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Old 6th Dec 2013, 08:10
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Screwballs
 
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How does your company describe circling approaches?

Hello all,

I would like to know how other companies describe the circling approach procedure, specifically the base turn to final from downwind. In my lot, with orange aircraft(Cat C), we start the stopwatch abeam the threshold as we pass downwind, timed 3 seconds per 100ft AAL corrected for wind. And then turn base.

The reason I am wondering about is to do with the protected area and the tightness of the turn to final. Cat C aircraft will have 4.2nm to manouevre inside safely. And this is based on a max speed of 180 knots with a 25 wind plus correction for TAS gives a speed of 215 knots for the circling area. (Jepp Text pg. 233 Table I-4-7-2) However, with that speed and timing based on 1,000ft AAL circle to land, you would end up approximately 2.7nm from the threshold.* Plus a turn inbound would still give you a margin on the 4.2nm. And that's at 215 knots! The normal reality would be closer to approximately 160 knots or so.

So my question is do other companies stick to something like 3 seconds per 100ft AAL? And if so why? Is there a EASA regulation there or is it up to the operator? Why not give a little bit more margin to create an easier final descent path? In practise, the AP is engaged and the aircraft is in level flight and well below the 3 degree path to land(being level downind). If we extended downwind just a little bit further then the final turn could be divide into more distinct parts 1) use the AP to establish on the centerline 2) disconnect and fly the descent manually. As opposed to the current procedure which is to do both at the same time. And give little time for a correction.

(Bearing in mind the responses that we should be able to do it all manually anyway etc etc, this is a particularly specific question about why the timing is the way it is)
*based on being 2nm distant from the threshold once abeam and a GS of 215kts for 30 seconds.

Thanks for any and all helpful replies.
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