Re: Fed Ex MD-11 crash was mechanical

Date:         28 Aug 97 02:30:43 
From:         "nite rider" <guesswho@memphisonline.com>
Organization: Big and Purple
References:   1 2
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matt weber <mweber@cyberltd.com.au> wrote in article
<airliners.1997.1829@ohare.Chicago.COM>...
>
<snip>
>
> Current published reports in Aviation Week report that the decent rate
> was 500fpm, and the initial landing impact was 1.7G, the aircraft bounced,
> and the second impact was at 1.69G. Sounds to me like a very hard landing.
> The wheel assembly may well have failed, but this was a very hard landing.

Yes I had heard a figure of about 1.6g and another of 1.2g. The second
figure seemed more consistent with a sink of around 460 fpm (touchdown fpm
or approach?, with or without ground effect? --questions I still have ),
though a 1.7g landing seems intuitively more consistent with a landing gear
collapse.

I don't think even a 1.7g touchdown should cause a gear collapse. If every
1.7g touchdown resulted in a crash, most pilots would never live long
enough to get an ATP certificate, or to pay alimony to their first ex-wife.
However, accompanied with a yaw (we still don't know how much yaw) and roll
(don't know how much roll either) the sideload stresses on the landing gear
assembly increase exponentially.

Why did the aircraft roll and yaw after the first touchdown? Was it caused
by mechanical failure? Aggravated by pilot input? Autopilot (and/or
autothrottle) input?

The point I was making was that the NTSB was focusing the investigation on
mechanical failure, based on the condition of landing gear components found
in the wreckage, review of preliminary data, and aircrew interviews.

For those following this thread the Aviation Week article is posted at
http://www.awgnet.com/safety/nzfedx11.htm

nite rider