FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceMedium
An airplane has a glide ratio (L/D) of 12:1 in its best-glide configuration. Following an engine failure at 6,000 feet AGL in no-wind conditions, and disregarding altitude lost while establishing the glide, approximately how many nautical miles can the airplane glide?
- A15 NM
- B6 NM
- C9 NM
- D12 NM
Show answer & explanationAnswer & explanation
Correct answer: D. 12 NM
Glide distance = glide ratio x altitude = 12 x 6,000 ft = 72,000 ft. Converting to nautical miles: 72,000 ft ÷ 6,076 ft/NM ≈ 11.85 NM, which rounds to approximately 12 NM.
Why the other options are wrong
- A. This overestimates the distance beyond what the glide ratio and altitude support.
- B. This underestimates by roughly half the correct distance.
- C. This is too low; it does not correctly apply the 12:1 ratio to 6,000 feet.
Glide Ratio Distance Calculation
Glide ratio (L/D) represents how far an airplane travels horizontally for every foot of altitude lost; horizontal distance = L/D ratio x altitude available.
- Distance (ft) = L/D ratio x altitude (ft)
- Convert feet to NM by dividing by 6,076
- No-wind assumption simplifies the calculation
Memory trick: Multiply the ratio by the altitude, then shrink to nautical miles.