What’s a good pilot cockpit technique to aid with spotting traffic? When flying, nothing quite gets our attention like those words from ATC or an onboard Traffic Advisory System – “Traffic!” Here are three steps to determine an aircraft’s position in the sky:
- The azimuth or clock position is given first i.e. “Traffic! Eleven O’Clock, . . . . We naturally turn our eyes to the correct clock position outside the aircraft, but then what?
- The altitude of an intruder tells us where to look relative to our aircraft. A simple equation can help us derive the angle – The tangent of a one-degree angle is almost exactly one-sixieth, which means, an airplane 1 mile away and 100 feet above you is almost one-degree above you. We can quickly derive the elevation to our target by dividing range into relative altitude.
- Let’s use this example, an airplane at 11 o’clock, is 1 mile away and -500 feet below. The Traffic Advisory System will display -05. A quick calculation is (-05 / 1 mile = -5 degrees).
- In this example, the plane should be about 4-degrees below the horizon at our 11 o’clock, because the horizon is about one to two degrees below you in typical GA cruising altitudes. Your finger, parallel to the horizon and at arms length is about two-degrees. So, look for this aircraft about 2 fingers below the horizon at 11 o’clock.
This may sound a little complicated but try it a few times and see if it doesn’t become second nature.
Sources:
Tally Ho – Traffic in Sight, Cirrus Owners and Pilots Association COPA, Cirrus Pilot, March 2006, Vol. 1, No 2. p53.
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