TFE731 Inspection Intervals

• Engine Intervals
• Classic Engines
• -20/-40/-60 Carbon Seal Health Checks
• TFE731 Tech Reps

October 2009

Duncan Aviation Tech Reps and Sales Reps field many questions regarding inspection intervals. Most often these pertain to the newer model engines: TFE731-20/-40/-60 and the -5BR. Intervals for the -20/-40/-50/-60 models can be found in chapter five of the LMM 7 Ch 5-20-00 scheduled maintenance checks Table 801.

Engine Intervals

• All -50 engines are 3000 MPI/6000 CZI intervals.
• -20/-40/-60 engines are either 2500 MPI/5000 CZI or 3000 MPI/6000 CZI intervals, depending on the service bulletins that have been accomplished.
• -40 and -60 engines will be on the 2500 MPI/5000 CZI intervals unless service bulletin 72-5194 has been completed. This SB had a limited release in December 2007 and full release in April 2008. There are several other bulletins that are part of the extension. If SB 72-5194 is not done there is no need to look any further.
• -20 engines engine serial number P-116487 and later will have all of the internal parts upgraded for the 3000 MPI/6000 CZI hour intervals. Some simple external bulletins may need to be complied with to make the interval extension official, such as checking the Fuel Control serial number and putting heat shrink on the N1 monopole. If you have any questions, please give us a call and we will help you clarify the intervals.

Classic Engines

In the case of classic engine models, the official answer is to reference the following Service Bulletins:

TFE731-2	SB 72-3105
TFE 731-2C	SB 72-3630
TFE 731-3	SB 72-3106
TFE 731-3B	SB 72-3233
TFE 731-3C & 3D	SB 72-3527
TFE 731-4	SB 72-3466
TFE 731-5R, 5AR, 5BR	SB 72-3263

The basic rules for these classic engines can be best explained as follows:

• Almost all -2 and -3 engines that have not been upgraded to -2C/-3C/-3D are on a 1400 M PI/4200 CZI intervals.
• All -2C/-3C/-3D engines are on a 2100 MPI/4200 hour CZI schedule.
• The -4/-5 engines are either 2100 MPI/4200 CZI or 2500 MPI/5000 CZI intervals, again depending on which service bulletins have been accomplished. If you have any questions, please call and we will clarify.

The MPI can be overrun by 100 hours and the CZI by 200 hours on all of these models of the TFE 731 engine.

-20/-40/-60 Carbon Seal Health Checks

If your engine is pre-service bulletin TFE731-72-5147, the carbon seal health checks may be extended to 650 hours. This is allowed only if the last three checks indicated a transfer gearbox pressure of less than 2.0 PSI and the SOAP results are normal with a filter weight of less than 150 milligrams.

Please note: The maintenance manual 72-03-06 states a check of Fan Gearbox Pressures, The current Temporary Revision 72-197, dated June 2009, specifically says Transfer Gearbox Pressure.

Additionally, the requirement for the Carbon Seal Health checks are based on the total number of hours on the #4 and #5 carbon seals installed. The Carbon Seal Health Checks will be out of sequence with the other inspections if the engine had a core repair that was not performed in conjunction with a scheduled MPI or CZI.

Another question we receive a lot is about SOAP samples due after maintenance. The manual simply states:

An Oil and Filter Analysis is required at 25 hours after any of the following maintenance actions: Oil fill at engine installation, major periodic inspection or unscheduled maintenance of the fan gearbox. This check establishes a baseline for subsequent oil filter checks.

The 20/40/50/60 manual gives a range of 25 to 30 hours.

TFE731 Technical Support

Heier, Shane - Engine Tech Rep - Lincoln, NE (LNK). Aviation professional since 1991. Airframes: Astra, Citation, Falcon, Hawker, Learjet, Westwind Engines: TFE731, CFE738 Direct: 402.479.8166 Mobile: 402.304.3332

( Return to top )