TFE731 Summer 2000

• Slow & Warm Starts?
• Drain P2T2 Sense Lines
• TFE731 Engine Oscillations
• When Should I Upgrade To An N1 DEEC Computer?

Slow & Warm Starts?

If your TFE731 engine is experiencing slow and warm starts, there are some airframe checks that need to be performed prior to investigating the engine. First, check your batteries and GPU for proper output. Next, while leaving the throttles in cut-off, attempt a start and observe the peak N2 spool speed. The attempted start should achieve around 20% N2. If the spool speed is less than 20% N2, check your starter. If it’s more than 20% N2, investigate the engine.

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

Drain P2T2 Sense Lines

For TFE731 engines, operators need to be certain to drain P2T2 Sense Lines often of moisture. After draining, be sure that all drains are completely closed. If the drain is not closed or if the mositure is not drained, this may create an improper pressure signal to the engine computer. This would show up as power or throttle splits in flight or RPM splits between engines when the throttles are brought back to flight idle.

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

TFE731 Engine Oscillations

When the flight crew reports fluctuations in engine RPM, there are several questions you can ask to make finding the problem easier. First, does the engine RPM actually oscillate, do all other parameters move also? If not, this may be isolated to an indication problem. Second, assuming all parameters are oscillating, does it continue with the fuel computer switched off? If the oscillation stops with the fuel computer off, the problem is related to the fuel computer operation, and most likely electrical. If the oscillation continues with the fuel computer off, the cause is mechanical, and will be related to fuel pressure, P-3 pressure, or the fuel control. The engine light maintenance manual offers detailed troubleshooting procedures.

When Should I Upgrade To An N1 DEEC Computer?

The current non-MSP cost for an N1 DEEC computer is $20,375 (exchange). For MSP operators, the customer cost is affected by timing of the installation. MSP will provide N1 DEECs at no cost (exchange) under three conditions:

1. At the time of scheduled or unscheduled CZI.
2. Whenever an existing EEC fails.
3. At the time of engine upgrade, like 2C, 3C, 3D, or 5B.

If an MSP operator chooses another time to upgrade to N1 DEECs there is a “pull-up” fee that MSP will charge. This pullup fee is currently $3,000 per computer. Duncan Aviation is authorized by Honeywell to perform all MSP work.

There may be airframe modifications that are required concurrent with the installation of N1 DEECs. The cost of performing these modifications are in addition to the cost of the computers, and are not covered by MSP. Some airframes require these modifications, some do not.

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