Certified Flight Instructor (CFI) Practice Exam

Which of the following best defines Vlof?

1. Lift off speed

2. Maximum operating limit speed

3. Speed at which the critical engine fails

4. Never exceed speed

The correct answer is: Lift off speed

Vlof, or "Velocity at Lift Off," specifically refers to the speed at which an aircraft becomes airborne during takeoff. This is the pivotal point where the lift generated by the wings is sufficient to overcome the weight of the aircraft, allowing it to leave the ground. Achieving Vlof is crucial for a successful takeoff, as it ensures that the aircraft can safely transition from the ground to flight. Understanding this definition helps in piloting, as pilots must be aware of this speed to ensure that they are at an appropriate rotation and lift-off speed during takeoff. It signifies the moment when the aircraft has enough aerodynamic performance to continue its ascent safely. This knowledge is essential for flight instructors to teach to their students. The other terms do not reflect the specific measurement represented by Vlof. For instance, maximum operating limit speed pertains to the maximum speed an aircraft can safely operate, while the critical engine failure speed relates to specific performance characteristics after losing an engine, and never exceed speed is the ultimate limit before potential structural failure occurs. None of these definitions encompasses the concept of lifting off, which is the core definition of Vlof.