Originally Posted by
bubbers44
Not to keep going back to the same A300 crash but does anybody know exactly where rudder inputs are measured? Mechanically at the rudders or before the rudder actuator which apparently was the cause of the MIA uncommanded rudder inputs. This has been reported to be a hydraulic valve malfunction to the actuator. Was the rudder pedal input measured before or after the faulty valve?
The sensor for the rudder pedal position is located under the cockpit floor, it is directly attached to a bellcrank aft of the FO's rudder pedals.
The rudder position is measured with a sensor attached to the lower corner of the actual rudder, directly measuring the movement of the rudder relative to the vertical fin.
Look, I understand that for reasons known only to yourself, you're searching for ways to blame this on the airplane and not the pilots. I have to ask, do you imagine that the NTSB, upon finding that there were multiple rapid rudder reversals which caused the vertical stabilizer failure just said: "Hey, let's blame it on the pilots and not investigate any other possible sources of the reversals. That way we can wrap this up and go home early" ?
That seems to be the common thread of all your posts, that the NTSB didn't investigate any other possible causes of the rudder reversals. That the reversals were caused by something else and that the NTSB just blamed it on the pilots because that was what was easy. I'd recommend that you go read the NTSB report, yourself. You'll find that they spent a lot of time on investigating everything that might have caused the ruder reversals. This included inspection of the system components recovered from the crash, analysis of the rudder control system together with the yaw damper and autopilot system, the rudder servo system, and extensive testing of all of the above on identical aircraft. A great deal of that testing was focused the question: "Is it possible that the rudder position and rudder pedal position data which indicates pilot input could have bee caused by something *other* than pilot input" It's not that nobody ever thought to ask the question. They did. And the answer was: "probably not"
As as far as your references to the MIA incident, that was due to an autopilot yaw actuator clutching mechanism which failed to disconnect when the autopilot was selected off. This has already been discussed in this thread previously. That also was investigated by the NTSB in their investigation of AA587. The airplane was being hand flown, the autopilot had not been engaged so a disengagement failure was improbable, the controls had been checked on the ground and there was no interference as was present in the MIA incident, and the Yaw control autopilot servomotor was disassembled and examined and the autopilot yaw input was found to be disengaged.
So, yes, the NTSB *did* consider that this might be related to the MIA incident. Yes, they *did* investigate this possibility, and no, there was nothing which indicated this was the same cause.