Ranamin...Quote:
http://www.atsb.gov.au/publications/...70_interim.pdf
In-flight upset
154 km west of Learmonth, WA
7 October 2008
VH-QPA
Airbus A330-303
Thanks for the pointer Ranamin. I found that report most interesting and was rather disturbed by the following statements in it:-
Scenario where AOA spikes could influence flight controls.
The aircraft manufacturer advised that the AOA processing algorithms would prevent most types of erroneous AOA inputs provided by the ADIRUs having an influence on flight control commands. This included situations such as an AOA ‘runaway’ (or a continuous divergence from the correct value), single AOA spikes and most situations where there were multiple AOA spikes. However, the manufacturer identified that, in a very specific situation, the PRIMs could generate an undesired nose-down elevator command. This specific situation involved multiple AOA data spikes with the following properties:
• there were at least two short duration, high amplitude spikes
• the first spike was shorter than 1 second
• the second spike occurred and was still present 1.2 seconds after the detection of the first spike.
Simulation studies.
As part of the investigation, the manufacturer reported that it had performed simulation studies concerning the filtering of AOA spikes by a PRIM. The simulation studies confirmed that the input of two AOA spikes which met the conditions listed above, were not effectively filtered by the PRIM, and could lead to undesired nose-down elevator commands. The aircraft manufacturer advised that the 10-degree elevator command associated with the first in-flight upset, was the result of 4 degrees of alpha prot and the 6 degree authority of the anti pitch-up compensation. The 10-degree command was close to the worst possible scenario that could arise from the design limitation in the AOA processing algorithm.
Relevance to other aircraft types.
The manufacturer advised that the AOA processing algorithms used by A330 aircraft were also used by A340 aircraft. However, different algorithms were in use on other Airbus types, which were reported to be more robust to AOA spikes. The manufacturer advised that AOA spikes matching the above scenario would not have caused a pitch-down event on Airbus aircraft other than an A330 or A340.