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

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

ENGINE ANTI−ICING SYSTEM

MAINTENANCE PRACTICES

Engine Anti−Icing System Description and

handle in both ON and OFF positions.

Operation

There is no intermediate heat position.

(1). Compressor inlet guide vanes and the

(3). Model 250-C20/R2, 250-C30 and

front bearing hub are the only compo

250-C47 Engines: The engine installa

nents supplied anti-icing air on the

tions use an electrically controlled

helicopter engines.

anti-ice system. Compressor bleed air,

supplied to the inlet guide vanes and

the number one bearing housing, is

(2). Model 250-C20B Engines: The anti-ice

controlled by the ANTI-ICE circuit

system consist of a manually operated

breaker/switch, CB143 on the 369FF -

push-pull control cable, mechanical

500/600N, and CB122 on 369D/E

anti-icing valve, air distribution tubing

helicopters fitted with a 250-C20/R2

and, attaching hardware. The poppet-

engine. Moving the console mounted

type anti-icing valve is mounted on the

switch to ANTI-ICE de-energizes a

engine compressor scroll and controls

solenoid fastened to the engine heat

compressor bleed air used for engine

shield that controls the anti-icing

anti-icing. The control cable is as

system.

sembled of rigid and flexible sections

clamped along the right side of the

(4). Refer to the applicable Allison engine

overhead cabin heat duct. Moving the

manual for additional engine anti-ice

control handle forward opens the

information.

anti-icing valve. Control handle travel

is approximately 1.44 inches (3.66 cm)

from OFF to ON. A detent holds the

2. Engine Anti−Icing System Fault Isolation

Table 201. 250−C20B Engine Anti−icing System Fault Isolation

Symptom

Probable Trouble

Corrective Action

Anti−ice ON does not restore

System not rigged correctly.

Check rigging.

normal engine operation when

compressor icing occurs.

Lack of anti−icing air.

Defective anti−ice air lines.

Check engine air lines for leaks.

Anti−icing air valve stuck closed.

Replace valve.

Cable wire sheared.

Replace cable.

Cable clevis pin sheared or

Replace clevis pin.

missing.

Anti−ice OFF has no effect. Inflight

Anti−icing air valve stuck open.

Replace valve.

symptom is continuation of

Corroded, pinched or crushed

Replace cable.

approximately 10% reduction in

cable.

available power or torque.

Cable clevis pin sheared or

Replace clevis pin.

missing.

Cable wire sheared.

Replace cable.

Anti−ice air valve compres-

Loosen adapter nut. Torque nut to 10

sor scroll adapter nut

inch−pounds (1.13 Nm).

over−tightened.

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

Table 201. 250−C20B Engine Anti−icing System Fault Isolation

Symptom

Probable Trouble

Corrective Action

Anti−icing control drags or binds.

Control cable rigid sleeve kinked.

Check operation with cable clevis

One or more flexible cable section

disconnected from anti−ice valve lever.

bend radii less than 3 inch (7.62

Replace kinked or corroded cable.

cm) minimum.

Increase flexible cable bend radius.

Control handle creeps open or

ON−OFF detent−spring weak or

Replace detent−spring assembly.

closed.

broken.

Handle detent grooves worn or

Clean, repair or replace cable.

dirty.

Table 202. 250−C20/R2, 250−C30 and 250−C47 Engine Anti−icing System Fault Isolation

Symptom

Probable Trouble

Corrective Action

System ON fails to restore normal

Lack of anti−icing air.

Inspect air lines for leaks.

engine operation in compressor

Inoperative/defective anti−icing valve. Replace valve.

icing conditions.

Faulty switch or wiring.

Repair or replace switch/wiring as

required.

Switching anti−ice OFF has no

Anti−icing air valve stuck open.

Replace valve.

effect. Inflight symptom is

continuation of approximately 10%

reduction in available power or

torque.

250−C20B Engine Anti−Icing Valve

B. 250−C20B Engine Anti−Icing Valve

Control Cable Replacement

Control Cable Installation

Consumable Materials

A. 250−C20B Engine Anti−Icing Valve

(Ref. Section 91−00−00)

Control Cable Removal

Item

Nomenclature

CM430

Sealant, solvent resistant

(1). Open engine access doors.

CM707

Tape, fastener

(2). Remove right half of engine air inlet

Do not kink cable rigid sleeve

CAUTION

forward fairing.

section.

(1). Position bulkhead hole grommet on

(3). Remove heater duct outer box attaching

rigid sleeve section.

hardware.

(2). Install Velcro tape (CM707) on mating

surfaces of forward clamp, and block.

(4). Remove clamps and straps attaching

(3). Route cable assembly through bulk

the control cable to structure.

head, flexible cable bend radius shall

be, not less than 3.00 inches (7.62 cm),

minimum.

(5). Remove valve lever cable clevis attach

ing hardware.

NOTE: Check valve lever travel before tighten

ing clamp nearest anti-icing valve.

(6). Remove the heater duct box, and

(4). Install cable clamps, straps, and

control cable.

attaching hardware.

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

P9J

CB122

SP888

P307

Q516G20

Q516F20

Q516E20

ANTI-ICE

SOLENOID

VALVE

P535F20N

E12

G75−1002

Figure 201. 250−C20/R2, 250−C30 and 250−C47 Engine Anti−Icing System Wiring

(5). Perform an anti-icing system opera

(15). Install right half of engine air inlet

tional check.

forward fairing.

(a). Determine that control operates

(16). Close and latch engine access doors.

valve through full range of travel

250−C20/R2, 250−C30 and 250−C47

from ON to OFF.

Engine Anti−Icing System Controls

(6). Secure clamp nearest anti-icing valve.

Replacement

(7). Apply sealant (CM430) around engine

(1). Refer to the applicable Allison Mainte

side of air inlet pan cable hole (Ref.

nance and Operation Manual for

Figure 202).

anti-ice system maintenance instruc

tions (Ref. Sec. 01-00-00).

(8). Move anti-ice handle to OFF. Ensure

(2). Refer to Figure 201 for airframe wiring.

handle is locked in OFF position by

detent.

250−C20B Engine Anti−Icing System

(9). Move engine anti-ice valve lever to the

Inspection

closed position (poppet plunger down).

(1). Inspect anti-ice system controls as

follows:

(10). Loosen cable clevis jamnut.

(a). Controls for freedom of movement,

NOTE: Do not push, or pull actuator cable to

and control handle detent-spring for

get lever-arm and clevis-pin hole align

positive lock.

ment.

(2). Isolate stiff control operation problems

(a). Screw clevis up or down cable

as follows:

end-fitting threads to align cable

clevis with valve lever-arm pin holes.

(a). Disconnect cable clevis from valve

lever. Check for binding as control

(b). Check hole alignment by inserting

lever is moved from ON to OFF.

clevis pin. Remove pin.

1). If control binds, inspect flexible

(c). Extend cable length by 1 to 2 full

cable length for bend radii less

counterclockwise turns of clevis.

than the three inch minimum.

Look for kinks, a crushed outer

(11). Install clevis-pin, washer, and cotter-

sleeve, and corrosion.

pin.

2). Inspect rigid cable section for

(12). Tighten clevis jamnut.

corrosion, kinks, and dents.

(13). Install heat duct outer box.

3). Repair or replace damaged cable.

(14). Adjust handle position parallel to

(3). Inspect anti-icing valve lever assembly

windshield glass using handle set

for wear, lost motion, and freedom of

screw, as required.

movement.

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MD Helicopters, Inc.

MAINTENANCE MANUAL

(4). Repair or replace system components as

1). Valve lever is at forward travel

required.

limit (valve closed).

250−C20/R2, 250−C30 and 250−C47

(3). Adjust cable to correct insufficient

Engine Anti−Icing System Inspection

anti-icing valve lever travel or cable

distortion.

(1). Inspect solenoid valve for secure

attachment.

NOTE: Check that poppet guide, and lever as

sembly are parallel with top of engine (Ref.

(2). Check wire insulation for abrasion, and

Figure 202, view B).

connections for security. Repair as

required.

250−C20/R2, 250−C30 and 250−C47

(3). Inspect tubes for cracks, and connec

Engines Anti−Icing System Test

tions for security.

(1). Perform anti-icing system test per the

250−C20B Engine Anti−Icing System Test

appropriate Pilot's Flight Manual (Ref.

Sec. 01-00-00).

(1). Test system operation as follows:

(a). Pull control handle ON.

250−C20B Engine Anti−Icing System

Control Cable Repair

(b). Check control detent locks handle in

ON position and does not creep

(1). The control cable assembly is normally

toward OFF.

replaced as a unit. However, disassem

bly to the extent shown in the illustra

(c). In engine compartment, check

tions can be accomplished for inspection

anti-icing air valve as follows:

purposes (Ref. Figure 202). No repairs

1). Valve lever is at aft travel limit

are recommended except for replace

(valve open), and cable is not

ment of lever mechanism parts.

distorted by overdrive.

10. 250−C20/R2, 250−C30 and 250−C47

(2). Return control handle to OFF position.

Engine Anti−Icing Valve Repair

(a). Check control detent locks handle in

(Ref. Figure 203)

OFF position and does not creep

toward ON.

(1). Repair or replace engine anti-icing

(b). In engine compartment, check

valve per Allison Engine Operation and

anti-icing valve position:

Maintenance Manual.

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

FLEXIBLE SLEEVE

NYLON STRAP

(TYP)

GROMMET

(TYP)

RIGID SLEEVE

CONTROL HANDLE

INSTALLATION

2 PLCS

RIGID SLEEVE

HANDLE

SETSCREW

1 PLS

TAPE

(NOTE 2)

CONTROL HANDLE

HANDLE DETENT

CANOPY FRAME

SPRING

CLEVIS ATTACHING

POINT

FLEXIBLE SLEEVE

PLENUM CHAMBER

CABLE SPLICE

120°

AIR INLET PAN

CABLE SUPPORT

RIGID TUBING

ANTI-ICING VALVE

BLOCK (3 PLCS)

OUTER BOX

6 PLCS

NOTE 1

OPEN

HEAT DUCT

MOUNTING

SCREW

CLOSED

VERTICAL CENTERLINE OF

LEVER ASSY

ENGINE (LOOKING AFT)

CABLE CLEVIS

ANTI-ICING VALVE

INSTALLATION ANGLE

POPPET VALVE

(ANTI-ICING VALVE)

CONTROL CABLE TO

VALVE ATTACHMENT

NOTE:

SEAL HOLE ON ENGINE SIDE OF PAN WITH ADHESIVE.

APPLY VELCRO TAPE TO FORWARD BLOCK AND CLAMP

MATING SURFACES.

G75-1000

Figure 202. 250−C20B Engine Anti−Icing System

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Revision 22

MD Helicopters, Inc.

CSP−HMI−2

MAINTENANCE MANUAL

TABLE OF CONTENTS

Para/Figure/Table

Title

Page

76-00-00 Engine Power Controls (250-C20B, 250-C20R/2 and 250-C30)

Description and Operation

1. Engine Power Controls Description and Operation

A. Power Turbine Governor Controls

B. Power Turbine Governor Trim Actuator

C. Gas Producer Controls

D. Rigging

Figure 1. Engine Control Systems

Fault Isolation

101

1. Engine Power Controls Fault Isolation

101

Table 101. Engine Control Fault Isolation

101

Figure 101. N2 Trim Actuator Wiring Schematic

102

76-10-00 Power Turbine Governor Controls (250-C20B, 250-C20R/2

and 250-C30)

Maintenance Practices

201

Engine Governor Control Rigging

201

Figure 201. Power Turbine Governor Controls Rigging

203

Governor Lever Pointer Rigging for 250-C20B (P/N 2524769-10 and Prior)

204

Figure 202. Power Turbine Governor Adjustments (P/N 2524769-10 and Prior)

205

Governor Lever Pointer Rigging for 250-C20B / -C20R2 (P/N 2524769-11, -12)

206

Figure 203. Power Turbine Governor Adjustments (P/N 2524769-11, -12)

207

Governor Lever Pointer Rigging for 250-C20B / -C20R/2 (P/N 2524667-13)

208

Figure 204. Power Turbine Governor Adjustments (P/N 2524667-13)

209

Governor Lever Pointer Rigging for 250-C20B (P/N 2524667-14 and Higher,

P/N 2524769-13 and Higher and P/N 2549170-1 and Higher)

210

Figure 205. Power Turbine Governor Adjustments (P/N 2524667-14 and Higher,

P/N 2524769-13 and Higher and P/N 2549170-1 and Higher

on 250-C20B Engine)

211

Governor Lever Pointer Rigging for 250-C20R/2 (P/N 2524667-14 and Higher,

P/N 2524769-13 and Higher and P/N 2549170-1 and Higher)

212

Figure 206. Power Turbine Governor Adjustments (P/N 2524667-14 and Higher,

P/N 2524769-13 and Higher and P/N 2549170-1 and Higher

on 250-C20R/2 Engine)

213

Governor Lever Pointer Rigging for 250-C30

214

Figure 207. Power Turbine Governor Adjustments (250-C30 Engine)

215

Governor Controls Final Check and Adjustment (250-C20B, -C20R/2)

216

Governor Controls Final Check and Adjustment (250-C30)

217

Page i

76 Contents

Revision 44

CSP−HMI−2

MD Helicopters, Inc.

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

10. Governor Controls Replacement

218

11. Control Rod Inspection

218

12. Bellcrank Inspection

219

13. Droop Compensation Link Inspection

219

14. Droop Control Override Link Repair

219

Figure 208. Power Turbine Governor Controls (Sheet 1 of 2)

220

15. Control Rod Repair

222

16. Bellcrank and Support Fitting Repair

222

17. N2 Trim Actuator Test

222

Figure 209. N2 Trim Actuator Test Hookup

223

18. N2 Trim Actuator Repair

223

19. Sta. 68.00 Bellcrank Rework, P/N 369A7717-3 and 369N2606 Only

223

Figure 210. Station 68.00 Bellcrank Rework

224

76-20-00 Gas Producer Controls (250-C20B, 250-C20R/2 and 250-C30)

Maintenance Practices

201

1. Gas Producer Controls Rigging (250-C20B and 250-C20R/2)

201

2. Gas Producer Controls Rigging (250-C30)

203

Figure 201. Gas Producer Controls Rigging (Sheet 1 of 3)

204

A. Gas Producer Fuel Control De-richment Valve Adjustment

210

B. Power Controls Operational Test/Final Adjustments

210

3. Gas Producer Controls Linkage Replacement

210

4. Sta. 124.00 Support Fitting Replacement

210

A. Sta. 124.00 Support Fitting Removal

210

B. Sta. 124.00 Support Fitting Installation

210

5. Gas Producer Controls Inspection

211

6. Gas Producer Control Rod Repair

211

7. Bellcrank Repair

212

Figure 202. Gas Producer Controls Replacement

213

76-47-00 Engine Power Controls (250-C47)

Maintenance Practices

201

1. Engine Controls Description

201

2. Engine Controls Operation

201

3. Engine Controls Fault Isolation

201

Table 201. Engine Controls Fault Isolation

201

Figure 201. Engine Control Unit Wiring Diagram (Sheet 1 of 2)

202

4. ECU (Electronic Control Unit) Replacement

204

Page ii

TR12−001

76 Contents

MD Helicopters, Inc.

CSP−HMI−2

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

A. ECU Removal

204

B. ECU Installation

204

Engine Control Potentiometer Replacement

204

A. Collective Potentiometer Removal

204

B. Collective Potentiometer Installation

204

C. Directional Potentiometer Removal

205

D. Directional Potentiometer Installation

205

CIT (Compressor Inlet Temperature) Sensor Replacement

206

A. CIT Sensor Removal

206

B. CIT Sensor Installation

206

Engine Control Box Replacement

206

A. Engine Control Box Removal

206

B. Engine Control Box Installation

206

Engine Control Cable Replacement

206

A. Engine Control Cable Removal

206

B. Engine Control Cable Installation

207

Figure 202. Engine Controls Installation (Sheet 1 of 2)

208

Engine Throttle Control Cable Mounting Bracket Replacement

210

A. Engine Throttle Control Cable Mounting Bracket Removal

210

B. Engine Throttle Control Cable Mounting Bracket Installation

210

10. Engine Control Cable Rigging

210

11. Engine Controls Inspection

210

Figure 203. Engine Control Cable Rigging

211

12. Engine Control Cable Shipping and Handling

211

A. Control Cable Removal From Shipping Box

211

Figure 204. Effective Bend Angle

212

B. Control Cable Installation into Shipping Box

212

Page iii

76 Contents

TR12−001

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

ENGINE POWER CONTROLS

DESCRIPTION AND OPERATION

Engine Power Controls Description and

train driving a ram equipped with an

Operation

adjustable rod-end. The actuator,

operated by an N₂

trim (beep) switch on

(1).

The engine control system consists of

the collective pitch stick, moves gover

gas producer (N₁) throttle controls and

nor linkage that varies engine N₂ speed

power turbine (N₂) governor controls.

from 94 to 105% rpm. Operating stroke

The throttle twist grip mechanically

of the actuator ram is approximately

actuates a lever on the gas producer

1.00 inch (2.54 cm); speed is 0.15 inch

fuel control that establishes a base line

(3.81 mm) per second; travel time from

from which the unit schedules metered

full retraction to full extension is

fuel to the gas producer portion of the

approximately 7 seconds. The actuator

engine. An electrically operated trim

is lubricated when manufactured and

actuator and mechanical rpm droop

requires no further lubrication service.

compensator in the main rotor collec

tive pitch control mechanism changes

C. Gas Producer Controls

power turbine governor lever position

when collective is increased or reduced

(1). The gas producer portion of the engine

and when N₂ speed increase or decrease

is controlled by the pilot's throttle twist

is commanded with the beep switch on

grip which effects gas producer fuel

the collective stick. Either, or both

control lever position through a system

actions regulate power output by

of torque tubes, gears, push-rods,

biassing the gas producer fuel control to

bellcranks, bellcrank support fittings,

increase or decrease fuel flow to

levers and attaching hardware (Ref.

compensate for rotor system torque

Figure 1).

requirements.

(2).

Refer to the applicable Allison Engine

(2). Refer to Allison Engine Operation and

Operation and Maintenance Manual for

Maintenance Manual for engine fuel

additional engine fuel system theory,

system theory, operation and mainte

operation and maintenance data.

nance data.

A. Power Turbine Governor Controls

D. Rigging

(1). Power turbine governor (N₂) controls

include the N₂ trim actuator controlled

(1). Rig engine control system prior to the

by the beep switch on the pilot's

next flight when engine operation

collective stick. Governor trim droop

reveals a rigging problem, or after

control override components and

replacing any system component.

linkages are installed within the pilot's

seat structure. A fuselage routed

NOTE: Perform a deceleration time check per

control rod assembly, engine compart

pilot's flight manual after rigging and test

ment linkages, bellcranks and supports

ing power turbine controls. Refer to Allison

transfer motion to the power turbine

Operation and Maintenance Manual for ad

governor. A droop control override

justment procedures if deceleration time is

spring compensates for over-travel in

less than allowable minimum.

maximum collective pitch/speed

conditions.

(2). Rig gas producer controls per (Ref. Sec.

76-20-00).

B. Power Turbine Governor Trim Actuator

(1). The actuator consists of a reversible

(3). Rig power turbine governor controls per

continuous duty 26Vdc motor and gear

(Ref. Sec. 76-10-00).

Page 1

76-00-00

Revision 22

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

ENGINE POWER CONTROLS

FAULT ISOLATION

1. Engine Power Controls Fault Isolation

Table 101. Engine Control Fault Isolation

Symptom

Probable Trouble

Corrective Action

Throttle movement springy;

Lost motion; gas producer

Tighten torque tube pipe plug for

response lags behind control

interconnect torque tube loose in

zero backlash.

movement.

collective stick gear shafts.

Worn rod−ends; worn bellcrank

Replace worn parts.

bearings.

Stiff control action.

Rod−ends binding/jammed.

Realign rod−end bearings to

eliminate jamming.

Low power; improper idling speed;

Incorrectly adjusted gas producer

Adjust gas producer or power turbine

improper acceleration; variable

or power turbine governor controls.

governor controls for correct

power output at constant setting.

operation.

Defective gas producer or power

Replace faulty unit per Allison

turbine governor assembly.

Engine Operation and Maintenance

Manual.

Stagnated or hot engine starts.

Fuel control derichment valve out

Adjust derichment valve.

of adjustment.

Excessive TOT readings during

Engine controls out of adjustment. Adjust engine controls per the

engine shutdown.

applicable Allison manual.

Fuel cut−off valve not closing.

Adjust, repair or replace gas

producer control per Allison manual.

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

POWER TURBINE GOVERNOR CONTROLS

MAINTENANCE PRACTICES

1. Engine Governor Control Rigging

D 250-C30 engine installations may re

quire replacement of the 369A7717-3

(Ref. Figure 201)

droop compensation adjustment fork to

the longer 369A7717-7 fork to achieve

NOTE: The rigging procedures for the C20B,

the necessary 1/2% to 1% droop compen

C20R/2 and C30 engine controls are similar,

sation. Upon installation of the longer

differing mostly in adjustments.

369A7717-7 fork assembly, ensure that

no interference occurs between the collec

tive torque tube and the 369A7712 link

CAUTION

assembly. Also check between the pro

D Do not make any adjustments to governor

truding end of the droop fork and N₂ ac

stops, adjustment screws or nut positions.

tuator.

D To identify forks with obscured part num

D Replace worn linkage components prior to

bers, measure distance between threaded

rigging engine controls or adjusting en

shank end-flat to clevis bolt hole center:

gine fuel controls. Several worn rod-end,

369A7717-3 fork:

fitting and bellcrank bearings in the gov

3.00 inches (76.20 mm)

ernor control system compound otherwise

369A7717-5 fork:

minimal lost motion. Loose control sys

2.63 inches (66.802 mm)

tems will not hold rigging adjustments,

369A7717-7 fork:

and if continued in service may result in

3.87 inches (98.298 mm).

engine power creep, hunting or flame out.

(2). Set the initial reference dimension

NOTE: Gas producer throttle control tube, in

between center of Sta. 68.00 bellcrank

terconnect torque tube, collective pitch

pivot bolt and droop compensation fork

stick, interconnecting collective pitch torque

clevis bolt-center.

tube and linkage maintenance practices are

covered under `Main Rotor Flight Controls'

Droop Fork Settings

(Ref. Sec. 67-10-00) and `Gas Producer Con

trols' (Ref. Sec. 76-20-00).

Engine

Length

Installation

In.

(mm)

(1). Disconnect control rod between idler

250−C20B

2.20 ±0.03

(55.880 ±0.762)

bellcrank and governor lever at idler

bellcrank. Secure rod to avoid damage.

250−C20R/2

2.20 ±0.03

(55.880 ±0.762)

250−C20R/2 (1)

2.50 ±0.03

(63.500 ±0.762)

CAUTION

250−C30

(2)

D 250-C20R/2 engines equipped with a

(1) With 2524667-13 governor

2524667-13 engine governor require re

(2)

3.40 ±0.03 inches (86.360 ±0.762 mm) with

moval of the 369A7717-5 droop compen

369A7717-7 ext. fork and 369A7704 bell

sation adjustment fork and installation of

crank

the longer 369A7717-3 fork to achieve

2.60 ±0.03 inches (66.040 ±0.762 mm) with

the necessary 1/2% to 1% droop com

369A7717-3 ext. fork and 369A7704-7 bell

pensation (approximately 2% for 500N).

crank

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

NOTE:

proper engine installation as indicated

below.

D Make control rod-end adjustments to the

nearest half turn that produces correct

rigging.

Idler Bellcrank Control Rod Setting

D Stabilize rod-end with a backup wrench

Engine

Length

when torquing rod-end jamnut.

Installation

In.

(mm)

D Inspect rod-end thread engagement

250−C20B, R/2

14.38 ±0.03 (365.252 ±0.762)

through witness hole to ensure a safe, se

250−C30

13.70 ±0.03 (347.980 ±0.762)

cure installation.

(3). Connect 28Vdc external power. Reset

(7). Verify that collective is FULL DOWN

N₂ GOV circuit breaker. Set battery

and governor trim actuator is at

switch to EXT PWR.

maximum extension.

(4). With pilot's collective stick the FULL

(8). Check governor lever and pointer

DOWN position, beep N₂ actuator to

position, as follows.

maximum extension. Adjust actuator

ram as required to get 5.47 ±0.03 inches

Governor and fuel control levers

CAUTION

(138.938 ±0.762 mm) measured be

can be installed on the wrong

tween pivot bolt-centers.

fuel system component shaft. Governor le

ver is relatively short with an offset angle of

(5). Adjust fuselage-routed governor control

about 65°. Fuel control lever offset angle is a

rod length to move Sta. 124.00 bell

more moderate 38°.

crank. The lower arm pivot bolt-center

measurement from the firewall should

NOTE:

be set to the applicable engine installa

D Specified pointer/lever angular relation

tion as indicated below.

ships are standard production settings.

Slight variations in position may be re

Station 124 Bellcrank Setting

quired to obtain proper travel and satis

Engine

Setting

factory engine operation. Such variation

Installation

In.

(mm)

is acceptable provided all other rigging

and engine performance requirements

250−C20B, R/2

3.63 ±0.03

(92.20 ±0.762)

are met.

(Multi−Engine)

D Governor lever travel produced by trim

250−C30

3.34 ±0.03

(84.84 ±0.762)

actuator operation, from forward travel

(Current)

point (trim actuator retracted and collec

250−C30

3.75 ±0.03

(95.25 ±0.762)

tive stick down) to aft travel point (trim

(Early)

actuator extended and collective stick

down), is 31° to 32°. Approximately 36° to

(6). In engine compartment; set idler

38° of governor lever travel from mini

bellcrank control rod length to the

mum N₂ stop is unused.

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MAINTENANCE MANUAL

GOVERNOR

LEVER

GOVERNOR LEVER

CONTROL ROD

IDLER

SUPPORT

RODEND ANGULAR RELATIONSHIPS

CONTROL ROD

ANGLE

FUSELAGE ROUTED

IN LINE

COLLECTIVE

TORQUE TUBE

N2 IDLER BELLCRANK

90°

GOVERNOR LEVER

90°

DROOP CONTROL

OVERRIDE LINK

NOTE 4

DROOP COMPENSATION

ADJUSTMENT FORK

STA. 124.00

BELLCRANK

STA. 124.00

FIREWALL

STA 68.00

BELLCRANK

NOTE 1

NOTE 3

STA. 124.00 SUPPORT

FITTING

250-C30 ENGINE

STA. 72.00

INSTALLATION

BELLCRANK

FUSELAGE-ROUTED

CONTROL ROD

5.47 +0.03 (138.938 ±7.62 MM)

MULTI-ENGINE

(NOTE 2)

POWER TURBINE CONTROL LINKAGE

NOTES:

INITIAL SETTINGS.

DROOP FORK.

N₂ ACTUATOR RAM.

STA. 124.00 BELLCRANK.

G76-1002B

IDLER BELLCRANK CONTROL ROD

Figure 201. Power Turbine Governor Controls Rigging

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MAINTENANCE MANUAL

2. Governor Lever Pointer Rigging for

and D of the word SPEED on the

250−C20B (P/N 2524769−10 and Prior)

governor.

NOTE:

(Ref. Figure 202)

D The pointer control arm shall not hit the

(1). Reposition the lever arm only, not the

mechanical stops.

pointer, one serration (15°) counter

D As stick is raised, the Sta. 124.00 bell

clockwise from pointer centerline.

crank will bottom out on the support and

until it reaches FULL UP travel, the

Do not overtorque governor con

CAUTION

droop control override spring will com

trol lever nut. Exceeding nut

press.

torque limit may cause binding.

(6). Bottom collective stick and beep N₂

(2). Torque lever nut to 40 - 50 inch-

trim to minimum; The governor pointer

pounds (4.52 - 5.65 Nm) while

shifts back to approximately the first

holding lever center screw with a hex

vertical leg of the letter N of N₂ on the

wrench. Apply a torque stripe.

governor.

(3). Verify collective stick is FULL DOWN

If any interference exists at gov

CAUTION

and governor actuator is at maximum

ernor lever, check that correct

extension.

lever is installed.

(4). Connect short control rod between idler

(7). Verify that all jamnuts, bolts, nuts,

bellcrank and governor control arm.

lockwire and cotter pins are properly

Adjust the rod to locate the N₂ pointer

installed and secured.

between the letters P and E of the word

(8). Pull the N₂ GOV circuit breaker reset

SPEED embossed on the governor.

button, as required.

(5). Raise the pilot's collective stick until

(9). Set the battery switch OFF.

the Sta. 124.00 bellcrank bottoms on

support and ensure the governor

(10). Shut down and disconnect external

pointer shifts to between the letters E

power.

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MINIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE DOWN

86°

POINTER AT THE FIRST VERTICAL LEG

36° - 38°

31° - 32°

OF THE LETTER ``N'' OF N₂ (94-98%)

68°

UNUSED TRAVEL

MAXIMUM N₂

ACTUATOR EXTENSION

GOVERNOR LEVER

COLLECTIVE DOWN

CONTROL ROD

POINTER BETWEEN ``P'' AND ``E'' OF THE

WORD SPEED (103-105%)

TORQUE NUT

40-50 IN. LBS.

(4.52-5.65 NM)

MAXIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE RAISED

POINTER BETWEEN ``E'' AND ``D'' OF THE

WORD SPEED

POINTER C

GOVERNOR LC

ONE SERRATION 15°

NOTE:

DROOP CONTROL OVERRIDE LINK SPRING STARTS TO

COMPRESS; ARM IS NOT REQUIRED TO HIT MAXIMUM STOP

G76-1004A

WITH FULL COLLECTIVE AND ACTUATOR EXTENDED.

Figure 202. Power Turbine Governor Adjustments (P/N 2524769−10 and Prior)

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MAINTENANCE MANUAL

3. Governor Lever Pointer Rigging for

the first letter E in the word SPEED on

250−C20B / −C20R2 (P/N 2524769−11, −12)

the governor.

NOTE:

(Ref. Figure 203)

D The pointer control arm shall not hit the

(1). Position the governor lever arm in line

mechanical stops.

with the pointer.

D As stick is raised, the Sta. 124.00 bell

crank will bottom out on the support and

Do not overtorque governor con

CAUTION

until it reaches FULL UP travel, the

trol lever nut. Exceeding nut

droop control override spring will com

torque limit may cause binding.

press.

(2). Torque lever nut to 40 - 50 inch-

(6). Bottom collective stick and beep N₂

pounds (4.52 - 5.65 Nm) while

trim to minimum; The governor pointer

holding lever center screw with a hex

shifts back to approximately the first

wrench. Apply a torque stripe.

vertical leg of the letter R of INCR on

the governor.

(3). Verify collective stick is FULL DOWN

and governor actuator is at maximum

If any interference exists at gov

CAUTION

extension.

ernor lever, check that correct

lever is installed.

(4). Connect short control rod between idler

bellcrank and governor control arm.

(7). Verify that all jamnuts, bolts, nuts,

Adjust the rod to locate the N₂ pointer

lockwire and cotter pins are properly

between the letters S and P of the word

installed and secured.

SPEED embossed on the governor.

(8). Pull the N₂ GOV circuit breaker reset

button, as required.

(5). Raise the pilot's collective stick until

the Sta. 124.00 bellcrank bottoms on

(9). Set the battery switch OFF.

support and ensure the governor

pointer shifts to a position approxi

(10). Shut down and disconnect external

mately aligning with the vertical leg in

power.

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N₂ GOVERNOR ARM

PARALLEL TO POINT

MAXIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE UP

APPROXIMATE POINTER LOCATION

TORQUE NUT

40-50 IN. LBS.

(4.52-5.65 NM)

MAXIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE DOWN

POINTER GREATER THAN LETTER ``S'' IN SPEED

MINIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE DOWN

POINTER APPROXIMATELY AT VERTICAL

MINIMUM N₂ ACTUATOR EXTENSION

LEG OF LETTER ``R'' IN INCR

COLLECTIVE UP

POINTERLC

POINTER APPROXIMATELY AT LEADING

EDGE OF LETTER ``S'' IN SPEED

NOTE:

DROOP CONTROL OVERRIDE LINK SPRING

STARTS TO COMPRESS; ARM IS NOT REQUIRED

TO HIT MAXIMUM STOP WITH FULL COLLECTIVE

AND ACTUATOR EXTENDED.

ACCORDING TO STA. 124.00 BELLCRANK

INSTALLATION, POINTER LOCATIONS ARE

APPROXIMATE.

G76-1005B

Figure 203. Power Turbine Governor Adjustments (P/N 2524769−11, −12)

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MAINTENANCE MANUAL

4. Governor Lever Pointer Rigging for

NOTE:

250−C20B / −C20R/2 (P/N 2524667−13)

D The pointer control arm shall not hit the

(Ref. Figure 204)

mechanical stops.

D As stick is raised, the Sta. 124.00 bell

(1). Position the governor lever arm in line

crank will bottom out on the support and

with the pointer.

until it reaches FULL UP travel, the

Do not overtorque governor con

droop control override spring will com

CAUTION

trol lever nut. Exceeding nut

press.

torque limit may cause binding.

(6). Bottom collective stick and beep N₂

(2). Torque lever nut to 40 - 50 inch-

trim to minimum; The governor pointer

pounds (4.52 - 5.65 Nm) while

shifts back to approximately the aft end

holding lever center screw with a hex

of the letter R of INCR on the governor.

wrench. Apply a torque stripe.

If any interference exists at gov

(3). Verify collective stick is FULL DOWN

CAUTION

ernor lever, check that correct

and governor actuator is at maximum

lever is installed.

extension.

(7). Verify that all jamnuts, bolts, nuts,

(4). Connect short control rod between idler

bellcrank and governor control arm.

lockwire and cotter pins are properly

Adjust the rod to locate the N₂ pointer

installed and secured.

greater than the letter P in the word

(8). Pull the N₂ GOV circuit breaker reset

SPEED embossed on the governor.

button, as required.

(5). Raise the pilot's collective stick until

the Sta. 124.00 bellcrank bottoms on

(9). Set the battery switch OFF.

support and ensure the governor

pointer is greater than the second letter

(10). Shut down and disconnect external

E in the word SPEED on the governor.

power.

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MAINTENANCE MANUAL

N₂ GOVERNOR ARM

PARALLEL TO POINT

MAXIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE UP

APPROXIMATE POINTER LOCATION

TORQUE NUT

40-50 IN. LBS.

(4.52-5.65 NM)

MAXIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE DOWN

POINTER GREATER THAN LETTER ``P'' IN SPEED

MINIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE DOWN

POINTER APPROXIMATELY AT AFT END

OF LETTER ``R'' IN INCR

MINIMUM N₂ ACTUATOR EXTENSION

COLLECTIVE UP

POINTER APPROXIMATELY AT LEADING EDGE

POINTER

OF LETTER ``S'' IN SPEED

NOTE:

DROOP CONTROL OVERRIDE LINK SPRING

STARTS TO COMPRESS; ARM IS NOT REQUIRED

TO HIT MAXIMUM STOP WITH FULL COLLECTIVE

AND ACTUATOR EXTENDED.

ACCORDING TO STA. 124.00 BELLCRANK

G76-1010B

INSTALLATION, POINTER LOCATIONS ARE

Figure 204. Power Turbine Governor Adjustments (P/N 2524667−13)

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MAINTENANCE MANUAL

5. Governor Lever Pointer Rigging for

support and ensure the governor

250−C20B (P/N 2524667−14 and Higher,

pointer is approximately at 81°.

P/N 2524769−13 and Higher and P/N

NOTE:

2549170−1 and Higher)

D The pointer control arm shall not hit the

(Ref. Figure 205)

mechanical stops.

(1). Position the governor lever arm, not the

D As stick is raised, the Sta. 124.00 bell

pointer, to the first serration counter-

crank will bottom out on the support and

clockwise from pointer centerline.

until it reaches FULL UP travel, the

droop control override spring will com

Do not overtorque governor con

press.

CAUTION

trol lever nut. Exceeding nut

(6). Bottom collective stick and beep N₂

torque limit may cause binding.

trim to minimum; The governor pointer

(2). Torque lever nut to 40 - 50 inch-

shifts back to 38° ±3°.

pounds (4.52 - 5.65 Nm) while

If any interference exists at gov

holding lever center screw with a hex

CAUTION

ernor lever, check that correct

wrench. Apply a torque stripe.

lever is installed.

(3). Verify collective stick is FULL DOWN

(7). Verify that all jamnuts, bolts, nuts,

and governor actuator is at maximum

lockwire and cotter pins are properly

extension.

installed and secured.

(4). Connect short control rod between idler

(8). Pull the N₂ GOV circuit breaker reset

bellcrank and governor control arm.

button, as required.

Adjust the rod to locate the N₂ pointer

at 69° ±3°.

(9). Set the battery switch OFF.

(5). Raise the pilot's collective stick until

(10). Shut down and disconnect external

the Sta. 124.00 bellcrank bottoms on

power.

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N₂ GOVERNOR ARM POSITION TO FIRST

SERRATION COUNTER-CLOCKWISE

FROM POINTER CENTERLINE

10°

POINTER LC

N₂ ACTUATOR EXTENDED

COLLECTIVE UP 1/3 TO 1/2 TRAVEL

APPROXIMATE POINTER LOCATION 81°

N₂ ACTUATOR EXTENDED

COLLECTIVE DOWN

N₂ ACTUATOR RETRACTED

POINTER AT 69° +3°

COLLECTIVE DOWN

POINTER AT 38° +3°

N₂ ACTUATOR RETRACTED

COLLECTIVE UP

POINTER AT 63° +3°

NOTE:

DROOP CONTROL OVERRIDE LINK SPRING STARTS TO

COMPRESS; ARM IS NOT REQUIRED TO HIT MAXIMUM

STOP WITH FULL COLLECTIVE AND ACTUATOR

EXTENDED.

-14GOV - C20B

ACCORDING TO STA. 124.00 BELLCRANK INSTALLATION,

Figure 205. Power Turbine Governor Adjustments (P/N 2524667−14 and Higher,

P/N 2524769−13 and Higher and P/N 2549170−1 and Higher on 250−C20B Engine)

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MAINTENANCE MANUAL

6. Governor Lever Pointer Rigging for

support and ensure the governor

250−C20R/2 (P/N 2524667−14 and Higher,

pointer is approximately at 94°.

P/N 2524769−13 and Higher and P/N

NOTE:

2549170−1 and Higher)

D The pointer control arm shall not hit the

(Ref. Figure 206)

mechanical stops.

(1). Position the governor lever arm, not the

D As stick is raised, the Sta. 124.00 bell

pointer, to the first serration counter-

crank will bottom out on the support and

clockwise from pointer centerline.

until it reaches FULL UP travel, the

droop control override spring will com

Do not overtorque governor con

press.

CAUTION

trol lever nut. Exceeding nut

(6). Bottom collective stick and beep N₂

torque limit may cause binding.

trim to minimum; The governor pointer

(2). Torque lever nut to 40 - 50 inch-

shifts back to 44° ±3°.

pounds (4.52 - 5.65 Nm) while

If any interference exists at gov

holding lever center screw with a hex

CAUTION

ernor lever, check that correct

wrench. Apply a torque stripe.

lever is installed.

(3). Verify collective stick is FULL DOWN

(7). Verify that all jamnuts, bolts, nuts,

and governor actuator is at maximum

lockwire and cotter pins are properly

extension.

installed and secured.

(4). Connect short control rod between idler

(8). Pull the N₂ GOV circuit breaker reset

bellcrank and governor control arm.

button, as required.

Adjust the rod to locate the N₂ pointer

at 77° ±3°.

(9). Set the battery switch OFF.

(5). Raise the pilot's collective stick until

(10). Shut down and disconnect external

the Sta. 124.00 bellcrank bottoms on

power.

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N₂ GOVERNOR ARM POSITION TO FIRST

SERRATION COUNTER-CLOCKWISE

FROM POINTER CENTERLINE

10°

POINTER C

N₂ ACTUATOR EXTENDED

COLLECTIVE UP 1/3 TO 1/2 TRAVEL

APPROXIMATE POINTER LOCATION 94°

N₂ ACTUATOR EXTENDED

COLLECTIVE DOWN

N₂ ACTUATOR RETRACTED

POINTER AT 77° +3°

COLLECTIVE DOWN

POINTER AT 44° +3°

N₂ ACTUATOR RETRACTED

COLLECTIVE UP

POINTER AT 63° +3°

NOTE:

DROOP CONTROL OVERRIDE LINK SPRING STARTS TO

COMPRESS; ARM IS NOT REQUIRED TO HIT MAXIMUM STOP

WITH FULL COLLECTIVE AND ACTUATOR EXTENDED.

ACCORDING TO STA. 124.00 BELLCRANK INSTALLATION,

POINTER LOCATIONS ARE APPROXIMATE.

-14GOV - C20R2

Figure 206. Power Turbine Governor Adjustments (P/N 2524667−14 and Higher,

P/N 2524769−13 and Higher and P/N 2549170−1 and Higher on 250−C20R/2 Engine)

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MAINTENANCE MANUAL

7. Governor Lever Pointer Rigging for

(6). Move collective stick FULL DOWN.

250−C30

Beep governor trim actuator to maxi

mum extension. The pointer will point

(Ref. Figure 207)

to approximately the 50° mark.

(1). At the governor unit position the

governor lever to within 10 degrees

(7). Raise the collective stick until Sta.

parallel with the pointer arm.

124.00 bellcrank bottoms on support,

Do not overtorque governor con

the pointer will point approximately the

CAUTION

trol lever nut. Exceeding nut

58° mark.

torque limit may cause binding.

(2). Torque lever nut to 40 - 50 inch-

NOTE: The control arm of the pointer should

pounds (4.52 - Nm) while holding

not hit the mechanical stops.

lever center screw with a hex wrench.

Apply a torque stripe.

(8).

Continue raising the pilot's collective

(3). Verify that collective is FULL DOWN

stick; droop control override spring

and governor trim actuator is at

compression continues to increase until

minimum extension.

the stick reaches FULL UP. The

(4). Adjust governor lever control rod link

governor pointer should remain

so that the governor pointer points to

approximately stationary on the 58°

20° mark on the N₂ governor plate.

mark.

(5). Raise the pilot's collective stick,

minimum beep, and check that pointer

(9).

Verify that all jamnuts are torqued to

is at is at the 35° mark on the in the N₂

25 - 30 inch-pounds (2.82 - 3.39

governor plate.

Nm). Check all bolts, nuts and cotter

pins for proper installation and securi

NOTE:

ty.

D If pointer is above 35° mark, lengthen the

369A7706 rod. If the pointer is below the

35° mark, shorten the rod. After adjusting

(10).

Pull the N₂ GOV circuit breaker reset

rod, repeat steps (3). and (4)..

button, as required.

D Specified pointer/lever angular relation

ships are standard production settings.

Slight variations may be required to ob

(11).

Set the battery switch OFF.

tain proper travel and satisfactory engine

operation. Variations are acceptable pro

vided all engine performance require

(12).

Shut down and disconnect external

ments are met.

power.

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MAINTENANCE MANUAL

Governor Controls Final Check and

Make all engine compart

WARNING

Adjustment (250−C20B, −C20R/2)

ment control rod adjust

ments with engine shut down.

(1).

Have an assistant move collective

(10).

Mark N₂ lever position on governor

through full range of travel while

quadrant.

inspecting all movable linkage for

clearance with adjacent parts. Check

(11).

Connect external electric power.

that control rod, N₂ actuator and

override link bearings are not jammed

(12).

With collective at bottom stop, beep N₂

when linkage is at extreme control

trim to maximum rpm.

positions.

(13).

Adjust governor lever control rod (105%

(2).

Start and operate engine at idle with

N2 maximum: 369D/E) (104% N₂

main rotor blades in flat pitch per

maximum: 500N).

Pilot's Flight Manual.

(14).

Start engine. With main rotor blades in

flat pitch, beep N₂ trim to (102% rpm:

(3).

Decrease N₂ trim to minimum.

369D/E) (100% rpm: 500N). Lift off and

hover.

(4).

Throttle up to maximum rpm.

(15).

Observe N₂ tachometer pointer when

(5).

Observe N₂ tachometer pointer for (98%

pointer of N_l tachometer is stabilized.

or less rpm: 369D/E) (94% or less:

N₂ pointer indication, that is, droop

500N) when rotor rpm pointer is

compensation, should be (1/2% to 1%

superimposed on N₂ pointer and N_l

rpm: 369 D/E) (1% to 2% rpm: 500N)

tachometer pointer is stabilized.

above indication in previous step.

(6).

Check for the following engine power

(16).

Land and shut down engine.

out (EPO) indications:

(17).

If droop compensation occurred as

(a). Engine-out flashing light.

required, no further adjustments are

required.

(b). Audio signal in headset.

(18).

If droop compensation did not occur per

step (15)., check and re-rig power

(c). Horn; sounds when N₂ pointer on

turbine and gas producer linkage

dual indicator is stable.

systems as required.

(7). With collective stick down, increase N₂

(19).

Where N_l and N₂ linkage are correctly

trim to (104% to 105% rpm: 369D/E)

adjusted, additional adjustment may be

(103% to 104% rpm: 500N). Observe N₂

made to droop compensation adjust

tachometer pointer when rotor rpm

ment fork; as follows:

pointer is superimposed on N₂ pointer

and N₁ tachometer pointer is stabilized.

NOTE: Three to five turns of droop compensa

tion fork may be necessary to change droop

(8). Without decreasing N₂ trim, rotate

compensation approximately 0.5% rpm.

pilot's throttle to ground idle.

(a). Shorten droop compensation adjust

NOTE: Perform a deceleration time check per

ment fork to increase compensation.

PFM after rigging and testing power tur

(b). Lengthen fork extension to decrease

bine controls. Refer to Allison Operation

compensation.

and Maintenance Manual for adjustment

procedures if deceleration time is less than

(c). Align fork with override link rod-end

allowable minimum.

before tightening fork jamnut.

(9). Shut down engine per Pilot's Flight

(20). Move collective through full travel after

Manual.

adjustment and check for clearance

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MAINTENANCE MANUAL

between movable linkage and adjacent

(9). Restart engine. With main rotor blades

parts.

in flat pitch, actuate N₂ trim for 100

percent, lift-off and hover.

(21). When full power is demanded in flight

and high N₁ and TOT operating range

(10). Observe N₂ tachometer pointer when

cannot be reached, gas producer fuel

pointer of N₁ tachometer is stabilized.

control maximum throttle stop may

N₂ pointer indication (droop compensa

require adjustment. Refer to Allison

tion) should be 1 to 2 percent above N₂

Operation and Maintenance Manual for

setting in step (9).

adjustment procedure.

(11). Land and shut down engine.

Governor Controls Final Check and

Adjustment (250−C30)

NOTE: If droop compensation occurs as re

quired in (10). above, skip steps (12). and

(1).

Have an assistant move collective

(13). below.

through full range of travel while

inspecting all movable linkage for

(12). If droop compensation does not occur as

clearance with adjacent parts. Check

required in step (10). above, recheck

that control rod, N₂ actuator and

entire power turbine governor (N₂

override link bearings are not jammed

RPM) control linkage rigging and gas

when linkage is at extreme control

producer (N₁ fuel control) linkage

positions.

adjustment.

(2).

Start and operate engine at idle with

Any change to initial droop com

CAUTION

main rotor blades in flat pitch per

pensation fork length may re

Pilot's Flight Manual.

sult in interference between N₂ trim actua

tor case and fork threaded end. Move

(3).

Rotate pilots throttle counterclockwise

collective through full travel after adjust

up to maximum rpm.

ment and check for clearance between mov

able linkage and adjacent parts.

(4).

Decrease N₂ trim to minimum.

(5).

Observe N₂ tachometer pointer for 94%

(13). If N₁ and N₂ linkage are correctly

or less rpm and N₁ tachometer is

installed, an additional adjustment may

stabilized.

be made at droop compensation adjust

ment fork. Shorten droop compensation

(6).

With collective stick down, increase N₂

adjustment fork to increase compensa

trim to maximum.

tion. Lengthen fork extension to

decrease compensation. Align fork with

(7).

Observe N₂ tachometer pointer for

override link rod end before tightening

103% to 104% rpm and N₁ tachometer

fork jam nut. Three to five turns of

pointer is stabilized.

droop compensation fork may be

Make all engine compart

necessary to change droop compensa

WARNING

tion fork approximately 0.5 percent.

ment control rod adjust

ments with engine shut down.

NOTE: Perform a deceleration time check per

(8). Stop engine. Adjust length of governor

PFM after rigging and testing power tur

control lever rod until N₂ trim is within

bine controls. Refer to Allison Operation

limits specified in steps (5). and (7).

and Maintenance Manual for adjustment

above. Adjust one rod end not more

procedures if deceleration time is less than

than one turn at a time.

allowable minimum.

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MAINTENANCE MANUAL

10. Governor Controls Replacement

(11). The sleeve bushings in Sta. 68 bell

crank arm must rotate freely, without

(Ref. Figure 208)

any binding, after the actuator is

attached and the connecting hardware

(1). Remove and replace control rods,

is tightened.

bellcranks and supports as required,

except as follows:

(12). Connect replacement droop control

override link to collective torque tube.

Only high temperature all

WARNING

metal self-locking nuts are

(13). Push on rod end and check that the link

to be used for attaching control idler

assembly plunger head is free to slide

support to engine gearcase accessory

back and forth in the link housing end

pad.

fitting.

NOTE: Remove droop control override link, N₂

(14). Connect rod end to droop compensation

trim actuator, and Sta. 72.00 bellcrank from

fork; the rod end should align with the

airframe as a unit.

fork.

(15). Connect the bonding jumper and

(2).

Leave Sta. 72.00 bellcrank attached to

electrical connector to the actuator.

N₂ trim actuator and remove as a unit.

NOTE: Replacement trim actuator may have a

(3).

Disconnect the bonding jumper and

tab or use a bonding strap/clamp for connec

electrical connector from the actuator.

tion of the bonding jumper.

(4).

Disconnect the actuator from Sta. 68

(16). Rig power turbine governor controls if

bellcrank.

any linkage components have been

removed and replaced.

(5).

Disconnect Sta. 72 bellcrank from the

fuselage-routed control rod end.

NOTE: Perform a deceleration time check per

PFM after rigging and testing power tur

(6).

Remove the pivot bolt that attaches

bine controls. Refer to Allison Operation

Sta. 72 bellcrank to structure rib and

and Maintenance Manual for adjustment

controls support bracket; remove

procedures if deceleration time is less than

actuator and bellcrank.

allowable minimum.

(7).

Disconnect the trim actuator from Sta.

72 bellcrank. Use care to keep sleeve

11. Control Rod Inspection

bushings with bellcrank.

(Ref. Figure 208)

(8).

Check replacement actuator for a

(1). Inspect rod end bearings for binding

maximum extended length of 5.44-5.50

and excessive wear, 0.040 inch (1.013

inches (13.82-13.97 cm) measured

mm) maximum axial play).

between bolt hole centers. Test actuator

for proper operation (Ref. N₂ Trim

(2). Inspect control rod for surface damage

Actuator Test).

and evidence of bending.

(9).

Assemble original or replacement trim

(3). When necessary, perform straightness

actuator to original or replacement Sta.

check on control rods that appear bent

72 bellcrank with a bolt, two washers,

or bowed. Total length of gas producer

nut and new cotter pin.

control rods (excluding rod ends) must

be straight within the following

(10).

Check that both sleeve bushings are in

tolerances, with straightness variation

place in Sta. 68 bellcrank arm before

limited to maximum of 0.010 inch

connecting the actuator; then install

(0.254 mm) in each foot of length.

assembled unit in controls support

bracket and connect linkage as shown

(a). Fuselage-routed control rods: 0.050

in Figure 208.

inch (1.27 mm).

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MAINTENANCE MANUAL

(b). Governor lever control rod: 0.020

14. Droop Control Override Link Repair

inch (0.508 mm).

(Ref. Figure 208)

(c). Idler bellcrank control rod: 0.020 inch

(0.508 mm).

Consumable Materials

(4). Inspect for loose rivet at fixed rod ends.

(Ref. Section 91−00−00)

Item

Nomenclature

(5). Inspect bearings in bellcranks for

CM117

Grease

binding.

CM321

Surface primer locking compound

(6). Perform fluorescent dye penetrant

CM431

Sealing, locking and retaining compound

inspection of any suspect part.

Control rods, part number

(1). Install link end-fitting bearing (detail

CAUTION

369A7706-3, between the idler

B) using surface primer (CM321) and

bellcrank and governor control lever were

locking compound (CM431) per contain

made of aluminum and must be replaced

er instructions.

with a steel part, P/N 369A7706-5, or the

complete assembly, P/N 369A7706-11.

(2). Replace rod-end or spring as follows:

NOTE: After replacement and inspection of the

(a). Remove four retaining rivets from

power turbine governor controls linkage,

housing rod-end.

perform a deceleration check in accordance

with procedures found in the PFM. If con

(b). Drill out rod-end rivet and dismantle

firmed deceleration time is less than the al

spring assembly. Discard rod-end

lowable minimum, refer to the appropriate

and plunger.

Allison Operation and Maintenance Manu

al.

(c). Assemble plunger, retainers, spring

and jam nut. Thread jamnut onto

12. Bellcrank Inspection

plunger until there is minimum

spring free-play.

(Ref. Figure 208)

(d). Thread rod-end onto plunger until it

(1).

369D Only: Inspect droop compensation

contacts jamnut.

bellcrank for installation of a spacer

between fork extension jamnut and

Plunger must be free to travel to

bellcrank threaded insert.

CAUTION

bottom of end-fitting oblong slot

As required, install spacer.

without binding.

(2). Perform a fluorescent penetrant crack

(e). Align plunger-head hex-flats so that

inspection on all suspected parts.

two parallel flats are at a right angle

(90°) to rod-end bearing. Tighten jam

13. Droop Compensation Link Inspection

nut.

(Ref. Figure 208)

(f). Using No. 50 drill, drill through

(1). Inspect droop compensation spring

rod-end and plunger at witness hole.

cartridge for condition and wear.

Install rivet.

Cartridge total end play is not to exceed

0.015 inch (0.381 mm).

(g). Lubricate interior of housing, spring

retainers and plunger with grease

NOTE: Perform a deceleration time check per

(CM117). Install spring assembly in

PFM after rigging and testing power tur

housing so that plunger hex enters

bine controls. Refer to Allison Operation

end fitting slot and rod-end aligns

and Maintenance Manual for adjustment

vertically with housing bearing.

procedures if deceleration time is less than

allowable minimum.

(h). Install four plunger retaining rivets.

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MAINTENANCE MANUAL

COLLECTIVE TORQUE TUBE

NOTE 3

DROOP

GROUND JUMPER

COMPENSATION

FORK

AIRFRAME

N₂ TRIM ACTUATOR

STRUCTURE

JAM NUT

STA. 68.00 BELLCRANK

SPACER

BEARING

SLEEVE BUSHING

LOCKED

THREAD

AIRFRAME

INSERT

STRUCTURE

BRACKET

FLANGED

BUSHING

STA. 72.00

SLEEVE

BELLCRANK

BUSHING

STA. 64.00 SEAT

STRUCTURE

BRACKET

NOTES:

BEARING

STA. 124.00

BUSHINGS AND BEARINGS MUST ROTATE

BELLCRANK

FREELY AFTER ASSEMBLY.

ASTERISK ( * ) INDICATES CORROSION

FUSELAGE-ROUTED

RESISTANT STEEL.

CONTROL ROD

JAM NUT

NOTE 3

RETAINER

HOUSING END

RETAINER

RIVET

BEARING

FITTING

ROD END

SPRING

PLUNGER

LINK HOUSING

DROOP CONTROL OVERRIDE LINK

G76-1007-1

Figure 208. Power Turbine Governor Controls (Sheet 1 of 2)

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MAINTENANCE MANUAL

15. Control Rod Repair

(3). With actuator ram approximately

halfway between stops, measure ram

(Ref. Figure 208)

end-play with dial indicator. End-play

must not exceed 0.005 inch (0.127 mm)

(1). Repair rod assemblies as follows:

total indicator reading when measured

under 10 pound (4.5 kg) reversing load.

Fluorescent penetrant crack in

CAUTION

spection shall be performed af

(4). Set test switch to RETRACT and allow

ter cold-straightening control rods. Replace

actuator ram to fully retract. Using end

a cracked rod. Replace a cracked or bent

of ram sleeve as reference point,

rod-end.

measure portion of ram that remains

out of sleeve to nearest 1/64 inch

(2). Cold-straighten bent rods provided

(0.3968 mm). Record this measurement

there are no nicks or sharp dents in

for use in the following step.

bend length. Do not use rod-ends to

support rod during straightening

(5). Set test switch to EXTEND and run

process.

ram to extend stop. Measure length of

extended ram. Subtract result of step

Use care when drilling to re

CAUTION

(4). from extended ram value. Result

move or install riveted rod-end.

should be 0.97-1.03 inches

Tighten jam nut before drilling or riveting.

(24.638-26.162 mm).

(3). Replace control rod end if bearing axial

(6). Actuator current draw at 26.0Vdc shall

play is more than 0.040 inch (1.016

be:

mm).

(a). Under no-load; 0.60-1.25 amperes.

16. Bellcrank and Support Fitting Repair

(b). Stalled; 2.0 amperes, maximum.

(Ref. Figure 208)

(7).

Operate actuator motor in both extend

Consumable Materials

and retract directions. Over-travel

(Ref. Section 91−00−00)

must not exceed 0.020 inch (0.508 mm)

Item

Nomenclature

maximum when power is switched off.

CM321

Surface primer locking compound

(8).

Reduce voltage input to 21 volts.

CM431

Sealing, locking and retaining compound

Actuator ram must retract and extend

to stops without binding on or between

stops.

(1). Install replacement bearings using

surface primer (CM321) and grade A

(9).

Increase input voltage to 28 volts.

locking compound (CM431) per contain

Actuator ram must retract and extend

er instructions.

to stops without binding on stops or

(2). Replace distorted or cracked bellcranks

between stops.

and support fittings. Replace parts that

have elongated holes.

(10).

Run actuator to full extended position.

Extended actuator overall length shall

be 5.47-5.50 inches (13.894-13.970 cm)

17. N₂ Trim Actuator Test

between pivot bolt centers.

(Ref. Figure 209)

(11).

Torque rod-end jamnut to 30 - 40

(1). Connect N₂ trim actuator to test

inch-pounds (3.39 - 4.52 Nm).

equipment.

(12).

Turn off power.

(2). Turn on dc power and adjust output to

25.75 to 26.25 volts.

(13).

Disconnect actuator.

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MAINTENANCE MANUAL

19. Sta. 68.00 Bellcrank Rework, P/N

369A7717−3 and 369N2606 Only

MS3106-10L-3S

(Ref. Figure 210)

CONNECTOR

SPDT

EXTEND

SWITCH

Consumable Materials

RETRACT

(Ref. Section 91−00−00)

26 VDC

Item

Nomenclature

V M2

POWER

CM318

Primer

N/A

Dichromate

N/A

Anodizing compound

ITEM

EQUIPMENT DESCRIPTION

Special Tools

(Ref. Section 91−00−00)

6-INCH SCALE

Item

Nomenclature

DC VOLTMETER, CALIBRATED 0-5 VOLTS.

(WESTON MODEL 931 OR

N/A

Spotface cutter, 0.687 inch (17450 mm)

EQUIVALNET)

dia., 0.030 inch (0.762 mm) corner radius

DC MILLIAMMETER, CALIBRATED 0-5AMPERES.

(WESTON MODEL 931 OR

N/A

Spotface cutter pilot, 5/16-24 UNF-3A

EQUIVALENT)

thread

VARIABLE DC POWER SUPPLY, 10-36 VOLTS,

(N.J.E. MODEL SY36-10 OR

EQUIVALENT)

(1).

Remove panels required to get at power

DIAL INDICATOR GAGE

turbine governor controls linkage.

(BROWN AND SHARP MODEL 740

OR EQUIVALENT)

G76-1008

(2).

Unbolt and remove Sta. 68.00 bellcrank

assembly.

Figure 209. N₂ Trim Actuator Test Hookup

(3).

To expedite reassembly, measure and

note distance between the center of

droop compensation fork clevis bolt hole

and bellcrank pivot bolt hole. Remove

droop compensation fork from bell

18. N₂ Trim Actuator Repair

crank.

(4).

Screw spotface cutter pilot into bell

crank. Cut away only enough material

(1). N₂ actuator repairs are limited to

to provide a 360° flat surface around

actuator ram rod-end replacement. Set

hole. Do not cut into thread insert.

distance between pivot-bolt centers to

(5).

Coat bare metal surface with Dow #7 or

5.44-5.50 inches (13.818-13.970 cm)

#17 chemical treatment per manufac

with ram fully extended. Torque

turers instructions.

rod-end jamnut to 30 - 40 inch-

(6).

Apply primer (CM318) over reworked

pounds (3.39 - 4.52 Nm).

surfaces. Allow primer to dry.

(7).

Assemble locknut, spacer and droop

compensation fork on bellcrank. Get as

All other actuator repairs are to

close to previously noted dimension as

CAUTION

possible.

be performed by an authorized

overhaul station or the actuator manufac

(8).

Rig power turbine governor controls.

turer.

(9).

Note compliance in helicopter log book.

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MAINTENANCE MANUAL

GAS PRODUCER CONTROLS

MAINTENANCE PRACTICES

1. Gas Producer Controls Rigging

D Rigging check/adjustments are required

(250−C20B and 250−C20R/2)

when pilot's compartment linkage, or con

trol rod lengths have been disturbed, or

(Ref. Figure 201)

when there is less than a 0.010 inch

(0.254 mm) gap between Sta. 129.00 fire

wall bellcrank upper arm and its support

Special Tools

fitting with the throttle in CUT-OFF.

(Ref. Section 91−00−00)

Item

Nomenclature

(1).

Remove gas producer lever control rod

ST404

Wrench, ground idle adjusting

(Detail B).

ST501

Collective rigging fixture

(2).

Position pilot's collective stick at

(LH command)

mid-travel. Insert rigging fixture

ST502

Collective rigging fixture

(ST501) or (ST502) in collective friction

(RH command)

guide link slot. Rest collective stick on

fixture (Detail A).

NOTE:

(3).

On dual control installations; check for

D The following throttle control rigging pro

asynchronous motion between collective

cedures are applicable to Allison

stick throttle assemblies with the

250-C20B and 250-C20R/2 engines

throttle wide open and in CUT-OFF.

equipped with Bendix or Chandler Evans

Dual control throttle movement should

(CECO) fuel control systems.

be synchronized, but with the pilot's

(command position) throttle dominating

D Make fuel flow metering adjustments per

the copilot's throttle at idle.

Allison Engine Operation and Mainte

nance Manual except for 369/500 series

(4).

Position pilot's throttle twist grip so

helicopter specific idle speed variances

that twist grip set-screws are at six

explained in the following steps.

o'clock.

Failure to bleed fuel supply

(5).

Remove gearbox inspection plate on the

WARNING

system after opening system

bottom of the collective stick. Ensure

to atmosphere can result in power loss

that the centerline of the cutaway on

or engine flameout. Bleed trapped air

the large bevel gear is aligned on the

after opening any fuel lines between

collective stick lengthwise centerline. If

fuel tank and combustion chamber

gear is not properly positioned, remove

nozzle. Bleed fuel system following re

gearbox side plate and reposition the

moval and replacement of any part of

gear.

the engine or aircraft fuel system (Ref.

Sec. 28-00-00).

NOTE: When a ring adjustment is made, check

engagement of ring gear and pinion. Cutout

Do not exceed adjustable rod-

CAUTION

in ring gear should face aft with throttle in

end maximum extension/thread

CLOSED position. When dual controls are

engagement. Inspect rod-end thread en

in installed, check for override or interfer

gagement through witness hole.

ence between collective stick assemblies

with with the throttle grip in the CLOSED

NOTE:

and FULL OPEN position. Return throttle

D Refer to Collective Controls (Ref. Sec.

grip to MID travel position.

67-10-00) for information on rigging

throttle gas producer control tube, inter

(6). Find and remove all lost motion in the

connect torque tube and associated link

throttle system before making rigging

age.

adjustments.

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MAINTENANCE MANUAL

NOTE: It is important that all assembly toler

Governor and fuel control levers

CAUTION

ances between the gas producer intercon

can be erroneously installed on

nects and torque tube assemblies are correct

the wrong fuel system component shaft.

and all backlash removed to assure accurate

Governor lever is relatively short with an

rigging of the fuel control system.

offset angle of about 65°. Fuel control lever

offset angle is a more moderate 38°.

(7). Check idler for interference with its

(14). Move throttle twist grip from wide open

support.

to CUT-OFF to ensure that the throttle

lever is contacting open and closed fuel

(8). Adjust Sta. 73.00 control rod length so

control mechanical stops. Adjust gas

that lower arm of Sta. 70.00 bellcrank

producer lever control rod as required

is parallel to seat structure (Detail B).

to cause lever contact. Do not adjust

stops.

(9). Adjust fuselage-routed control rod

(15). Turn pilot's throttle to maximum rpm,

length so that bolt center in lower arm

then to idle.

of Sta. 129.00 bellcrank is 4.97-5.03

(16). Bendix Fuel Control: With pilot's

inches (12.624-12.776 cm) from Sta.

throttle held at idle, adjust gas produc

124.00 firewall bulkhead.

er lever control rod until gas producer

pointer is at 30° (View C).

(10). Move throttle to CUT-OFF.

(17). CECO Fuel Control: With pilot's

throttle held at idle, adjust gas produc

(11). Adjust the fuselage routed control rod

er lever rod until gas producer pointer

to provide a gap of 0.010-0.050 inch

is at 30° to 32°.

(0.254-1.270 mm) between Sta. 129.00

bellcrank upper arm and support

CAUTION

fitting. Push the rod and bellcrank

toward the firewall bulkhead to remove

D Do not alter gas producer lever position or

all friction errors before checking gap.

control linkage to adjust idle speed. Idle

speed is to be checked during engine op

erational test and adjusted with fuel con

NOTE:

trol idle screw, not with the linkage.

D Bendix Fuel Control: Pointer position

D Check linkage at extreme travel posi

may range from 0° to 10° when contacting

tions. Ensure gas producer lever hits fuel

the CUT-OFF stop, depending on calibra

control mechanical stops before throttle

tion settings peculiar to the fuel control.

twist grip stops are contacted.

D Bendix fuel control lever and shaft serra

D Interference or binding anywhere in link

tions are at 15° intervals.

age is not allowed.

D Be sure that linkage movement is clear of

(12). Set fuel control lever against CUT-OFF

wires, tubes and hoses.

stop. Pointer position should range

(18). Rotate pilot's throttle counterclockwise

between the 0° and 10° quadrant

to maximum rpm.

marks. Set the fuel control throttle

shaft lever, without moving the pointer,

(19). Make sure gas producer lever strikes

15° counterclockwise from parallel with

maximum speed stop.

the engine compartment door frame

(20). Raise collective stick to up stop.

while keeping the pointer at CUT-OFF

and inboard lever half in contact with

(21). Gas producer lever must remain in

stop.

contact with maximum speed stop; if

lever comes off stop, check gas producer

controls for binding.

(13). Torque fuel control lever nut to 40 - 50

inch-pounds (4.52 - 5.65 Nm). Do not

(22). Release idle detent and roll pilot's

over-tighten nut. Apply a torque stripe.

throttle to CUT-OFF. Make sure that

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MAINTENANCE MANUAL

gas producer lever strikes CUT-OFF

fault isolation procedures per Allison

stop.

Manual.

(29). Accelerate and decelerate engine three

(23). Lower collective stick. Ensure gas

times to ensure repeatability.

producer lever does not move off

CUT-OFF stop.

Throttle snap to idle must be

WARNING

performed to ensure that en

(24). When dual controls are installed, move

gine will not flame out.

copilot's throttle twist grip to its idle

stop. Fuel control pointer shall not be

(30). Accelerate engine to to normal operat

more than 5/64 inch (1.9844 mm) below

ing rpm with pilot's throttle; then snap

the idle degree mark specified for a

clockwise to idle. Repeat this check

Bendix fuel control (30°) or a CECO

using copilot's throttle where installed.

fuel control (30 to 32°) as applicable.

If flameout occurs, adjust engine idle

speed per the applicable Allison

(25). Have an assistant cycle the throttle

Operation and Maintenance Manual.

from CUT-OFF to wide open. Ensure

control rods do not roll over or jam

Perform a deceleration time

CAUTION

when linkage is at extreme travel

check per PFM following gas

positions.

producer or linkage replacement or adjust

ment. Refer to Allison Engine Operation

NOTE: Refer to your Allison Operation and

and Maintenance Manual for adjustment

Maintenance Manual for complete gas pro

procedures when deceleration time is less

ducer fuel control rigging procedures to

than allowable minimum.

make the following adjustments.

(31). Shut down engine.

(26). Start and operate engine at idle with

main rotor in flat pitch per Pilot's

2. Gas Producer Controls Rigging (250−C30)

Flight Manual (PFM).

(Ref. Figure 201)

Operating requirements de

CAUTION

mand that idle rpm be adjusted

Special Tools

within minus 1% of the Allison specified up

(Ref. Section 91−00−00)

per limit of 65% rpm. Achieving required

Item

Nomenclature

idle rpm is particularly important for heli

ST404

Wrench, ground idle adjusting

copters equipped with dual controls.

ST405

Rigging fixture, collective stick

(27). With pilot's throttle at idle, observe N_l

ST406

Alignment fixture

tachometer indicator. Ensure N_l speed

ST407

Rigging pin

stabilizes between 64 - 65 %. To adjust

ST501

Collective rigging fixture

idle rpm, proceed as follows:

(LH command)

ST502

Collective rigging fixture

(a). Bendix: Adjust idle speed with

(RH command)

adjusting tool (ST404) per the

applicable Allison Operation and

Maintenance Manual.

NOTE:

D The following throttle control rigging pro

(b). CECO: Adjust idle speed with a 5/32

cedures are applicable to Allison 250-C30

hex-wrench per the 250-C20 Allison

engines equipped with Bendix fuel control

Operation and Maintenance Manual.

systems.

(28). Accelerate engine to 100%, stabilize,

D Make fuel flow metering adjustments per

then decelerate to idle after each

Allison Engine Operation and Mainte

adjustment. If idle adjustments do not

nance Manual except for 369/500 series

consistently stabilize rpm within 64% -

helicopter specific idle speed variances

65% limit, follow engine fuel control

explained in the following steps.

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MAINTENANCE MANUAL

IDLE POSITION

(NOTES 10, 11)

GAS

PRODUCER

MID POSITION

CUT-OFF

(NOTE 1

POSITION

LEVER

TORQUE NUT

(NOTE 8)

40-50 IN. LBS.

(4.52-5.65 NM)

GAS PRODUCER

CUT-OFF

LEVER CONTROL

(NOTE 7)

CONTROL ROD

POINTER

QUADRANT

CECO FUEL CONTROL

IDLE RANGE

(NOTES 9, 11)

OVERTRAVEL

POINTER

(NOTE 1)

(NOTE 12)

BENDIX FUEL CONTROL

LEVER CONTROL

ROD

LEVER POSITION

QUADRANT

250-C30 FUEL CONTROL

FUEL CONTROL LEVER

AND POINTER

GAS PRODUCER

SUPPORT

LEVER CONTROL ROD

FITTING

STA. 129.00

BELLCRANK

STA. 74.87

GAP

(NOTE 6)

STA. 73.00

CONTROL ROD

IDLER ASSY.

DISTANCE

(NOTES 4, 5)

STA. 70.00

STA. 124.00

BELLCRANK

FIREWALL

(NOTES 2, 3)

FUSELAGE-ROUTED

CONTROL ROD

LINKAGE INSTALLATION

(NOTE 1)

G76-2000-2A

Figure 201. Gas Producer Controls Rigging (Sheet 2 of 3)

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MAINTENANCE MANUAL

COLLECTIVE STICK

(NOTE 1)

C COLLECTIVE

VERTICAL (PARALLEL)

WITH FORWARD SEAT

TORQUE TUBE

STRUCTURE

STA. 70.00

BELLCRANK ASSY.

STA. 73.00 CONTROL

(NOTE 2)

ROD ASSY.

14.47

THROTTLE

OPEN

13.10

THROTTLE

54° 30'

CUT-OFF

FUSELAGE-ROUTED

CONTROL ROD ASSY.

STA. 78.21

COLLECTIVE STICK LINKAGE RIGGING, 250-C20B

AND 250-C20R/2 ENGINE EQUIPPED HELICOPTERS

COLLECTIVE

(NOTE 1)

THROTTLE TWIST GRIP

IN FLIGHT IDLE

PILOT'S SEAT

STRUCTURE

(REF)

99° 55' 12”

38° (REF)

(REF)

20.03

ALIGNMENT

FIXTURE

VERTICAL

IDLER

STA. 74.87

L COLLECTIVE

STA. 70.00

TORQUE TUBE

BELLCRANK

(NOTE 3)

STA. 73.00 CONTROL

ROD ASSY.

14.47

13.10

THROTTLE

OPEN

IDLE

5° 45'

FUSELAGE-ROUTED

THROTTLE

ROD ASSY.

37° 30'

CUT-OFF

STA. 78.21

54° 30'

MID

STA. 70.35

COLLECTIVE STICK LINKAGE RIGGING

250-C30 ENGINE EQUIPPED HELICOPTERS

G76-2000-3A

Figure 201. Gas Producer Controls Rigging (Sheet 3 of 3)

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MAINTENANCE MANUAL

Legend (Ref. Figure 201)

EXCEPT AS NOTED, GAS PRODUCER AIRFRAME

ON ALL ENGINE INSTALLATIONS: ROLL THROTTLE

CONTROL LINKAGE RIGGING ADJUSTMENTS AND

TO CUT−OFF AND PUSH CONTROL ROD AND

MEASUREMENTS ON ALL 369/500 SERIES

BELLCRANK TOWARD FIREWALL TO ELIMINATE

HELICOPTER MODELS ARE NORMALLY STARTED

PLAY. ADJUST FUSELAGE ROUTED CONTROL ROD

WITH FUEL CONTROL LEVER CONTROL ROD

TO GET A GAP OF 0.010−0.050 INCH (0.254−1.270

DISCONNECTED, COLLECTIVE STICK AT

MM) BETWEEN UPPER BELLCRANK ARM AND

MID−TRAVEL; I.E., RIGGING FIXTURE (ST501) OR

SUPPORT FITTING.

(ST502) INSTALLED, AND THE PILOT’S THROTTLE

BENDIX FUEL CONTROL CUT−OFF POINTER

TWIST GRIP ROTATED TO MID−POSITION; I.E., TWIST

POSITION NORMALLY RANGES BETWEEN 0 − 10°

GRIP SET−SCREWS AT SIX O’CLOCK.

WITH FUEL CONTROL LEVER AGAINST CUT−OFF

ON 250−C20B AND 250−C20R/2 ENGINE EQUIPPED

STOP. CUT−OFF RANGE IS DUE TO FACTORY SET

HELICOPTERS; ADJUST STA. 73.00 CONTROL ROD

CALIBRATION VARIATIONS BETWEEN FUEL

SO LOWER ARM OF STA. 70.00 BELLCRANK IS

CONTROL UNITS.

VERTICAL WHEN THROTTLE TWIST GRIP IS AT IDLE

CECO FUEL CONTROL CUT−OFF POINTER

POSITION.

POSITION IS 2° TO MINUS, 1/32 INCH (0.7938 MM)

FOR 250−C30 ENGINE EQUIPPED HELICOPTERS;

FROM QUADRANT EDGE, WITH FUEL CONTROL

ALIGN FORWARD FACE OF STA. 70.00 BELLCRANK

LEVER AGAINST CUT−OFF STOP.

WITH AFT EDGE OF FIXTURE (ST406).

WITH PILOT’S THROTTLE TWIST GRIP HELD AT IDLE:

FOR 250−C20B AND 250−C20R/2 ENGINE EQUIPPED

BENDIX FUEL CONTROL IDLE POINTER POSITION IS

HELICOPTERS; WITH THROTTLE AND COLLECTIVE

30°.

IN MID−POSITION, ADJUST FUSELAGE ROUTED

10.

CECO FUEL CONTROL IDLE POINTER POSITION IS

CONTROL ROD SO CENTER OF STA. 129.00

30 − 32°.

BELLCRANK LOWER ARM PIVOT BOLT IS 4.97−5.03

11.

MAXIMUM ALLOWABLE POINTER MOVEMENT

INCHES (12.624−12.776 CM) FROM FIREWALL

BELOW THE OPTIMAL IDLE POSITION ON ALL

BULKHEAD.

ENGINE INSTALLATIONS FROM ALL CAUSES IS, 5/64

FOR 250−C30 ENGINE EQUIPPED HELICOPTERS;

INCH (1.9844 MM).

WITH THROTTLE AND COLLECTIVE IN

12.

NORMAL SETTING IS 40° WITH PILOT’S THROTTLE

MID−POSITION, ADJUST FUSELAGE ROUTED

AT IDLE.

CONTROL ROD SO CENTER OF STA. 129.00

BELLCRANK LOWER ARM PIVOT BOLT IS 5.47 − 5.50

INCHES (13.894−13.970 CM) FROM FIREWALL

BULKHEAD.

Failure to bleed fuel supply

D Rigging check/adjustments are required

WARNING

system after opening system

when pilot's compartment linkage or fuse

to atmosphere can result in power loss

lage-routed control rod length adjust

or engine flameout. Bleed trapped air

ments have been disturbed, or when there

after opening any fuel lines between

is less than a 0.010 inch (0.254 mm) gap

fuel tank and combustion chamber

between Sta. 129.00 firewall bellcrank

nozzle. Bleed fuel system following re

upper arm and its support fitting with the

moval and replacement of any part of

throttle in CUT-OFF position.

the engine or aircraft fuel system (Ref.

(1). Remove gas producer lever control rod

Sec. 28-00-00).

(Detail B).

(2). Position pilot's collective stick at

Do not exceed adjustable rod-

mid-travel. Insert rigging fixture

CAUTION

end maximum extension/thread

(ST501) or (ST502) in collective friction

engagement. Inspect rod-end thread en

guide link slot. Rest collective stick on

gagement through witness hole.

fixture.

(3). On dual control installations; check for

NOTE:

a synchronous motion between collec

tive stick throttle assemblies with the

D Refer to Collective Controls (Ref. Sec.

throttle wide open and in CUT-OFF.

67-10-00) for information on rigging

Dual control throttle movement should

throttle gas producer control tube, inter

be synchronized, but with the pilot's

connect torque tube and associated link

(command position) throttle dominating

age.

the copilot's throttle at idle.

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(4).

Position plot's throttle twist grip so that

(15). Torque control rod jamnuts to 25 - 30

twist grip set screws are at six o'clock.

inch-pounds (2.82 - 3.39 Nm).

(5).

Remove gearbox inspection plate on the

CAUTION

bottom of the collective stick. Ensure

that the centerline of the cutaway on

D Adjusting fuel control mechanical stop

the large bevel gear is aligned on the

settings for any reason is not allowed.

collective stick lengthwise centerline. If

D Governor and fuel control levers can be

gear is not properly positioned, remove

erroneously installed on the wrong fuel

gearbox side plate and reposition the

system component shaft. Governor lever

gear.

is relatively short with an offset angle of

about 65°. Fuel control lever offset angle

(6).

Find and remove all lost motion in the

is a more moderate 38°.

throttle system before making rigging

adjustments.

NOTE:

D Pointer position may range from 0° to 10°

(7).

Put throttle in idle position and secure

when contacting the idle CUT-OFF stop,

with friction lock.

depending on calibration settings pecul

(8).

Locate and secure alignment fixture

iar to the fuel control unit.

(ST406) on the pilot's seat structure.

D The Bendix fuel control features a double

The forward face of the Sta. 70.00

serrated washer between the lever and

bellcrank should align with the aft edge

fuel control input shaft. There are 24 (15°

of the fixture. Adjust Sta. 73.00 control

each) serrations on the lever side and 25

rod as required to align bellcrank with

(14.4° each) serrations on the fuel control

fixture. Remove the rigging fixture.

side that allow coarse or fine lever posi

tion adjustments to be made. Make 0.6°

(9).

Bottom the collective stick and check

incremental adjustments by moving the

the idler assembly for clearance with

washer one serration in one direction and

support.

the lever one serration in the opposite di

rection. Fifteen degree adjustments are

(10).

Set collective and throttle at mid-tra

made by moving the lever against the

vel.

washer; 14.4°

adjustments by moving the

(11).

Adjust fuselage-routed control rod

washer and lever together against the fuel

length so bolt center through lower arm

control shaft.

of Sta. 129.00 bellcrank is 5.50 ±0.03

(16). Rotate the throttle twist grip to idle.

inches (139.7 ±0.762 mm) from Sta.

124.00 firewall bulkhead.

(17). Insert rigging pin (ST407) through fuel

control lever. Position the lever on the

(12).

Rotate throttle twist grip to CUT-OFF.

fuel control throttle shaft so that lever

is close to parallel to, or a maximum of

(13).

Adjust the fuselage routed control rod

5° forward of the Sta. 137.50 engine

to provide a gap of 0.010-0.050 inch

compartment bulkhead. Torque lever

(0.254-1.270 mm) between Sta. 129.00

nut to 40 - 50 inch-pounds (4.52 -

bellcrank upper arm and support

5.65 Nm). Do not over-tighten the nut.

fitting. Push the rod and bellcrank

Apply a torque stripe.

toward the firewall bulkhead to remove

all friction errors before adjusting gap.

(18). Set gas producer lever control rod to a

preliminary length of 16.4 inches (41.66

NOTE: It will be necessary, during the rigging

cm) measured between rod-end bolt

procedure to remove and reinstall the rig

hole centers.

ging fixtures as required.

(19). Set throttle twist grip in the idle

(14). Move collective through full range of

position. Connect gas producer lever

travel. Ensure throttle movement is

control rod. Adjust rod length as

unrestricted in all collective stick

required to align it with the fuel control

positions.

lever.

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To prevent flameout, the fuel

(24). Move and hold throttle at idle. Check;

CAUTION

control pointer should not move

gas producer pointer is at 40° quadrant

more than 5/64 inch (1.9844 mm) below the

position.

fuel control quadrant 40° mark with throttle

at idle and commanded by either the pilot's

CAUTION

or copilot's twist grip.

D Do not alter gas producer lever position or

NOTE:

control linkage to adjust idle speed. Idle

speed shall be adjusted by the fuel control

D When dual controls are installed, move

idle screw, not the linkage.

copilot's throttle twist grip to its idle stop.

Fuel control pointer shall not be more

D Check linkage at travel extremes to en

than 5/64 inch (1.9844 mm) below the idle

sure that the linkage does not bind at any

degree mark.

point and the gas producer lever hits the

fuel control mechanical stops before the

D Throttle twist grip stopped at idle setting

throttle twist grip stops make contact.

must produce a 40° pointer/quadrant

alignment on the fuel control with the rig

(25). Set pilot's throttle wide open. Raise

ging pin inserted.

collective stick to upper stop. Check

that fuel control lever remains on max

(20). Remove rigging pin and operate pilot's

speed stop. Inspect the fuel control

throttle twist grip from CUT-OFF to

linkage for binding if the fuel control

wide open while an assistant deter

lever comes off the max speed stop.

mines that the fuel control lever

contacts the max open and CUT-OFF

(26). Leave throttle wide open and bottom

mechanical stops and the following

pilot's collective stick. Check that fuel

pointer positions are indicated.

control lever remains in contact with

the max stop.

(a). With pilot's throttle wide open, fuel

(27). Have an assistant move throttle and

control pointer shall align with

collective stick through entire range of

quadrant 100° mark and fuel control

travel while inspecting installation for

max stop shall be in contact with

operating clearances, control rod

lever.

bearing jamming and rod roll-over.

(b). With pilot's throttle in CUT-OFF;

(28). Check that the copilot's throttle

fuel control pointer shall be between

operates N₁ fuel control the same as the

0° and 10° quadrant marks with

pilot's with the following exception:

lever in contact with fuel control

minimum stop.

(a). When the copilot's throttle twist grip

is rotated to its idle stop, the fuel

(21). Adjust the gas producer lever control

control pointer shall move no more

rod length as required to move lever

than 5/64 inch (1.9844 mm) below the

into stop contact. If the Sta. 124.00

quadrant 40° mark (Detail C).

bellcrank bottoms on its support fitting,

(29). Inspect all bolts, nuts, control rod

adjust fuselage routed control rod one

jamnuts, cotter pins and lockwire

turn away from the bellcrank bottoming

installations for security.

problem.

NOTE: Refer to your Allison Operation and

(22). Return pilot's throttle twist grip to idle

Maintenance Manual for complete gas pro

detent. Ensure fuel control pointer

ducer fuel control rigging procedures to

aligns with 40° mark.

make the following adjustments.

(23). Bottom the pilot's collective stick.

(30). Start and operate engine at idle with

Rotate throttle to wide open. Check for

main rotor in flat pitch per Pilot's

stop/lever contact.

Flight Manual.

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MAINTENANCE MANUAL

Operating requirements de

B. Power Controls Operational Test/Final

CAUTION

mand that idle rpm be adjusted

Adjustments

within minus 1% of the Allison specified up

(Ref. Sec. 76-10-00)

per limit of 65% rpm. Achieving required

idle rpm is particularly important for heli

3. Gas Producer Controls Linkage

copters equipped with dual controls.

Replacement

(31). With pilot's throttle at idle, observe N_l

(Ref. Figure 202)

tachometer indicator. Ensure N_l speed

stabilizes between 64% - 65%.

(1). Disassemble linkage only to point

required to make repairs.

(a). Adjust idle speed with adjusting tool

(2). Measure and note control rod length

(ST404) per the applicable Allison

before removing rod-ends to expedite

Operation and Maintenance Manual.

reassembly and rigging.

(32). Accelerate engine to 100%, stabilize,

4. Sta. 124.00 Support Fitting Replacement

then decelerate to idle after each

adjustment. If idle adjustments do not

(Ref. Figure 202)

consistently stabilize rpm within 64% -

65% limit, follow engine fuel control

A. Sta. 124.00 Support Fitting Removal

fault isolation procedures per Allison

Manual.

(1). Remove lockbolt from Sta. 124.00

support fitting as follows:

(33). Accelerate and decelerate engine three

(2). Split collar axially with a sharp chisel.

times to ensure repeatability.

Have an assistant support opposite side

with a bucking bar to prevent hole

Throttle snap to idle must be

deformation or breakout. Drive pin out

WARNING

performed to ensure that en

with a drift.

gine will not flame out.

NOTE: Lockbolt hole enlargement beyond

(34). Accelerate engine to to normal operat

0.1870 inch (4.7498 mm) diameter requires

ing rpm with pilot's throttle, then snap

an oversize lockbolt pin installation.

to idle. Repeat this check using copilot's

B. Sta. 124.00 Support Fitting Installation

throttle where installed. If flameout

occurs, adjust engine idle speed per the

applicable Allison Operation and

Special Tools

Maintenance Manual.

(Ref. Section 91−00−00)

Item

Nomenclature

Perform a deceleration time

ST2009

Inspection gauge

CAUTION

check per PFM following gas

producer or linkage replacement or adjust

ment. Refer to Allison Engine Operation

(1). Position support fitting on Sta. 124.00

and Maintenance Manual for adjustment

lower frame. Install standard bolts,

procedures when deceleration time is less

washers and nuts. Do not tighten.

than allowable minimum.

NOTE: A standard size pin may be used where

pin hole does not exceed 0.1870 inch (4.7498

(35). Shut down engine.

mm) diameter; otherwise, proceed as fol

lows:

A. Gas Producer Fuel Control De−richment

Valve Adjustment

(2). Use a No.7 drill to enlarge a damaged

hole to 0.2015 inch (5.1181 mm)

(1). Refer to Allison Engine Operation and

maximum diameter. Use a 3/16 inch

Maintenance Manual.

(4.7625 mm) diameter replacement pin.

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MAINTENANCE MANUAL

NOTE: Up to three washers may be used under

1). Bearing wear is limited to 0.040

pin head to establish correct lockbolt grip.

inch (1.016 mm) maximum axial

looseness.

(3). Install lockbolt pin and collar; best fit

results when pulling gun air pressure is

(b). Surface damage.

90-125 psi (621-862 kPa).

(c). Cracks

(4). Inspect lockbolt installation with gauge

(d). Gouges

(ST2009) or equivalent.

(e). Nicks

(a). No gap is allowed under either pin

head or collar. If pin grip length or

(f). Loose end rivets

collar swage quality is questionable,

(g). Misalignment, bent or bowed

replace lockbolt.

Control rod variation from a

(5). Torque control support fitting/Sta.

CAUTION

straight line is limited to 0.010

124.00 attaching hardware.

inch (0.254 mm), maximum, in each foot.

Do not jam bearing against fit

CAUTION

(3). Bent or bowed gas producer control

ting. Hold rod-end with a

rods, excluding rod-ends, must fall

wrench when tightening adjustable end jam

within the following tolerances:

nut. Ensure bearing misalignment is di

vided equally between each control rod

(a). Fuselage-routed control rods: Not

bearing assembly.

more than 0.050 inch (1.270 mm),

total variation.

(6). Rig gas producer controls (Ref. Model

250-C20B and 250-C20R/2 Gas

(b). Sta. 73.00 control rod: Not more than

Producer Controls Rigging).

0.010 inch (0.254 mm), total varia

tion.

5. Gas Producer Controls Inspection

(c). Gas producer lever control rod: Not

(Ref. Figure 202)

more than 0.020 inch (0.508 mm),

total variation.

(1). Check gas producer linkage for lost

motion due to wear as follows:

(4). Inspect bellcrank and support fitting

bearings for binding.

(a). Open throttle to maximum speed

stop, then slowly back to to idle stop.

(5). Fluorescent penetrant inspect sus

pected parts for cracks.

(b). Mark pointer position on gas produc

er fuel control quadrant.

Check control system rig

WARNING

and engine operation follow

(c). Use light finger pressure to move gas

ing any repair that required gas pro

producer lever toward CUT-OFF.

ducer control or linkage disassembly

Mark pointer position on quadrant.

or replacement; prior to releasing heli

Relax pressure.

copter for flight.

(d). Measure distance between lever

Perform a deceleration time

CAUTION

position marks. Measurement

check per pilot's flight manual

exceeding 5/64 inch (1.9844 mm)

after adjusting or replacing gas producer

indicates unacceptable wear in

fuel control or linkage parts. Make adjust

throttle control linkage. Inspect

ments per Allison Operation and Mainte

individual linkage components for

nance Manual if deceleration time is less

loose fasteners and wear.

than allowable minimum.

(2). Inspect control rods for:

6. Gas Producer Control Rod Repair

(a). Worn or binding end bearings.

(Ref. Figure 201)

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7. Bellcrank Repair

Consumable Materials

(Ref. Figure 202)

(Ref. Section 91−00−00)

Item

Nomenclature

(1). Replace bellcranks or control supports

that are distorted, cracked or have

CM321

Surface primer locking compound

elongated holes.

CM431

Sealing, locking and retaining compound

(2). Replace unserviceable bellcrank

bearings.

Fluorescent penetrant crack in

Do not get primer or locking

CAUTION

spection shall be performed af

compound on bearing surfaces.

ter cold-straightening. Replace a cracked or

bent rod, or rod-end.

(a). Apply surface primer and grade A

locking compound (CM321 and

CM431) to bearing outer race and

(1). Cold-straighten a bent rod provided

installation hole per manufacturers

there are no nicks or sharp dents in

instructions. Install bearing.

bend length. Do not use rod-ends to

Check control system rig

support rod during straightening

WARNING

and engine operation follow

process.

ing any repair that required gas pro

ducer control or linkage disassembly

Use care when drilling to re

or replacement; prior to releasing heli

CAUTION

move or install riveted rod-end.

copter for flight.

Tighten jam nut before drilling and riveting

Perform a deceleration time

to prevent hole enlargement.

CAUTION

check per pilot's flight manual

after replacing or adjusting gas producer

(2). Replace control rod-end if bearing axial

fuel control or linkage parts. Make adjust

play is more than 0.040 inch (1.016

ments per Allison Operation and Mainte

mm). Set initial control rod length and

nance Manual if deceleration time is less

bearing angularity as shown.

than allowable minimum.

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MAINTENANCE MANUAL

ENGINE CONTROLS

MAINTENANCE PRACTICES

1. Engine Controls Description

modulates fuel flow to the engine in

conjunction with the position of the

(1). The 250-C47 engine control system

power lever angle (PLA) which is

consists of a full authority digital

connected to the throttle grip on the

engine control (FADEC) system for

collective stick by a control cable. The

automatic operation and a hydrome

PLA will be set with the throttle grip to

chanical backup system for emergencies

either the Cutoff, Ground Idle or Flight

or manual operation.

Idle position. The ECU provides hot

start and overspeed protection, over

(2). Refer to the 250-C47M Rolls-Royce

speed test function and auto-reignition

Engine Operation and Maintenance

and rotor speed trim capability.

Manual for additional engine fuel

system theory, operation and mainte

(2). In the Manual Mode, the fuel flow is

nance data.

modulated by the PLA on the Hydrome

chanical Control Unit with the throttle

2. Engine Controls Operation

grip and control cable. The ignition

exciter operates continuously in this

(1). Engine control mode is selected by the

mode.

Auto/Manual Switch. In the Auto Mode,

the Electronic Control Unit (ECU)

3. Engine Controls Fault Isolation

Table 201. Engine Controls Fault Isolation

Symptom

Probable Trouble

Corrective Action

ECU FAIL on Warning/Caution

Faulty ECU.

Replace ECU.

panel.

Faulty wiring.

Test and repair wiring.

Flight controls unresponsive.

Faulty ECU.

Replace ECU.

Faulty collective potentiometer.

Replace Collective Potentiometer.

Faulty directional potentiometer.

Replace Directional Potentiometer.

Faulty wiring.

Test and repair wiring.

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MAINTENANCE MANUAL

4. ECU (Electronic Control Unit)

5. Engine Control Potentiometer

Replacement

(Ref. Figure 202)

A. Collective Potentiometer Removal

(1). Detach electrical connector from

A. ECU Removal

collective potentiometer.

(2). Loosen potentiometer mounting screws

(1). Disconnect engine harness and air

and remove drive belt.

frame harness connectors from ECU.

(3). Remove screws and washers and

remove potentiometer assembly from

(2). Remove screw, lockwasher and washer

mounting bracket.

and disconnect bonding jumper from

ECU.

B. Collective Potentiometer Installation

Special Tools

(3). ECU P/N - 23068338, 23070259,

(Ref. Section 91−00−00)

23072949 and 23080491 - Remove

Item

Nomenclature

bolts, washers, large area washers and

ST1010

Volt-ohmmeter

bushings and remove ECU from

mounting bracket.

N/A

Laptop computer with MT35 program

(1). Prepare potentiometer mounting

(4). ECU P/N - 23088905, 23089311 -

surfaces for electrical bonding (Ref.

Remove bolts and washers and remove

CSP-HMI-3, Section 96-00-00).

ECU from mounting bracket.

(2). Install potentiometer with screws and

washers. Torque screws to 20 - 25

B. ECU Installation

inch-pounds (2.25 - 2.82 Nm).

(3). Rig potentiometer to collective stick.

(1). ECU P/N - 23068338, 23070259,

23072949 and 23080491 - Install

(a). Place collective stick in full down

ECU on mounting bracket with bush

position and connect an ohmmeter

ings, large area washers, bolts and

(ST1010) between pins 1 and 2. Turn

washers. Torque bolts to 36 - 46 inch

potentiometer gear until resistance is

pounds (4.06 - 5.19 Nm).

between 1000 and 1175 ohms.

Attach electrical connector to poten

(2). ECU P/N - 23088905, 23089311 -

tiometer. Connect MT35 to the ECU

Install ECU on mounting bracket with

and apply power to aircraft. Reading

bolts and washers. Torque bolts to 36 -

on MT35 should be 0.0% - 5.0%.

46 inch pounds (4.06 - 5.19 Nm).

Excessive tension on drive belt

CAUTION

may damage potentiometer.

(3). Connect bonding jumper to ECU with

screw, lockwasher and washer. Torque

(b). Install drive belt over both pulleys

screw to 20 - 25 inch-pounds (2.25 -

with teeth fully engaged. Tension

2.82 Nm).

belt with potentiometer mounting

screws so that the belt does not

noticeably sag over the span. Retor

(4). Connect engine harness and airframe

que screws to 20 - 25 inch-pounds

harness connectors to ECU.

(2.25 - 2.82 Nm).

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MAINTENANCE MANUAL

(c). Place collective in full up position and

(3). Rig potentiometer to directional

verify that potentiometer resistance

controls.

is between 4500 and 4675 ohms.

(a). Place directional control pedals to full

With electrical connector attached to

left pedal position and connect

potentiometer and MT35 connected

ohmmeter (ST1010) between pins 2

apply power to aircraft, reading

and 3. Turn potentiometer gear until

should be 98.6% - 105.0%.

resistance is between 1000 and 1250

ohms.

(d). If necessary, belt may be adjusted

one tooth on either pulley (one tooth

Attach electrical connector to poten

equals 450 ohms).

tiometer. Connect MT35 to the ECU

and apply power to aircraft. Reading

(e). If more adjustment is required,

on MT35 should be 0.0% - 7.1%.

loosen pulley to bracket bolts on

collective (view B) and rotate pulley

to obtain desired resistance. Retor

Excessive tension on drive belt

CAUTION

que bolts to 20 - 25 inch-pounds

may damage potentiometer.

(2.25 - 2.82 Nm).

(b).

Install drive belt over both pulleys

(4). If not already connected, attach

with teeth fully engaged. Tension

electrical connector to potentiometer.

belt with potentiometer mounting

screws so that the belt does not

C. Directional Potentiometer Removal

noticeably sag over the span. Retor

(1). Detach electrical connector from

que screws to 20 - 25 inch-pounds

directional potentiometer.

(2.25 - 2.82 Nm).

(2). Loosen potentiometer mounting screws

(c).

Place directional control pedals to full

and remove drive belt.

right pedal position and verify that

potentiometer resistance is between

(3). Remove screws and washers and

4500 and 4675 ohms.

remove potentiometer assembly from

mounting bracket.

With electrical connector attached to

D. Directional Potentiometer Installation

potentiometer and MT35 connected

apply power to aircraft, reading

should be 98.6% - 105.0%.

Special Tools

(Ref. Section 91−00−00)

(d).

If necessary, belt may be adjusted

Item

Nomenclature

one tooth on either pulley (one tooth

ST1010

Volt-ohmmeter

equals 400 ohms).

N/A

Laptop computer with MT35 program

(e).

If more adjustment is required,

loosen pedal pulley bolt and rotate

(1). Prepare potentiometer mounting

pulley to obtain desired resistance.

surfaces for electrical bonding (Ref.

Retorque bolt to 20 - 25 inch-

CSP-HMI-3, Chap. 96).

pounds (2.25 - 2.82 Nm).

(2). Install potentiometer with screws and

washers. Torque screws to 20 - 25

(4). If not already connected, attach

inch-pounds (2.25 - 2.82 Nm).

electrical connector to potentiometer.

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HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369D/E/FF-500/600N HELICOPTERS (ISSUED: 1990) - page 30