What does Vef speed represent?

Vef speed specifically refers to the "velocity of engine failure," which is the speed that an aircraft is expected to reach at takeoff when an engine failure occurs. This measurement is crucial for pilots to ensure that they have sufficient control of the aircraft and can maintain proper flight performance even if one engine becomes inoperative. Understanding Vef helps in determining the aircraft's performance characteristics during critical phases of flight, particularly during takeoff, ensuring safety standards are maintained.

The other options, while related to flight speeds, do not correctly define Vef. For example, the landing approach speed is different from Vef as it pertains specifically to landing maneuvers. Maximum cruising speed is about the overall performance during flight, not engine failure conditions. Velocity of engine forward thrust does not align with the definition of Vef, which focuses on the operational limits during engine failure scenarios.