FAA Commercial Pilot Airplane (CAX)Navigation and Flight PlanningEasy
An aircraft flies 165 nautical miles in 55 minutes with no change in heading or power setting. What is the aircraft's groundspeed?
- A150 knots
- B180 knots
- C200 knots
- D165 knots
Show answer & explanationAnswer & explanation
Correct answer: B. 180 knots
Groundspeed equals distance divided by time, expressed in nautical miles per hour. GS = 165 NM / (55/60 hr) = 165 x (60/55) = 180 knots.
Why the other options are wrong
- A. This results from dividing distance by 66 minutes instead of 55.
- C. This overstates the speed by rounding time down too aggressively.
- D. This is the raw mileage figure, not a rate per hour.
Groundspeed Calculation
Groundspeed is the actual speed of the aircraft over the ground, computed as distance flown divided by time elapsed, converted to a per-hour rate.
- GS (kt) = distance (NM) / time (hr)
- Convert minutes to hours by dividing by 60
- Groundspeed differs from true airspeed due to wind
Memory trick: D = S x T, so S = D / T — 'Dirt Sticks to Tires' reminds the order.