Re: A330/340 vs. B777

Date:         13 Jan 97 18:35:33 
From:         Andrew Weir <100637.616@CompuServe.COM>
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>Interestingly enough  the  first 767 delivered with PW4000 is the Lauda
>Air 767 that went down in Thailand a few years  ago.   To  this  day  I
>don't the official accident report has ever been published, although it
>apparently isn't  any  secret  what  happened.  What they don't want to
>talk about is what didn't happen.  Aircraft should never have  crashed,
>major major screwup in the cockpit.  There was an obviously solution to
>the problem,  and  to  this day, no one has any idea why they didn't do
>it.  It takes some 23 minutes from first indication until the  aircraft
>augers in, so isn't as if they didn't have time.

Whoa, there! "23 minutes"? I think you must be thinking of a different
accident.  The plane crashed 15 minutes after take-off when a thrust
reverser deployed without command, leading to an in-flight break-up. While
we are getting on the backs of dead pilots, let us remember that the 767
was certificated for recovery from such a situation. Investigators
questioned this when they attempted to reproduce the plane's problems in
the sim. So, new wind tunnel tests were performed and these showed that
instead of a lift loss of 10 per cent resulting from thrust reverser
deployment, giving plenty of chance of recovery, the real figure was 25
per cent. Boeing's own engineering simulator was reconfigured to include
this data and Boeing's chief test pilot found that if corrective action
were not taken within 4 to 6 seconds after the event, recovery was
impossible.  The recovery manoeuvres were not, however, part of normal
airline training.  Uncommanded thrust reverser deployment sounds to me
like a "major major screw-up" -- but not by  the unfortunate pilots. All
PW4000-powered 767s were subject to ADs to correct the problem, which
seems to have been due to an overlooked failure mode in the
thrust-reverser's electronic controls. As an aside for the FBW debate,
this accident could not have happened on an older model plane with
mechanical controls for thrust reversal.