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Old 7th November 2002 | 19:05
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drauk
 
Joined: Sep 2002
Posts: 778
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From: London, UK
Procedure turn accuracy

I recently got my GPS to record my track whilst carrying out some published holds and instrument approaches. I then overlaid this track on the approach map (on a computer - I didn't sit there plotting points on a paper chart!). I was a bit surprised to see how far off I was in respect of the radius of the turns (particularly in a holding pattern - base turns weren't so bad as I was then tracking something back to the airfield so didn't do a strict rate 1 turn for 1 minute).

I was doing this in about 30knts of wind, but let's assume nil wind. The turns on the map, for a standard hold, are approximately 1.6nm wide (by wide I mean the diameter of the circle of which the turn is a half of). The base turn for a category A aircraft is a similar size. However, a rate 1 turn at 100knts is only about 1nm wide. So clearly doing a rate 1 turn isn't going to follow the track on the map.

My question is, therefore, am I correct in assuming that a properly flown procedure is one which follows the rules (a rate 1 turn for 1 minute) rather than one which follows the track on the map?
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