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hihson GAS TURBINE DIVISION

SUBJECT: CECO Field Service Information

The following information, which pertains to the CECO fuel system, is providedas a supplement to the 250-C20 Operation and Maintenance Manual.

ProblemAir in fuel system

Maintenance orSvmotom Preventive Action

1. Unstable or errat ic 1. Break tube "B" nut at theoperation governor bypass port (PO)and cover with a rag.

2. Loss of governor 2. Disconnect fuel line at theaction nozzle.

3. Place container underaircraft to collect fueldrainage.

4. Plug in battery cart or APUpower source.5. Pull ignition CB.6. Open fuel fire wall valve.7. Turn on boost pumps.8. Open throttle to full open.9. After 30 seconds of fuel

flowing from the bypassline, loosely install "8"nut tithe oovernor bypassport (PO) with boostpressure on. (Accomplishby moving wrench undercover of rag previouslyplaced; the rag wil l keepfuel from spraying.)

January 21, 1972Revision No. 3October 15, 1993

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ALLISON GAS TURBINECommercial Service Letter

1. PLANNING INFORMATION: (Continued)

ProblemAir in fuel system(continued)

Svmotom

January 21, 1972Revision No. 3October 15, 1993

Maintenance orPreventive Action10. With nozzle line still

open and boost pressurestil l on, now motor starterto purge air from nozzleline. (Observe flow after30 seconds for absence ofair. Repeat motoring stepsif necessary to clear allair from system.) Closethrottle and instal l fuelline to nozzle and tighten"B" nut at governor bypassport (PO).

11. Turn boost pumps off,clean up area. Performground run as soon aspossible.NOTE: Use boost pumps(s)to fil l fuel lines andcomponents (1) after engineor fuel componentinstallation and (2) afterlong idle periods.To prevent air in fuelsystem, ALWAYS start andoperate your engine withboost pump(s) ON (if theaircraft fuel systemrequires boost pumps).

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ALLISON GAS TURBINECommercial Service Letter

1. PLANNING INFORMATION: (Continued)

Problem SvmotomDirt in fuel system 1. Abnormally high or

low powera. Erratic operationcaused by moveablecomponent stuck inopened or closedposition

b. Reduced orificesize caused from dirtbuildup

Adjustment fails to 1. No change or an un-correct problem anticipated change re-sults from adjustment

Governor droop

January 21, 1972Revision No. 3October 15, 1993

1. Excessive NR droopat takeoff, hover, orcruise.

Maintenance orPreventive Action

1. Check condition of fuelfilters:a. Aircraftb. Fuel pumpc. Fuel control

Return contaminated units forrepair or overhaul.

2. Review fuel handling tech-niques and facilities.1. Ensure you have the correctlocat iorl of adjustment

screw (refer to 250-C20Operation and MaintenanceManual). Frequently, thewrong screw or plug isadjusted.

2. While adljusting startderichment or max flowstop, &r& loosen thesmall locking screw whichis perp6:ndicular to theadjustment screw. Acompletely loosened lockingscrew can affect theoriginal setting.

1. If the diroop occurredovernighlt or aftermaintenance, bleed thegovernor bypass (PO) portper "Air in fuel system."

2. Review beep motoradjustmeint and riggingbefore replacing thegovernor.

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ALLISON GAS TURBINECommercial Service Letter

1. PLANNING INFORMATION: (Continued)

ProblemFuel leaks

Svmotom1. Fuel dripping fromoverboard vent line

Power limited 1. Unable to obtain(Bell only) specified power

Fuel cutoff

Unlisted problems

January 21, 1972Revision No. 3October 15, 1993

1. Engine experiencedhigh TOT after it isshut off or enginefailed to shut off.

1. Unlimited symptoms

Maintenance orPreventive Action

1. Replace the unit if itsmaximum leakage rate isexceeded.

Vnit Max Leakaqe RateControl 5 drops/minuteGovernor 5 drops/minute1. After you have turned theMax Flow Stop adjustment

screw from (+) to (-),ensure that the adjustmentscrew mark and (-) mark areprecisely aligned.

2. Can you return the Max FlowStop screw mark to the (-)mark if you overshoot it?No!-always return the MaxFlow Stop adjustment screwto the (+) mark beforestarting over.

1. Refer to 250-C20 CSL-1009.This revises the regularshutdown procedure, whichwill be included in thenext 250-C20 Operation andMaintenance Manualrevision. It also providesmaintenance action intendedto prevent high TOT afterengine shutdown.

1. This information isprovided from "someoneelse's" experience. If youhave encountered a problem,please report:

Engine S/N, Unit S/NSymptomsOperating conditionsPrevious maintenanceAction taken

CUSTOMER SUPPORT

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