FAA Private Pilot Airplane (PAR)Performance, Weight and BalanceMedium
A pilot is performing a preflight inspection in hot, humid conditions. Which of the following combinations of factors would lead to the longest takeoff distance for a given aircraft, assuming maximum gross weight?
- AHigh density altitude, headwind, wet runway.
- BLow density altitude, tailwind, wet runway.
- CLow density altitude, headwind, smooth runway.
- DHigh density altitude, tailwind, soft-field runway.
Show answer & explanationAnswer & explanation
Correct answer: D. High density altitude, tailwind, soft-field runway.
High density altitude reduces engine performance and lift, increasing takeoff distance. A tailwind increases ground speed required for lift, increasing ground roll. A soft-field runway increases rolling friction, requiring more power and distance. All three combined result in the longest takeoff distance.
Why the other options are wrong
- A. Incorrect. While high density altitude and wet runway increase distance, a headwind helps reduce it.
- B. Incorrect. Low density altitude reduces takeoff distance, despite the tailwind and wet runway.
- C. Incorrect. Low density altitude and headwind reduce takeoff distance. Smooth runway is also favorable.
Factors Increasing Takeoff Distance
Conditions that reduce aircraft performance or increase drag/resistance during the takeoff roll, thus requiring a longer distance to achieve liftoff.
- High density altitude (high temp, high humidity, high elevation) reduces engine power and lift.
- Tailwind increases ground speed required for liftoff.
- Soft-field, wet, or rough runways increase rolling friction/drag.
- Heavy weight increases inertia and required lift.
Memory trick: Hot, Heavy, Humpy, Headwind's Not, but Tail's Got.