The Duncan Download Blog: Business Aviation Advice & Observations

Contributed by Lanny Renshaw, Assistant Manger Turbine Engine Services  

There are many reasons that your TFE731 engine may be leaking oil. The hardest part is determining where it is leaking and what to do about it. The following is a list of the most common places you will find oil leaks and their causes.

Oil Leaking from the Breather Pressurizing Valve (BPV)

If there is oil leaking from the BPV after the engine has been shutdown and idle for a day or so, the oil tank may have a cracked internal tube that is allowing oil to flow out of the tank and into the accessory gearbox. When the accessory gearbox is full, the oil will begin to run out the BPV.

If your engine has just come out of its Compressor Zone Inspection (CZI) however, verify that oil pump P/N 3060785-XX is installed. Oil gets trapped in the oil coolers or other areas and moves through the oil pump, filling the accessory gearbox and eventually leaking out of the BPV. This happens on the RH engine installations and sometimes on the #2 position on the F50/900s.

Oil Leaking in the Third LPT/Exhaust Area

If oil begins to pool in the exhaust nozzle area after engine shutdown, the cause may be one of the following:

1. Over-servicing the engine oil level
2. Defective #6 carbon seal/rotor
3. Oil pump P/N 3071949-11 or 3060785-X on RH engine installations allow oil to get trapped in the oil coolers and fill up the #6 bearing area. This oil will eventually run out the #6 carbon seal and down the Third LTP blades. This can be easily fixed with the installation of oil pump P/N 3071949-12, which has a redesigned regulator allowing oil to flow back to the oil tank.

Oil Leaks in the Fan Inlet Area

There are several reasons that oil will leak into the Fan Inlet Area. Here are some of the more common:

1. #1 carbon seal leaking—oil will be running down the fan blades.
2. #3 carbon seal leaking— oil will be running out of the Compressor Inlet Stator.
3. A cut o-ring on the Fan Support Housing or some other areas in or around the Fan Inlet area.

Oil Leaks from the Hot End

If oil is leaking from the hot end, it might be one of the following:

1. N1 Monopole leaking on the cover plate or the cover plate itself is leaking.
2. Loose #6 oil pressure and/or scavenge lines.
3. Oil leak coming from the oil cooler area.

 Duncan Aviation holds service authorizations for Honeywell TFE731-2/-3/-4/-5/20/40/60 Major (MPI) engines at its full-service facilities in Lincoln, NE (LNK), and authorized line services in Battle Creek, MI (BTL). Our TFE731 engine program has been in place since 1980, and we have assembled teams with some of the most talented engine technicians in the industry.

Lanny Renshaw, Assistant Manager of Turbine Engine Services in Lincoln, NE (LNK), manages Duncan Aviation’s modern 20,000-square-foot facility with 12 separate engine bays dedicated to support of the Honeywell TFE731. He started his aviation career in 1982.