FAA Flight Instructor Airplane (FIA)Performance, Weight and BalanceMedium
An airplane has 48 gallons of usable fuel remaining and burns fuel at 8 gallons per hour at cruise power while achieving a groundspeed of 120 knots. What is the maximum still-air range before fuel exhaustion?
- A720 nm
- B480 nm
- C576 nm
- D960 nm
Show answer & explanationAnswer & explanation
Correct answer: A. 720 nm
Endurance = 48 gal ÷ 8 GPH = 6 hours. Range = endurance × groundspeed = 6 hr × 120 kt = 720 nm.
Why the other options are wrong
- B. Uses only 4 hours of endurance, an incorrect division.
- C. Multiplies by an incorrect groundspeed value.
- D. Overstates endurance beyond the actual 6-hour figure.
Fuel Endurance and Range
Endurance is how long fuel will last (fuel quantity ÷ fuel flow); range is the distance covered in that time (endurance × groundspeed).
- Endurance (hr) = usable fuel ÷ fuel flow (GPH)
- Range (nm) = endurance × groundspeed
- Range decreases with headwind, increases with tailwind
- Always plan for a fuel reserve beyond calculated range
Memory trick: 'Fuel divided by flow gives time; time times speed gives distance.'