FAA Instrument Rating Airplane (IRA)Regulations and CurrencyMedium
A pilot's airplane burns fuel at 12 gallons per hour. The flight plan shows 2 hours 30 minutes en route to the destination, followed by an additional 30 minutes to the filed alternate. Under 14 CFR 91.167, what is the minimum fuel (in gallons) that must be aboard at takeoff?
- A36 gallons
- B45 gallons
- C39 gallons
- D51 gallons
Show answer & explanationAnswer & explanation
Correct answer: B. 45 gallons
91.167 requires fuel to fly to the destination, then to the alternate, then 45 minutes at normal cruising speed. Total time = 2.5 hr + 0.5 hr + 0.75 hr = 3.75 hr. At 12 GPH, 3.75 × 12 = 45 gallons.
Why the other options are wrong
- A. Incorrect — this omits the 45-minute reserve entirely.
- C. Incorrect — this uses only a 30-minute reserve instead of 45 minutes.
- D. Incorrect — this overstates the reserve time beyond 45 minutes.
91.167 Fuel Reserve Calculation
IFR fuel must cover flight to destination, then to the alternate (if required), then 45 minutes at normal cruising speed.
- Add all three legs: destination + alternate + 45 min
- Convert 45 minutes to 0.75 hours for calculation
- Multiply total hours by fuel burn rate (GPH)
Memory trick: Fly there, fly to the backup, then fly 45 more minutes just in case.