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Old 30th Dec 2012, 23:59
  #133 (permalink)  
fdr
 
Join Date: Jun 2001
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Quote:
So at very worst here the touchdown would be some 700-800m in. This would still allow 2000m plus to stop the aircraft. Something doesn't quite add up.
Be that as it may, passing the last touchdown marker at 50 feet and not going around...
Permafrost...

the image of the aircraft in the late approach has it approaching the 500' markers, and yes it is slightly high, but the crew are adjusting the flightpath. with a normal flare, the aircraft would be touching down in the normal touchdown zone, albeit on the long side but within the first 3000' or 1/3rd of the runway. It's height is around 10-12m, whereas it would normally be around 5m at that point and already in a flare, or without flare, it would be around 2-3m. AOTBI, the plane is going to touch down around 1700' into the runway, or slightly further down if the flare has errors. While it may not be pretty, or optimal, it is not out of the bounds of a reasonable approach.

Aviation is a risk management exercise as is life in general. It is not reasonable for the crew to have to have precognition of abnormal system operation that may affect an off nominal operation that is otherwise acceptable. A normal healthy deceleration rate is in the order of 0.2-0.3g, and at the speed this aircraft has gone off the end, it was slated to go off the end in all cases, the only difference of an early touchdown would have been a lower speed at the off. the residual speed is high enough that it is questionable whether there would have been any difference in the outcome, i.e., would the aircraft had stopped in the overrun before entering the tank trap...

Put this in perspective, the approach is still more stable than AF's A340 off at Lester B., by a lot. Having spent a fair bit of time looking at QAR exceedences and events, I would not get too excited about the touchdown on the basis of a single photo, in the absence of the DFDR.

On some Russian sites they show a diagram where this aircraft was when flaring. Apparently it was still about 50 ft up when 2000 ft down range from the threshold. If this is true they had little chance regardless if their brakes functioned properly.

http://img-fotki.yandex.ru/get/5625/...eb_e6a94bf_XXL
OlASEK...

If this is based on the photo, russianplanes.net - it is just wrong, a simple look at google maps shows that the distance markers are those of the 500', look at the rwy lights, they show up well, and are still in front of the aircrafts nose at this point.

As far as being 50' up at this, point, the aircraft stands 45' 7" high when on the ground.... (on slightly compressed/untilted gear) so it is definitely well less than that above the center line marking of the runway, and that is before the 500' markings.

Last edited by fdr; 31st Dec 2012 at 00:10.
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