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Asked by: 4385 views Aircraft Systems, Commercial Pilot

The question below appears supposedly on a major US airline’s pilot knowledge test. Mathematically, how is the answer solved? You are on the XYZ VOR 090 radial at 20 DME. You are instructed to proceed direct to the XYZ VOR 180 radial at 70 DME. The direct, no wind heading is: a) 185° b) 190° c) 195° d) 200°

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1 Answers



  1. Wes Beard on Sep 17, 2015

    This is a simple triangle formula. The key to understanding the answer is to determine your reference point. For my answer, the reference point is going to be 20 NM out on the 090 degree radial. Notice, the airplane is east so that direction will be positive and west will be negative. In the same regard, we will fly south, so a south direction will be positive and north would be negative.

    Since it is a right triangle, the formula A^2 + B^2 = C^2 will yield the distance flown from the 090 radial to the 180 radial at the given distances. 20^2 + 70^2 = 72 NM.

    to find the heading, it is the formula tan(x) = opposite / adjacent. or tan(x) = 20/70 which will result in a 74 degree angle. 270 degrees (to fly to the station) – 74 equals 196 degrees.

    Thus the answer is 196 degrees. Skyvector shows the heading as 197 degrees.

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