• No electrical power to starter/generator.
• Starter shaft sheared-starter only spins.
• Starter shaft spline work out-starter only spins.
• N1 indication defective-is oil pressure rising? Could be defective indicator or sheared shaft on shaft on tach drive.
• N1 rotor system seized-remove starter and attempt to turn drive.

• Insufficient voltage to starter-check power source and leads. Are the batteries low?
• Check N1 RPM indicating system-indicator may read low, hung up or be sticking.
• Check N1 rotor system for rub-check turbine tip clearance. If okay, the compressor is rubbing.

• Accessory gearbox input shaft is disconnected. Further start attempt by initiating fuel will cause an overtemp.

• Improper start technique-check the flight manual.
• Fuel manifold adapters improperly positioned
• Fuel nozzle restriction-flow check fuel nozzles.
• Air in the fuel system-bleed the system. Check the reason for air entering the system.
• Check spark igniters-replace as necessary.
• Check ignition exciter-check on air start and while motoring. Replace as necessary.
• Check voltage to ignition exciter-low voltage may be accompanied with low cranking RPM. Can cause hot start.

• Improper start technique-though not usually.
• No fuel to the engine-check aircraft valve on. Check fuel boost pump pressure.
• Excessive air in fuel system-bleed fuel system. Check the reason for air entering thesystem.
• No ignition-will give wet stacks. Caused by open circuit. Let engine drain and dry motorthe engine. Attempt start using air start igniters. Start accomplished -problem in aircraftelectrical system. No start-change igniters and/or ignition exciter. Caution: Allowignition exciter of snap type ignition to bleed off energy.
• Fuel manifold adapters improperly installed-check proper position by proper ServiceBulletin.
• Fuel pump failure-attach direct reading line in fuel pump to FCU line. Check for properpressure while cranking engine. Check FCU fuel filter.
N1 RPM Fuel Pressure 15% 141 PSIG 20% 250 PSIG 25% 391 PSIG
• Contaminated fuel system-check all filters. Clean fuel system as necessary.
• FCU bypass valve stuck open. Check bypass valve for closing. Remove FCU cap fueloutlet and bypass fittings. Apply 5 PSI air pressure to bypass return port. If air leak isdetected at fuel inlet, replace the FCU (PT6A-6, -20, -27, -28, -34)
• Start control defective-check primary fuel line for flow. If no flow, replace unit(PT6A-27, -28, -34)
• Flow divider and dump valve stuck-replace unit.
• Fuel nozzle restriction-flow check fuel nozzles.

• Improper start technique-early removal of starter. Will also cause hotter than normalstarts.
• Leaking or restricted P3 signal lines-check all lines for obstruction, cracks and security.Check P3 filter for contamination.
• Pneumatic section of prop governor or fuel topping governor affecting Py signal blank Pyline. PT6A-41, blank also torque limiter.
• Corrosion and/or ice in FCU bellows section-replace FCU.
• Contaminated or defective FCU-check all fuel filters. Check FCU bypass valve.
• Minimum fuel flow stop set too low-check minimum fuel flow. Remove Py line fromprop governor or fuel topping governor and leave open. Perform normal start. Check N1RPM per maintenance manual. Caution: Do not attempt this procedure on PT6A-41engines. Note: Usually PT6A-27 and -28 engines.
• Hung start on PT6A-27, -28 and -34-check SFC dump port for fuel. If dumping, replaceunit.
• Prop slow to attain idle RPM-prop shaft transfer sleeve binding. Check covers on transfertube bosses. Binding accessories, remove one at a time.

• Improper start technique-usually caused by entering fuel too early and/or early starterremoval.
• Insufficient voltage to the starter-causes lower than normal cranking RPM and loss ofstarter assist.
• Deficient starter-replace unit.
• Engine bleed air open or leaking-blank the engine bleed air port and try again.
• Delayed igniters-check the system.
• Minimum fuel flow stop setting too high-replace FCU.
• Fuel nozzle restriction-flow check fuel nozzles. Spray pattern does not reach the igniters.Will cause flame out the exhaust.
• Incorrect FCU or start rigging-rerig as necessary.
• Fuel manifold adapters in the wrong position-check for proper position by proper ServiceBulletin.
• Start control transfer valve stuck open-remove valve, clean and polish. Will causesecondary fuel flow during start cycle.
• Dump valve in flow divider stuck closed-replace unit. Will not allow fuel to dump.
• Defective N1 indicator-reads high-causes early entry of fuel.

• Defective prop governor-check setting. Replace unit if not adjustable.
• Defective pneumatic section of prop or fuel topping governors-replace units.
• Defective overspeed governor-replace unit.
• Binding or disconnected rigging-repair or replace as necessary.
• Defective RPM indicator-replace unit.

• Sheared FCU drive coupling-replace FCU and coupling.
• Defective FCU bypass diaphragm-replace FCU.
• FCU bypass valve stuck closed-replace unit.

• Prop governor rigging incorrect-rerig as necessary. Not contacting feather stop.
• Defective prop governor-replace unit.
• Propeller binding-check low pitch stop rods for binding. Have approved shop checkfeathering spring assembly for binding. Check prop blade bearings for binding-repair asnecessary.

• Prop shaft transfer housing seals leaking-remove power section at A flange and replaceseals.
• Transfer bobbin seals leaking-remove bobbins and replace seals. Do not mix bobbincovers.
• Defective prop governor-replace unit.
• Defective overspeed governor-replace unit.
• Obstructed prop shaft oil passage-remove prop and inspect.
• Propeller binding-check as above.

• Defective indicating system-check system.
• Defective or maladjusted compressor bleed valve-may not be closing all the way. Will cause ITT and N1 RPM higher than normal.
• P3 air leaks-check all gaskets on gas generator case for integrity and security.

• Leak originates from fuel pump drive seals-replace fuel pump. Check FCU drive bearings, if excessive wash of grease, replace unit.

• Prop out of balance-check prop for damage and balance. If unable to balance out vibration, check blade angle and twist.
• Compressor out of balance-cause steady hum. Check for FOD. Check bleed valve for being stuck shut-will cause higher than normal ITT at idle.
• Compressor out of balance-cause intermittent hoot. This condition is okay if hoot goes away by 60% N1 RPM. Check turbine balance.
• Power turbine out of balance-check turbine for balance and failure.

• Check indicating system-replace indicator as necessary.
• Compressor dirty-perform compressor wash.
• Compressor FOD-check first stage blades for FOD.
• Compressor bleed valve(s) open-will give accompanying high ITT. Have bleed valve(s) bench checked.
• Excessive P3 air leaks-check all gas generator gaskets for integrity and security.

• FCU drive sheared-replace coupling and FCU.
• FCU bypass diaphragm ruptured, replace unit.
• FCU bypass valve stuck closed-replace unit.

• P3 inlet elbow at FCU does not have metering orifice.
• Compressor bleed valve (s) stuck shut-replace unit(s). Will cause continuous hum atidle.
• Compressor bleed valve (s) out of calibration-have unit(s) bench checked and adjusted.
• Defective FCU-overfueling. Replace unit.
• Compressor FOD-check first stage compressor blades for FOD.

• Check P3 inlet elbow at FCU for metering orifice-the fast accelerating engine may nothave it.
• Incorrect setting of acceleration dome-maximum adjustment three (3) clicks either sideof datum. May have to speed one engine up and slow other down. (Clockwise toincrease acceleration rate.)
• FCU air system contaminated-send unit in for cleaning or exchange.

• P3 sense line restricted or leaking-check line for obstruction.
• Px metering orifice contaminated-remove and clean Px orifice or send in FCU forcleaning.
• Corrosion or ice in FCU bellows section-remove FCU for cleaning. Check P3 line forwater.
• Defective FCU-replace unit.
• Dirt in pneumatic section of FCU.
• Contaminated P3 filter-check and change filter. Will also cause slow start.
• Defective temperature compensator-replace unit. Try bypassing unit with slave line.

• Disconnected or improperly rigged FCU-repair or rerig as necessary.
• FCU bypass valve stuck-replace unit.
• Binding control linkage-check control linkage, repair as necessary

• Interrupted fuel supply-aircraft fuel valve shut off inadvertently.
• Fuel pump drive failure-preceded by slight increase in N1 RPM. Check fuel pumpcranking pressure.
• Air in fuel system-flameout at idle after a start. Bleed fuel system. Check reason for airentering fuel system. Has a part of the system been apart?
• Minimum fuel stop setting too low-flameout during deceleration. Remove Py line fromprop governor or fuel topping governor. Perform normal start and check N1 RPM.
• Contaminated FCU-check all fuel filters. Clean fuel system and replace filters asnecessary.

• Incorrect idle setting-set per maintenance manual.
• Incorrect riging-lengthen rod to relieve cam.
• Minimum fuel flow stop setting too high-check minimum fuel flow. Will not decrease toidle fuel flow.
• Air leak in P3 or Py signal lines-usually causes low idle RPM. Check lines for cracksand security.
• FCU control rod binding-will not return to idle position. Lubricate or replace bearingends. Lubricate and/or cam assembly.

• Faulty instrument (s)-have all instruments calibrated.
• Selected wrong torque from graph-recompute desired torque.
• Incorrectly rigged FCU linkage-not contacting maximum stop at full throttle. RerigFCU.
• Air leak in P3 or Py sense line-check P3 and Py lines for cracks and security.
• FCU maximum stop set too low-perform part power check.
• Fuel nozzle restriction-partially plugged. Clean and flow check fuel nozzles. Will causehot section distress.
• Contaminated or defective FCU-disconnect FCU outlet and check for flow whilemotoring. If no flow-remove FCU for bypass valve check.
• Dirt in pneumatic section of FCU-caused incorrect signal effect. Clean or replace unit.
• Contaminated P3 filter-restricts P3 signal. Will cause slow acceleration. Change P3filter.
• Defective prop governor pneumatic section or fuel topping governor-plug Py line andrecheck power.
• Prop governor pneumatic or topping governor incorrectly rigged-check arm for contactagainst maximum stop.
• Torque limiter setting too low-cap Py line at torque limiter and recheck power. Adjustas necessary.

• Instruments out of calibration-have all instruments calibrated.
• Faulty T5 system-check T5 system per the maintenance manual.
• Excessive accessory loading-place generator off line and recheck. Replace generatorand/or supercharger.
• Torque indication low-have instrument calibrated.

• Instruments out of calibration-have all instruments calibrated.
• Selected wrong torque from graph-recheck.
• Dirty compressor-perform compressor wash. Open inlet screen and check compressor.
• Excessive accessory load-place generator off line. Check accessories for extra loading.
• Defective compressor bleed valve (s)-blowing air overboard. Cause high N1 RPM.
• Compressor FOD-check compressor first stage blades. Will have high N1 RPM.
• Air leaks-check all gas generator case P3 gaskets and flanges for leaks.
• Hot section distress-N1 speed down, T5 up. Perform HSI.

• Instruments out of calibration-have all instruments calibrated.
• Selected wrong torque from graph-recheck.
• Dirty compressor-perform compressor wash. Will cause high N1 RPM.
• Compressor bleed valve (s) open-bench check and/or replace bleed valves. N1 RPMand ITT will be high.
• Compressor FOD-check first stage-compressor blades.
• T5 system defective-should have been caught on first step.
• Air leaks-check all gas generator case P3 gaskets and flanges for leaks.
• Hot section distress-turbine tip clearance excessive, compressor turbine vanes bowedor burned, changes classification.
• Compressor turbine vane ring class is changed, first stage power turbine vane ring classmay need changing.

• Hot section distress-perform HSI.

• Low oil level-check the tank oil level. Check oil consumption.
• Defective oil pressure indication-check with direct reading gauge.
• Pressure relief valve malfunctioning-probably stuck open. Replace unit.
• Internal oil leak-will cause oil smoke on start or shutdown and oil smell in cabin area.
• Failed heat shield in power section-causes excessive heating of oil. Oil cooler may notbe able to handle the added temperature.
• Oil pressure follows the throttle- can not adjust or adjustment is less than expected.Check oil pump housing for cracks.
• No oil pressure-all models. Can happen after normal filter check. Oil filter is installedbackwards.

• Defective oil pressure indication-check with direct pressure gauge.
• Pressure relief valve malfunctioning-stuck closed. Oil pressure will follow N1 RPM.

• Insufficient supply-check tank level. Replenish supply, check consumption.
• Defective cooling system-check oil cooler thermostat. Check oil cooler for airnoneage.
• Excessive idling in feather-reduces air volume to oil cooler.
• Failed heat shield in power section-causes excessive heating of oil. Remove and repairpower section.

• Extended leakage-repair oil leak.
• Restriction in scavenge tubes -check all tubes for noneage. Unable to scavengeoil-will cause bearing area flooding.
• Defective packing on oil filter housing-check packings.
• Clogged scavenge screen in rear case-check main oil filter for carbon. If excessivecarbon is found, pull engine to clean scavenge screen. Carbon originates at #3 bearingarea.
• Defective labyrinth seals-check inlet and exhaust for oil. Will cause smoke during startand/or oil smell in cabin area. #1 bearing-leak at inlet. #2 bearing-smoke during start (turbine side)
• Oil to fuel heater leak-oil migrating to fuel system and is burned. Change unit.
• Oil from breather excessive-cocked or defective carbon seal.
• Defective or missing packings on oil tank center tube-remove rear case and checkpackings.
• No. 1 bearing pressure and/or scavenge tube packings defective-remove rear case andcheck packings.
• Defective filter check valve-will allow oil to migrate to pressure system overflowingbearing areas.
• Seal on pressure pump backwards-will cause excessive oil in scavenge systemoverloading oil separator.
• System overserviced-keep level at one quart to maximum level. Check oilimmediately after shutdown.
• If consumption still exceeds 12 lbs/hr-return engine to overhaul shop.

• Overfilled system-same as above
• Breather carbon seal defective-same as above.
• Excessive back pressure in scavenge system-check scavenge tubes, oil lines and oilcooler for restriction.

• Insufficient oil supply-replenish supply and check consumption.
• Defective indication-loose wire in connector. Check with direct reading gauge.
• Restricted oil filter-bypassing. Check oil filter. Debris may have clogged oil jets.
• Pressure relief valve sticking-change or polish relief valve.

• Defective packings oil tank tubes-replace.
• Defective packings on oil filter housing-replace packings

• Defective packings on #2 bearing scavenge bobbin.

• Faulty instruments-not usually.
• loose control linkage-repair or replace control linkage.
• Power turbine pneumatic governor not on maximum stop-can cause low power. Cap Pyline to confirm problem. Rerig control.
• Fuel pump shaft seal leaking-has washed grease from FCU bearings and started failureof these bearings.
• FCU coupling defective-loose cooupling will cause erroneous RPM signal.

• Loose linkage-check all linkage for security.
• Defective CSU-replace unit.
• Defective OSG-install blank to pad and run engine, replace unit.
• Prop sticking-check low pitch top rods for sticking or rubbing. Check or change featherspring assembly.

• Blade angle incorrectly set-reset blade angle

• FCU interconnect rods of different lengths. FCU arms not installed envenly. Dead bandidle screws projection vary.

• Preload difference between engines-recheck preload.
• Adjustable low pitch stops set differently-recheck low pitch stop. 8-10 threads showingnormal.
• "Z" gaps set different-check blade angles setting.