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Old 12-11-2011, 05:54 AM
IvanK IvanK is offline
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Join Date: Oct 2007
Location: Australia
Posts: 886

Originally Posted by cheesehawk View Post
Wow, thanks for the link, very crazy read. It's hard to imagine that the controls in modern planes would let pilots do two opposite things, and average them out. Beyond the human error, that's simply unbelievable to me.
Its not quite as bad as that. Airbus mechanisation is such that Control inputs from both sticks are Algebraically summed and then transmitted to the Flight control computers.

However if 2 pilots are actively polling (an absolute no no in Airbus ideology) a voice alert "DUAL INPUT" is repeated. Its not subtle and clearly lets you know. Each joystick also has a Takeover button. When pressed this automatically prevents the inputs from the other stick getting to the flight control computers. When the button is pressed another voice alert blares "PRIORITY LEFT or RIGHT" together with a visual indication (an arrow) placed directly in the pilots line of sight indicating exactly who has control. In addition if the takeover button is pressed and held the other side stick is deactivated.

As to the reversion from "NORMAL" law to "ALTERNATE" law this is a very (imo) subtle indication. All you see is a small amber X in each corner of the attitude indicator. A better cue imo would be another voice alert like "ALTERNATE LAW" to leave you in no doubt that you are in a mode with reduced protections. The link makes mention that none of these pilots may have flown the aircraft in Alternate Law. Well maybe not in the actual aeroplane but they would have done a reasonable amount of Alternate law handling in the Simulator.

This accident presented the pilots with an horrific set of conflicting cues. A lot is going to be learnt from this accident. Changes to training and certification will undoubtedly result.

Last edited by IvanK; 12-11-2011 at 05:57 AM.
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