A mechanic is servicing a ground-adjustable pitch propeller on a light aircraft. When can the blade angle of this type of propeller be changed?
- AContinuously in flight by moving a cockpit propeller control lever
- BOnly during full-power engine runup using a hydraulic pitch-change unit
- CAutomatically in flight through governor oil pressure acting on a piston
- DOnly with the engine stopped, by loosening the clamping mechanism at the hub and manually resetting each blade
Show answer & explanationAnswer & explanation
Correct answer: D. Only with the engine stopped, by loosening the clamping mechanism at the hub and manually resetting each blade
A ground-adjustable propeller has a fixed pitch during flight; the blade angle can only be reset on the ground with the engine stopped by loosening the hub clamping mechanism, rotating the blades to the desired angle, and re-tightening. There is no in-flight or governor-controlled pitch change capability on this type of propeller.
Why the other options are wrong
- A. There is no cockpit control for in-flight pitch change on ground-adjustable props.
- B. No hydraulic pitch-change unit exists on a ground-adjustable propeller.
- C. Governor-controlled pitch change describes constant-speed propellers, not this type.
Ground-Adjustable Pitch Propeller
A propeller whose blade angle can only be changed on the ground with the engine stopped, by loosening a hub clamp, rotating the blades, and re-securing them; it then operates as a fixed-pitch propeller in flight.
- Blade angle set only on the ground
- Engine must be stopped for adjustment
- Acts as fixed pitch once set and locked
- No in-flight pitch control capability
Memory trick: Set it on the ground, fly it fixed — no in-air changes allowed.