An airplane's best-glide speed of 65 KIAS yields a 10:1 glide ratio in still air. During an engine failure at 5,000 feet AGL, the pilot maintains the same best-glide airspeed while gliding directly into a steady 20-knot headwind. Compared to a no-wind glide from the same altitude, the horizontal distance covered over the ground will be:
- AReduced, because the headwind increases the airplane's stall speed and shortens the usable glide
- BUnchanged, since glide ratio depends only on L/D and indicated airspeed, not wind
- CReduced, because groundspeed decreases while the airplane's rate of descent and time aloft remain about the same
- DIncreased, because the headwind increases the effective lift-to-drag ratio
Show answer & explanationAnswer & explanation
Correct answer: C. Reduced, because groundspeed decreases while the airplane's rate of descent and time aloft remain about the same
Glide ratio (10:1) describes distance through the air relative to altitude lost and is unaffected by wind. However, ground distance covered depends on groundspeed, not airspeed. A headwind reduces groundspeed while the descent rate (governed by airspeed through the air) stays essentially the same, so the airplane covers less horizontal distance over the ground during the same descent time — reducing usable glide range toward a headwind landing site.
Why the other options are wrong
- A. Headwind does not affect stall speed (an IAS quantity); it only affects the groundspeed/ground track.
- B. Glide ratio through the air is unaffected by wind, but GROUND distance covered is affected — the question asks about ground distance.
- D. Headwind does not change L/D ratio; it only affects the component of motion relative to the ground.
Glide Range vs Wind
Glide ratio (L/D) determines distance through the air for a given altitude loss and is unaffected by wind, but actual ground distance covered is reduced by a headwind and increased by a tailwind because groundspeed changes while descent rate does not.
- Headwind reduces groundspeed, not airspeed or descent rate
- Same time aloft but less ground distance into a headwind
- Plan glide approaches accounting for wind to reach a suitable landing site
Memory trick: Same fall through the air, shorter walk across the ground when the wind pushes back.