I just hate the idea that a mode change can occur because of inadvertent contact with a flight control by the pilot, with the pilot not immediately being notified (or made aware) of the mode change resulting from the physical contact.
On a somewhat related issue, I've heard that on older Airbus models (300/310) the autopilot can disengage in one axis only due to physical contact with the flight controls, and the system will not notify the pilot immediately that a mode change has occurred. My understanding is that this has resulted in a small number of crashes in that series. Is this also true in the newer 320/330/340 Airbus series? Are there any other instances where this can occur?
Correct me if I'm wrong, but is seems to me that the pilot should ALWAYS be notified (with a light, chime, ECAS display, whatever) when a system is designed to disconnect after a pilot manually takes the controls. The reason for the notification is to alert the pilot in case of an accidental disconnect (or mode change) due to accidental physical contact with the flight controls.
If the mode change is accidental, then the pilot did not intend to initiate it, and therefore he remains unaware of the mode change until it's discovered by other means (as in the example in this thread). It's just good system design to simply notify the pilot of the mode change.
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Safe flying to you...
[This message has been edited by Flight Safety (edited 28 March 2001).]