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Old 16th August 2009 | 07:46
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OzExpat


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Joined: Jun 2000
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From: Cairns FNQ
Changing to a high category, as has been suggested, is unlikely to be helpful because the procedure is speed limited to 180 knots for initial approach. You are, however, in a very serious situation in this unlikely scenario and should be able to remain within the protection area of the procedure, due to the conservative limits applied. Pans Ops allows use of a "statistical wind" or, if that isn't available to the designer, the formula is 2h+47, where h=height in thousands of feet.

Therefore, if the "h" factor is 2000 then the value is 2*2+47 = 51 knots. You probably won't know the height factor that has been used and, indeed, might be subject to the "statistical wind", which might actually be less. This will be the factor that limits the size of the primary protection area, but there is still a secondary area of 2.5 NM outside the primary area. Obstacle clearance reduces to 0 at the outer edge of this area, but it's unlikely that a 50 or 60 knot wind will displace you that far in the time it takes to complete the turn to the inbound track.

You will have to fly very precisely and probably use a bank angle steeper than the design angle of 25 degrees to remain within the protection area. This will lead to the next problem - the time (and therefore distance) needed to bring the aeroplane within the tracking tolerance for final approach - usually + or - 5 degrees - before continuing descent to the MDA. You might not have enough time/distance to reach the MDA unless you can accept a higher ROD than usual.

So, yes, it'd be a pretty serious situation but I'd have to say that, pending any factual information to the contrary, there hasn't been any incident of this kind, so the chances of it actually happening are really pretty remote. But I guess that's why Captains are paid such big money!
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