FAA Aviation Mechanic Powerplant (AMP)PropellersHard
During cruise, a turboprop engine's torque drops sharply due to an internal engine malfunction while the propeller governor continues trying to hold selected RPM by moving toward a finer pitch, which would create high drag and yaw. Which propeller system is designed to sense this condition and automatically move the blades toward a coarser pitch to reduce drag?
- AFeathering accumulator
- BBeta control system
- CSynchrophaser system
- DNegative torque sensing (NTS) system
Show answer & explanationAnswer & explanation
Correct answer: D. Negative torque sensing (NTS) system
The negative torque sensing (NTS) system detects when the propeller begins driving the engine (negative torque) after a power loss and automatically increases blade pitch to reduce drag and asymmetric thrust until the pilot can feather the propeller. Synchrophasers only match blade phase between engines, the accumulator only assists feathering, and Beta control governs ground/reverse pitch.
Why the other options are wrong
- A. Accumulators store oil pressure to speed feathering, but don't sense torque.
- B. Beta range controls ground handling and reverse pitch, not in-flight torque loss.
- C. Synchrophasing matches propeller phase angles, not power loss protection.
Negative Torque Sensing (NTS)
A turboprop propeller protection system that automatically increases blade pitch when the propeller starts driving the engine (negative torque) due to a power loss, reducing drag and asymmetric thrust.
- Senses reversed torque flow
- Automatically coarsens pitch
- Protects against excessive drag/yaw
- Common on turboprop engines like PT6
Memory trick: NTS = 'No Torque, Stop the drag' — coarsens pitch when power dies.