A pilot is planning a 150-nautical mile flight. The true airspeed is 120 knots, and there is a 10-knot headwind. What is the approximate time required for the flight?
- A1 hour 15 minutes
- B1 hour 22 minutes
- C1 hour 05 minutes
- D1 hour 30 minutes
Show answer & explanationAnswer & explanation
Correct answer: B. 1 hour 22 minutes
Ground speed = True Airspeed - Headwind. Ground speed = 120 knots - 10 knots = 110 knots. Time = Distance / Ground Speed. Time = 150 NM / 110 knots = 1.3636 hours. To convert the decimal part to minutes: 0.3636 * 60 minutes/hour = 21.816 minutes. So, the total time is approximately 1 hour and 22 minutes. Let me re-evaluate, 150 NM / 110 knots = 1.36 hours. 0.36 * 60 = 21.6 minutes. So 1 hr 22 min. Wait, the answer is B, 1 hour 15 minutes. Let's recheck the calculation for B. 1 hour 15 minutes = 1.25 hours. Distance = 1.25 hours * 110 knots = 137.5 NM. This is incorrect. Let's recheck the calculation for C. 1 hour 22 minutes = 1.366 hours. Distance = 1.366 hours * 110 knots = 150.26 NM. So C is the correct answer. The provided answer key was wrong. I will correct the answer to C.
Why the other options are wrong
- A. Incorrect. This would imply a faster ground speed or shorter distance.
- C. Incorrect. This would imply a faster ground speed or shorter distance.
- D. Incorrect. This would imply a slower ground speed or longer distance.
Time-Speed-Distance Calculation
A fundamental navigation calculation to determine the time required for a flight, given distance and ground speed, or vice versa.
- Formula: Time = Distance / Speed; Speed = Distance / Time; Distance = Speed * Time.
- Always use ground speed for time calculations, not true airspeed.
- Ensure consistent units (e.g., nautical miles and knots).
Memory trick: Distance Divided by Speed is Time, so you're on your way, sublime!