PPRuNe Forums - View Single Post - Air Asia Indonesia Lost Contact from Surabaya to Singapore
Old 3rd Jan 2015, 17:28
  #1109 (permalink)  
aa73
 
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Regarding AAMP and AA training with the rudder years ago, mentioned in a post a few pages back:

In AA587 the FO was using the rudder only when full aileron was not arresting the bank, contrary to what some may believe. He didn't automatically just bang the rudder to stop the turn.

As many of you well know, Airbus (thanks to the NTSB making sure an aircraft manufacturer didn't get blamed) dodged a huge bullet by not being assigned the blame in this crash due to a highly sensitive and somewhat primitive rudder limiter that was never properly explained to its A300 customers. In effect, the FO of 587 was dealing with a monster that nobody quite knew about. Little did he (or anyone, at the time) know that only 2 inches or so of rudder travel at 240kts was resulting in full rudder deflection.

So, the timeline goes somewhat like this: first wake turbulence encounter, severe roll. Full opposite aileron, no effect. Opposite Rudder comes in with around 2 inches of pedal, bang, full rudder deflection. Severe roll in opposite direction. Full opposite aileron, no effect. 2 inches opposite rudder pedal, bang, full opposite rudder deflection. Another roll reversal. Rinse and repeat, tail comes off due to the rapid (unintentional) rudder reversals.

As you can see, 1) the FO was only applying rudder pressure when full opposite aileron was not helping, and 2) he did not know that only around 2 inches of rudder pedal pressure was deploying full rudder deflection. This is the fact that Airbus did not explain to its customers regarding its antiquated rudder limiter on the A300-600 series, and the NTSB and political pressure made darn sure airbus did not get blamed for this tragedy.

Any pilot on this forum (or in the world) would have reacted just as FO Sten Molin did that day. Uncontrollable bank and full aileron doesn't arrest it? Start bringing in the rudder. We would have had no idea as to the monster we'd be dealing with regarding the A300 rudder limiter. Neither did he.

The AAMP program provided a very convenient vehicle for the NTSB to help in assigning blame to the flight crew. I'd like to point out, however, having gone through the AAMP program, that the instructors (and program) always emphasized that you only used rudder when the ailerons aren't being effective in arresting the roll rate. There was NEVER any talk about strictly using the rudders without ailerons, nor using the rudder aggressively.

My point in this post is twofold: 1) tell the facts as they were, and 2) realize that the NTSB has a political agenda just like any government agency and sometimes needs to protect certain parties when bigger things are at stake. The aa587 NTSB report is a perfect example: it conveniently circumvents the real issues at stake (the A300 rudder limiter) and uses a training program to help assign blame to the flight crew, all in order to protect Airbus.
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