It has been a practice at BVM to operate our turbine engines a bit more conservative then the manufacturers published limits. Most recently, we applied this practice to the PNP L-39 Albatros powered by a KingTech K-140G. The factory set idle RPM is 33,000, we bumped it up to 34,500. The factory set maximum RPM is 123,000, we trimmed it down to 121,000.

  Most jet airframes feature high drag devices such as open landing gear bays (gear down), landing flaps, and speed brakes. Additionally, high angles of attack on landing induce drag. So, the slight increase in idle thrust is not noticed.  The benefit is a more reliable idle RPM - it's not searching or surging, and, if a "go-around" is commanded, the engine spool-up time is reduced.

  The 32 pound L-39 has all of the high end performance it needs with the 2,000 RPM reduction. We proved that with a good showing at Top Gun 2016 and with air show routines at the "First In Flight" event during very hot weather conditions.

  Removing that extra bit of centrifugal stress on the engine's spinning parts and about 50C of temperature stress goes a long way toward ultimate engine life and reliability.

  Know that when you fly commercially, the pilots are selecting reduced power for take-off unless the gross weight, runway length, and pressure altitude do not allow. This extends engine life and time between major maintenance checks.

Conclusion

  This conservative turbine engine operation is working for BVM.

 

NOTE:  For operation at high elevations (above 3000ft. M.S.L.), do not use reduced power for first few flights. Then, re-evaluate the application.

NOTE:  Consult your engine's operation manual for how to adjust the engine RPM limits.