tm 55-1520-242-mtf

T M 5 5 - 1 5 2 0 - 2 4 2 - M T F

M A I N T E N A N C E T E S T

F L I G H T M A N U A L

A R M Y M O D E L

U H - 1 , E H - 1 H E L I C O P T E R

T M 5 5 - 1 5 2 0 - 2 4 2 - m t f i s p u b l i s h e d f o r t h e u s e o f a l l

c o n c e r n e d .

* T h i s m a n u a l s u p e r s e d e s T M 5 5 - 1 5 0 0 - 2 1 9 - M T F , 2 8

February 1979, including all changes.

HEADQUARTERS

D E P A R T M E N T O F T H E A R M Y

2 0 D e c e m b e r 1 9 8 5

TM 55-1520-242-MTF

A maintenance test flight is an exception-ally demanding operation and requires athorough flight readiness inspection (pre-flight). The flight readiness inspection isprescribed in TM 55-1520-210-10 and TM55-1520-220-10 Operator’s Manual andmust be completed prior to the main-tenance test flight. Emergency proceduresare found in the applicable -10 or checklistand are not duplicated in this publication.Prior to each maintenance test flight, thepilot will contact maintenance/quality con-trol personnel to determine the main-tenance that has been performed. Thismanual should be used only by qualifiedmaintenance test flight pilots as requiredin AR 95-1.

NOTE

A copilot or observer is required for the checks listedbelow:

(1)

(2)

(3)

Hydraulic system check (pg. 2-15)

Power cylinder check (pg. 2-34)

Hydraulics off check (pg. 2-41)

C-3 a/(b blank)

TM 55-1520-242-MTFC5

CHANGE HEADQUARTERSDEPARTMENT OF THE ARMY

NO. 5 WASHINGTON, D.C., 18 July 2005

Maintenance TestFlight Manual

Army ModelUH-1, EH-1 HELICOPTER

TM 55-1520-242-MTF, 20 December 1985 is changedas follows:

1. Remove and insert pages as indicated below. New or changed text material is indicated by a verticalbar in the margin. An illustration change is indicated bya miniature pointing hand.

Remove Pages Insert pages

i and ii i and ii1-1 and 1-2 1-1 and 1-22-1 and 2-2 2-1 and 2-22-9 and 2-10 2-9 and 2-102-13 and 2-14 2-13 and 2-14

2. Retain this sheet in front of manual for referencepurposes.

}

2-15 and 2-16 2-15 and 2-162-29 and 2-30 2-29 and 2-302-39 and 2-40 2-39 and 2-40

TM 55-1520-242-MTF

By Order of the Secretary of the Army:

Official:

PETER J. SCHOOMAKER General, United States Army Chief of Staff

Administrative Assistant to the Secretary of the Army DISTRIBUTION: To be distributed in accordance with DA Form 12-31-E, block no. 0800, requirements for TM 55-1520-242-MTF.

SANDRA R. RILEY

0516005

C5

TM 55-1520-242-MTFC 3

CHANGE HEADQUARTERSDEPARTMENT OF THE ARMY

NO. 3 WASHINGTON, D.C., 15 November 1991

Maintenance TestFlight Manual

Army ModelUH-1, EH-1 HELICOPTER

TM 55-1520-242-MTF, 20 December 1985, ischanged as follows:

1. Remove and insert pages as indica-ted below. New or changed text material isindicated by a vertical bar in the margin.An illustration change is indicated by aminiature pointing hand.

Remove pages

a/b2-1 and 2-22-33 and 2-342-43 through 2-463-71 and 3-72

4-1 and 4-24-11 and 4-12

2. Retain thismanual for reference

Insert pages

a/b2-1 and 2-22-33 and 2-342-43 through 2-463-71 and 3-72

4-1 and 4-24-11 and 4-12

sheet in front ofpurposes.

TM 55-1520-242-MTFC 3


GORDON R. SULLIVANGeneral, United States Army

Official: Chief of Staff

MILTON H. HAMILTONAdministrative Assistant to the

Secretary of the Army00213

DISTRIBUTION:

To be distributed in accordance withDA Form 12-31-E, block no. 0800, MTFmaintenance requirements forTM 55-1520-242-MTF.

TM 55-1520-242-MTF

TABLE OF CONTENTS

REPORTING ERRORS AND RECOMMENDINGIMPROVEMENTS

You can help improve this manual. If you find anymistakes or if you know of a way to improve these pro-cedures, please let us know. Mail your letter, DAForm 2028 (Recommended Changes to Publicationsand Blank Forms) located in the back of the applica-,

directly to: Commander, U.S. Army Aviation andand Missile Command, ATTN: AMSAM-MMC-MA-NP,Redstone Arsenal, AL 35898-5000. A reply will befurnish to you. You may also provide DA Form2028 information to AMCOM via e-mail, fax, orthe World Wide Web. Our fax number is DSN 788-6546 or Commercial 256-842-6546. Our e-mail address

SECTION PAGEI Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

II Maintenance Test Flight Checklist . . . . . 2-1Prior to Maintenance Test Flight . . . . . . . 2-1Before Starting Engine . . . . . . . . . . . . . . . . 2-2Starting Engine . . . . . . . . . . . . . . . . . . . . . . . 2-9Engine Runup . . . . . . . . . . . . . . . . . . . . . . . . 2-15Before Takeoff . . . . . . . . . . . . . . . . . . . . . . . . 2-29Hover Checks . . . . . . . . . . . . . . . . . . . . . . . . 2-30Takeoff and Climb Checks.. . . . . . . . . . . . 2-37Level Off Checks . . . . . . . . . . . . . . . . . . . . . . 2-38In-Flight Checks . . . . . . . . . . . . . . . . . . . . . . 2-39Before Landing Checks. . . . . . . . . . . . . . . . 2-47After Landing and Engine ShutdownChecks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-48

C5 i

is: [email protected]. Instructions for sendingan electronic 2028 may be found at the back of theOperator's Manual immediately preceding thehard copy 2028. For the World Wide Web use:https://amcom2028.redstone.army.mil.

ble Operator's Manual (when using the 2028 fromthe Operator's Manual, make sure the publicationnumber and title are changed to reflect this MTF),

TM 55-1520-242-MTF

TABLE OF CONTENTS (CONT)

SECTION PAGE

III Troubleshooting . . . . . . . . . . . . . . . . . . . . . . 3-1Troubleshooting Guide A -Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2Troubleshooting Guide B -Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7Troubleshooting Guide C -Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16Troubleshooting Guide D -Caution Panel . . . . . . . . . . . . . . . . . . . . . . . . 3-38Troubleshooting Guide E -PowerPlant . . . . . . . . . . . . . . . . . . . . . . . . . . 3-48Troubleshooting Guide F -Power Train . . . . . . . . . . . . . . . . . . . . . . . . . . 3-57Troubleshooting Guide G -Hydraulic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60Troubleshooting Guide H -Flight Controls . . . . . . . . . . . . . . . . . . . . . . . 3-63Troubleshooting Guide I -Nonapplicable . . . . . . . . . . . . . . . . . . . . . . . 3-74Troubleshooting Guide J -Vibrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-75Troubleshooting Guide K -Communications/NavigationEquipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-79

IV Special Procedures . . . . . . . . . . . . . . . . . . . . 4-1a.b.c.d.e.f.g.h.

Radar AltimeterSelf-Test . . . . . . . . . . 4-1Electronic Altimeter Self-Test . . . . . . 4-2Radar Warning Receiver Self-Test . . 4-3Tail Rotor Tracking . . . . . . . . . . . . . . . 4-5Main Rotor Tracking . . . . . . . . . . . . . . . 4-9Health Indicator Test(HIT) . . . . . . . . . 4-13Engine Topping . . . . . . . . . . . . . . . . . . . 4-15Fuel Control Flight Check . . . . . . . . . 4-21

V Charts and Forms . . . . . . . . . . . . . . . . . . . . . 5-1

ii

TM 55-1520-242-MTF

SECTION I. - INTRODUCTION

1. PURPOSE. The purpose of this manual is toprovide complete instructions for performing amaintenance test flight of UH-1, C/M, H/V andEH-1H/X aircraft. For the specific conditionswhich require a general or limited maintenance testflight refer to TM 55-1500-328-25 and the applicableaviation unit and intermediate maintenancemanual.

2. DEFINITIONS.a. Maintenance Test Flight. A functional test

flight for which the primary purpose is to deter-mine whether the airframe, power plant, accessoriesand other equipment are functioning in accordancewith predetermined requirements while subjected tothe intended environment.

b. Warnings, Cautions and Notes. Warnings, Cau-tions and Notes are used to emphasize important andcritical instructions and are used for the followingconditions:

An operation procedure, practice, etc.,which, if not correctly followed, will resultin personnel injury or loss of life.

An operating procedure, practice, etc.,which, if not strictly observed, will resultin damage to or destruction of equipment.

1-1

TM 55-1520-242-MTF

NOTE

An operating procedure, condition, ect., whichis essential to highlight.

3. GENE RAL INFORMAT I ON .

a. T hi s m anu al c ov er s o nly ma int ena nc e t es t f li ght o fUH-1, C, H, M, V and EH/1H/X aircraft and in no waysupercedes any information contained in TM 55-1520-210-10, TM 55-1520-220-10, TM 55-1520-247-10 or-CL, but is to be used in conjunction with the -10 or-CL. This manual covers all the requirements of theappropriate -10 and -CL from “Before Starting Engine”through “Engine Shutdown”.

b. C r ew r equ ir em ents w i ll be as s pec if ied in A R 95- 1 ,TM 1-1500-328-23 and TM 55-1520-210-10, TM55-1520-220-10 and TM 55-1520-247-10.

c. T he du ra tio n o f the ge ner al or l im ite d t es t f l igh t w i llbe in accordance with the requirements of TM 1-1500-328-23.

4. SP EC IAL I NST R U C T I O N S .

a. Cargo a nd Pas senge rs. C ar go and pas s eng er sare pr ohi bi ted on ma in tena nc e te st fl ig hts .

b. Forms and Rec ords. F or ms an d r ec or ds wi ll bechecked prior to the maintenance test flight to deter-mi ne m ai nten anc e p er for me d an d t h e ty pe o f ma int e-nance test flight required (i.e., general or limited).

c. Confi g ur at ion. T h e co nfi gur at ion o f t he ai r cr af tshould be determined prior to the maintenance testflight in order to determine performance parameters.Prior to the actual test flight, the pilot will computeweight and balance as required.

1-2 C5

TM 55-1520-242-MTF

d. Post Test Flight Inspection. A thorough visualinspection will be performed to the extent necessaryto assure that deficiencies or shortcomings deve-loped as a result of the maintenance test flight aredetected.

e. References. When a maintenance test flight isrequired to assure proper operation of a specificsystem(s), refer to the applicable maintenancemanual for the limits of that system.

f. Asterisked Checks. An asterisk (*) prior to acheck requires that the Test Flight Check Sheet beannotated with a specific reading, a check ( ✔ ) forsatisfactory performance, or an (X) for problemdetected will be recorded and a short statemententered in the “remarks” block of the check sheet.

g. Maintenance Test Flight Check Sheet. Thesample check sheet contained in section V will(refer to figure 5-12) be used for all test flights.When a test flight is performed for the purpose ofdetermining if specific equipment or systems areoperating properly, completion of only that portionof the maintenance test flight check sheet ap-plicable to the specific equipment or systems beingtested is required. The aircraft test flight checksheets may be locally reproduced. Continuationsheets may be used when necessary. Items that,during maintenance test flights prove to be un-satisfactory and require corrective action, shouldbe listed in the remarks block during flight andtransferred to DA Form 2408-13 immediately aftertermination of the flight. The sheet will be attachedto DA Form 2408-13 upon completion. After accrualof two or more sheets, the data should be reviewedto determine if trends are developing.

h. Crew Briefings. Prior to accomplishment ofthe test flight the aircraft crew (co-pilot/technicalobserver/inspector, etc) will be briefed by theMaintenance Test Pilot on the maneuvers to be per-formed and any special requirements/inspectionsrequiring assistance by these personnel.

1-3/(1-4 blank)

TM 55-1520-242-MTF

SECTION II. MAINTENANCE TESTFLIGHT CHECKLIST

General. This section contains the maintenance testflight requirements peculiar to Army Model UH-1, C,H, M, V and EH/1H/X aircraft. Conditions requiringaccomplishment of test flights shall be in accordancewith TM 1-1500-328-23. The requirements containedherein are established to assure a thorough inspectionof the aircraft before flight, during flight, and uponcompletion of the maintenance test flight. the rightside of the check list (Troubleshooting Reference) iscross-indexed to the troubleshooting guides containedin Section III. A dash between the references means“through”; a comma means “and”. The references listthe possible abnormal conditions, indications or mal-functions which could be encountered while performingthe procedure.

PROCEDURE TROUBLESHOOTINGREFERENCE

PRIOR TO MAINTENANCE TEST FLIGHT* 1. Forms and records - Check.* 2. Through flight readiness

inspection in accordance withthe requirements containedin TM 55-1520-210-10, TM55-1520-247-10 Performed.

3. Special pre-flight checks -a. Landing/Searchlight - Check

Operation and Limit Switches.C11

C 5 2-1

TM 55-1520-242-MTF


PRIOR TO MAINTENANCE TEST FLIGHT (CONT)b. Cockpit/Cargo Compartment

Lights - Condition/Operation(Includes all NVG LightingSystems).

C9, 53-54

c. Special Equipment - Check(MTF Equipment).

BEFORE STARTING ENGINE1. Ignition lock switch - On. Check

condition and security.2. Doors - As desired.

Kicking pedal adjuster with the heel to adjustpedals can break the shaft. Adjust pedals byhand only.

3. Seat and pedals - Adjust.Freedom of adjustment.

H1

4. Seat belts and shoulder harness- Fasten. Inertia reel functionsproperly.

5. Pedals - Freedom of movementthrough range of travel, neutral.

H2

6. Cyclic and collective friction -OFF.

2-2 C5

TM 55-1520-242-MTF


7. Cyclic and collective (except UH-1 H3;4C/M) - Freedom of movementthrough range of travel. Check blademovement corresponds to controlmovement, ensure pilots cyclic doesnot contact the instrument panel whenfull forward, cyclic centered. Placecollective full down.

8. AC circuit breakers - In.

9. Heater outlets, fresh air ducts (frontand rear) - Condition, no foreignmatter.

10. Overhead checks - (Pilot and co pilot).

a. Greenhouse - Condition andsecurity.

b. Windshield wiper motor, motorguards, cannon plugs, wires -Condition and security.

c. Windshield - Condition andsecurity.

d. Spare lamp kit - Complete.

11. Collective and cyclic control headand switches - Check, set as re-quired. (pilot and co-pilot).

C4 2-3

TM 55-1520-242-MTF


BEFORE STARTING ENGINE (CONT)

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

Radios - Check, set as required.

GOV switch - AUTO.

DE-ICE switch - OFF.

INT AUX FUEL/transfer pumpswitches - OFF.

LOW RPM AUDIO - Checkspringloaded AUDIO.

MAIN and START FUEL switches- OFF, main fuel switch guard in-stalled.

HYD CONT switch - ON orspring-loaded BOTH (C/M).

FORCE TRIM switch - ON.

HOIST CUT switch - OFF, Coverdown; if installed.

CHIP DET switch - Spring-loadedto BOTH.

COMPASS slaving switch - IN orMAG.

EMERGENCY COLLECTIVEACCUMULATOR switch - OFF(UH-1C/M).

2-4

TM 55-1520-242-MTF


24. Instruments - Check condition,security, position, range markings,slippage marks and static indica-tions. Check both pilots and copilots when applicable.

a. Turn and Slip indicator - Full offluid, no bubbles, needle centered.Marked four minute turn.

b. Omni indicator - Course selectorfree.

c. Marker beacon rheostat - OFF.

d. Clock - Set and running.

e. Standby compass - Full of fluid,no bubbles, no discoloration, com-pensated within last 12 months.Compensation card posted withCardinal Headings and each 45°.

f. VSI's - needle zero.

g. Gyro-Compass - ADF position.

h. Altimeter’s - Set to field elevation(not with AIMS altimeter.).

NOTE

The altimeter will give a slightly dif-ferent reading after the rotor commencesturning.

B1

B3

2-5

TM 55-1520-242-MTF



i. Attitude indicators-check.

j. Airspeed indicators-Check.

k. Radar altimeter - Check.

l. Dual tachometer - Check.

m. Torquemeter - Check.

NOTE

Redline (except UH-1C) should becalibrated to the engine Data Plate Tor-ques.

Data Plate Torque

58596061626364

Gage Redline

474849505151.552

n. Gas producer tach - Check.

o. EGT gage - Check, (may indicateFAT).

p. Voltmeters - Check.

q. Loadmeters - Check.

r. XMSN oil pressure gage - Check.

B4

Change 1 2-6

TM 55-1520-242-MTF


s.

t.

u.

v.

w.

x.

y.

XMSN oil temperature gage -Check.

R a d a r w a r n i n g d i s p l a y(AN/APR-39) - Check.

Engine oil pressure gage - Check.

Engine oil temperature gage -Check.

Fuel pressure gage - Check.

Fuel quantity gage - Check.

Gyro-Compass correction card -Installed, - compensated withinlast 12 months, with cardinalheadings and every 45°.

25. Overhead Console Checks:

a.

b.

c.

d.

e.

f.

CABIN HEATING controlswitches - OFF.

CARGO REL switch - OFF.

panel

WIPERS - OFF, do not recycle.

ANTI-COLL light switch - ON.

POSITION/NAVIGATION lightswitch - OFF.

PITOT HTR switch - OFF.

2-7

TM 55-1520-242-MTF



g. NVG switch - OFF.

h. FWD DOME LT switch - OFF(if installed).

i. DC circuit breakers - ALL IN.

j. INST LTG rheostats - OFF

k. INVTR switch - OFF.

l. AC voltmeter selector ACphase

m. DC voltmeter selector -- BAT. C1A minimum of 24 volts shouldbe indicated on the DC volt-meter before attempting start.Battery, starts can be made whenvoltage is less than 24 volts. pro-vlded the voltage is at/or above14 volts when cranking thru 10percent N1 speed.

n. MAIN GEN switch -- ON. EH-IH Phase 1B/EH-IX GENswitch ON

o. NON - ESS BUS switchNORMAL ON.

p. START/GEN switch - STARTposition. EH-IH Phase 1B/EH-IX, Start/Converter Switch -START position.

C4 2-8

TM 55-1520-242-MTF


BEFORE START ENGINE (CONT)q. BAT switch - On. C2-4, 52

* r. F r ee - air te mpe r atur e g age -Check, condition

STARTING ENGINE1. Ground power unit - Connect

for GPU start. The externalpower caution light should beilluminated.

2. Inverter - Spare on GPU start)CATION panel light out. Notethe copilot Attitude IndicatorOFF flag disappears, after15 seconds pull out and thenrelease the Pull To Cage knob.The gyro should settle to aproper display. The Pilotsattitude indicator OFF flagshould disappear within twominutes.

3. Low RPM audio - OFF. C6* 4. All press to test lights - Test,

Check cat-eyes. The CARGORELEASE ARMED light andIFF light should also betested utilizing their respectiveswitches.

C5

5. MASTER CAUTION light - ON. D16. RPM WARNING light - ON. C6

C 5 2-9

TM 55-1520-242-MTF


STARTING ENGINE (CONT)

*7. FIRE detector light - Test Light C7,8should come on within 10seconds after depressing button.Do not leave light on for more than15 seconds.

*8. CAUTION Panel Lights - Check D2-4proper lights illuminated. 26-28

a.

b.

c.

d.

e.

f.

g.

h.

30-32

CAUTION Panel TEST - Alllights should illuminate.

BRIGHT/DIM switch - DIM;lights should remain bright.

PILOT lighting rheostat - ON.

BRIGHT/DIM switch - DIM;lights should dim.

BRIGHT/DIM switch - BRIGHT;lights should return to full bright.

BRIGHT/DIM switch - DIM.

PILOT lighting rheostat - OFF;lights should return to bright.

MASTER CAUTION - RESET.

2-10

TM 55-1520-242-MTF


NOTE

The governor switch caution panel lightis wired through the governor controlswitch. It is possible for the fuel controlto be in the emergency mode and the cau-tion light out under some circumstances.

9.

10.

11.

12.

13.

*14.

Engine and transmission tempera-ture gages - Check indications.

Altimeter(s) (AIMS) - Set fieldelevation (insure DC power hasbeen applied for one minute priorto setting).

MAIN FUEL switch - ON; Check D5, 6BOOST pump light(s) out.

START FUEL switch - ON (ifinstalled).

GOV RPM INCR-DECR switch -DECR for 10 seconds.

Throttle System - Check:

Use of excessive force may causedamage to the throttle linkage orbellcranks.

B2

E1-3

2-11

TM 55-1520-242-MTF



a.

b.

c.

d.

e.

Friction Check - Ensure frictioncan be overridden, then off.

Full Open Check - Record cushionat full open position.

Idle Stop Check - Note presence ofmechanical stop and properoperation.

Full Closed Check - Recordcushion at full closed position.

Freedom of Travel Check - Notefreedom of travel through entirerange; Set throttle for start.

NOTE

Ridge to ridge on the knurled throttlefriction knob represents 10° travel onthe fuel control arm. By aligning a pencilwith any ridge, the degrees of cushioncan be measured by opening and closingthe throttle to the point where resistanceis met until the throttle stop is hit.Cushion should be 5° ± 2°.

15.

16.

17.

Rotor blades (main and tail) - Clearand untied.

Fire guard - Briefed and posted.

Starting Engine - Proceed asfollows:

2-12

TM 55-1520-242-MTF

PROCEDURE TROUBLESHOOTING

a.

b.

c.

d.

e.

f.

h.

i.

j.

k.

l .

REFERENCE

Starter switch - Energize; start A1-3clock.

DC Voltmeter - check minimum14VDC passing through 10% N1speed, voltage increases as N1gains speed.

EGT - Rising normally. A4, 6

N1- Normal acceleration. A4, 5

Main Rotor Blades - Turning by15% N1.

Engine oil press light - out as N1gains speed (27±1 PSI).

START FUEL - Off (if installed)400°c L-11, 40% N1L13.

Starter switch - Release at 40% A7-9N1, or after 40 seconds, whicheveroccurs first. Note increase involtmeter.

Transmission oil press light - out D15as N1 gains speed. (35± 2 PSI).

Fire Warning light - OUT. C8

Rotor - Turning normally. A9, 10

Throttle - Engine Idle.

D7

2-13

g.

TM 55-1520-242-MTF



The copilot attitude indicator should becaged and held momentarily as inverterpower is applied.

18. INVTR switch - SPARE ONcaution panel light out. Notecopilot attitude indicator off flagdisappears. The gyro shouldsettle to a proper display. Thepilot’s attitude indicator off flagshould disappear within twominutes.

C12-14

If no engine or transmission oil pressure isevident, shut down engine immediately andinvestigate cause.

19. Engine oil pressure - Check 25PSI minimum.

B23, E4-8

20. Engine oil temp - Check forrising indication.

B2, E9

21. XMSN oil pressure - Check 30PSI minimum.

B23, F1-5

22. XMSN oil temp - Check for risingindication.

B2, F6

23. Fuel pressure - Check 5 PSIminimum.

B5

24. CAUTION panel lights - All out;MASTER CAUTION light out.

D3, 5, 7-24

25. Torquemeter - Some indication. B9-11, 23

2-14 C5

TM 55-1520-242-MTF



To properly check N1 speed at engine idlethrottle must be rolled slightly into the cush-ion to ensure contact with the engine idlestop. Use of excessive force may causedamage to the throttle linkage or bellcranks.

* 26. Engine idle speed - Check N1 atengine idle, L13 68-72%, L-1155-59%.

E10, 11

* 27. GOV switch - EMER; let N1decrease 2 to 5%. Note cautionlight on, then switch back to autowithin 5 seconds; note increaseto initial reading and cautionlight out.

E10, 11D12, 25E12, 13

28. Ground power unit (GPU Start) -Disconnect. The external powercaution light should be out.

29. DELETED.

ENGINE RUNUP1. Radios - All ON (monitor

loadmeter).K1

* 2. HYDRAULIC SYSTEM (UH-1,H/V, EH-1H/X) - Check.

C15, D1,16, 26

G1

C5 2-15

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

Full movement of the cyclic at lowRPM may result in damage to the maindriveshaft.

Brief copilot/observer not to remove hishand from hydraulic control switchunless instructed to do so. Be preparedfor possible cyclic and collective hard-overs. If forces are excessive, returnswitch to ON position. This conditionmust be corrected before continuing.

a.

b.

c.

FORCE TRIM switch - OFF.

HYD CONT switch - OFF, cautionlight on reset master caution.

Flight controls - Check within oneinch of cyclic center.

(1) No excessive forces or feed-back.

(2) Collective can be increased tomid travel and pushed down.

d. HYD CONT switch - ON, cautionlight out.

e. FORCE TRIM switch - ON,Proceed to step #4.

2-16

TM 55-1520-242-MTF


*3. Hydraulic system (UH-1C/M) - C46, D1,Check. 16,26,

a.

b.

c.

G1

FORCE TRIM switch - OFF.

HYD CONT switch - System 1;note system 2 caution light on.

Flight Controls - Check within

d.

e.

one inch of cyclic center.

(1) No excessive forces orfeedback.

(2) Collective can be increased tomid travel and pushed down.

HYD CONT switch - BOTH, thento system 2; note system 1 cautionlight on.

Flight controls - Check.

(1) No excessive forces orfeedback. Pedals will be stiffer.

(2) Collective can be increased to

f.

g.

mid travel and pushed down.

HYD CONT switch - BOTH; notecaution light out.

FORCE TRIM switch - ON.

2-17

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

NOTE

The tail rotor servo is powered bySYSTEM 1 (except on earlier modelswithout the emergency collectivehydraulic accumulator). With the con-trol switch in the SYSTEM 1 ON POSI-TION the caution light for SYSTEM 2should be ON and vice versa.

*4. Fuel Tank Sump Pump - Check. B6, D5,

a.

b.

c.

d.

e.

24, 27,29

BLEED AIR and DE-ICEswitches - OFF.

Fuel Tank Sump Pump CircuitBreaker OUT, record pressure(5-35 PSI), note caution light on.

BLEED AIR and DE-ICEswitches - ON, note increase inEGT, some fuel pressure remain-ing, Left caution light out.

Fuel Tank Sump Pump CircuitBreaker - IN, record pressure (8-25PSI), caution light out.

BLEED AIR and DE-ICEswitches - OFF, note decrease inEGT, possible increase in fuelpressure.

2-18

TM 55-1520-242-MTF


*5. Bleed Band Operation - Check.

a.

b.

c.

d.


Very slowly increase throttle,watching EGT gage until suddendecrease of 5 to 10 degrees (in-dicates bleed band is closed); noteN1, FAT.

Very slowly decrease throttle,watching EGT gage until suddenincrease of 5 to 10 degrees (in-dicates bleed band is open); noteN1.

Opening and closing (L-11), andclosing (L-13) N1 readings shouldbe within limits as indicated onbleed band charts (section V).

NOTE

The bleed band is temperature sensitiveand opening and closing points will varyat different temperatures. A more exac-ting method, if required, is to station anobserver alongside the engine compart-ment to determine exactly when thebleed band has opened and closed. If air-craft is operated in dusty areas, it isrecommended that the bleed check beperformed twice to detect possiblemodulation.

E14

2-19

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

*6. Variable inlet guide vanes-Checkbegin to open point

7.

*8.

9.

*10.

a.

b.

c.


Station observer alongside enginecompartment.

Slowly increase N1 until VIGVActuator Rod begins to move,note N1 speed and FAT.

NOTE

The begin to open check is a recommend-ed starting point for adjustment of theVIGV’S. If the begin to open point, asplotted on the VIGV opening chart, isnot within the chart limits, perform afull open check IAW TM 55-2840-229-23before making any adjustments.

Throttle full open - Slowly increase; E15, 16note N2 RPM 6000± 50.

Fuel quantity gage - Check to zero B7, 8,22and returns to initial reading.

Gyro Compass - Nulled if the K2, 3heading indicator is 180° out ofphase the annunciator may in-dicate alignment.

PITOT HTR switch - ON; check C17Ioadmeter for rise then OFF.

2-20

TM 55-1520-242-MTF


*11.

*12.

AC voltmeter (INVTR SPARE) - C18-22Check each phase for 115V± 3V.

INVTR switch - OFF, note caution C12, 13,lights on; MAIN ON, note caution D20, 28lights out; check voltage indicationto ensure MAIN INVTR isoperating.

*13. DC voltage system - Check: C1, 23-31,

a.

55

DC voltmeter selector - Check allpositions, leave in NON-ESSBUS. STBY GEN should be 1Vlower then MAIN GEN.

NOTE

Main generator voltage will be depen-dent upon the average ambienttemperature.

b.

c.

27.0 volts 80°F (26°C) and above28.0 volts 32 to 80°F (0 to 26°C)28.5 volts 32°F (0 °C) and below

STARTER GEN switch - STBYGEN position.

MAIN GEN switch - OFF, note C32-36caution light on; loadmeter goes tozero ± 0.1 and standby loadmeterregisters the load.

2-21

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

NOTEThe loadmeters indicate percentage oftotal generator output being used. Onaircraft equipped with 200 amperestarter generator shunts, the standbygenerator loadmeter will indicate ahigher value than main generatorloadmeter with the same load.

d.

e.

f.

g.

h.

*14.

*15.

DC Voltmeter - Check voltagezero with NON-ESS BUS switchNORMAL ON.

NON-ESS BUS switch -MANUAL ON, note standbygenerator voltage on voltmeter.

NON-ESS BUS switch -NORMAL ON.

DC voltmeter selector - ESS BUS.

MAIN GEN switch - ON, notemain loadmeter registers load,standby zero ± 0.1. Caution lightout.

AC voltmeter (INVTR MAINCheck each phase for 115 ± 3V.

BLEED AIR heater - ON, noteEGT rise, Check operation, ther-mostat set (if installed), defrost,and aft outlets. The heater shouldnot be noisy. Heater OFF or asdesired.

C37

C42

C28,38-40,

56, D19

C18-22

C44, 45

2-22

TM 55-1520-242-MTF


*16. DE-ICE switch - ON; note EGT C42-43 rise. Then off; note EGT drop.

NOTE

If no change in EGT is observed, the hotair valve may be open at all times.Under these circumstances the turbineengine analysis check (TEAC) and/orhealth indicator check (HIT), baselineEGT values will be inaccurate.

* 17. LOW RPM AUDIO warning switch C6, 63- ON, check level, no bleed-over onrear ICS.

*18. N2 Systems - Check: C47-51,57, 58,

E15, 16

A steady state N2 RPM of 6900 is per-missible and is not considered an engineoverspeed provided 15 PSI torque (L-13)or 85% N1, (L-11) is not exceeded. Collec-tive pitch must be in full down positionat all times.

a. GOV RPM INCR/DECR switch -carefully increase to maximumRPM (6700 ± 50). Note warninglight and audio off by 6200 ± 100.

C2 2-23

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

b. At full increase check high RPMwarning light on at 6800 ± 100,(334 ± 5 Rotor RPM).

c. GOV RPM INCR/DECR switch -Full decrease. Note travel time(5-10 seconds), RPM warning lightand audio on at 6200 ± 100 RPM.Actuator shou ld operatesmoothly.

NOTE

If high RPM warning light came on dur-ing step 18b proceed to step 20.

*19. High RPM warning light - Check: C6, D25,E12

Throttle must be at engine idle prior toswitching governor to emergency.

a.

b.

c.

d.

Throttle - Engine idle.

GOV switch - EMER.

Throttle - Slowly increase N1, notehigh RPM warning light on at6800 ± 100 (334±5 rotor) RPM.

Throttle - Engine idle, GOV D12switch to AUTO, carefully in-crease throttle to full open, checkN2 6000±50 RPM.

C 2 2-24

TM 55-1520-242-MTF


*20. Cyclic and Pedal Systems - Check:

a. FORCE TRIM switch - OFF, C15, H2,Check cyclic friction, then OFF. 5-11

b. Controls - without input, controlsshould not creep. Check formotoring by lightly tapping thecontrols, movement should stopwhen input stops. Controls shouldoperate smoothly; no binding,chattering, feedback or excessivefriction within 1 inch of center.

c. FORCE TRIM switch - ON, check C15, H12,cyclic gradient forces nearly the 13same in all directions, no play.Recheck within one inch of center.Insure mag brakes release usingcyclic buttons. Check pedalssimilarly.

*21. Collective lever - Check Frictions:

a. Apply collective friction - Insure H15collective friction can be over-ridden, friction off.

b. Collective system friction - Check G3, 4built in friction. Forces should be H148-10 lbs up and down.

2-25

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

NOTE

Up and down force should be equalwithin one pound. It is recommendedthat a calibrated spring scale be used tomake this check with greater accuracy.(Attach the spring scale to center oftwist grip ± 1/2 inch.) Friction may benoticeably less on abnormally dampdays. Friction adjusted on damp daysmay be too heavy on dry days.

22.

23.

*24.

*25.

*26.

*27.*28.

*29.

Deleted.

GOV INCR/DEC switch - INCR to C476600 RPM.

Engine oil pressure - Record. B23, E4-8

Engine oil temp - Record. B2, E9

XMSN oil pressure - Record. B23, F1-5

XMSN oil temp - Record. F6Fuel pressure - Record. B5, 12, 13

Torquemeter - Flat Pitch record: B9, 11,14, 15, 23

L-11 10 to 15 PSIL-13 8 to 15 PSI

NOTE

Ensure pedal position is neutral. Left pedal for-ward of neutral will result in a higher torque in-dication.

C2 2-26

TM 55-1520-242-MTF


*30. EGT-Record. E17-19

31. Dual tachometer - Needles joined B16-18and steady.

NOTE

A small amount of N2 fluctuation (25RPM) is not abnormal. If the N1, torque,and EGT gages are also fluctuating, itcould indicate a serious problem withthe overspeed governor, fuel control,engine deterioration, etc.

*32. Dual Electric Boost Pumps - B5, 19Check: D5, 27

a. Fuel Boost Circuit Breakers - Pullindividually and record pressure8-25 PSI on one pump. Allowengine to run 60 seconds,minimum, with zero fuel pressure.Note caution lights on.

b. Fuel Boost Circuit Breakers - IN(use same order as pulled out)record pressure on oppositepump, caution lights out.

33. Rotors - Observe main rotor track.Track tail rotors if necessary, (SeeSection IV).

2-27

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)

NOTE

This is simply a visual check of the mainrotor track and does not call for movingthe tip path plane with the cyclic. If theblades appear to be 2 to 4 inches out oftrack, this condition must be correctedbefore flight. (See Section IV).

34. Listen for any abnormal noises.

NOTE

Listen for a low pitched roar, whichcould indicate engine trouble, or anygrinding noises, etc. Some normal noisesare tape popping when working a lateralvibration, window vibration, and in-verters.

35.

36.

37.

*38.

Doors - Secured for flight.

Attitude indicators - Set.

Radios - Check; obtain altimetersetting.

Altimeters - Check tower settingagainst setting for field elevation.Unreliable for flight if more than70-foot error exists from fieldelevation. If more than 50-foot er-ror exists, corrective action shouldbe initiated.

2-28

TM 55-1520-242-MTF


ENGINE RUNUP (CONT)a. Altimeter Set, Electronic

AN/APN-171A(V)1 - Check(See Section IV).

b. Altimeter Radar, AN/APN-209- Check (See Section IV).

NOTE

Note the decrease in altimeter readinginduced by rotor downwash effect. Thisdecrease will be approximately 20 feet withcollective pitch setting calling for 15 poundstorque.

39.Radar Warning Receiver,AN/APR-39 - Check (SeeSection IV).

40.FORCE TRIM switch - Off.

BEFORE TAKEOFF1. RPM - 6600.

NOTE

Setting N2 RPM precisely at 6600 will pro-duce a much more accurate steady statedroop check.

2. Warning lights - Checked.3. Fuel quantity - Checked.4. Instruments - Checked.

Change 5 2-29

TM 55-1520-242-MTF


BEFORE TAKEOFF (CONT)5. Caution lights - Checked.6. Transponder - Standby.7. Crew and mission equipment -

Check.* 8. HIT check - Complete. (See

Section IV.)

NOTE

HIT check may be deferred until arrival in testflight hover area if conditions in runup areapreclude accurate and/or safe completion ofcheck. HIT check must be completed beforetakeoff.

9. Accomplished main rotortracking as required.

HOVER CHECKS

WARNING

Do not operate aircraft below 6600 RPM ex-cept during low RPM Hover, Hover in emer-gency, Engine vibration analysis and TurbineEngine Analysis Check (TEAC).

WARNING

Binding or lack of proper control responseis cause to terminate flight and determinecause.

2-30

TM 55-1520-242-MTF


*1. Takeoff to Hover: G1, H5,6, 16-23,

J1-3

Any excessive control displacement re-quires a static rigging check.

a.

b.

c.

d.

Control Response - Carefullybring aircraft light on skids insur-ing all control responses are nor-mal.

Hover - Closely monitor controlresponse and CG hang as aircraftdeparts the ground. Note smoothpower increase.

Droop Cam - Check rigging, noteN2 RPM constant within ± 40RPM.

Controls - note position, cyclicnearly centered, normal pedalposition.

NOTE

The wind must be taken into considera-tion, as well as fore and aft and lateralcenter of gravity loading (fuel, tools, per-sonnel, etc.).

2 - 3 1

TM 55-1520-242-MTF


HOVER CHECKS (CONT)

e. Move off hover pad and checkground for oil spots which couldindicate oil leakage.

2. Hover slowly to test area.

*3.

*4.

NOTE

If HIT check has been deferred, per-formance of the check is required at thistime.

An abnormal torquemeter reading willbe investigated before continuing flight.

Torquemeter/Power Check - B11, 14,Compare with PPC. 15,23

Control Response Checks:

a. Hovering Turns - Check 90° in H11.each direction.

b. Sideward Flight - Checkresponse and rigging indirections.

21,24

cyclic H22, 25both

2-32

TM 55-1520-242-MTF


NOTE

Hover speed should be consistent withautorotation requirements, yet sufficient todetermine control reaction.

c. Forward flight - Check control H22,response and rigging. 25,26

*5. Pylon mounts check - Move F7,8,J6cyclic to induce pylon rock. Bumpingshould dampen out after 4 or 5 cycles.No abnormal vibrations or enginesurges should occur. The hydrauliccaution light must not illuminate.

*6. Engine response check - Make E20,positive application of up collective; 21,26engine should respond both smoothlyand rapidly; then back down b e f o r eexcessive altitude is gained.

NOTE

Be alert for any evidence of compressorstall or lag in engine response. Duringthis check some transient droop may beevident.

C4 2-33

TM 55-1520-242-MTF


HOVER CHECKS (CONT)

Ensure co-pilot/observer understandsinstructions contained in this paragraphbefore proceeding with check. If cyclicmovement is too rapid, or if theirreversible valve(s) fails, a controllockup may occur. Therefore the co-pilots hand will be kept on the hydrauliccontrol switch. In the event of a controllockup the co-pilot will, on the pilotscommand, rapidly recycle (OFF, thenON) the hydraulic control switch.Simultaneously the pilot will beattempting to land the aircraft.Recycling the HYD CONT switch shouldonly be attempted twice, If possible. Ifcontrol is not regained, the HYD CONTswitch will be turned OFF and ahydraulics OFF landing accomplished.

In checking the UH-1C/M, it isnecessary to move the control switch tothe opposite system and then back toboth if the controls should jam.

*7. Power cylinder check - Hover air- G1, 2craft at 10 feet minimum. Isolate eachpower cylinder using a 6 to 8 inch stroke.No restrictions to movement or feedbackshould be felt. The hydraulic boost systemshould function adequately with faster thannormal control input. The hydrauliccaution light must not illuminate.

*8. Low RPM hover - Check: C47,H21C4 2-34

TM 55-1520-242-MTF


a. Reduce N2 RPM - 6000.

b. Note controllability at low RPM, controlpositions, and check anti-torquecontrollability by performing 45° turns.

If aircraft controllability or controlresponses become abnormal duringRPM reduction, the maneuver will beterminated and static control rigging willbe checked.

c. Note any lateral vibrations.

d. Increase N2 RPM - 6600.

NOTE

Generally, a lateral vibration willbecome more pronounced at low RPMand may be determined at this time. Alateral vibration of noticeable intensityshould be corrected before continuingflight since it can manifest itself as avertical in flight. (See Section IV).

9. Land aircraft.

*10. Hover in emergency: E22

C4 2-35

TM 55-1520-242-MTF


HOVER CHECKS (CONT)

Throttle movements must be smooth and wellcoordinated. Too rapid movements can causeengine overspeed, compressor stall, flameout,and/or excessive EGT.

a. Throttle - Engine idle, GOV switch toEMER.

b. RPM - INCR to 6400 RPM with throttle.

c. Hover - Maintaining 6400 RPM. Aircraftshould hover normally in EMER.

d. LAND - Throttle to engine idle, GOV toAUTO.

e. Throttle - Increase to full open (6600RPM).

NOTEA fluctuation of the torquemeter may occurbetween 6300 and 6500 RPM as a result oftransient opening and closing of the bleed bandand is not abnormal. N2 may have to bebeeped down to eliminate bleed band cycling.

*11. Torquemeter indication - Check at a 2 foothover into the wind, for use in airspeed indicatorcheck.

C4 2-36

TM 55-1520-242-MTF


TAKEOFF AND CLIMB CHECKS

1. RPM-6600.

Ensure throttle is in the full open posi-tion. Under reduced rotor loading condi-tions, and indication of normaloperating RPM (6600) may be obtainedwhile the throttle is not in the full openposition. Upon application of collectivepitch, a decrease in RPM may result.

2.

3.

4.

5.

6.

7.

*8.

9.

Warning lights - Checked.

Fuel quantity - Checked.

Instruments - Checked.

Caution lights - Checked.

Transponder - As required.

Crew and mission equipment -Check.

Power Check - if not performed B11, 14,previously in direction of takeoff. 15,23

Make normal takeoff and climb at60(N)/70(R) KTS. Note controlpositions normal, engine andtransmission instruments for nor-mal indication and check for ab-normal vibrations.

2-37

TM 55-1520-242-MTF


TAKEOFF AND CLIMB CHECKS (CONT

NOTE

A normal takeoff is used because it isthe safest type. In the event of an enginefailure the nose will drop, possibly to apoint from which recovery could not bemade during a nose low takeoff. Fromany point in a normal takeoff and climb,a successful autorotation can normallybe made. This possibility must be con-sidered on all flights, maintenanceflights in particular.

LEVEL OFF CHECKS

1.

*2.

*3.

*4.

*5.

*6.

Climb to predetermined altitude.Allow engine to stabilize forminimum of one minute.

Engine oil pressure - Record.

Engine oil temperature - Record.

Transmission oil pressure - Record.

Transmission oil temperature -Record.

EGT - Record.

B23,E4-8

B2, E9

B23,F1-5

B2, F6

E17-19

2-38

TM 55-1520-242-MTF


LEVEL OFF CHECK (CONT)* 7. Airspeed indicators - Check

using 2' hover torque for straightand level flight at 90(N)/(100(R).Indicators should be nearly thesame (± 5 KTS), no excessivefluctuation (± 3 KTS).

H26, 2734, 35

* 8. Fuel consumption check -Initiate.

IN-FLIGHT CHECKS G3* 1. Control rigging - Check: B4, 11, 21

C16a. FORCE TRIM - ONb. Increase airspeed - 90

(Nose mounted), 100 (Roofmounted) using 30 PSItorque, needle ball centered.

WARNING

Lack of proper pedal position is cause to ter-minate flight. Adjustments are to be madeprior to proceeding with the test flight.

c. Note cyclic nearly center;force trim holds controls inposition.

d. Right pedal should be 1.0 to2.0'' forward of left.

e. The collective should notcreep up or down.

f. FORCE TRIM - OFF.* 2. Autorotation RPM - Check:

C5 2-39

TM 55-1520-242-MTF


IN-FLIGHT CHECKS (CONT)

The autorotation should be entered at analtitude that will allow a power recoveryto be completed at or above 500 feetabove ground level (AGL). A malad-justed or malfunctioning engine idlestop can allow the throttle to be retardedto the cutoff position.

a. Airspeed - adjust to 60 knots (roofmounted).

adjust to 50 knots (nosemounted).

b. Collective - full down.

c. Throttle - engine idle.

(1) N1 Speed - check.

(2) N2 and Rotor tach needles -split.

(3) Torquemeter - zero indication.

d. Rotor RPM - approximately:

UH-1, H/V, EH-1H/X 310-315rpm (approximately, 7,000 lbsgross weight).

UH-C/M 320-325 rpm (approx-imately, 7,000 lbs gross weight).

2-40

TM 55-1520-242-MTF


NOTE

Autorotational RPM will varysignificantly with gross weight and am-bient conditions. In no event will RPMbe set to exceed 339 at maximum grossweight nor be less than 294 at minimumgross weight.

e. Vibration Level - Note. C59

f . Right Pedal - Suff ic ientremaining.

Ensure throttle is in the full open posi-tion. Under reduced rotor loading condi-tions, an indication of normal operatingRPM (6600) may be obtained while thethrottle is not in the full open position.Upon application of collective pitch, adecrease in RPM may result.

g. Make power recovery - Prior to H21, 28,500 ft AGL. J3,5,6

*3. Hydraulics Off Check (except C46, D16UH-1C/M) - Accomplish: 26, G1,

H29, 30

2-41

TM 55-1520-242-MTF



Brief copilot/observer not to remove hishand from hydraulic control switchunless instructed to do so. Be preparedfor possible cyclic and collective har-dovers. If control hardover occurs pro-ceed IAW the operators manual.

a. HYD CONT switch - OFF.

b. Caution lights - Caution panellights and Master Caution light il-luminated, RESET.

c. Check that aircraft is easilycontrollable, no excessive forces

d.

to the cyclic and pedals. Collec-tive should go down to 13 PSI tor-que and up to 33 PSI with approx-imately equal force.

HYD Cont Switch - ON, powerrestored.

NOTE

It will take slightlv more force to movethe cyclic right and forward than to theleft and forward. A common cause forexcessive pressure being required to theright and forward is a maladjusted ormissing swashplate balance spring.

2-42

TM 55-1520-242-MTF


*4. Turbine Engine Analysis Check—Perform Baseline or Normal as ap-plicable. (See Section IV).

NOTE

For baseline TEAC:

Under certain climatic conditions,the “topping” portion of TEAC proceduremay not be possible. When such condi-tions exist, the test pilot will verify en-gine power by climbing to highestobtainable altitude and confirm thatmaximum torque is available without ex-ceeding sny engine or airframe limits.Maximum torque will be determined fromappropriate -10 operators manual basedon actual pressure altitude and tempera-ture for that flight level. Engine mustprovide at least maximum torque withoutN2 bleed or exceeding engine or airframelimitations. Refer to TM 55-2840-229-23-1 for additional requirements and in-structions.

For normal TEAC:

If during the conduct of a generaltest flight, engine topping cannot be per-formed due to adverse environmentalconditions the TEAC may be deferreduntil conditions improve. An entry on DAForm 2408-13 will be made and a reddiagonal status symbol will be entered inBlock 16. Block 17 will state: NormalTEAC deferred until environmental con-ditions improve.

C - 3 2-43

TM 55-1520-242-MTF



5.

*6.

*7.

Deleted.

Stabilizer Bar Dampner–Check C15,16,following time for 5 ± 1 seconds in H 31each direction.

a. Airspeed-Adjust to 80 ± 10 knots.

b. FORCE TRIM switch-ON.

c. Turns-Left or Right to 10 to 20degree bank.

d. FORCE TRIM switch-OFF.

Vibration Analysis-Check

NOTE

For aircraft equipped with compositeblades, vibration analysis check may beaccomplished at 6400 N2 RPM.

C-3 2-44

TM 55-1520-242-MTF


a. Starting at 70 kias slowly increase airspeed toa point where a 1.1 vertical vibration becomesnoticeable. Establish a 10 psi torque descent atthat airspeed and note any changes in vibra-tion level from straight and level flight.

NOTE

Generally, 1:1 vibrations felt pre-dominantly in a low power descent arecaused by a basic difference in blade liftand can be corrected by rolling a bladegrip. Note also any excessive 2:1 vibra-tion.

b. Level off and slowly increase J4, 5airspeed from 70 Knots up toVNE (unless vibrations get un-comfortably severe). Note any in-crease in 1:1 vibrations andairspeed at which it became evi-dent. Note any excessive 2:1vibration or higher frequencyvibrations. Aircraft should flysmoothly through entire speedrange.

NOTE

Vertical 1:1 vibrations felt mostly in for-ward flight, that get worse as airspeed isincreased, are usually due to one bladedeveloping more lift as airspeed increases.This can most often be corrected by ad-justment of trim tabs.

C - 3 2-45

TM 55-1520-242-MTF



Minimize or eliminate all abnormalvibrations and compute VNE for air-craft configuration and ambient condi-tions prior to performing this check.Roof or nose mounted pitot tube changesVNE significantly.

*8. Cyclic Rigging - Check: H26,32,33

Increase airspeed to VNE ormaximum attainable in level flight(if less than VNE). With normal air-craft configuration and CG aboutneutral, observe the pilots cyclicstick has a minimum of 2 inchesclearance from the instrumentpanel, a slight spring cushion mayor may not be felt.

*9. Flight Instruments - Check:

a.

b.

c.

Altimeters - Proper indication, B20nearly the same as before take-off,no large fluctuations.

Attitude indicators - Correct B24indications, no excessive preces-sion or vibrations.

Standby compass - Nearly correct B25heading, no excessive fluctuation.

2-46

TM 55-1520-242-MTF


d.

e.

f.

g.

h.

Vertical speed inciators (VSI) - B3Proper indication, nearly thesame, no excessive fluctuations.

Gyro compass - Correct heading, K3-5operates smoothly, no fluctua-tions, co-pilots same as pilotswithin 2°.

Clock - Still indicating correcttime.

Turn and slip indicator - Properindication, needle movement.

Instrument panel - No excessivevibration. Note any looseness orcracks at pedestal mounts.

*10. Communication and navigationequipment - Check operation of allequipment as indicated in the ap-propriate TM.

*11. Fuel consumption check -Complete.

B1

B21

B26

K6

BEFORE LANDING CHECK

1. RPM -6600.

2. Warning lights - Checked.

2-47

TM 55-1520-242-MTF


BEFORE LANDING CHECK (CONT)

3.

4.

5.

6.

7.

Fuel quantity - Checked.

Instruments - Checked.

Caution lights - Checked.

Crew and mission equipment -Check.

Landing light - As required.

AFTER LANDING AND ENGINESHUTDOWN CHECKS

1.

2.

3.

*4.

*5.

*6.

*7.

Landing light - As required.

Transponder - OFF.

Controls - collective full down,cyclic centered, pedals neutral,FORCE TRIM ON. Apply cyclicfriction.

EGT - Record.

Engine oil pressure - Record.

Engine oil temp - Record.

XMSN oil pressure - Record.

C16

E17-19

B23,E3-8

B2, E9

B23,F1-5

2-48

TM 55-1520-242-MTF


*8.

9.

10.

11.

*12.

13.

*14.

REFERENCE

XMSN oil temp - Record. B2, F6,E1

Throttle - Engine idle, start clock.

LOW RPM AUDIO switch-OFF.

START/GEN switch - STARTposition.

Engine idle speed - Check N1, E10, 11Record.

Special equipment - Checkoperation of cargo hook, rescuehoist, and other special equipmentif installed.

Battery check. BAT switch OFF. If C60, 61drop in loadmeter is 0.02 or less,this indicates a charge rate of sixamperes and the battery is con-sidered fully charged. BAT switchON.

NOTEEnsure engine has idled for 2 minutes toallow internal engine components tostabilize before shutdown.

*15. Engine Shutdown:

a. Throttle - Full off, check N1 E23, 24coastdown time (25 seconds rein).

2 - 4 9

TM 55-1520-242-MTF


AFTER LANDING AND ENGINESHUTDOWN CHECKS (CONT)

b. EGT - Monitor, listen for any E25abnormal noises.

c. ENG oil press light - On by 25 D31PSI.

d. XMSN oil press light - On D31between 28-32 PSI.

e. MAIN FUEL switch - OFF.

16.

17.

18.

19.

*20.

AVIONICS - OFF.

INVTR switch - OFF.

ANTI-COLLISION light switch -OFF (after rotor stops).

BAT switch - OFF (except C62UH-1C/M).

Emergency collective hydraulicysystem (UH- 1C/M) - Check imme-diately after rotor stops:

a. With the EMER COLL HYD G5switch OFF, attempt to raise thecollective pitch, If the collectivepitch cannot be raised, the ac-cumulator switch is functioningproperly.

2-50

TM 55-1520-242-MTF


21.

22.

*23.

24.

25.

b.

c.

d.

REFERENCE

G7

EMER COLL HYD switch - ON. G6Move the collective pitch up onefull stroke and down one fullstroke.

BAT switch - OFF. Move thecollective pitch up one full strokeand down one full stroke. This in-dicates that the collective ac-cumulator will function withoutelectrical power.

EMER COLL HYD switch - OFF.

NOTE

Movement of collective should be madeslowly to preclude premature bleedingof accumulator.

Ignition lock switch - OFF. Removekey as required.

Bleed Collective accumulator andcheck gage in the GREEN, (UH-1C/M).

Post Flight Inspection - Performed.

Check sheet - Completed andsigned.

Maintenance Personnel - Debriefedas necessary.

2-51

TM 55-1520-242-MTF


AFTER LANDING AND ENGINESHUTDOWN CHECKS (CONT)

*26.

27.

28.

All entries from remarks column ofcheck sheet - Transcribe to DAForm 2408-13.

HIT Worksheet and Log - Updateto latest baseline HIT EGT.

Engine Historical Records - updateDA Form 2408-15 Turbine EngineAnalysis Checks.

2 - 5 2

TM 55-1520-242-MTF

SECTION III. TROUBLESHOOTING

General. This section contains troubleshooting in-formation that has been referenced in Section IIchecklists. This section shall list possible conditions,abnormal conditions and indications and probablecauses. The information is to be used only as a quickreference and may not be all encompassing.

3-1

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE A - STARTING

CONDITION

PROBABLE CAUSE

A1. No starter action.

a. Starter-generator switch in the wrongposition, or malfunction.

b. Circuit breaker out.

c. Starter switch inoperative.

d. Starter failure.

e. Faulty wiring.

f. Internal seizing of compressor.

A2. No N1 indication, but starter turns.

a.

b.

c.

d.

Faulty N1 tach generator or gage.

Faulty wiring.

Starter drive failed.

N1 gearbox internal failure.

A3. Failure to start.

a. Weak battery.

b. GPU (if used) underrated.

c. Faulty igniter plugs.

3-2

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d.

e.

f.

g.

h.

i.

Faulty ignition unit (exciter box or leads).

Ignition key not on.

Throttle not open.

Faulty fuel control.

Internal failure.

Fuel switch not on.

A4. N1 hangs at about 15%, EGT holds at about100ºC.

a.

b.

c.

A5. N1

a.

b.

c.

d.

e.

f.

Fuel control malfunction.

Flow divider malfunction.

Main fuel line restricted.

hangs, will not increase, EGT holds high.

Hanging start due to air in fuel control.

Starter switch released too soon.

Weak battery.

GPU (if used) underrated.

Fuel control malfunction.

In-line filters clogged.

3-3

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

A6. Normal start except EGT rises too rapidly.

a.

b.

c.

d.

e.

f.

g.

h.

i.

j.

k.

l.

Hot start due to starting in high tail wind,starting engine shutdown short timeprevious, or starting in extremely hotweather.

Governor changeover solenoid inemergency position.

Weak battery.

Start fuel valve fails to close.

Throttle improperly rigged.

Wrong type fuel.

Air intake obstructed.

Dirty compressor.

GPU (if used) underrated.


Combustion chamber dump valve sticking.

T1 sensor dirty or clogged.

A7. Starter continues to motor, and/or igniterscontinue to fire when start switch is released.

a. Faulty start switch (pilot or copilot).

b. Faulty starter relay.

3-4

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

A8. Start quits, N1 falls.

a.

b.

c.

d.

e.

f.

g.

h.

Starter switch released too soon.

Main fuel valve shut off.

Main fuel line quick disconnect notconnected tightly.

Air in fuel control.

Circuit breaker out (starter or ignition).

Starter failure (electrical or mechanical).

Ignition system failure (exciter or igniter).


A9. N1, EGT, indication but main rotor does notturn as soon as normal. No N2 indication.

a.

b.

c.

d.

e.

Rotor still tied down, either main or tail.

Foreign object(s) binding rotatingcomponents.

Transmission or gearbox failure.

N2 turbine failed or locked.

Engine reduction gearing failure.

3-5

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

A10. N1, EGT indication but main rotor does notturn with N2 tachometer engine indication.

a. Engine drive shaft failed.

b. Free-wheeling unit failure.

c. Transmission failure.

3-6

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE B -INSTRUMENTS

CONDITION

PROBABLE CAUSE

B1. Clock not accurate.

a.

b.

c.

Not wound.

Wound too tightly.

Defective clock.

B2. No indication on engine and/or transmissiontemperature gages.

a. Faulty wiring.

b. Faulty gage(s).

c. Faulty temperature bulb.

B3. Vertical velocity indicator inaccurate, notzeroed, or fluctuates excessively.

a. Mechanism shifted (adjustment off).

b. Loose connections.

c. Static port or line clogged.

d. Leak in line.

e. Faulty indicator.

3-7

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

B4. Airspeed indicator reads incorrectly orfluctuates excessively.

a. Pitot tube restricted.

b. Line not completely connected.

c. Static port or line clogged by water or dirt.

d. Leak in line.

e. Faulty indicator.

B5. Fuel pressure too low.

a.

b.

c.

d.

e.

f.

Electric pump(s) circuit breaker out.

Faulty bleed air pump (H/V models).

Bleed air line leakage (H/V models).

Faulty pressure transmitter and/or gage.

Faulty fuel check valve manifold.

Restriction in lines.

B6. No fuel pressure indicated from bleed air boostpump (H/V models).

a. Bleed air line leakage.

b. Restricted lines.

3-8

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c. Faulty transmitter and/or gage.

d. Faulty boost pump.

B7. Fuel quantity indicator reads low or remainsat one point.

a. Improper gage.

b. Out of adjustment.

c. Faulty fuel probe(s).

d. Faulty wiring.

e. Faulty test switch.

f. Faulty indicator.

138. Fuel quantity indicator reads high.

a. Improper gage.

b. Faulty fuel probe(s).

c. Faulty wiring.

d. Faulty test switch.

B9. No torquemeter indication.

a. Faulty wiring.

b. Clogged pressure line.

c. Disconnected or broken pressure line.

3-9

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d.

e.

f.

g.

h.

No oil in system.

Faulty gage or transmitter.

Torquemeter internal system malfunction.

Faulty torquemeter boost pump.

N2 gearbox internal failure.

B10.

B11.

B12.

Torquemeter indication rises rapidly afterstart, or pegged.

Faulty transmitter.

Torquemeter fluctuates - no other instrumentsfluctuating.

Faulty transmitter.

Fuel pressure erratic.

a. Air in system.

b. Faulty pump.

c. Fuel leak.

d. Faulty transmitter or gage.

e. Faulty wiring.

f. Pump inlet restricted.

g. Faulty fuel check valve manifold.

3-10

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

B13. Fuel pressure too high.

a. Faulty transmitter or gage.

b. Faulty wiring.

c. Restricted lines.

B14. Low torquemeter indication.

a.

b.

c.

d.

e.

f.

g.

h.

Faulty transmitter or gage.

Low torquemeter boost pressure(adjustment or malfunction).

Clogged boost pump screen.

Damaged torquemeter seal ring.

Main rotor blades pitch angle set too low(6600 RPM, flat pitch).

Gross weight lower than computed.

Abnormal density altitude.

PPC calculation incorrect.

B15. High torquemeter indication.


b. Torquemeter valve fails to close.

3-11

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c.

d.

e.

f.

g.

Vent hose plugged.

Faulty internal torquemeter system.

Main rotor blade pitch angle set to high(6600 RPM, flat pitch).

Gross weight higher than computed.

Abnormal density altitude.

B16. N2 needles not joined.

a. Faulty instrument.

b. Faulty tachometer generator.

B17. N2 tachometer fluctuates. No other engineinstruments fluctuating.

a, Faulty wiring.

b. Faulty instrument.

c. Faulty tachometer generator.

B18. Excessive tachometer error high or low.

a. Faulty instrument.

b. Faulty tachometer generator.

c. Faulty wiring, leads connected to wrongterminals at indicator.

3-12

TM 55-1520-242-MTF

CONDITION

B19.

B20.

B21.

B22.

PROBABLE CAUSE

Engine fails to run with both electric boostpumps disabled.

a. Air leak between fuel control and fueltanks.

b. Restriction in lines.

Altimeter reads incorrectly or fluctuatesexcessively.

a.

b.

c.

d.

Leak in static line.

Clogged port or line.

Faulty instrument.

Water in static system.

Turn and slip indicatorinoperative.

a. Sticking gyro.

b. No electric power.

needle erratic or

Fuel quantity gage will not decrease whenpress-to-test button pressed.

a. Faulty inverter.

b. Faulty press-to-test button.

c. Fuel gage stuck.

3-13

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d.

e.

Faulty wiring.

Loose connections.

B23.

B24.

B25.

Pressure instruments inoperative, inverterson.

a. Faulty transformer.

b. Transformer circuit breaker out.

c. Inverter voltage excessively high or low.

d. Faulty wiring.

Attitude indicator does not work properly.

a. AC power failure, one or all phases.

b. Circuit breaker out.

c. Loose connections.

d. Faulty components.

Standby compass inaccurate, sluggish orerratic.

a.

b.

c.

Improper compensation.

Mounting bracket loose.

External magnetic interference.

3-14

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d. Insufficient liquid.

e. Faulty instrument.

f. Improper hardwarepanel or windshields.

used on instrument

B26. Excessive instrument panel vibration.

Mounts loose.

3-15

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE C - ELECTRICAL

CONDITION

PROBABLE CAUSE

C1. No voltage indicated when DC voltmeterturned to BAT position.

a.

b.

c.

d.

e.

Battery circuit breaker out.

Faulty wiring at battery relay.

Battery circuit diode faulty or incorrectlyinstalled.

Internal failure of battery.

Wiring at meter or VM selector faulty.

C2. Battery does not come on.

a.

b.

c.

d.

e.

Switch or switch wiring faulty.

Battery relay faulty or incorrectly wired.

Battery voltage low.

Internal failure ofconnection.

Feeder relay faulty orH/V models.

battery or faulty

incorrectly wired on

3-16

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C3. Battery relay chatters when battery is turnedon.

a. Battery voltage low.

b. Internal failure of battery.

c. Faulty wiring at battery relay.

C4. GPU does not provide current to aircraft.

a.

b.

c.

d.

e.

External power relay or wiring faulty.

Polarity of GPU reversed.

GPU voltage low.

Diode incorrectly installed or faulty.

External power plug faulty or wiringfaulty.

C5. Press-to-test light fails to illuminate.

a. Bulbs burned out or missing, cat-eyeclosed.

b. Faulty wiring.

c. Faulty cargo release armed switch.

3-17

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C6. RPM WARNING light and/or audioinoperative.

a.

b.

c.

d.

e.

Bulbs burned out or missing.

Break in circuit wiring or cannon plugsdisconnected.

RPM warning box faulty, disconnected ornot installed.

RPM warning box not adjusted properly(did not follow published procedures).

Tachometer generator faulty.

C7. FIRE WARNING light inoperative.

a.

b.

c.

d.


Break in circuit wiring or cannon plugdisconnected.

Fire detector relay faulty, not installed orincorrectly wired.

Faulty test button.

3-18

TM 55-1520-242-MTF

CONDITION

C8.

C9.

C10.

PROBABLE CAUSE

FIRE WARNING light on (no actual fire).

a.

b.

c.

d.

e.

Moisture or foreign matter in cannon plug.

Wiring frayed, chaffed, shorted, orgounded out.

Fire detector relay faulty.

Fire sensing wire damaged or has sharpbends or is kinked.

Faulty test button.

Interior lights fail to illuminate or brighten.

a.

b.

c.

Faulty switch or rheostat.

Faulty or broken wiring.

Bulb(s) burned out.

Navigation lights fail to illuminate, dim, orflash.

a. Bulbs burned out.

b. Faulty switch.

c. Faulty wiring.

d. Faulty or incorrect flasher.

e. Faulty dimmer resistor.

3-19

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C11.

C12.

C13.

Searchlight/landingextend, or retract.

a. Faulty switch.

b. Bulb burned out.

light fails to illuminate,

c. Faulty wiring.

d. Faulty motor/gears.

e. Faulty relay switch.

Main or spare inverter fails to operate.

a. Switch or switch wiring faulty.

b. Inverter power relay faulty or wiringincorrect.

c. Faulty inverter.

d. Faulty wiring.

Inverter comes onto the instruments.

a. Faulty wiring.

but no AC voltage applied

b. Faulty inverter relay.

c. Faulty switch.

3-20

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C14. Instrument inverter caution panel light on,inverter on.

a.

b.

c.

Fail relay circuit breaker out or faulty.

Faulty wiring.

“C” Phase out or inoperative in theinverter.

C15. Force trim holds in all or some positions withswitch OFF.

a.

b.

c.

d.

e.

Magnetic brakes not completely releasing.

Rough spots in brake travel.

Residual magnetism in magnetic brake.

Improperly rigged.

Electrical Failure.

C 16. Force trim inoperative.

a. Faulty switch(s).

b. Faulty wiring.

c. Faulty magnetic brake(s).

d. Arm disconnected.

e. Electrical failure.

3-21

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C17. No loadmeter indication when pitot heater isturned on.

a. Heater inoperative.

b. Faulty switch.

c. Loadmeter malfunction (see C40).

C18. AC voltage high or low.

a. Generator voltage excessively high or low.

b. Faulty inverter.

c. AC voltmeter improperly adjusted.

d. One phase inoperative.

e. Faulty VM selector.

f. Faulty wiring.

C19. Excessive difference between AC phases.

a. Faulty inverter.

b. Power factor correction network faulty orcircuit breakers out.

c. Faulty wiring at VM selector.

3-22

TM 55-1520-242-MTF

CONDITION

C20.

C21.

C22.

PROBABLE CAUSE

AC voltage indication varies or fluctuates.

a. Faulty meter wiring.

b. Faulty wiring.

c. Faulty VM selector.

d. Faulty inverter.

e. Faulty inverter relay.

f. Faulty power factor correction circuit orcircuit breaker.

g. Fail relay or fuel quantity circuit breakerwiring faulty.

AC voltmeter inoperative, inverters on andcurrent applied to instruments.

a.

b.

c.

d.

Faulty wiring.

Faulty VM selector.

Faulty voltmeter.

Fail relay or fuel quantity circuit breakersout or faulty.

AC voltmeter indicates low voltage in the ACposition, and either 0 or 115 volts in the AB orBC position, with current applied to the in-struments and inverter on.

a. Faulty wiring.

3-23

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

b.

c.

Fail relay or fuel quantity circuit breakerout .

Faulty VM selector.

C23.

C24.

Main generator ON but no DC voltageindicated for main generator position of VMselector.

a.

b.

c.

d.

Faulty wiring at reverse current relay.

Main generator VM circuit breaker out orfaulty.

Faulty VM selector switch or faulty wiringat switch.

Faulty wiring at the generator.

Generator voltage high.

a.

b.

c.

d.

e.

f.

Voltage regulator faulty or out ofadjustment.

Voltage regulator wiring faulty, loose orincorrect.

Regulator base plate faulty, contactscorroded, loose or damaged.

Faulty field relay wiring.

Field circuit breaker wiring incorrect.

Voltmeter out of adjustment.

3-24

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

g. Faulty overvoltage relay (main) (see C26).

C25. Generator voltage low.

a.

b.

c.

d.

e.

f.

Field circuit breaker out or faulty.

Faulty generator or wiring.

Faulty voltage regulator or out ofadjustment.

Voltage regulator wiring faulty, loose orincorrect.

Regulator base plate corroded, loose ordamaged.

Faulty field relay or wiring incorrect.

g. Faulty overvoltage relay (see C26).

h. Voltmeter out of adjustment.

C26. Overvoltage relay does not function properly.

a.

b.

c.

d.

Faulty relay.

Faulty wiring.

Faulty field relay.

Generator and bus reset circuit breaker outor faulty.

3-25

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C27. Generator voltage fluctuates.

a. Faulty field circuit breaker.

b. Faulty field relay.

c. Faulty voltmeter.

d. Faulty generator.

e. Faulty voltage regulator.

f. Voltage regulator base plate loose,corroded or damaged.

g. Faulty wiring.

C28. Main generator does not come on with switchin the ON position.

a.

b.

c.

d.

e.

f.

g.


Switch or switch wiring faulty.

Generator voltage excessively low.

Field relay wiring or field relay faulty.

Overvoltage relay wiring faulty or relayfaulty.

Generator field circuit breaker out orfaulty.

Faulty generator, residual magnetic fieldgone.

3-26

TM 55-1520-242-MTF

CONDITION

C29.

C30.

C31.

PROBABLE CAUSE

h. Faulty reverse current relay or wiring.

i. Generator drive shaft sheared orimproperly installed.

Standby generator operating but no DCvoltage indicated for STANDBYGENERATOR position of VM selector.

a.

b.

c.

Faulty standby generator.

Standby generator VM circuit breaker outor faulty.

Faulty VM selector switch or faulty wiringat switch.

No reading when VM selector is placed in theESS BUS position.

a. Faulty wiring at the VM selector switch orfaulty VM selector.

b. GEN and BUS reset circuit breaker out orfaulty.

Non-essential bus VM selector position doesnot indicate voltage with main generator ON,and switch in NORMAL ON.

a. Faulty non-essential bus relay.

b. Faulty bus control relay.

3-27

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c.

d.

e.

f.

g..

Faulty switch.

Generator and bus reset circuit breaker outor faulty.

VM selector faulty.

Faulty voltmeter.

Faulty wiring.

C32.

C33.

Main generator will not go off when switch isplaced in the OFF position.

a. Reverse current relay faulty or wiring atrelay faulty.

b. Faulty switch or switch wiring.

Standby generator will not come on withswitch in STBY position, main generator OFF.

a.

b.

c.

d.

e.

f.

Reverse current relay faulty.

Faulty bus control relay.

Faulty switch.


Standby generator’s field relay faulty.


3-28

TM 55-1520-242-MTF

CONDITION

C34.

C35.

C36.

C37.

PROBABLE CAUSE

g. Starter switch faulty activating field relay.

h. Faulty wiring.

Standby generator ON, no indication onloadmeter.

a. Circuit breaker out.

b. Faulty meter.

c. Faulty wiring at shunt.

Standby generator will not come on, voltmeterindicates negative in STBY position.


Standby generator ON, loadmeter indicatednegative (below zero) when VM selector is plac-ed in STBY GEN position.

a.

b.

c.

Circuit breaker out.

Faulty meter or wiring.

Faulty wiring at shunt.

Non-essential bus indicates voltage withswitch in NORMAL ON and main generatorOFF.

a. Faulty non-essential bus relay or faultywiring at relay.

3-29

TM 55-1520-242-MTF

CONDITIONPROBABLE CAUSE

b. Main generator reverse current relay wiringfaulty.

c. Faulty bus control relay.d. Fa u l t y s w it ch .

e . Fa ul ty wi r ing .

C38. DC GEN caution panel light OFF whenmain generator is off, comes on whenmain generator comes on.a. Faulty wiring.


C39. Main generator ON, but no indication onloadmeter.a. Wiring at loadmeter faulty.

b. Wiring at shunt faulty.

C40. Main generator goes off, switch is in theON position.a. Faulty wiring at the reverse current relay or

faulty relay.

b. Faulty switch.c. Generator voltage excessively high,

activating overvoltage relay.

3-30

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d.

e.

f.

g.

h.

i.

j.


Faulty field relay,

Faulty overvoltage relay.


Faulty generator.

Faulty voltage regulator and/or baseplate.

Faulty wiring.

C41. Main generator will not reset when switch isplaced in the RESET position.

a. Faulty switch.

b. Faulty field relay.

c. Faulty overvoltage relay.

d. Field circuit breaker out or faulty.

e. Faulty generator.

f. Faulty wiring.

C42. No increase in EGT when DE-ICE switch isturned on.

a. Faulty switch.

b. Bleed air valve stuck open.

3-31

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c.

d.

e.

Bleed air leakage.

Electrical failure to valve solenoid.

Faulty de-ice valve.

C43. No decrease in EGT when DE-ICE switch isturned off.

a. De-ice valve stuck open.

b. Faulty switch.

c. Electrical failure to valve solenoid.

C44. Insufficient or no heat from outlets.

a. Obstructed, disconnected or leakingducting.

b. Faulty air control switch.

c. Faulty bleed air valve.

d. Faulty air mixing valve.

e. Faulty wiring.

f. Faulty overtemp switch.

g. Faulty thermostat.

h. Faulty defrost circuit.

3-32

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C45. Excessive hot air.

a. Faulty thermostat.

b. Faulty overtemp switch.

C46. HYDRAULIC CONTROL switch ineffective.

a. Hydraulic system circuit breaker out.

b. Faulty switch.

c. Faulty wiring.

d. Faulty solenoid valve.

e. Electrical failure.

C47. No change in governor RPM whenINCR/DECR switch is activated.

a. Governor control circuit breaker out.

b. Faulty overspeed governor.

c. Faulty or binding actuator.

d. Faulty wiring.

e. Faulty switch.

C48. Governor RPM increase when beep decreasedor vice versa.

a. Faulty wiring.

b. Connections crossed.

3-33

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C49. Excessive time for actuator to complete travel.

a. Actuator binding.

b. Faulty actuator.

c. Overspeed governor binding.

d. Faulty wiring.

C50. Governor RPM too low or too high at full openthrottle and increased beep.

a. N2 system improperly rigged.

b. Faulty overspeed governor.

c. Air in fuel control.

d. Droop compensator shear pin sheared.

C51. RPM warning light and/or audio on, dualtachometer indicating normal.

a. Faulty wiring.

b. Faulty warning box or improperlyadjusted.

c. Water or moisture in warning box orcomponents.

C52. Main generator motors with battery on.

a. Faulty wiring at reverse current relay.

b. Faulty reverse current relay.

3-34

TM 55-1520-242-MTF

CONDITION

C53.

C54.

C55.

C56.

PROBABLE CAUSE

Transmission sump inspection lightinoperative.

a.

b.

c.

d.

e.

Battery circuit breaker out.

Bulb burned out.

Faulty light socket or wiring.

Faulty switch.

Battery circuit diode faulty or incorrectlyinstalled.

Battery comes on when transmission sumpinspection switch is pushed.

Faulty wiring at battery relay.

DC voltmeter does not indicate in somepositions.

a. Faulty wiring.

b. Faulty switch.

When main generator turned back on, standbyloadmeter maintains indication.

a. Voltage improperly set, standby should be1 volt lower than main generator.

b. Faulty relay.

c. Faulty main generator or circuit.

3-35

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

C57. RPM WARNING light and audio on, rotor orN2 needle on dual tachometer fluctuating or in-dicating zero.

a. Faulty wiring.

b. Cannon plug disconnected.

c. Faulty tachometer generator(s).

C58. RPM warning system activates at varioussettings.

a. Faulty wiring.

b. Faulty warning box.

c. Faulty tachometer generator(s).

d. Water or moisture in components.

C59. RPM WARNING light and audio do not comeon during autorotation, or come on excessivelylow.

a. Faulty warning box.

b. Warning box out of adjustment, did notfollow published procedures.

C60. Battery will not hold charge, or will not charge.

a. Incorrect servicing/maintenance.

b. Generator voltage low.

c. Internal failure of battery,

3-36

TM 55-1520-242-MTF

CONDITION

C61.

C62.

C63.

PROBABLE CAUSE

Battery spewing electrolyte, gasing and/oroverheating.

a. Generator voltage too high for ambientconditions.

b. Internal battery failure.

c. Incorrect servicing/maintenance.

Battery will not turn off.

a. Faulty switch.

b. Faulty battery relay.

c. Faulty wiring.

Low RPM audio too weak.

a.

b.

c.

d.

Audio level adjusted too low.

Faulty warning system.

High resistance wiring.

Faulty interphone control box.

3-37

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE D -CAUTION PANEL

CONDITION

PROBABLE CAUSE

D1. MASTER CAUTION light fails to illuminate.

a. Faulty wiring.

b. Faulty caution panel box.

c. Bulbs burned out or missing.

D2. Caution panel lights dotest switch is depressed.

a.

b.

c.

d.

Faulty test switch.

not illuminate when

Faulty caution panel box.

Faulty wiring.

Bulbs burned out.

D3. All or many caution panel lights illuminateddimly.

a. Moisture in cannon plug or internally.

b. Defective caution panel box.

D4. Caution panel lights dim, pilot instrumentlight rheostat off or caution panel lights do notdim pilot instrument light rheostat on.

a. Faulty pilot instrument light rheostat.

3-38

TM 55-1520-242-MTF

CONDITION

D5.

D6.

PROBABLE CAUSE

b. Faulty wiring.

c. Faulty caution panel box.

RIGHT FUEL, LEFT FUEL BOOST pump(electric) caution panel light illuminated.

a.

b.

c.

d.

e.

f.

g.

h.

i.

Circuit breaker(s) out.

Boost pump inoperative.

Ejector pump (H/V) clogged.

Pump inlet screen restricted.

Flow switch inoperative (H/V).

Pressure switch inoperative (C/M).

Main fuel switch faulty.

Faulty caution panel.

Fuel line clogged.

LEFT FUEL BOOST (bleed air) caution panellight goes out when main fuel is turned on.

a. Faulty fuel check valve manifold.

b. Faulty caution panel.

3-39

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

D7.

D8.

D9.

D1O.

ENGINE OIL PRESSure caution panel lightilluminated.

a. Check gage, if pressure is up and pressurechanges with power changes, trouble isfaulty caution panel, or pressure switch.

b. If pressure not correct, see E5.

SPARE caution panel light illuminated.

a.

b.

c.

Faulty wiring.

Segmented title in wrong location.


ENG CHIP DET and/or CHIP DETECTORcaution panel light(s) illuminated.

a. Metal chips on detector plugs.

b. Faulty wiring or plug.

c. Faulty caution panel.

ENGine FUEL PUMP caution panel lightilluminated.

a. One or both elements of dual pump failed.

b. Loose or clogged lines between pressureswitch and fuel control.

c. Faulty pressure switch.

3-40

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

D11. 20 MINUTE FUEL caution panel lightilluminated.

a.

b.

c.

d.

e.

Low fuel supply.

Faulty float switch.

Flapper valve installed wrong (H/V).

Faulty wiring.


D12. GOVernor EMERgency caution panel lightilluminated.

a.

b.

c.

Governor switch in the emergencyposition.


Faulty switch or wiring.

D13. FUEL FILTER caution panel light illuminated.

a. Fuel filter impending bypass or bypassing.

b. Filter iced.

c. Faulty fuel filter pressure switch.

d. Faulty caution panel.

e. Faulty wiring.

3-41

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

D14.

D15.

D16.

AUXiliary FUEL LOW caution lightilluminated.

a. Faulty wiring (with no auxiliary systeminstalled).

b. Faulty fuel transfer relay.


XMSN OIL PRESSure caution panel lightilluminated.

a. Check gage. If pressure up and pressurechanges slightly with RPM changes trou-ble is faulty caution panel, faulty pressureswitch, or faulty wiring.

b. If pressure not correct, see F2.

HYDraulic PRESSURE cautionilluminated (No. 1 or No. 2 C/M).

a.

b.

c.

d.

e.

f.

Switch in off position or faulty.

Faulty solenoid.

Leak in system.

Faulty pressure relief valve.

Oil level low.

Faulty pump.

panel light

3-42

TM 55-1520-242-MTF

CONDITION

D17.

D18.

D19.

PROBABLE CAUSE

g. Check valve in pump pressure lineinstalled backwards.

h. Faulty pressure switch or wiring.

i. Faulty system module (C/M).

j. Faulty caution panel.

ENGINE INLET AIR caution panel lightilluminated.

a. Faulty wiring.

b. Faulty pressure switch,

c. Clogged inlet screens.

XMSN OIL HOT caution panel lightilluminated.

a. Check gage. If it indicates normal, troubleis faulty caution panel, thermoswitch orwiring.

b. If gage is indicating high, see F6.

DC GENERATOR caution panel lightilluminated.

a. Main generator inoperative, see C28.



3-43

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d. Faulty reverse current relay (main gen)IND terminal.

e. Faulty wiring.

D20. Instrument INVERTER caution panel lightilluminated.

a. Faulty inverter, see C12.


D21. EXTERNAL POWER caution panel lightilluminated.

a. External power door open, faulty orincorrectly adjusted micro-switch.


D22. APX-68 IFF caution panel light illuminated.

a. Faulty wiring.


D23. MASTER CAUTION light illuminated only.

a. Small resistance in a chip detector plug.


3-44

TM 55-1520-242-MTF

CONDITION

D24.

D25.

D26.

PROBABLE CAUSE

LEFT FUEL BOOST pump (bleed air) cautionlight illuminated (H).

a.

b.

c.

d.

e.

f.

g.

h.

Faulty boost pump.

Boost pump outlet screen restricted.

Ejector pump restricted.

Boost pump inlet restricted.

Leak or obstruction in bleed airline.

Faulty flow switch.

Faulty wiring.

Line clogged.

GOVernor EMERgency caution panel lightdoes not illuminate when placing governorswitch in the EMERgency position.

a. Faulty switch.

b. Faulty wiring.

c. Faulty governor control circuit breaker.

d. Faulty caution panel.

HYDraulic PRESSUREdoes not illuminate.

caution panel light

a. Faulty pressure switch.

b. Faulty wiring.

3-45

3-46

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE


D27.

D28.

D29.

d. Faulty hydraulic module (C/M).

e. Bulbs burned out or missing.

RIGHT FUEL, LEFT FUEL BOOST (electric)pump caution panel light does not illuminate.

a. Faulty wiring.


c. Faulty pressure switch (C/M).

d. Faulty fuel check valve manifold.


Instrument INVERTER caution panel lightremains out, inverter off.

a. Faulty fail relay.


c. Faulty wiring.

LEFT FUEL BOOST pump (bleed air) cautionpanel light comes on above 40° N1.

a.

b.

c.

Faulty boost pump.

Bleed air leakage.

Faulty flow switch.

TM 55-1520-242-MTF

CONDITION

D30.

D31.

D32.

PROBABLE CAUSE

LEFT FUEL BOOST pump (bleed air) cautionpanel light does not illuminate.

a. Faulty caution panel.

b. Faulty flow switch.

c. Faulty fuel check valve manifold.

d. Faulty wiring.


ENGINE OIL and/or XMSN OILcaution panel light not illuminated.

PRESSure

a.

b.

c.

d.

Faulty wiring.



Faulty pressure switch.

DC GENERATOR caution panel light does notilluminate.

a. Faulty bus control relay.

b. Faulty wiring.


d. Bulbs burned out or missing.

3-47

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE E - POWER PLANT

CONDITION

PROBABLE CAUSE

E1. Throttle stiff or binding.

a. Fuel control power lever binding.

b. Throttle friction on or bound up.

c. Deck firewall boot rubbing control tube.

d. Engine idle stop misaligned or rough.

e. Segment gears (base of collective) worn,broken or dirty.

f. Throttle linkage rod end bearings worn ordirty.

E2. Incorrect throttle cushion.

a. Incorrect throttle rigging.

b. Throttle linkage, bell cranks or supportsdamaged or improperly installed.

E3. Unable to go to idle cutoff.

a. Idle stop solenoid improperly adjusted.

b. Electrical failure.

c. Faulty solenoid.

3-48

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

E4.

E5.

E6.

No engine oil pressure indication. Cautionpanel light out.


b. Faulty wiring.

c. Faulty caution panel combine with actualoil system problem.

d. No AC power, either 115V or 28V (will alsohave no transmission oil pressure indica-tion).

No engine oil pressure indication. Cautionpanel light on.

a. Loose hose connection(s).

b. No oil in system.

c. Restriction in lines.

d. Pressure relief valve malfunction.

e. Oil pump failure.

f. Oil leak.

Low engine oil pressure.

a. Low oil level.

b. Torque pressure line connected to engineoil pressure transmitter.

3-49

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c. Faulty indicating system.

d. Oil pump inlet restricted.

e. Oil pump relief valve setting wrong.

f. Oil leak.

E7. Fluctuating engine oil pressure.

a. Low oil level.

b. Sticking pump relief valve.

c. Pump inlet restricted.

d. Faulty transmitter or gage.

e. Air in oil system.

E8. High engine oil pressure.

a. Cold ambient conditions.

b. Faulty transmitter or gage.

c. Oil pump relief valve setting wrong.

E9. High engine oil temperature.

a. Low oil supply.

b. Oil cooler blower inoperative.

c. Faulty or obstructed oil cooler.

3-50

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d.

e.

f.

g.

Faulty thermal valve.

Restriction in oil system; clogged jets.

Scavenge pump inoperative.

Faulty indicating system.

E10. N1 above 59% (L-11) or 72% (L-13) with throttleat engine idle.

a. Throttle positioned above engine idle.

b. Engine idle stop improperly rigged.

c. Faulty fuel control.

d. Wrong idle trim setting on fuel control.

e. Tachometer system failure.

E11. N1 below 55% (L-11) or 68% (L-13) with throttleat engine idle.

a.

b.

c.

d.

e.

f.

Engine idle stop improperly rigged.

Fuel control in emergency.

Wrong idle trim setting on fuel control.


Overspeed governor malfunction.

Throttle linkage bell crank or supportloose or broken.

3-51

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

g.

h.

i.

Fuel flow restricted.

Wrong fuel.

Tachometer system faulty.

E12. N1 does not decrease when placingswitch in the EMERgency position.

a. Faulty switch.

b. Faulty wiring.

c. Faulty changeover solenoid.

d. Faulty fuel control.

governor

e. Faulty governor control circuit breaker.

E13. N1 does not increase when placing governorswitch in the AUTOmatic position.

a.

b.

c.

d.

e.

Faulty switch.

Faulty changeover solenoid.

Faulty wiring.


Faulty governor control circuit breaker.

3-52

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

E14. Bleed band opening/closing abnormal.

a.

b.

c.

d.

e.

f.

h.

i.

Adjustment incorrect.

Clogged strainer or actuator valve.

Actuator sensing hoses obstructed or notconnected (L-11).

Teflon seal binding.

Sticky actuator valve.

Fuel control sensing hose obstructed.

g. Faulty fuel control.

Faulty airbleed actuator.

P-3 air lines disconnected or loose.

E 15. N2 exceeds 6050 RPM at full open throttle anddecreased beep.

a.

b.

c.

d.

Sticking or dirty actuator.

Faulty wiring.

Faulty overspeed governor.

Improper N2 rigging.

3-53

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

E16. N2 below 5950 RPM at full open throttle anddecreased beep.

a. Improper N2 rigging.

b. Air in fuel control.

c. Faulty overspeed governor.

E17. EGT fluctuating, no other engine instrumentsfluctuating.

a. Faulty indicating system.

b. Loose connections.

c. Faulty resistance box wiring.

E18. Low EGT.

Faulty indicating system.

E19. EGT abnormally high.

a. Engine inlet dirty, filters clogged.

b. De-ice valve open.

c. Faulty inlet guide vanes,

d. Faulty bleed band.

e. Combustion chamber drain open.

3-54

TM 55-1520-242-MTF

CONDITION

E20.

E21.

E22.

PROBABLE CAUSE

f. Dirty or damaged compressor.

g. Bleed air heater on.

h. Faulty indicating system.

i. Faulty fuel control.

j. Damaged internal components.

Engine surge (compressor stall), fluctuatingengine instruments.

a. Engine deterioration or dirty air inlet.

b. Dirty compressor.


d. Faulty bleed band actuator.

e. Faulty inlet guide vanes.

Excessive overshooting of RPM or hunting byengine during collective applications.


Unable to attain hover power in EMERgencyposition.

a. Improper throttle rigging.

b. Faulty fuel control.

c. Faulty inlet guide vanes.

3-55

TM 55-1520-242-MTF

CONDITION

E23.

E24.

E25.

E26.

PROBABLE CAUSE

Unable to move throttle below engine idle.

a. Solenoid stuck or improperly rigged.

b. Electrical failure to solenoid.

c. Throttle binding.

d. Faulty fuel control.

Engine fails to shut off, with throttle belowengine idle.

a. Throttle improperly rigged.

b. Fuel control improperly rigged.


Coastdown time of N1 too short.

Internal binding of engine.

Engine response slow, RPM does not recover.

a. Faulty overspeed governor.

b. Faulty droop compensator.

c. Shear pin sheared or shearing.

3-56

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE F -POWER TRAIN

CONDITION

PROBABLE CAUSE

F1. No transmission oil pressure indication.Caution light out.

a.

b.

c.

d.


No AC power, either 115V or 28V (will alsohave no engine oil pressure indication).

Faulty wiring.

Faulty caution panel combine with actualoil system problem.

F2. No transmission oil pressure indication.Caution light on.

a.

b.

c.

d.

e.

f.

g.

h.

Loose hose connection(s).

No oil in system.

Restriction in lines.

Quick disconnect loose (closed).

Pressure relief valve faulty.

Clogged pump inlet screen.

Oil pump failure.

Oil leak.

3-57

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

F3. Low transmission oil pressure.

a. Pressure relief valve faulty.

b. Clogged inlet screen.

c. Faulty oil pump.

d. Faulty indicating system.

e. Leakage or restriction between pressurerelief valve and transmitter.

F4. Fluctuating transmission oil pressure.

a.

b.

c.

d.

e.

f.


Instrument clamped too tight in panel.

Faulty relief valve.

Clogged pump inlet screen.

Low oil level.

Air in transmitter lines.

F5. High transmission oil pressure.

a. Faulty indicating system.

b. Pressure relief valve malfunction orimproperly set.

c. Clogged jets.

3-58

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

F6. High transmission oil temperature.

a. Faulty pressure relief valve.

b. Clogged oil jets.

c. Seized bearing or other internaltransmission failure.

d. Oil cooler clogged or obstructed.

e. Faulty bypass valve.

f. Faulty oil cooler blower.

g. Faulty indicating system or wiring.

F7. Pylon rocking continues abnormally long orpresent in normal flight.

a.

b.

c.

d.

e.

Faulty transmission mount dampers.

Wrong dampers installed.

Pylon mounts worn.

Faulty fifth mount.

Mount bolts bottomed, loose or stripped.

F8. Abnormal vibrations or engine surges duringpylon mounts check.

Engine to transmission alignment incorrect.

3-59

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE G -HYDRAULIC

CONDITION

PROBABLE CAUSE

G1. Excessive feedback in controls.

a. Air in hydraulic system.

b. Servo control head bolts too tight.

c. Internal leakage in irreversible valve.

d. Power cylinder assembly faulty.

e. Hydraulic pump faulty.

G2. Cyclic gets hard to move along 45° line withfeedback.

a. Faulty hydraulic servo pilot valve.

b. Faulty irreversible valve.

c. Faulty hydraulic pump.

d. Low hydraulic pressure.

e. Faulty check valve.

f. Restriction at pump outlet.

g. Low fluid level.

3-60

TM 55-1520-242-MTF

CONDITION

G3.

G4.

G5.

G6.

PROBABLE CAUSE

Collective motors up or down, boost on.

a. Collective servo balance spring out ofadjustment.

b. Faulty irreversible valve.

c. Faulty servo valve.

Collective comes up easier than it goes down orvice versa (boost on).

a. Collective servo balance spring out ofadjustment.

b. Faulty servo valve.

Collective moves freely with emergencyaccumulator switch off and battery on (C/M).

a. Faulty switch.

b. Faulty emergency solenoid.

c. Check valve installed backwards.

Collective does not move freely withemergency accumulator switch and batteryswitch on.

a. Hydraulic fluid level low.

b. Faulty switch.

c. Faulty emergency solenoid.

3-61

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

d.

e.

Faulty collective lockout valve.

Collective lockout valve closing at too higha pressure.

G7. Accumulator gage reads above or below greenarc and less than four strokes are available oncollective pitch.

a.

b.

c.

d.

Low or high nitrogen charge.

Check valve installed backwards.

Faulty collective lockout valve.

Friction collect too high.

3-62

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE H -FLIGHT CONTROLS

CONDITION

PROBABLE CAUSE

H1. T/R pedal adjustmentadjust.

binding or hard to

a. Dirt in adjustment assembly.

b. Worn assembly.

c. Pedals at limits.

H2. Stiff or binding T/R pedals.

a. Worn or frayed T/R cables.

b. Mag brake/force gradient assemblybinding or sticking.

c. Worn pitch change mechanism.

d. Faulty T/R servo.

H3. Binding or limited travel of cyclic control.

a. Misrigged.

b. Wiring bundle at base or cyclic improperlyrigged.

c. Mag brake/force gradient assemblybinding or sticking.

d. Adjustable friction not completely off.

3-63

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

e.

f.

Foreign matter at base of cyclic stick.

Bearings worn or dirty.

H4. Binding or limited travel of collective control.

a. Bearings worn or dirty.

b. Adjustable friction not completely off.

c. Improperly rigged.

d. N2 improperly rigged.

H5. Controls do not operate smoothly.

a.

b.

c.

d.

e.

f.

g.

Servo valve sticking.

Bearing worn or dirty.

Servo valve improperly set.

Servo control head bolts too tight.

Faulty hydraulic pump.

Relief valve malfunction.

Bent or binding control tubes.

H6. Cyclic chatters when being moved.


3-64

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

b. Power cylinder mounting bearings loose.

c. Power cylinder mount uniball loose.

H7. Cyclic binding in certain areas with force trimoff.

a.

b.

c.

d.

e.

Adjustable friction not completely off.

Wiring harness binding in base of cyclic.

Foreign matter in base of stick.

Bearings worn or dirty.

Cyclic jackshaft too tight (improperlyshimmed).

H8. With force trim off, cyclic continues movingafter a small force is applied or moves withoutforce application.

a. Power cylinder control head bolts binding.

b. Collective pilot valve spring inadvertentlyinstalled on cyclic cylinders(s).

c. Faulty hydraulic cylinder.

d. Faulty irreversible valve.

3-65

TM 55-1520-242-MTF

CONDITION

H9.

H1O.

H11.

H12.

PROBABLE CAUSE

Pedals chatter when being moved.


b. Power cylinder mounting bearings loose.

c. Misalignment of T/R power cylinder.

With force trim off, left or right pedal creepsforward.

a.

b.

c.

Hydraulic cylinder lines putting force oncylinder.

Faulty hydraulic cylinder.

Servo balance spring missing orimproperly adjusted.

Excessive play in pedals.

a. Worn pitch change mechanism.

b. Worn tube rod ends or pedal adjuster.

c. Cable tension low.

Force trim weak or allows play in cyclic.

a. Maladjusted spring tension.

b. Improperly rigged.

c. Faulty magnetic brake.

3-66

TM 55-1520-242-MTF

CONDITION

H13.

H14.

H15.

H16.

PROBABLE CAUSE

Force trim excessively stiff.

a. Improperly rigged.

b. Maladjusted spring tension.

Collective built-in friction too light or tooheavy.

a. Improperly adjusted at base or stick.

b. Bearings worn or dirty.

c. Collective jackshaft improperly shimmed.

Unable to increase collective friction usingpilot adjustable friction device.

a. Friction knob jammed.

b. Threads need cleaning.

c. Friction pads excessively worn.

d. Malfunction in base of collective stick.

Aircraft tries to turn in wrong direction withpedal input.

Improperly rigged.

3-67

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

H17. Unable to get collective up sufficiently (booston).

a. Faulty hydraulic cylinder.

b. Improper rigging.

c. Fouled controls.

H18. Collective stick binds, sticks or has breakawayforce.

a. Friction device worn, rough or adjustedtighter on one side than the other.

b. Fouled electric harness at base of stick.

c. Droop compensator sticking or pinshearing.

d. Faulty hydraulic cylinder.

H19. N2 increases more than 40 RPM whencollective raised.

a. Faulty droop compensator.

b. Wrong droop cam installed.

c. N2 system improperly rigged.

d. Improper collective control rigging.

3-68

TM 55-1520-242-MTF

CONDITION

H20.

H21.

H22.

PROBABLE CAUSE

N2 droops off more than 40 RPM whencollective is raised. (Not to be confused withnormal transient droop caused by rapid collec-tive movement.)

a.

b.

c.

d.

e.

f.

g.

Improperly rigged droop compensator.

Maladjusted droop compensator.

Excessive play in linkage.

Throttle not fully open.

Wrong droop cam installed.


Droop compensator pin sheared.

Insufficient pedal travel, or pedal position.

a.

b.

c.

Improper tail rotor rigging.

Fouled control tubes or controlcomponents.

Wrong tail rotor installed.

Unable to get normal cyclic travel.

a. Improper rigging of cyclic.

b. Improperly installed control components,

3-69

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c. Fouled controls.

d. Force trim improperly rigged.

e. Jackshaft counterweight installedbackward (C/M).

H23. Cyclic stick not centered in stable hover.

a. Fore and aft CG off center.

b. Lateral CG off center.

c. Improper rigging at swashplate.

d. Improper rigging in cockpit.

H24. Aircraft responds faster in one direction thanthe other with equal pedal inputs.

a. Improper tail rotor rigging.

b. Wrong tail rotor installed.

c. Gusty wind conditions.

H25. Rotor response to cyclic inputs slow, orinconsistent.

a. Improper rigging.

b. Leaking hydraulic cylinder.

3-70

TM 55-1520-242-MTF

CONDITION

H26.

H27.

H28.

H29.

PROBABLE CAUSE

c.

d.

e.

Faulty stabilizer bar dampers, see H31.


Faulty relief valve.

Cyclic position abnormal for flight conditions.

a. Improper swashplate or elevator rigging.

b. CG not as computed.

c. Faulty airspeed indicator.

T/R pedals improperly positioned with 30 PSItorque and 90 (N)/100(R) KTS airspeed.

a. Improper tail rotor rigging.

b. Incorrect component installed.

Autorotation RPM too high or low.

a. Gross weight different than computed.

b. Abnormal density altitude.

c. Improper main rotor blade pitch angle set.

With boost off it is harder to move cyclic rightand forward than to left.

a. Normal, unless excessively hard.

b. Balance spring on right cyclic swashplatehorn missing, or improperly set.

3-71

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

H30. Collective comes up too easy and goesdown too hard or vice versa (boost off).

NOTE

Collective becomes more negative as den-sity altitude increases.

a.

b.

Deleted.

Blade tabs either too high or low in both blades.

c.

H31.

a.

b.

c.

d.

e.

f.

g.

T/T bundle improperly adjusted.

Bank response abnormal. Ship unusuallysensitive or unusually stable.

Faulty stabilizer bar dampers.

Incorrect damper rod adjustment.

Wrong stabilizer bar weights installed.

Wrong damper lever arms.

Rod end to damper lever arms connection incor-rect.

Dampers low on fluid.

Wrong type fluid on damper.

C-3 3-72

TM 55-1520-242-MTF

CONDITION

H32.

H33.

H34.

H35.

PROBABLE CAUSE

Too much or too little spring cushion onforward cyclic travel.

a. Maladjusted force gradient spring.

b. Magnetic brake sticking.

Unable to get normal cyclic travel.

a.

b.

c.

d.

e.

Improper cyclic rigging.

Control components installed wrong,

Fouled controls.

Force trim improperly rigged.

Jackshaft counterweight installedbackward (C/M).

Normal flight, tail boom intermittently kicksright or left.

Tail rotor pitch change rod end bearings ex-cessively worn or crosshead improperly shim-med.

Rail rotor pedals not rigged properly.

Adjust pitch change links.

3-73

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE I -NOT APPLICABLE

3-74

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE J -VIBRATIONS

CONDITION

J1.

J2.

PROBABLE CAUSE

1/REV vibration at a hover.

a.

b.

c.

d.

e.

f.

g.

Blade balance (lateral felt as a vertical)spanwise or chordwise unbalance.

Severe out of track.

Stabilizer bar out of balance.

Excessively worn dynamic components.

Grip bearings binding.

Incorrect grip spacing.

Internal leak in blade grip (H/V andEH-1H/X).

1/REV vibration, intermittent (C/M).

a.

b.

c.

d.

e.

f.

Collective friction (mast) loose.

Collective sleeve bearings worn.

Collective lever pivot bearing worn.

Swashplate uniball torque incorrect.

Grip bearings worn or sticking.

Excessive tab differential.

3-75

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

J3. Excessive high frequency vibration.

a.

b.

c.

d.

e.

f.

g.

h.

i.

j.

k.

l.

m.

n.

o.

p.

q.

Tail rotor out of balance.

Tail rotor out of track.

Loose tail rotor pitch change link bearings.

Hanger bearings worn, bearing assemblyloose, or dry of lubricant.

Worn or loose crosshead.

Faulty engine.

Faulty generator bearings.

Tail rotor drive shaft balance.

Tail rotor drive shaft bent.

Tail rotor drive shaft out of alignment.

Worn or loose tail rotor trunnion.

Start-generator cooling fan worn (H/V).

Oil cooler fan or mount.


Hydraulic modules (C/M).

Loose tail rotor grip bearing.

Loose tail rotor retaining nut.

3-76

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

J4.

r.

s.

t.

u.

v.

w.

Bent tail rotor pitch change link.

Engine alignment or mounts.

Main drive shaft clamps not matchedproperly.

Main drive shaft clamps not installed at90°.

Faulty inverters.

Bad bearings in any quill assembly.

1/REV vertical vibration in forward flight.

a.

b.

c.

d.

e.

f.

g.

h.

Blade out of track.

T/T straps not set equally or not holdingsetting (H/V).

Pitch change rod end bearings worn.

Grip bearings sticking.

Radius rings worn (C/M).

Carbon insert missing (C/M).

Worn stabilizer bar pivot bearings.

Worn mixer lever bearings.

3-77

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

i. Swashplate unibail torque incorrect (C/M).

j. Scissors bearings or bushings worn.

k. Worn trunnion bearings.

1. Undertorqued pillow block bolts.

m. Loose power cylinder mountings.

J5. Excessive 2/REV vibration.

a. Transmission mounts deteriorated.

b. Loose, worn or improperly shimmed dragbrace bolts.

c. Worn rod end bearings.

d. Excessive play in swashplate assembly.

J6. Medium frequency vibration felt in airframe.

a.

b.

c.

d.

e.

Loose skids.

Loose radio or electronic equipment.

Loose equipment in cabin.

Excessive elevator play.

Loose airframe components.

3-78

TM 55-1520-242-MTF

TROUBLESHOOTING GUIDE K -COMMUNICATIONS/NAVIGATIONEQUIPMENT

CONDITION

PROBABLE CAUSE

K1. High loadmeter indication when turning radioon, or radio inoperative.

a.

b.

c.

d.

e.

f.

Faulty wiring.

Internal failure.

Improperly tuned.

Improper radio switch position.

Faulty ICS panel.

Headset not plugged in completely.

K2. Gyro compass will not null.

a. Compass slaving switch in wrong position.

b. Internal failure.

c. Faulty flux valve.

d. Faulty wiring.

K3. Gyro operated instruments processingexcessively.

a. Inverter frequency output incorrect.

b. Faulty inverter.

3-79

TM 55-1520-242-MTF

CONDITION

PROBABLE CAUSE

c. Faulty power correction network or circuitbreakers out.

K4. Copilot RMI card inoperative, inverters on.

a.

b.

c.

d.

Faulty transformer.

Transformer circuit breaker out.

Inverter voltage excessively high or low.

Faulty wiring.

K5. Gyrocompass inaccurate or erratic.

a. Improper position of compass slavingswitch.

b. Improper adjustment of transmitting unit.

c. External magnetic interference.

d. Faulty components.

e. Faulty indicating system.

K6. Communication and/or navigation equipmentdoes not operate properly.

a.

b.

c.

d.

Faulty wiring.

Faulty interphone control box.

Internal failure of radio.

Faulty antenna or connection.

3-80

TM 55-1520-242-MTF

SECTION IV-SPECIAL PROCEDURES

General. This section contains special procedureswhich were referenced in Section II.

A. Altimeter, Radar-AN/APN-209-Self-Test

1. Set LO SET index to 0 feet and observe:

2.

3.

4.

a.

b.

c.

Indicator pointer is driven behind no trackmask above 1500 feet.

OFF flag is displayed.

Digital display and warning lamps illuminated(may flash momentarily when power is firstapplied).

Set LO SET index to 100 feet, set HI SET indexto 800 feet, (allow two minutes warmup) observe:

a.

b.

c.

d.

e.

OFF flag disappears.

Indicator pointer indicated 0 ± 3 feet.

Digital display indicated 0 (-0) to 3 feet.

LO warning lamp illuminated.

HI warning lamp out.

Press and hold the push-to-test (HI SET) knoband observe:

a.

b.

c.

d.

Indicator pointer indicates 1000 ± 100 feet.

Digital display indicates 1000 ± 100 feet.

LO warning lamp out.

HI warning lamp illuminated.

Release push-to-test (HI SET) knob and observeindication shown in item b.

C-3 4-1

TM 55-1520-242-MTF

B. Altimeter Set, Electronic AN/APN-171 A(V)1 -Self-Test

Test Step Test Instructions

1. PUSH-TO-TEST,OFF, SETcontrol-ON Allow3 minutes forsystem warm up.

2. Low WarningIndex - Set to 50Feet

3. PUSH-TO-TESTSwitch - PUSH

4.

5.

PUSH-TO-TESTSwitch - Release

End of Test

Normal Indications

The NO TRACKflag should remainvisible and the dialpointer should re-main behind the NOTRACK mask for 2to 3 minutes afterpower is turned on.The pointer willthen rotate to the0±5 foot gradua-tion on the dial andthe flag will disap-pear.

Low warning lightshould illuminate.

The height in-dicator pointershould indicate100±50 feet. TheLOW warning lightshould go out.

The pointer shouldreturn to zero andthe LOW warninglight illuminate.

4-2

TM 55-1520-242-MTF

C. Self-Test, Radar Warning Receiver, AN/APR-39- Self-Test

Test Step Test Instructions

1. Apply power toA N / A P R 3 9 .Wait one minutefor warm up.

2.

3.

4.

5.

Set control unitDSCRM-OFF.Monitor CRT andaudio and pressand hold SELFTEST.

Rotate indicatorBRIL control CWand CCW.

Rotate controlunit AUDIO CWand CCW.

Release SELFTEST.

Normal indications

Control unit panellamps illuminate.

a. Fwd and aftstrobes appear,extending to ap-prox. the thirdcircle on theCRT. A 2.5 kHzP R F a u d i oshould be heardimmediately.

b. Within 6 secondsalarm audio pre-sent and MAl a m p s t a r t sflashing.

Indicator strobesshould brighten anddim.

Audio not audibleat max CCW andclearly audible atmax CW.

All indicationscease.

4-3

4-4

TM 55-1520-242-MTF

Test Step Test Instructions Normal Indications

6. Set DSCRM to a.ON. Press andh o l d S E L FTEST.

b.

c.

Within 4 secondsa fwd or aftstrobes (eithermay appear first)and 1.2 kHz PRFaudio present.

Within 6 secondsthe other strobewill appear andPRF audio fre-quency will dou-ble.

Several secondslater alarm audiopresent and MAlamp starts flash-ing.

7. Release SELF All indicationsTEST cease.

8. END OF TEST

TM 55-1520-242-MTF

D. Tail Rotor Tracking and Balance

NOTE

This section has instructions for onlythe strobe-type tracking device. Ifmanual methods are to be used con-sult the appropriate airframemaintenance manual.

1. Tail Rotor Tracking

a.

b.

c.

d.

e.

Install the tracking and balancing hardware onthe aircraft as prescribed in the strobex in-struction manual.

Set Balancer as Follows:

(1) “Function” switch to “B”

(2) “RPM Range” to “X10”

(3) “RPM Tune” to “165”

Set strobex as follows:

(1) (135 M-11) mode switch to “D”

(2) “RPM dial to 662

Run helicopter to 6600 RPM, with flatpitch and centered pedals. Head aircraft in-to the wind, on-the-ground.

Stand to the side of the tail rotor andobserve the four images of the single griptarget. Fine tune the “RPM” dial so thefour targets are stopped.

4-5

4-6

TM 55-1520-242-MTF

f. Reposition, with Balancer and Strobex, toaft left portion of fuselage. Look aft at edgeof tail rotor disc to view the super-imposedTip Targets and judge track (left to rightrelation). Adjustment of “RPM” knob willposition and stop targets as desired.

NOTE

If the horizontal bar appears above orbelow the vertical it indicates thetargets were not placed an equaldistance aft of the leading edge of theblade. This is not important if the dif-ference is only an inch or two; the im-portant observation is the left-to-rightrelation of the vertical to horizontalbars.

g. Shut down and adjust track if required.

2. Tail Rotor Balance.

NOTE

The rotor must be in track at the timebalance readings are taken.

a. Set Strobex mode switch to “A”

b. Set Balancer to Channel “B” and RPM to1650.

NOTE

The Phazor section of the balancer is notoperable when working the tail rotor, soignore the Phazor lights when workingthe tail rotor.

TM 55-1520-242-MTF

c.

d.

e.

Standing alongside the tailrotor view the“Clock Angle” of the single grip target. Pushthe “verify Tune” button and, while the buttonis depressed, adjust the “RPM Tune” dial toreturn the target to the “Clock Angle” observ-ed BEFORE the button was pushed. Releasebutton, observe angle, push and adjust againto match new “unpushed” angle. Repeat untilthere is no change whether button is pushed orreleased.

Record in Balance Chart (Section V) the“Clock Angle” and “IPS” (Read “IPS”without strobex flashing).

Shut the aircraft down. Plot point at theintersection of the “Clock Angle” and “IPS”circle. Determine the required changes. Runthe aircraft and check results. Continue untilbalance is 0.1 “IPS” or less.

NOTE

It is important that only the larger of thetwo indicated weights be changed on thetail rotor for the first move. The “moveline” should be parallel to the fine linesextending perpendicular from the un-changed axis.

If the “move Line” is not in the cor-rect direction, use “Clock Angle Correc-tor” #3597, and assign new numbers toclock.

Both weights can be changed if thetail rotor is fitted with Balance Arms sothe axes on the Balance Chart are at 90°to each other.

4-7

TM 55-1520-242-MTF

NOTE

If the rotor does not respond in an order-ly fashion after a few moves, the weightsshould be restored to original and thefirst reading should be repeated. If thefirst reading cannot be repeated, look forfaulty bearings, shafts, etc.

4-8

TM 55-1520-242-MTF

E. Main Rotor Tracking and Balance

NOTE

If Manual tracking procedures are tobe used, follow the instructions inthe appropriate airframe mainte-nance manual.

NOTE

This section has instruction for onlythe strobe-type tracking device.

1. Balancing the Main Rotor.

a. Install the associated accelerometers, mag-netic pick-ups, targets, and interrupters asprescribed in the instructions includedwith the device.

b. Insure both trim tabs are at zero degreesbefore starting tracking procedures.

c. Set Balancer (177M-6A or 7A) as follows:

(1) “Magnetic Pickup” to “Common”

(2) “Interrupter Logic” to “Double”

(3) “Function switch to “Track”

(4) “RPM Range” to “X1”

(5) “RPM Tune” to “324”

4-9

TM 55-1520-242-MTF

d. Set strobex (135M-11) as follows:

(1) “Mode switch” to “B”

(2) “RPM” to “129”

Setting the “Mode Switch” to “B”puts the strobe light in the high inten-sity mode.

e.

f.

g.

Hover the aircraft and search the tip pathto find the Tip Targets. Fine tuning theStrobex RPM may bring the targets intobetter view. Record track on Track andBalance Sheet (Section V).

Correct main rotor track, as required,using pitch-links.

When hover track is set, switch Balancer“Function” Switch to “A”.

(1) While hovering, push “test” buttonand check for 12:00 and 6:00 o’clocklights in phazor.

(2) Release “Test” button and observe“Clock Angle”.

(3) Push “Verify Tune” button, and ad-just “RPM Tune” dial while button isdepressed, to return light to angleobserved before button was pushed.Release, observe angle, push and ad-just again to match new “Unpushed”angle. Repeat until there is no changewhether button is pushed or released.

(4) After tuning, read, and record on theTrack and Balance Chart (Section V)“Clock Angle” and “IPS”.

4-10

(5)

TM 55-1520-242-MTF

Land aircraft and plot the point on the Trackand Balance Chart (Section V) at the inter-section of “clock angle” line and “IPS” circle.Determine changes required in blade boltweight and sweep, and record in data sec-tion.

h. Make the changes, hover again, repeat steps g,1, 2, 3, 4 and 5 until balance reading is 0.1“IPS” or less.

2. In-Flight Tracking Main Rotor

a. Switch Balancer “Function” Switch to Track,(everything else remains the same).

b. Set strobe as stated in 1, d, (1) and (2).

Minimize or eliminate all abnormal vibra-tions and compute VNE for aircraft con-figuration and ambient conditions prior toperforming this check. Roof or nosemounted pilot tube changes VNE sig-nificantly.

c. Fly the aircraft and sketch the track observedat 60, 90 and 110 knots on the in-flight track-ing sheet (section V).

d. While still flying, switch Balance “Function”Switch to “B”.

(1) Press “Test” button and look for 12:00 o’clocklights.

(2) Release “Test” button and observe “ClockAngle”.

C-3 4-11

e.

f.

g.

TM 55-1520-242-MTF

Isolate vibration “Clock Angle” and “IPS” asstated in 2, d, (1), (2) and record on the In-flight tracking Sheet for 60, 90 and 110 knots.

Land aircraft. Plot the 110 knot (or highestspeed attained) reading on the Tracking Sheetat the intersection of the “Clock Angle” lineand “IPS” circle.

If the blades are seen to spread as airspeed isincreased use trim tab. If the blades are out-of-track about the same amount at all airspeeds,use pitchlink.

NOTE

Use as little trim tab as possible. Exces-sive tab tends to wash out, and maydeteriorate the ride.

h. Fly the aircraft again to check the results.Repeat if required to reduce “B” readings (vertical 1:1) to 0.2 “IPS” or less.

After in-flight tracking, check theautorotation RPM, and correct as neces-sary by adjusting both pitch change linksequally.

i. After in-flight tracking, check the “A” (balance)reading in hover. “Fine Tune” if required.

✰ U.S. GOVERNMENT PRINTING OFFICE: 1991 654-121/41031

C-3 4-12

TM 55-1520-242-MTF

F. Health Indicator Test (HIT). Establish the HITbaseline EGT values as follows:

1. Perform normal engine runup and cockpitprocedures in accordance with the applicable -10manual.

2. Maintain N2 at 6600 RPM.

3. Turn off all bleed air, de-ice.

4. Turn aircraft into the wind and read free airtemperature on cockpit FAT gage.

5. Utilizing a blank HIT baseline EGT worksheetlocate OAT in first column nearest to the free airtemperature reading on the cockpit FAT gage.Circle this OAT. If OAT falls between twotemperatures listed on the worksheet, use thehigher reading.

6. Set N1% at the value indicated in column 2opposite this FAT. Allow EGT to stabilize.

7. Read EGT from indicator. Record EGT besidethe circled FAT.

8. Apply the ∆ EGT A Correction Factor in column 3adjacent to the circled FAT to indicate EGT andrecord the results in the open space in column 4.

NOTE

The blank form in Section V will only takeyou to this point. To proceed further willrequire an actual HIT EGT worksheet.

C4 4-13

TM 55-1520-242-MTF

9. Apply EGT B Correction Factor in column5 to the EGT in column 4. Record results foreach of the FAT/N1 combinations shown incolumn 8.

10. Enter baseline information in the respectivecolumns of the HIT EGT log.

4-14

TM 55-1520-242-MTF

G. Engine Topping.

1. Prior to topping the engine, perform allrequired inspections IAW TM 55-2840-229-23.

NOTE

In cold weather it may be impossibleto achieve topping without exceeding10,000 feet pressure altitude. Flightabove 10,000 feet pressure altitude isnot recommended. During periods ofcold temperatures, precise trimmingof the fuel control is less criti-cal since considerable reserve powerexists due to the low ambient tem-perature. If engine topping cannot beaccomplished the following condi-tions will apply:

FOR BASELINE TEACS: If ambienttemperature is below -15° C at TESTALTITUDE the engine topping por-tion of the Baseline TEAC may bedeferred until temperature conditionsimprove. An entry on DA Form2408-13 will be made and a reddiagonal status symbol will beentered in block 16. Block 17 willstate; Engine topping deferred untiltemperature conditions improve.(Temperature is the only reason todefer engine topping. All otherBaseline TEAC checks will be ac-complished IAW TM 55-2840-229-23and the aircraft will be flown to10,000’PA to insure the fuel controlhas not been inadvertently trimmeddown).

4-15

TM 55-1520-242-MTF

2. Predetermine Topping Altitude:

a.

b.

c.

d.

e.

f.

g.

Set one altimeter at 29.92.

Insure de-ice is off.

Insure bleed-air is off.

Increase collective to 40 psi torque.

Read N1 at any whole thousands altitudeat 40 psi and altimeter 29.92.

Subtract actual N1 reading frommaximum Nl, minus 2%.

For every 1% of N1 difference you willneed to climb another 2000 feet pressurealtitude to attain your predetermined top-ping altitude.

EXAMPLE: Max N1 . . . . . . . . . . . . . . . . . . . . . 101.5Subtract - 2 . 0Adjusted N1 . . . . . . . . . . . . . . . . . . . . 99.5N1 at 40 psi at 2000’ PA . . . . . . . -96.0Difference 3.5Multiply by . . . . . . . . . . . . . . . x2000Product . . . . . . . . . . . . . . . . . . . 7000Add altitude used . . . . . . . . . . +2000Predetermined Topping Altitude 9000

3. Top the engine as follows:

a. At a moderate rate, climb to 500 feetbelow predetermined altitude.

4-16

TM 55-1520-242-MTF

Do not exceed maximum N1, Torque,or EGT limits.

As altitude increases, VNE de-creases. At high power settings andlow rotor RPM, retreating blade stallcan occur below computed VNE.

b. Increase collective to maximum torqueavailable.

Certain T53-L-13 engines may expe-rience a torque oscillation at thetime of N2 droop. This may be caus-ed by transient opening and closingof the bleedband. Adjustment of thebleedband to a lower closing positionwithin the closing range and/or us-ing a higher topping altitude mayreduce or eliminate this torqueoscillation. If torque oscillation can-not be reduced to 4 PSI or below, thefuel control may be replaced. If tor-que oscillation is noted, record thenominal indication. If during torqueoscillation the maximum torque limitis exceeded, refer to the appropriatemanual for over-torque inspections.

c. Maintain maximum torque until N2droops to 6400 RPM. Record N1, TQ,EGT, FAT, PA.

4-17

TM 55-1520-242-MTF

If N2

NOTE

droops prior to reachingpredetermined altitude, maintain6400 RPM until reaching the nextwhole altitude, then record N1, Tor-que, EGT, FAT, PA. If N2 does notdroop prior to or at your predetermin-ed altitude, maintain maximum tor-que until N2 droops or 10,000 feetpressure altitude is exceeded. If N2droops prior to 10,000 feet pressurealtitude, record N1, Torque, EGT,FAT, and PA, at the next wholethousands altitude. If 10,000 feetpressure altitude is reached prior toN2 droops, note the torque at 10,000feet pressure altitude and tem-perature to insure that the fuel controlis not over trimmed. If necessary, ad-just IAW TM 55-2840-229-23. If fuelcontrol is not over trimmed (in excessof 3 PSI required torque) engine topp-ing must be deferred until tempe-rature conditions improve.

d. Further droop N2 to 6200 RPM insuringN1 does not increase.

4-18

e.

f.

g.

h.

TM 55-1520-242-MTF

NOTE

If N1 increases as N2 droops from6600 to 6500 RPM, the droop cam isprobably worn or out of adjustmentand the engine is not “topping” out at6600 RPM and should be corrected. IfN1 changes as N2 droops from 6400 to6200 RPM, the engine is probably notat maximum power and the droop cammust be adjusted before an accuratetopping check can be accomplished.

Reduce collective smoothly and slowly.Rapid reduction of collective could causeengine surge, compressor stall, and/orcomplete unloading of the main rotorsystem.

Reset altimeter to current setting.

Analyze topping data IAW TM 55-2840-229-23.

Record topping data on DA Form 2408-15over-print IAW DA PAM 738-751.

NOTE

ALL engine troubleshooting and fuelcontrol adjustments will be IAWTM 55-2840-229-23.

4-19

TM 55-1520-242-MTF

NOTE

The format in Section V may be usedto assist the MTP recording topppingdata and computation of predeter-mining topping altitude and does notdelete the requirement to record topp-ing data on the Maintenance TestFlight Check Sheet.

4-20

TM 55-1520-242-MTF

H. Flight Check - Model TA-2S Fuel Control P/N84200A Series.

1.

2.

3.

4.

5.

6.

7.

8.

Using the appropriate aircraft - 10 find MAXTQ available for ambient conditions.

Stabilize at an altitude of 1000 feet or higher.

Verify N2 at 6600 RPM.

Adjust airspeed to MAX rate of climbairspeed.

Increase collective to obtain MAX AVAILTQ. (Use the same pitch pull as that forEngine Response Check).

Do not exceed torque, EGT, or N1,Limits.

Climb at this rate for 500 feet.

Check N2 for decay.

If decay is evident, troubleshoot thefollowing systems:

a. Check bleed band for proper adjustment/closure range.

b. Check droop compensator rigging.

c. Check N2 rigging for play in linkage.

4-21

TM 55-1520-242-MTF

d. Check N1 rigging.

e. Insure proper droop cam is installed.

f. Insure shear pin in N2 linkage is notsheared.

g. Check for faulty overspeed governor.

h. Insure fuel control is trimmed properly.

i. Replace fuel control if the above itemsare found to be corrected.

4-22

TM 55-1520-242-MTF

SECTION V. CHARTS AND FORMS

General. This section contains the necessary chartsand forms required to ascertain that the aircraft isperforming to established standards and to recordreadings, pressures, RPM, etc., obtained during themaintenance test flight.

FIGURENUMBER

5-1

5-2

5-3

5-4

5-5

5-6

5-6.1

LIST OF CHARTS

TITLE

Bleed Band Closure Chart,Model TA-2S, P/N 84200-A7Fuel Control

Bleed Band Closure Chart,Model TA-7 P/N 100770-A4Fuel Control

Variable Inlet Guide VaneOpening Chart

Power Adjustment ChartT53-L-13B Engine

UH-1H/M HIT EGT Worksheet

Main Rotor Track and BalanceChart (UH-1H/V, EH-1H/X)

Main Rotor Track and BalanceChart (UH-1C/M)

PAGE

5-3

5-4

5-5

5-6

5-7

5-8

5-9

5-1

TM 55-1520-242-MTF

FIGURENUMBER

5-7

5-8

5-9

5-10

5-11

5-12

LIST OF CHARTS (CONT)

TITLE

In-Flight Main Rotor TrackingRecord Sheet

In-Flight Main Rotor TrackingChart

Tail Rotor Balance Chart(Old-Style)

Tail Rotor Balance Chart(New-Style)

Suggested TEAC DATAFormat

Maintenance Test Flight CheckSheet

PAGE

5-10

5-11

5-12

5-13

5-14

5-15

5-2

Figure 5-1.

TM

55-1520-242-MT

F

5-3

Figure 5-2.

TM 55-1520-242-M

TF

5-4

Figure 5-3.

TM

55-1520-242-MTF

5-5

TM 55-1520-242-MTF

Figure 5-4. Power Adjustment Chart T-53-L13B Engine

5-6

Figure 5-5.

TM 55-1520-242-MTF

5-7

TM 55-1520-242-MTF

Figure 5-6. Main Rotor Track and Balance Chart (UH-1H/V, EH-1H/X)

5-8

TM 55-1520-242-MTF

Figure 5-6.1. DELETED

5-9

TM 55-1520-242-MTF

Figure 5-7. In-Flight Main Rotor Tracking Recording Sheet.

5-10

Figure 5-8.

TM 55-1520-242-M

TF

5-11

TM 55-1520-242-MTF

Figure 5-9. Tail Rotor Balance Chart

5-12

TM 55-1520-242-MTF

Figure 5-10. DELETED

5-13

TM 55-1520-242-MTF

SUGGESTED FORMAT FOR TEAC DATA

MTP NAME TYPE TEAC DATE

ACFT / Ucdmt CAL FACTOR

Predetermine Topping Altitude:*

a. MAX M1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

b. Subtract 2% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- 2

c. Adjusted M1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

d. M1 at 40 psi at selected altitude . . . . . . . . . . . . . . . . . . . .

e .

f .

g .

Difference between "d" and "c" . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multiply "e" by 2000' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x 2 0 0 0

Product of "e" and "f" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Add altitude used in step "d" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Predetermined Tapping Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

h.

i .

TEAC

n?

BASELINE DATA

NONEADJ FACTOR (Temp/Alt)

REQUIRED DATA

ACTUAL INDICATIONS

DIFFERENCE

Figure 5-11. TEAC Data Format.

Change 1 5-14

* U.S. G.P.O. 1987 754 - 122/40037059474-001

TM 55-1520-242-MTF

Figure 5-12. Suggested Maintenance Test Flight Check Sheet(Sheet 1 of 2)

5-15

TM 55-1520-242-MTF

Figure 5-12. Aft Side of Maintenance Test Flight Check Sheet(Sheet 2 of 2)

5-16

TM 55-1520-242-MTF


JOHN A. WICKHAM, JR.General, United States Army

Official: Chief of Staff

MILDRED E. HEDBERGBrigadier General, United States Army

The Adjutant General

DISTRIBUTION:To be distributed in accordance with DA

Form 12-31, MTF Maintenance requirementsfor All UH-1 series aircraft and EH-1H/XHelicopter, Electronic Countermeasure &Intercept aircraft.

✰ U.S. G.P.O. 1986-652-126/20061

PIN: 059474-000

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