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
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
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
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
This conservative turbine engine operation is working
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.