FAA Private Pilot Helicopter (PRH)Performance and LimitationsEasy
Effective translational lift (ETL) begins when a helicopter transitions from a hover into forward flight and typically occurs at approximately
- A5 to 10 knots
- B60 to 70 knots
- C16 to 24 knots
- D40 to 50 knots
Show answer & explanationAnswer & explanation
Correct answer: C. 16 to 24 knots
Effective translational lift occurs as the helicopter accelerates through approximately 16 to 24 knots, where the rotor system moves into relatively undisturbed air, increasing lift efficiency and reducing power required.
Why the other options are wrong
- A. This speed range is too slow for the rotor to escape its own recirculating downwash.
- B. This is a cruise-range speed, far beyond where ETL begins.
- D. This speed exceeds the typical ETL range and occurs well after transition.
Effective Translational Lift (ETL)
An increase in rotor efficiency that occurs as the helicopter accelerates out of its own rotor downwash into clean, undisturbed air.
- Occurs at approximately 16-24 knots
- Rotor system requires less power for the same lift
- Often felt as a slight pitch-up or vibration change during transition
Memory trick: Around 20 knots, the rotor breaks free of its own turbulent air.