I A P 2 0 2 3 . 0 0 1 - A F M / I R I S T E X A N I I P A G E | 27
FOR SIMULATION USE ONLY – NOT A TRAINING AID
Both of these systems dump oil pressure from the propeller allowing the propeller
counterweights and feathering spring to rapidly feather the propeller. Either of
these systems will provide full propeller feathering.
If the PMU is in OFF, it will not send a signal to the prop servo valve. If the PROP
SYS circuit breaker is pulled, the prop feather dump solenoid will not be powered.
If the PCL is placed in cut-off with the PMU in OFF and the PROP SYS circuit breaker
pulled, the propeller will not rapidly feather and may not fully feather until after
landing.
If the rate of change of propeller RPM, due to, for example, a rapid feathering of the
propeller, exceeds the PMU sensor validity check limit, the PMU will assume a
sensor failure has occurred. It will switch the PMU to manual mode, and a red X will
be displayed for the RPM and torque values.
If the red X’s were caused by a propeller RPM rate limit exceedance, cycling the
PMU switch will restore the displays.
If the red X’s are the result of a faulty sensor and not a rate exceedance, cycling the
PMU switch will have no affect and the red X’s will remain.
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