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![]() "John Alger" wrote in message m... "John R Weiss" wrote in message news:S08%b.58709$4o.76896@attbi_s52... "Tarver Engineering" wrote... Since my servers seldom get me all the newsgroup messages and Google.groups can't seem to find the begining of this thread, please allow me to ask a question and pose some answers. And I apologize if any of this has been discussed previously. From the bits I have read subsequent to John's message above, I assume we are discussing the A-320 crash at Habshiem. If so, let me present some information relevant to the discussion, as I have not read anything as yet that indicates any of the posters knows much if anything about Airbus flight control systems. I do believe I am qualified to speak on the subject as I teach A-330 systems, which has a flight control system identical to the A-320. The A-320 which crashed into the trees in France was performing a fly-by demonstration, by a line pilot, not an Airbus test or demo pilot. The profile was to fly by at 500 feet. The pilot was making a scheduled revenue flight with passengers and came up with the low slow fly by all on his own. The aircraft was below 100 feet. This is significant to the incident (and not just because that is where we find trees). In the Airbus the computers have a group of flight control protections collectively known as "Laws". In Normal Law there is a low-speed, high AOA protection known as Alpha-Floor. Alpha-Floor is reached somewhere below Vls (the lowest speed the aircraft will fly with autopilot/autothrust on and sidestick in neutral), and prior to Alpha-Max (maximum AOA). At Alpha-Floor the autothrust commands TOGA power, and regardless of how much you pull back on the sidestick, the aircraft will not decelerate below Alpha-Max. It will just mush along at TOGA power until it runs out of gas or the pilot lowers the nose to accelerate. The low fly by was not an A-320 flight mode. The problem is, Alpha-Floor is not available between 100' and touchdown - otherwise you could never land! The pilot was expecting Alpha-Floor, but being too low, it did not happen. By the time he realized his error, he applied power, but it was too late. You can, in fact, hear the engines spooling up just prior to his impact with the trees in the video we show in class. That is what I have been attempting to communicate to Weiss. The aircraft performed as it should have. The pilot simply did not have an adequate understanding of his aircraft for the manuver he was doing. He also failed to follow the script. Two things the French apparently frown upon, expecially when used in combination. Yes. It is not just the French that believe the POH is part of the Type Certificate for an airplane. Lesson: if you don't fully understand your aircraft, it can reach out and bite you someday. Weiss is in danger every time he flys then. |
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