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Old 20th Sep 2008, 18:47
  #1893 (permalink)  
Dutch Bru
 
Join Date: Aug 2008
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Air/ground sensor and RAT-TOWS relay

Re Borghha's question in post 1914 the draft report as published by El Mundo mentions a number of significant issues:

On page 5 it says that at rotation the DFDR captured the change of signal from ground to air mode originating from the sensor the nose gear (N/G strut ground sense).

So, at least this part did not previously think the plane was in the air when it was still on the ground. This is in my view important for the origin of the TOWS-failure, since apart from the RAT, based on the data available, other parts of the aircraft were sensing that the plane was in ground mode when it was in take of run and the TOWS should normally have sounded in this case.

However, the said draft report also seems to state to me very significantly that the relay (R 2-5) of the RAT (which was switched off) is the same as the one feeding the CAWS of which the TOWS is a part. So "inop RAT" according to MEL is something completely different than switching the RAT off by pulling the C/B, which apparently also directly compromised the TOWS, which is clearly not MEL-covered.

Intrigingly so the draft report seems to state that on lift of the N/G sensor when transioniting into air mode will send a signal that desenergises the R2-5 relay, which would make the CAWS, including the TOWS as part of that inop.

What I also do not understand compeltely is the length of the take-off run stated in the draft report (1950 m) in relation to the airport CCTV-video, where the plane seems to only get airborne just before the end of the actual end (not the paved surface) of the very long runway. Didn't they commence take-off run at the very beginning ?

And I have difficulties to precisely understand the (elaborate part) of the report text that deals with where the thrust reversers were found and in which state.

Perhaps justme69 could shed more light on these issues in relation to the draft report and make the necessary precisions based on his far more advanced knowledge of the Spanish language than mine....
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