AF 447 Thread No. 8

[mm43]

The BEA's English translation of the recommendations issued following their report into the Tarom incident is as follows:-

Following several accident investigations in which the Bureau Enquêtes-Accidents participated, the following recommendation was issued on 24 January 1995:
Various incidents or accidents (see list below) involving public transport aircraft show the following common characteristics:

1. Configuration: Automatic Pilot and/or auto-throttle lever (or auto thrust) in operation.
2. Circumstances: pilot flying overrides (voluntarily or involuntarily) the Automatic Flight System, or acts contrary to the indications of the Flight Director.
3. Aggravating circumstances:
   • the pilot flying is not always aware of his action in opposition with the Automatic Flight Systems and never perceives the consequences thereof,
   • the pilot not flying (even instructors) is not aware of the conflict between the pilot at the controls and the Automatic Flight Systems.
4. Consequences:
   • the reaction of the Automatic Flight Systems leads to potentially dangerous configurations: out of trim, engine thrust incompatible with the trajectory chosen by the pilot, etc.
   • Flight crew,
     • either is not aware of the situation, and thus cannot take corrective measures,
     • or observes the aircraft configuration without understanding the causes. This incomprehension (also related to limited knowledge of systems) leads to a loss of time in analyzing the situation, or even to an erroneous analysis, generally associated with a lack of adequate communicationmbetween crew members

This has led to highly dangerous attitudes: extreme attitudes or rolls, loss of speed (including stalls) or excess speed, etc.
See preliminary report, published 3 November 1994.

As a result, the Bureau Enquêtes-Accidents recommends:
- that a study be launched so that the pilot’s priority over all Automatic Flight Systems is maintained in all circumstances.
This could be done :

a) by the disconnection of Automatic Flight Systems (automatic pilot and auto-throttle lever or auto thrust) in the event of conflict between the pilot’s actions and those of the Automatic Flight System or Flight Director.
b) and/or by clear information in the cockpit (possibly an alarm) warning the flight crew of such a conflict.

As far as I can ascertain, those basic recommendations have been fulfilled, e.g.

Auto Pilot :-
Auto OFF if abs(φ) >45°, or θ <-13°, or θ >+25°, or CAS < VLS, or CAS >(VMO/MMO or VLE/VFE), or Pitch Angle Protection ACTIVE.

Auto Pilot:-
Unavailable if abs(φ) >40°, or θ <-10°, or θ >+22°, or CAS < VLS, or CAS >(VMO/MMO or VLE/VFE), or Pitch Angle Protection ACTIVE.

• The A/P and A/THR disconnected when a couple of ADR's had a disagreement over speeds.
• The THS trim continued the way it was designed to, though due to a change in the control law, it would appear that the crew had no idea that the Alpha protections had been lost.
  • Except when the Abnormal Attitude Law has been triggered, auto trim is still functioning and a constant stick NU/ND command will cause the THS to follow in an attempt to maintain a load factor of +1g - be aware!
• The Stall Warning operated correctly while the aircraft was within the Normal Flight Envelope, but wasn't heeded.

In short, the visual and audio clues/warnings provided, possibly added to the cognitive overload. Would a pseudo artificial feedback to the SS helped?? Perhaps the centrifuge simulators of tomorrow may help to reinforce what it feels like when the aircraft is maneouvered in abnormal conditions.