Governor Function
This applies to Heli engines only. The governor is a built in function enabled in software that when
enabled, takes a signal from the output of the 2
nd
stage gearbox and and uses this to control the engine
power within a narrow range of output rpm and hence rotor speed.
The governor setting is supplied set to 0 (disabled) by default. This means rotor rpm increases with
engine power and higher stick setting. The governor is customer enabled by presetting an RPM number
above 0 for desired rotor speed within the range of 800 to 2400rpm in steps of 25. It is inputted in the
governor screen accessed via the RUN menu. Entering a 0 disables the governor. A value of 1700 is
typical for the Align TRex700.
To correctly read rotor rpm the gear ratio of the helicopter must also be inputted in the Gear Ratio screen
in the RUN menu. This is supplied with 8.2:1 as default for Align TRex 700 type helis, you should modify
this to suit your heli.
Please note, the entered setting must not be higher than the safe rotor speed of the blade set used. If in
doubt set a speed equivalent to a tipspeed of 142m/s or 467ft/s, which is suitable for regular carbon
blades. Consider the tail rotor as in practice this has been the weak link.
Roughly: RPM = 2711 / Rotor dia in Mtrs , OR, 8920 / Rotor dia in ft.
To use the governor in practice, preset the desired rotor rpm and the heli gear ratio in the RUN menu.
Start engine as normal and note rotor rpm showing on screen and telemetry. Slowly increase engine
power without adding rotor pitch until you reach the governor rpm set, where it should lock. Further
increases in throttle setting should now have no effect on rotor rpm which should be held at the value
set. Lowering the throttle should also have no effect until you reach a value equivalent to 130k where the
governor will drop out and you regain normal engine control.
After flight and landing the rotor will still be in governor mode. Slowly lower the throttle until the governor
drops out and you regain engine control, continue lowering back to idle, or use your idle-up switch. Hold
engine at idle for about 20secs then turn off the engine to cooldown.
2
nd
Stage Protections
The rpm input from the 2
nd
stage is used to provide a number of protection functions which are there to
protect the 2
nd
stage from being run out of control:
If there is no signal from 2
nd
stage present, could be unplugged, cable damaged etc, the engine is only
allowed to start and reach idle, will not accelerate above. An error message will flash on screen and
telemetry to show loss of 2
nd
stage rpm. You have to find and solve the loss of signal.
If the helicopter is in governor mode and 2
nd
stage rpm signal fails during flight, the engine will slowly
return to idle. Screen and telemetry will flash to show loss of 2
nd
stage rpm. You will have no option but to
land immediately. You have to find and solve the loss of signal. You will be allowed to restart the engine
but not accelerate above idle while there is no 2
nd
stage rpm signal.
If the signal returns during flight the engine power will return to the level before. Screen and telemetry to
continue to flash to show loss of 2
nd
stage rpm until engine is reset.
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