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within the governor range. If the RPM falls outside this range for more than 0.5 seconds, the governor will
declare the appropriate overspeed or underspeed fault and the throttle output is reverted back to the throttle
curve. The motor interlock has to be disabled to reset the governor.
H_RSC_GOV_COMP: Governor Torque Compensator - Determines how fast the governor will adjust the base
torque reference to compensate for changes in density altitude.
H_RSC_GOV_DROOP: Governor Droop Compensator - Proportional gain to compensate for error in rotor
speed from the desired rotor speed.
H_RSC_GOV_FF: Governor Feedforward - Feedforward governor gain to throttle response during sudden
loading/unloading of the rotor system.
H_RSC_GOV_RANGE: Governor Operational Range - RPM range above or
below H_RSC_GOV_RPM setting where governor is operational.
H_RSC_GOV_RPM: Main Rotor RPM - Main rotor RPM that governor maintains when engaged.
H_RSC_GOV_TORQUE: Governor Torque Limiter - Adjusts the engine’s percentage of torque rise during
ramp-up to governor speed.
You must first set your throttle curve and properly tune it. If the sensor fails, control fails over to the throttle
curve. Without a properly tuned curve, your helicopter will crash. When tuning your throttle curve, tune it for
an rpm that the aircraft can be easily flown. It doesn’t have to be perfectly tuned, but it should be “close
enough” to fly the heli with no surprises. You can tune your curve with H_RSC_MODE =3.
For ICE and turbine powered helicopters, H_RSC_IDLE is set so the engine can be started and run without
engaging the clutch or turning the main rotor. Arming the autopilot before engaging motor interlock will set the
RSC output to the idle position. Dis-engaging the motor interlock in ArduPilot will set the RSC output for motor
throttle to H_RSC_IDLE. With auto landings or the LAND mode, upon detecting landing, the system will
disable motor interlock which will disengage the governor and set the RSC output to idle (H_RSC_IDLE).
Once the spool down is complete, it will auto-disarm and shutdown the engine.
Once the throttle curve is tuned, set H_RSC_MODE = 4 to have the RSC use the governor. Initially it is
recommended that the governor be tuned for the RPM that the throttle curve was tuned. This will minimize the
need for the governor torque compensator to be used and allow tuning to be concentrated on the droop
compensator and feedforward settings. The feedforward setting adjusts the amount of the throttle curve is
used in the governor. The feedforward may need adjusting if the rotor speed droops significantly when loading
the rotor system using the collective. The droop compensator ensures the desired rotor speed is maintained
very precisely. Higher value is quicker response to large speed changes due to load but may cause surging.
Adjust this to be as aggressive as possible without getting surging or RPM over-run when the governor
responds to large load changes on the rotor system.
To investigate the effect of the torque compensator, set the desired rotor speed 100-200 RPM from the rotor
speed the throttle curve was tuned. The governor torque compensator (H_RSC_GOV_COMP) should slowly
adjust the reference output to aid the droop compensator in maintaining the desired RPM. If RPM is low or
high by more than 2-5 RPM, increase this setting by 1% at a time until the governor speed matches your RPM
setting. Setting the compensator too high can result in surging and throttle “hunting”. Do not make large
adjustments at one time.
The torque limiter (H_RSC_GOV_TORQUE) should not need to be adjusted unless desired rotor speeds are
set above the rotor speed tuned for the throttle curve. The governor failing to engage on spool up is an
indication that the torque limiter is too low. Raise this be 5% until the governor reliably engages. It is possible
to have this too high which would be indicated by immediately getting a governor overspeed fault (message
on GCS) on spool up and RSC will revert to throttle curve.
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