TFE731 Life Limited Components
June 1, 2016
In addition to the Honeywell inspection intervals, the life limits of TFE731 engine components can greatly influence your maintenance schedule. Most of the rotating components such as turbine and compressor discs and turbine blades have a life limit. While these items are usually addressed during an MPI or CZI event, understanding component life limits are critical since they tend to be expensive parts. There are two different types of Life Limits:
- Cycle Life Limits, which tracks the useful life of the component by cycles. Turbine and compressor discs are cycle life limited parts.
- Hourly Life Limits, which tracks the useful life by flight hours. Turbine blades are hourly life limited parts.
Component Life Limit References
For TFE731 New Generation Engine (-20,-40,-50,-60 series) engines
- Disc cycle limits are found in Chapter 5 of the Light Maintenance Manual (LMM), table 801.
- Turbine blade life limits are found in Service Bulletin 72-5172
For Classic TFE731 Engines (-2, -2C, -3, -3A, -3B, -3C, -3D, -4, -5R, -5AR and -5BR)
- Disc cycle limits are found in Service Bulletin 72-3001.
- Turbine blade life limits are found in Service Bulletin 72-3494.
Cycle Life Limits for Turbine and Compressor Discs
Turbine and compressor discs have life limits that range from 3,000 and 20,000 cycles and can cost $60,000-$200,000 each for new components. Maintenance tracking programs used by authorized service centers such as Dallas Airmotive, typically track the life limits of these discs for you to optimize your maintenance schedule and minimize your expense. The calculation however is not particularly difficult and you can do it yourself. Take the Life Limit for the disc and subtract how many cycles have been used to see how much useful life you have left in the component. No overruns or exceedances are allowed for turbine and compressor discs.
Hourly Life Limits for Turbine Blades
While it is relatively easy to calculate the life limit for turbine and compressor discs, the opposite holds true for turbine blades. The life limit on turbine blades can range between 1,400 and 12,000 hours, with the official hourly limit established by marks. In most cases, these marks are based off of the number of flight hours since the last MPI. Since most third-party maintenance tracking programs do not track the hourly life limits of turbine blades, it would be wise to consult a TFE731 engine expert given that turbine blades can cost up to $200,000 to replace per set.
These Tips and Tricks are for reference and they are only a starting point. They are not intended to be comprehensive instructions. Please:
- Seek the assistance of a professional mechanic for all repairs beyond your capabilities;
- Consult the OEM’s applicable maintenance manual, and any Airworthiness Directives and Service Bulletins; and
- Remember that the cornerstone of aircraft safety is redundancy — the "second set of eyes" inspection principle is non-negotiable.