Effect of Wind on a Round Trip

The problem

Your airplane cruises at 100 knots true airspeed (TAS).

You’re planning a 100 nautical mile trip to the north, followed with a cup of coffee, and the return flight.

At the altitudes you plan to fly, the wind is blowing directly from the north to the south at exactly 50 knots.

Questions:

  1. How long will it take to get there?
  2. How long will it take to get back?
  3. If there were no wind how long would each leg take?

Solution:

  1. If the airplane flies north at 100 knots through the air and the air is moving south at 50 knots over the ground, the airplane is flying north over the ground at 100-50 = 50 knots.

100 nautical miles (nm) at 50 knots requires 100 nm divided by 50 nm per hour or two hours to reach the northern airport.

  1. If the airplane flies north at 100 knots through the air and the air is moving north at 50 knots over the ground, the airplane is flying north over the ground at 100+50 = 150 knots.

100 nm at 150 knots requires 100 nm divided by 150 nm per hour or two thirds of an hour or 40 minutes to reach the northern airport.

So the round trip in a 50-knot wind would take 2:40 flying time

  1. In no wind, each leg each leg would take 1:00 for a total of 2:00 flying time.

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