte

nance per Allison Operation and

4. Engine Buildup

Maintenance Manual as required.

(Ref. Figure 403)

(b). Inspect inlet guide vanes for damage.

Consumable Materials

(c). Exhaust and inlet openings for FOD.

(Ref. Section 91−00−00)

Item

Nomenclature

(d). Turbine blades for damage.

CM113

Anti-seize compound low temperature

(e). Install covers over intake and

CM114

Petrolatum

exhaust ports.

CM118

Grease

CM502

Sleeving, fiberglass

(f). All fasteners for security, slippage

CM702

Lockwire CRES

marks for alignment, potting com

pound and, or correctly installed

CM808

Lacing cord

lockwire where applicable.

Special Tools

(g). Tubes and hoses for damage.

(Ref. Section 91−00−00)

Item

Nomenclature

(5). Record engine serial number and

ST401

Engine stand

start-counter reading in appropriate

log.

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CSP-HMI-2

MAINTENANCE MANUAL

Prevent damage to machined

Torque nuts to 70 - 90 inch-pounds

CAUTION

surfaces and contamination. Re

(7.91 - 10.17 Nm).

move covers from engine one at a time as re

Proper tightening of engine

quired by the installation sequence.

WARNING

tubing connections is criti

(6). Install side engine mount fittings with

cal to flight safety. Correct torque val

bolts and washers. Torque bolts to 140 -

ues must be used at all times. Excessive

160 inch-pounds (15.82 - 18.08 Nm);

torque on fuel or pneumatic sensing

lockwire bolts.

system connections can result in crack

ing of the flare causing an air leak

(7). Install engine in engine stand (ST401).

which can cause flameout, power loss,

or overspeed.

(8). Set fuel flow stop adjuster as follows:

(16). Inspect torquemeter and engine oil

(a). For Bendix P/N 2524944-5 or

pressure snubber and reducer bores for

2524922-7 and subsequent, set

metal shavings and debris. Clean

pointer at LO position.

hardware as required. Preassemble

both snubbers as follows:

(b). For Bendix P/N 2524944-1, -2, -3,

-4 or 2524922-3, -4, -5, -6, set

(a). Thread torquemeter snubber onto

pointer midway between LO stamped

reducer and O-ring. Torque assembly

mark and the middle scribed mark.

to 65 - 75 inch-pounds (7.34 - 8.47

Nm).

(c). Torque jam nut to 20 - 25 inch-

(b). Thread oil pressure snubber onto

pounds (2.26 - 2.82 Nm); lockwire

reducer and O-ring. Torque assembly

nut.

to 95 - 105 inch-pounds (10.73 -

(9). Remove cover from gearcase clutch

11.86 Nm).

mounting pad.

(c). Apply a thin coat of engine oil to

snubber threads and O-rings and

(10). Install overrunning clutch on gearcase

install in gearcase ports (Ref.

mount pad with wire harness support

Figure 403)

angle between 4 and 5 o'clock position

looking aft (Ref. Sec. 63-10-00).

The gear case is magnesium

CAUTION

alloy. Using relatively high

(11). Loosely attach wire harness clamp to

torque values applicable to threaded fittings

support angle with screw, washer and

and fasteners in metals other than magne

nut.

sium may result in stripped threads. Refer

to Allison Engine Maintenance Manual for

(12). Attach clutch firewall seal to clutch

additional fastener torque information.

flange with one washer under each bolt

head and nut. Torque nuts to 25 - 35

(d). Torque oil pressure snubber assembly

inch-pounds (2.82 - 3.95 Nm).

to 50 - 65 inch-pounds (5.65 - 7.34

Nm).

NOTE: Use new O-ring packings and gaskets

on all installations where the parts are re

(e). Torque torquemeter snubber assem

quired. Lubricate O-rings with clean sys

bly to 25 - 35 inch-pounds (2.82 -

tem fluids prior to installation.

3.95 Nm).

(13). Remove tachometer-generator cover

(f). Install union and O-ring in gearcase

plates from gearcase mount pads.

oil supply (inlet) port. Torque union

to 450 - 500 inch-pounds (50.84 -

(14). Install a gasket under each tachome

56.49 Nm).

ter-generator.

(g). Install union and O-ring in gearcase

(15). Lubricate splines with grease (CM118)

oil return port. Torque union to 180 -

and install N₁ and N₂ tachometer

200 inch-pounds (20.34 - 22.60

generators. Install washers and nuts.

Nm).

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MAINTENANCE MANUAL

(17). Install compressor bleed air duct with

(27). Assemble differential pressure switch.

screws washers and clamp (Ref.

(28). Install elbow with O-ring and jamnut

Figure 401).

in fuel pump seal drain port.

(18). Install inlet bell with one washer under

(29). Install oil inlet and outlet couplings and

each bolt head and nut. Install service

O-rings.

bleed air tube support bracket on aft

surface of engine inlet bell mounting

(30). Install fuel inlet reducer and O-ring.

flange at the 2 o'clock position looking

aft. Torque nuts to 5 - 7 inch-pounds

(31). Install starter/generator.

(0.56 - 0.79 Nm).

Always support the weight of

CAUTION

Only high-temperature self

the starter/generator during re

CAUTION

locking all metal nuts shall be

moval/installation. Damage can occur if

used to fasten governor control idler support

weight is supported by the shear shaft.

bracket to engine accessory pad.

(a). Remove starter/generator pad cover.

(19).

Install governor control idler support

Install starter/generator mount with

complete with bellcrank, short N₂

gasket, washers and nuts. Torque

control rod and lever.

nuts to 100 - 140 inch-pounds

(11.29 - 15.81 Nm).

(20).

Attach short control rod to N₂ governor

lever. Stack hardware with bolt head on

(b). Install starter/generator with V-

top, large washer under bolt head and

clamp. Torque clamp nut to 50

washer under castellated nut; Install

inch-pounds (5.64 Nm).

cotter pin.

(c). Tap around clamp with a rawhide

(21).

Install compressor bleed air service

mallet to seat clamp on flange.

fitting on compressor case with engine

Retorque clamp nut to 50 inch-

supplied washers and bolts. Lockwire

pounds (5.64 Nm).

bolts.

(d). Continue tapping around clamp and

retorquing clamp nut until nut no

(22).

Attach bleed air tube to service fitting.

longer turns when specified torque is

(23).

Install clamp on bleed air tube and

applied.

secure to support bracket with bolt,

(32).

Clamp engine electrical harness to

washer and nut. Torque bleed air tube

lower engine mount and starter-gener

nut on compressor case fitting to 450 -

ator.

500 inch-pounds (50.84 - 56.49 Nm).

Install a protective cap on tube end.

(33).

Connect ignition exciter wire lead and

starter-generator A and D wire leads.

(24).

Install union and O-ring in engine oil

tank vent gearcase boss. Torque union

(34).

Attach electrical connectors to both chip

to 180 - 200 inch-pounds (20.34 -

detectors and safety with lockwire

22.60 Nm).

(CM702).

(25).

Preassemble oil tank vent tube, clamp,

(35).

Connect N₁ and N₂ tachometer genera

union and hose. Torque union, hose and

tors.

tube end nuts to 450 - 500 inch

pounds (50.84 - 56.49 Nm).

(36).

Connect start counter lead and fuel

pressure switch wire lead splices.

(26).

Attach vent tube assembly to oil tank

Install fiberglass sleeving (CM502) over

vent gearcase union. Install tube clamp

splices and secure with high tempera

with screw, washer and nut. Using a

ture lacing cord (CM808).

backup wrench to hold union, torque

tube nut to 450 - 500 inch-pounds

(37).

Inspect engine connections for security

(50.84 - 56.49 Nm).

and proper routing.

Page 412

Revision 26

71-00-30

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

POWER PLANT

DESCRIPTION AND OPERATION

Power Plant Description

centrifugal flow compressor section, a

can-annular combustion section, a

(1).

MDHI 600N helicopter is powered by a

two-stage gas producer turbine section

250-C47M turboshaft engine manufac

and power and accessory gearbox. The

tured by the Allison Engine Company

gas producer geartrain drives the

Inc.

compressor, hydromechanical control

unit, fuel pump and internal pressure

(2).

The engine is secured in the helicopter

and scavenge oil pumps. An overrun

by three mount assemblies and ac

ning clutch, drive shaft, starter genera

cessed through two hinged air-sealed

tor, fuel, oil, drain and bleed air lines,

doors.

exhaust ducting, mounting and hoist

(3).

A belt-driven blower forces external

fittings and control levers adapt the

cooling air through strategically

engine to the helicopter.

positioned ducts that direct the air onto

(2). Allison Engine Operation and Mainte

engine exterior surfaces and through

nance Manuals are the primary

the engine and transmission oil cooler

information source for engine fault

heat exchangers. Spent cooling air is

isolation and maintenance data (Ref.

exhausted aft through an annular

Sec. 01-00-00). Refer to these manuals

opening between the engine exhaust

for specific engine maintenance proce

duct and fuselage.

dures.

(4).

Engine intake air may be filtered

(3). Starter operational limitations are in

through a standard screen or optional

the applicable Pilot's Flight Manual.

air particle separator assembly. Intake

air is drawn through a plenum chamber

and into the engine intake bell-mouth

3. Model 250−C47 Power Plant Fault

by the compressor. Engine compart

Isolation

ment air is separated from compressor

(Ref. Table 1)

intake air by a seal ring.

(1). Check engine support systems, i.e.; chip

(5).

The engine is equipped with a full

detectors, instruments, fuel supply,

authority digital engine control (FA

electrical systems, etc., to ensure that

DEC) system. A hydromechanical

helicopter equipment is functioning

control manual system is provided for

correctly before disassembling engine

backup if the electronic system fails.

systems for an indicated fault.

Power Plant Operation

(2). Inspect and isolate engine problems per

(1). The Allison 250-C47M turboshaft

the applicable Allison Engine Operation

engine consists of a single stage

and Maintenance Manual.

Table 1. Power Plant Fault Isolation

Symptom

Probable trouble

Corrective action

High frequency vibration (1)

Loose engine mount bolts

Retorque engine mount bolts to 100

− 140 inch−pounds (11.30 − 15.82

Nm).

NOTES:

(1) High frequency vibrations may be caused by other drive and rotor system components.

Page 1

71-00-47

Revision 22

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

P / J1202 IMS27466T25F2451

P1067A16

GCUI

GENERATOR CONTROL UNIT

P1203

P1068B16

POWER IN

32 1

P1203

(200 AMP GEN WIRING SHOWN)

P1053A16N

POWER GNDCURRENT

MIT

E38

P1055A22N

NEGATIVE SENLI

#3 CURRENT SENSE

GCU1A22N WHT

C G

#4 CURRENT SENSE

GCU1A22N ORN

GENERATOR SENSE

P1051A22

#2 CURRENT SENSE

P1052A22

P / J1201

#1 CURRENT SENSE

GCU1A22N BLU

W1250B22

GEN OUT LT.

FIELD

P1054A16

P1049A22

LINE CONTACTOR

S SENSE

P1050A22

P1069B22

GEN DISABBU

(369D24284-3)

AS301

BLU

P1125A22

WHT

CR204

TB1001

K308

FWD. LINE

CONTACT

P20003A10FEEDER

CR24

K1047B22

A2 A1

CR202

P1049C22

JUMPER

12 GA

CR2003

E37

P1048A22N

CB301

P1067A16

15A

JUMPER 16AWG

CB302

STARTER /

GENERATOR

JUMPER 22AWG

G300

P1063AON

E12

B C

P1059AO

P1065AO

P1063AO

P1060A22

K312

CR301

AFT LINE

CONTACTOR

P1066A22NE13

TB201-1

K1047A22

K1062A0

K1057B22

FADEC

P / J 113

K301

E38

CR33

START

START RELAY

RELAY

A B C

E13

S106

K1058A22N

START

SWITCH

TB200-7

J / P 112

ECU053A22N

1K1006D22

A B C D

2K1006D22

1K1006G22

S106

START SW.

ECU034B22

E F G H

2K1006G22

K1057A22

ECU035A22

J K L M

P1069B22

P1203-P

FROM AUTO RE-IGNITION RELAY

ECU049D22

N P R S

P1049B22

J1072B22

IGNITION

T W Y Z

P1060A22

K312-X1

FADEC

P1049A22

EXCITER

IGN RELAY

IGN.

J / P 1301

GAP

E13

GENERATOR / STARTER CIRCUIT

6G71-064-1

Figure 1. Starter/Generator System Wiring Diagram (Sheet 1 of 2)

Page 2

Revision 22

71-00-47

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

POWER PLANT

REMOVAL/INSTALLATION

1. Model 250−C47 Engine Replacement

(5). Loosen clamps and remove engine

cooling air ducts from engine compart

A. Engine Disconnecting for Removal

ment.

(6). Loosen clamps and remove compressor

(Ref. Figure 401 and Figure 402)

bleed hose from engine compartment.

After each opening, removal

(7). Detach engine electrical connections.

WARNING

or replacement of any part

of the engine and/or aircraft fuel sys

(a). Detach engine electrical harness

tem between the aircraft fuel tank and

connector.

the engine fuel nozzle, the fuel system

must be bled to remove trapped air.

(b). Detach electrical connections from

starter/generator.

Failure to comply with this procedure

can result in engine flameout or power

(c). Detach splice connector from fuel

loss.

filter bypass switch.

Cap fluid lines and fittings with

(8). Disconnect fuel inlet line at engine

CAUTION

approved devices. Do not use

mounted fuel pump.

tape to cover fuel and oil openings. Tape

adhesives loosened by fuel or oil can con

(9). Disconnect hydromechanical unit

taminate systems.

(HMU) vent line and drain line.

(10). Disconnect customer bleed air line at

(1). Set all switches OFF. Disconnect

firewall elbow.

external power. Disconnect battery (Ref.

Sec. 96-05-00).

(11). Disconnect torquemeter oil line at

firewall.

NOTE: Tag all hardware, wire terminals, fuel

and oil lines before removal to expedite in

(12). Disconnect oil pressure indicator line at

stallation. Identify and bag loose parts to

firewall.

prevent loss or damage.

(13). Disconnect engine control cable from

engine control box on HMU.

(2). Remove main transmission drive shaft

(Ref. Sec. 63-10-00).

The oil cooler is fragile. Unless

CAUTION

otherwise required, disconnect

(3). Remove engine exhaust duct (Ref. Sec.

oil supply and return lines only at engine.

78-30-00). Cover engine exhaust

Support oil cooler port boss with a backup

outlet.

wrench when oil line removal is required.

Do not strain or bend unsupported tubes.

(4). Loosen clamps and remove starter

cooling air duct from engine compart

(14). Disconnect engine oil inlet, outlet and

ment.

vent lines.

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

B. Removal of Disconnected Engine

transport and storage bar to engine

hoist fitting.

(Ref. Figure 401 and Figure 402)

C. Engine Installation in Mounts

Special Tools

(Ref. Figure 401 and Figure 402)

(Ref. Section 91−00−00)

Item

Nomenclature

Consumable Materials

ST401

Engine stand

(Ref. Section 91−00−00)

ST402

Engine hoist

Item

Nomenclature

CM702

Lockwire CRES

CAUTION

Special Tools

(Ref. Section 91−00−00)

D Do not remove engine mounts or disturb

Item

Nomenclature

engine mount adjustments to remove en

ST401

Engine stand

gine.

ST402

Engine hoist

D Engine to transmission alignment shall

be inspected whenever one or more en

gine mount assemblies is replaced or the

(1).

Open engine access doors.

existing alignment is disturbed. Do not

(2).

Position engine to line up engine hoist

disturb adjustable engine mount fittings

fitting under airframe hoist fitting.

unless an engine-transmission align

ment check is planned.

(3).

Remove detent pin from adjustable

support shaft on engine stand. Detach

(1). Install engine hoist tool (ST402)

transport and storage bar from engine

between engine hoist fitting and

hoist fitting.

airframe hoist fitting.

(4).

Install engine hoist (ST401) between

(2). Apply tension to engine with hoist and

airframe fitting and engine hoist

remove engine mount bolts.

fitting.

Do not use fuel or oil lines as

(5).

Apply tension to engine hoist to support

CAUTION

hand holds. Do not allow engine

engine. Unscrew engine stand adjust

to strike airframe while maneuvering it out

able support shaft.

of the helicopter.

(6).

Move engine to disengage fixed shaft.

(3). Align engine stand (ST401) under

Roll stand away from engine.

engine with adjustable support shaft on

left side.

CAUTION

(4). Slowly lower engine out of helicopter.

D Do not use tubes or hoses as hand holds.

Align engine side mount fittings

Do not allow engine to strike airframe or

between fixed and adjustable support

components. Avoid damaging engine in

shafts.

take bell.

(5). Screw in adjustable support shaft until

D Prevent FOD. Ensure that no foreign ob

engine mount fittings are securely

jects are in the engine plenum area.

engaged with support shaft sockets.

(7). Slowly raise engine while pushing back

(6). Insert detent pin through adjustable

of engine down to maintain correct

support shaft.

engine and transmission alignment.

(8). Align left and right engine mount

(7). Remove hoist from engine hoist fitting.

assemblies with engine mount fittings.

(8). If engine is to be stored or transported,

Install bolts and washers (Ref.

secure upper end of engine stand

Figure 403). Torque bolts to 220 - 360

Page 406

Revision 22

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

inch-pounds (24.85 - 40.66 Nm).

tube nut to 75 - 85 inch-pounds (8.47

Safety bolts with lockwire (CM702).

- 9.60 Nm).

(9).

Align hole in lower engine mount

(2). Connect oil pressure gauge line to

assembly with engine fitting. Install

bulkhead union on firewall. Torque tube

bolt, washers and nut. Torque nut to 95

nut to 75 - 85 inch-pounds (8.47 -

- 110 inch-pounds (10.73 - 12.43

9.60 Nm).

Nm).

(3). Connect engine oil vent line. Torque

(10).

Ensure inlet seal assembly contacts

hose nut to 230 - 260 inch-pounds

firewall around its entire circumfer

(25.98 - 29.36 Nm).

ence.

Do not bend oil return line.

CAUTION

(11).

Remove hoist from helicopter.

Bending loads are transferred to

oil cooler port and may fracture cooler.

(12).

Perform engine to transmission

alignment if applicable (Ref. CSP-

(4). Connect engine oil out line to elbow.

SRM-6, Section 53-30-00).

Torque hose nut to 230 - 260 inch-

pounds (25.98 - 29.36 Nm).

(13).

Using a mirror and light, check for

clearance between airframe and bleed

(5). Connect engine oil in line to union.

valve, any clearance is acceptable.

Torque hose nut to 460 - 500 inch-

pounds (51.96 - 56.48 Nm).

(14).

If bleed valve contacts firewall, readjust

engine mounts for clearance.

(6). Connect customer bleed air line to

elbow. Torque hose nut to 460 - 500

(a). Move engine back by adjusting the

inch-pounds (51.96 - 56.48 Nm).

left and right mounts, increasing the

top and decreasing the bottom.

(7). Connect engine fuel pump seal drain

line. Torque tube nut to 50 - 65 inch-

(b). Only make adjustments one flat at a

pounds (5.64 - 7.34 Nm).

time until bleed valve clears firewall.

NOTE: One flat will move the engine approxi

(8). Connect fuel inlet line to fuel pump.

mately 0.020 inch (0.508 mm) aft.

Torque hose nut to 230 - 260 inch-

pounds (25.98 - 29.36 Nm).

(c). Adjust lower mount to insure no

preload exists.

NOTE: Ensure burner drain valve and plug are

installed in combustion chamber with an O-

(d). Perform engine to transmission

ring on each part. Ensure drain valve is in

alignment if applicable (Ref. CSP-

the aft (lowest) position.

SRM-6, Section 53-30-00).

(9). Install combustion chamber drain line

D. Connecting an Installed Engine

on drain valve. Torque tube nut to 50 -

65 inch-pounds (5.64 - 7.34 Nm).

(Ref. Figure 401 and Figure 402)

(10). Attach engine electrical connectors.

Proper tightening of engine

WARNING

tubing connections is criti

(a). Attach engine electrical wire harness

cal to flight safety. Correct torque val

to to airframe connector at firewall.

ues must be used at all times. Excessive

torque on fuel or pneumatic sensing

(b). Attach fuel pressure bypass switch

system connections can result in crack

splice connector.

ing of the flare causing an air leak

which can cause flameout, power loss,

(c). Attach starter/generator electrical

or overspeed.

connections (Ref. Figure 403).

(1). Connect torquemeter indicator oil line

(11). Install main transmission drive shaft

to bulkhead union on firewall. Torque

(Ref. Sec. 63-10-00).

Page 407

71-00-47

Revision 36

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

STARTER / GENERATOR

(20). Inspect engine installation and connec

tions for proper routing and security.

2. Model 250−C47 Engine Stripping

P1063A0

(Ref. Figure 401)

Special Tools

K1062A

(Ref. Section 91−00−00)

P1061A

Item

Nomenclature

ST401

Engine stand

6G71-085

ST402

Engine hoist

Figure 403. Starter/Generator Electrical

Connections

Cap fluid lines and fittings with

CAUTION

approved devices. Do not use

(12). Install cooling air ducts and air duct

tape to cover fuel and oil openings. Tape

support bracket on airframe hoist

adhesives loosened by fuel or oil can con

fitting. Connect ducts and tighten

taminate systems.

clamps on firewall coupling and oil

NOTE: Discard all used O-ring packings.

cooler deflector.

(1). Remove engine control box from HMU.

(13). Install compressor bleed hose and

tighten clamps.

(2). Remove reducers from HMU.

(3). Remove starter/generator.

(14). Install starter cooling air duct and

tighten clamps.

Always support the weight of

CAUTION

the starter/generator during re

(15). Install exhaust duct (Ref. Sec. 78-00).

moval/installation. Damage can occur if

weight is supported by the shear shaft.

(16). Connect and rig engine control cable

(Ref. Chap. 76).

(a). Loosen V-clamp and remove starter/

generator.

After each opening, removal

(b). Remove bolts, washers, mounting

WARNING

or replacement of any part

flange and gasket.

of the engine and/or aircraft fuel sys

tem between the aircraft fuel tank and

(4). Remove oil vent line and associated

the engine fuel nozzle, the fuel system

hardware.

must be bled to remove trapped air.

(5). Remove fuel inlet fitting.

Failure to comply with this procedure

can result in engine flameout or power

(6). Remove unions from oil in port and oil

loss.

tank vent unions from gearcase.

(17). Perform fuel system bleed (Ref. Chap.

(7). Remove oil pressure tube, clamps and

28).

attaching hardware and reducer/snub

ber.

(18). Perform an engine deceleration check

(8). Remove torquemeter tube, clamps and

per the Pilot's Flight Manual.

attaching hardware and expander.

NOTE: Make engine adjustments per the Alli

(9). Remove customer bleed air line,

son Engine Operation and Maintenance

associated clamps and hardware and

Manual.

fitting.

(19). Perform an anti-icing system opera

(10). Remove N₁ and N₂ tachometer genera

tional check (Ref. Chap. 75).

tors and gaskets.

Page 408

Revision 29

71-00-47

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

(11). Remove hose, fuel pressure switch,

CAUTION

reducers, tee fitting and union from fuel

filter assembly.

D Prevent FOD. Inspect and clean all acces

sories and hardware prior to installing

(12). Remove engine air inlet bell and

parts on engine.

firewall inlet seal. Cover engine inlet.

D The gear case is magnesium alloy. Using

relatively high torque values applicable to

(13). Remove overrunning clutch and clutch

threaded fittings and fasteners in metals

firewall seal. Install cover on gear case.

other than magnesium may result in

stripped threads. Refer to Allison Engine

(14). Hoist engine and remove engine stand.

Maintenance Manual for additional fas

(15). Unbolt and remove engine mount

tener torque information.

fittings.

(b). Install engine hoist fitting and bolts.

Torque bolts to 140 - 160 inch-

(16). Install engine in shipping container.

pounds (15.81 - 18.07 Nm).

(17). Unbolt and remove hoist fitting.

(c). Install engine hoist tool (ST402)

between engine hoist fitting and

3. Model 250−C47 Engine Buildup

airframe hoist fitting.

(d). Raise engine off shipping container

(Ref. Figure 401)

base.

Proper tightening of engine

(2). Inspect engine as follows:

WARNING

tubing connections is criti

(a). If shipping container moisture

cal to flight safety. Correct torque val

indicator was other than a light blue

ues must be used at all times. Excessive

color, examine engine for corrosion.

torque on fuel or pneumatic sensing

Perform corrosion corrective mainte

system connections can result in crack

nance per Allison Operation and

ing of the flare causing an air leak

Maintenance Manual as required.

which can cause flameout, power loss,

or overspeed.

(b). Inlet guide vanes for damage.

(c). Exhaust and inlet openings for FOD.

Consumable Materials

(d). Install covers over intake and

(Ref. Section 91−00−00)

exhaust ports.

Item

Nomenclature

CM111

Grease, aircraft

(e). All fasteners for security, slippage

marks for alignment, potting com

CM126

Oil, turbine

pound and, or correctly installed

CM702

Lockwire CRES

lockwire where applicable.

(f). Tubes and hoses for damage.

Special Tools

(Ref. Section 91−00−00)

(3). Record engine serial number and

Item

Nomenclature

start-counter reading in appropriate

ST401

Engine stand

log.

ST402

Engine hoist

Prevent damage to machined

CAUTION

surfaces and contamination. Re

move covers from engine one at a time as re

(1). Prepare engine for buildup as follows:

quired by the installation sequence.

(a). Review Allison instructions for

(4). Install engine mount fittings with bolts

removing engine from shipping

and washers. Torque bolts to 140 - 160

container in Allison Operation and

inch-pounds (15.81 - 18.07 Nm).

Maintenance Manual.

Safety bolts with lockwire (CM702).

Page 409

71-00-47

Revision 29

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

(5). Install engine in engine stand (ST401).

(8). Install expander with O-ring on

existing engine torquemeter line fitting.

(6). Install clutch assembly.

Torque expander to 50 - 70 inch-

pounds (5.64 - 7.90 Nm).

(a). Remove engine power take off pad

cover from aft side of engine gearbox

(9). Install engine oil tank vent line.

and protective cover from forward

(a). Install union with O-ring in engine

side of engine gearbox.

gearcase oil tank vent port. Torque

union to 280 - 305 inch-pounds

(b). Lubricate clutch assembly and

(31.62 - 34.45 Nm).

engine power output shaft splines

before assembly. Pack all voids and

(b). Install oil tank vent tube on union.

gaps with grease (CM111).

Torque tube nut to 230 - 260 inch-

pounds (25.98 - 29.36 Nm).

(c). Install clutch assembly with angle,

(c). Install union on oil tank vent tube.

washers and nuts. Torque nuts to 50

Torque union to 230 - 260 inch-

- 70 inch-pounds (5.64 - 7.90 Nm).

pounds (25.98 - 29.36 Nm).

Use caution when installing bolt

CAUTION

(d). Install vent hose on union. Torque

to avoid cutting O-ring. Liberal

hose nut to 230 - 260 inch-pounds

ly coat O-ring with grease and install with

(25.98 - 29.36 Nm).

twisting motion.

(10). Install union with O-ring in engine

NOTE: Use new O-ring packings and gaskets

gearcase oil inlet port. Torque union to

on all installations where the parts are re

550 - 600 inch-pounds (62.12 - 67.77

quired. Lubricate O-rings with clean sys

Nm).

tem fluids prior to installation.

(11). Install customer bleed air line.

(d). Lubricate O-rings with grease

(a). Install customer bleed air fitting with

(CM111) and install on bolt. Install

engine supplied gasket, washers and

bolt in aft end of engine power output

engine supplied bolts. Torque bolts to

shaft. Thread bolt into clutch shaft

20 - 25 inch-pounds (2.25 - 2.82

and torque bolt to 250 - 300 inch-

Nm). Safety bolts with lockwire

pounds (28.24 - 33.88 Nm).

(CM702).

(e). Reinstall engine power take off pad

(b). Install bleed hose assembly on bleed

cover. Torque nuts to 50 - 70 inch-

air fitting. Torque hose assembly to

pounds (5.64 - 7.90 Nm).

230 - 260 inch-pounds (25.98 -

29.36 Nm). Clamp line to strap

NOTE: Install firewall seal with split at 6

attached to inlet bell mount bolt.

O'clock position.

(12). Install fuel switch.

(f). Install seal at end of clutch assembly

(a). Install union with O-ring in fuel

with washers and screws. Torque

filter housing. Torque union to 95 -

screws to 15 - 20 inch pounds (1.69

105 inch-pounds (10.73 - 11.86

- 2.25 Nm).

Nm).

To avoid contamination of en

(b). Install tee on union with O-ring and

CAUTION

gine oil system, inspect reducer

jam nut. Torque jam nut to 38 - 42

and snubber bores for metal shavings and

inch-pounds (4.29 - 4.74 Nm).

debris.

(c). Install reducer with O-ring on end of

tee. Torque reducer to 95 - 105

(7). Install engine oil pressure snubber,

inch-pounds (10.73 - 11.86 Nm).

reducer and O-ring on engine gearbox.

Connect oil pressure tube to snubber.

(d). Install union with O-ring on 90

Torque tube nut to 20 - 30 inch-

degree fitting of tee. Torque restrictor

pounds (2.25 - 3.38 Nm). Clamp tube

to 95 - 105 inch-pounds (10.73 -

to existing engine line.

11.86 Nm).

Page 410

Revision 29

71-00-47

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

(e). Install fuel switch with O-ring on

(c). Tap around clamp with a rawhide

reducer. Torque switch to 65 - 75

mallet to seat clamp on flange.

inch-pounds (7.34 - 8.47 Nm).

Retorque clamp nut to 50 inch-

pounds (5.64 Nm).

(f). Install reducer with O-ring in fuel

(d). Continue tapping around clamp and

filter housing. Torque reducer to 95 -

retorquing clamp nut until nut no

105 inch-pounds (10.73 - 11.86

longer turns when specified torque is

Nm).

applied.

(g). Install hose between fuel switch and

(15). Install engine control box on HMU.

reducer. Torque hose nuts to 20 - 30

(a). Hold engine control box in position

inch-pounds (2.25 - 3.38 Nm).

against HMU.

(13). Install inlet bell and inlet seal with

(b). Insert 0.1535-0.1545 inch

bolts, washers and nuts. Torque nuts to

(3.8989-3.9243 mm) rig pin (#23 drill

60 - 85 inch-pounds (6.77 - 9.60

blank) through engine control box,

Nm).

indexed HMU pointer and into HMU.

(c). Rotate serrated washer on shaft for

(14). Install starter/generator.

micro-adjustment until rig pin

inserts without interference.

Always support the weight of

CAUTION

the starter/generator during re

(d). Install mounting bolts, washers and

moval/installation. Damage can occur if

use shim washers as required

weight is supported by the shear shaft.

between engine control box and HMU

to prevent binding on rig pin. Torque

(a). Remove starter/generator pad cover.

bolts to 36 - 46 inch-pounds (4.06 -

Install starter/generator mount with

5.19 Nm).

gasket, washers and nuts. Torque

(e). Check rig pin fit again and repeat

nuts to 100 - 140 inch-pounds

previous steps as required.

(11.29 - 15.81 Nm).

(16). Install reducers with O-rings on HMU.

(b). Install starter/generator with V-

Torque reducers to 550 - 600 inch-

clamp. Torque clamp nut to 50

pounds (62.12 - 67.77 Nm) and 50 -

inch-pounds (5.64 Nm).

55 inch-pounds (5.64 - 6.21 Nm).

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MAINTENANCE MANUAL

ENGINE AIR INTAKE SYSTEM

MAINTENANCE PRACTICES

Description and Operation

intake air from accumulating in the

plenum chamber cavity.

(1).

The engine air intake system consists of

an air inlet screen, plenum chamber,

2. Air Inlet Screen Replacement

engine inlet bell, engine inlet firewall

A. Air Inlet Screen Removal (369D/E/FF −

seal, and engine firewall seal ring.

500N)

(2).

Air enters the inlet fairing, passes

(Ref. Figure 201)

through the inlet screen, plenum

chamber and air inlet bell into the

NOTE: The following procedures are to be used

engine compressor.

for all MDHI model helicopters. The differ

ent steps are noted for the 500N installa

(3).

The engine inlet screen assembly is

tion.

made of a lightweight 1/4 inch (6.35

mm) mesh metal screen material

(1). Remove engine air inlet forward

secured to a metal frame along its outer

fairings (Ref. Sec. 53-30-00/30).

edge. The engine air particle separator

option, when installed, replaces the

(2). Open plenum chamber bypass door.

inlet screen.

(3). Install a suitable cover over engine air

inlet bell though bypass door opening.

(4).

The inlet screen edge is 1-1/2 inches

(3.81 cm) from the top of air inlet

(4). On 500N installation, remove the

fairing to provide an intake air-bypass

engine plenum fairing attachment

area in the event that debris clogs the

hardware, open bypass door and

screen. The firewall seal separates

remove fairing assembly.

plenum chamber intake air from engine

compartment air.

Avoid FOD. Cover compressor

CAUTION

inlet prior to working in plenum

(5).

A differential pressure switch is

chamber. Vacuum all FOD debris out of ple

mounted with a reference to both sides

num chamber before removing protective

of the engine inlet screen. Blockage of

cover from engine inlet bell. Severe damage

the inlet screen will cause a pressure

to engine may result from entry of foreign

decrease on the engine plenum side and

objects.

the switch will activate a warning light

in the cockpit.

(5). Remove clamps or tie-down straps

securing tail rotor control rod boot to

(6).

A cable from the cockpit is manually

inlet screen fairing.

operated to open a bypass door which

(6). Disconnect Sta. 120.00 tail rotor control

allows unfiltered air into the engine

rod forward end. (Ref. Chap. 67).

inlet plenum if the engine inlet screen

is blocked.

(7). On 500N disconnect the intermediate

anti torque tube forward end. (Ref. Sec.

(7).

The molded nylon air inlet bell is

67-20-30).

retained on its mounting flange with

three flat springs and is required to

(8). Remove blower air inlet screen (Ref.

smooth air flow into the compressor.

Figure 201).

(8).

A plenum chamber drain system

(9). Remove attaching hardware and engine

prevents water condensed out of engine

air inlet screen.

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MAINTENANCE MANUAL

B. Engine Inlet Screen Removal (600N)

4. Firewall Seal Removal

(Ref. Figure 201)

(Ref. Figure 202)

(1). Remove screws, washers and inlet

screen from inlet frame.

Consumable Materials

(Ref. Section 91−00−00)

C. Air Inlet Screen Installation (369D/E/FF −

Item

Nomenclature

500N)

CM219

Methyl-ethyl-ketone

CM411

Adhesive, epoxy

(Ref. Figure 201)

Vacuum all FOD debris out of

CAUTION

(1). Remove engine.

plenum chamber before remov

ing protective cover from engine inlet bell.

(2). Pull seal from firewall.

Severe damage to engine may result from

entry of foreign objects.

Use Methyl ethyl ketone

WARNING

(MEK) in a well ventilated

(1). Install engine air inlet screen in reverse

area and away from heat and flame.

order of removal.

(3). Remove seal debris from firewall with a

D. Engine Inlet Screen Installation (600N)

wooden or plastic scraper.

(Ref. Figure 201)

(4). Remove residue from firewall with

(1). Install inlet screen on inlet frame with

MEK (CM219).

washers and screws. Torque screws to

20 - 25 inch-pounds (2.25 - 2.82

(5). Apply adhesive (CM411) to installation

Nm).

per manufacturers instructions. Center

seal over firewall opening and bond in

3. Air Inlet Bell Replacement

place.

A. Air Inlet Bell Removal

(6). Install engine.

(Ref. Figure 202)

5. Air Intake System Inspection

(1). Remove engine.

(1). Inspect air inlet screen for security,

deformation,inspect screen for cleanli

(2). Remove attaching hardware, air inlet

ness, clogged areas and foreign particle

bell and firewall seal ring.

accumulation. (Cleaning of engine air

inlet screens Ref. Sec. 20-20-00).

(3). Remove firewall seal ring from inlet

bell.

(2). Inspect screen for tears, cuts, breaks

and missing pieces.

B. Air Inlet Bell Installation

(3). Inspect anti-torque control rod boot for

(Ref. Figure 202)

condition and secure attachment (Ref.

(1). Model 250-C20B Only:

Chap. 67).

On early installations; attach firewall

(4). Inspect air inlet bell for cracks, breaks

seal ring to inlet bell by lifting and

and missing pieces. No cracks or

positioning leaf springs over bell flange.

missing pieces allowed.

(2). Position engine air inlet bell and seal

assembly on compressor inlet mounting

(5). Model 250-C20B Only:

flange and secure.

On early installations; inspect engine

firewall seal ring for cracked or weak

(3). Install engine.

springs.

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MAINTENANCE MANUAL

(6). Inspect engine-to-firewall seal ring at

6. Firewall Seal Ring Repair

the firewall for cracks, corrosion or

Replace damaged or broken springs on early

damage preventing a positive and

installations.

complete seal. Repair or replace seal

installation as required.

7. Air Inlet Bell Repair

(7). Inspect air inlet-to-firewall seal for

Engine air inlet bell repairs are not autho

cracks, corrosion or damage preventing

rized; replace a defective bell.

a positive and complete seal. Repair or

replace seal installation as required.

8. Plenum Chamber Drain Tube Replacement

(Ref. Figure 203)

(8). Inspect plenum chamber drain tubing

for deformation and corrosion. Ensure

(1). Replace drain tubing using standard

drain is open.

practices and procedures.

PLENUM CHAMBER

DRAIN TUBE

FIREWALL FITTING

FIREWALL

LOCKWIRE

FIREWALL

NYLON TWINE

DRAIN TUBE ATTACHMENT

GROMMET

G71-1022

Figure 203. Drain System

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CSP-HMI-2

MAINTENANCE MANUAL

ENGINE COMPRESSOR WATER WASH KIT

MAINTENANCE PRACTICES

1. Engine Compressor Water Wash Kit

2. Engine Compressor Water Wash Kit

Maintenance

Inspection

(1). Inspect hoses for chafing, damage and

deterioration.

Replace hoses, clamps and other hardware

only when necessary.

(2). Inspect all clamps for damage and

security.

(3). Inspect elbow for damage and security.

Whenever working in the en

CAUTION

gine plenum area, cover engine

(4). Inspect spray assembly for loose rivets,

with cardboard or other suitable object to

secure hose and clamp, no damage to

prevent foreign objects from entering en

grommet and silicone sealant around

gine.

tube intact.

(5). Inspect all mounting brackets for loose

rivets.

(1). Remove appropriate access panels to

gain access to area of water wash kit to

(6). Inspect lanyard for security and

be worked on.

damage; cap installed.

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HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369D/E/FF-500/600N HELICOPTERS (ISSUED: 1990) - page 27