FAA Private Pilot Helicopter (PRH)Navigation and AirspaceHard
A helicopter departs a point and, after 24 minutes of flight, has covered 36 nautical miles over the ground as measured on the sectional chart. If the pilot must fly an additional 135 nautical miles to the destination at the same groundspeed, how much more flight time is required?
- A90 minutes
- B60 minutes
- C105 minutes
- D75 minutes
Show answer & explanationAnswer & explanation
Correct answer: A. 90 minutes
Groundspeed = distance ÷ time = 36 NM ÷ (24/60 hr) = 36 ÷ 0.4 = 90 knots. Time for remaining 135 NM = 135 ÷ 90 = 1.5 hours = 90 minutes.
Why the other options are wrong
- B. This would require a groundspeed higher than 90 knots.
- C. This overestimates the time; the groundspeed was correctly 90 knots, not slower.
- D. This underestimates the time needed at 90 knots groundspeed.
Groundspeed and Time-Distance Calculation
Groundspeed is calculated as distance flown divided by time elapsed; it is then used to compute time required for remaining distance.
- Groundspeed (kt) = distance (NM) ÷ time (hr)
- Time (hr) = distance (NM) ÷ groundspeed (kt)
- Convert minutes to hours by dividing by 60 before calculating
Memory trick: Distance ÷ Time = Speed; flip it to find Time again.