During the before-takeoff runup, a pilot cycles the propeller control from high RPM to low RPM and back two or three times before setting takeoff RPM. What is the primary purpose of this check on a constant-speed propeller?
- ATo verify the propeller can fully feather in flight
- BTo circulate warm engine oil through the governor and propeller hub, purging trapped air or cold oil
- CTo confirm the landing gear warning horn functions correctly
- DTo test the magneto ignition system for proper operation
Show answer & explanationAnswer & explanation
Correct answer: B. To circulate warm engine oil through the governor and propeller hub, purging trapped air or cold oil
Cycling the propeller control during runup circulates warm, low-viscosity oil through the governor and propeller hub, which helps purge any trapped air bubbles or residual cold, thick oil that could cause sluggish or erratic pitch changes. This check does not test feathering capability (which requires a separate feathering check on applicable installations), the magnetos, or the landing gear warning system.
Why the other options are wrong
- A. Feathering checks (where applicable) are a distinct, separate procedure.
- C. The gear warning horn is unrelated to propeller control cycling.
- D. Magneto checks are performed separately using the ignition switch, not the prop lever.
Propeller Cycling Check
A runup procedure of moving the prop control through its range to circulate warm oil and purge trapped air from the governor/hub for reliable pitch response.
- Performed before takeoff along with other engine checks
- Helps ensure smooth, responsive governor operation
- Distinct from a feathering check, which is separate where applicable
Memory trick: Cycle it warm, purge the air, keep the pitch fair.