TFE731 Spring 2000

• Engine Oscillation Needs In-Flight Troubleshooting
• Checking TFE731 Performance Problems
• Keep Your Hot Section Distress To A Minimum
• Oil Leaks Can Sometimes Be Simple To Fix

Engine Oscillation Needs In-Flight Troubleshooting

If your TFE731 engine begins to oscillate in flight, you can help your ground crew by beginning to troubleshoot the oscillation in flight. The first step is to put your EEC/DEEC in manual mode. If the engine stops oscillating in manual mode, the cause of the oscillation is likely an electrical problem. If oscillation persists in manual mode, the cause may be fuel delivery.

If oscillation continued in manual mode, check the aircraft boost pump, motive flow pressure, engine driven fuel pump output pressure and look for loose P3 fittings. If oscillation stopped in manual mode, swap the EEC or perform a DEEC download or byte check. If oscillation continues or the byte check reveals an LRU defect, ring out the EEC/DEEC inputs per 72-00-00 troubleshooting of your Light Maintenance Manual. If oscillation follows the EEC you swapped, replace the defective EEC. These hints may help determine which LRU is causing the oscillation:

• T2 Sensor/harness can cause up to 15% N1 oscillation
• Synchronizer/Harness can cause about 10% N1 oscillation
• P2 leakage can cause up to 5% N1 oscillation
• ITT Harness can cause 8 to 10% N1 roll back

For more info, contact Doug Alleman in LNK at 800.228.4277 or contact Ken Kuchenreuther in BTL at 800.525.2376.

Checking TFE731 Performance Problems

If your TFE731 engine is experiencing performance problems, an engine performance evaluation run should be accomplished with bleed-air blocked. This will determine if your engine performance has degraded or if an airframe problem is influencing it. Prior to this, a surge valve check should be accomplished by matching N1’s with computers on and off and observing the ITT difference. If it’s not 15 to 30 degrees warmer with the computer off, the surge valve system should be checked.

For more info, contact Craig Bohling in LNK at 800.228.4277 or contact Ken Kuchenreuther in BTL at 800.525.2376.

Keep Your Hot Section Distress To A Minimum

Duncan recommends that you shut down your Honeywell APU loaded. This puts your hot section through only one thermal cycle, reducing hot section distress. Shutting off the bleed-air, then waiting for your APU to stabilize before shutting it down puts your APU hot section through two thermal cycles. This puts your hot section through unnecessary hot section distress.

Oil Leaks Can Sometimes Be Simple To Fix

When oil leaks are discovered both inside and outside of the engine cowling and the condition cannot be duplicated running the engines on the ground, the cause may be the breather pressurizing valve closing at altitude and pressurizing the system. This often causes weak or damaged seals to leak only during flight. A quick area to check for trouble is the oil tank cap and dipstick cap O-ring. The O-ring can wear out quickly from consistent pre-flight and servicing removal and installation. Replacing the O-rings is a good first step in checking to see if the leak will return.

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