Re: Aircraft not toppling onto rear (VC10)

From:         Mark.Brown@dcs.qmw.ac.uk
Date:         16 Feb 94 01:10:21 PST
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> 
> In <airliners.1994.918@orchard.Chicago.COM> julian@gatwick.sgp.slb.com writes:
> 
> >c) Overly strong fuelage and wing construction (Comet legacy) so lots of
> >   weight ahead of the main wheels.
> 
> Comet legacy?  I distinctly remember several Comets coming apart in
> mid-air.  Or are you saying that the redesigned Comets were over-engineered
> to avoid embarassment?
> 
> >d) 90% + of payload located ahead of main wheels (I think that's about right).
> 
> Is this true?  How the heck do you rotate, or flare, a VC10?  I find
> this hard to believe, considering they have four aft-mounted engines!
> 

Don't think 90% of payload is located ahead of main wheels in the VC-10,
but anyway, have you seen the size of the horizontal tail on the VC-10,
or seen how far above the ground it is (T-tailed)? With a mutha that size
and the nice moment arm you get, I'd say elevator authority was pretty good!

Re the overengineering on the Comet, the fuselage etc. were pretty strong,
and designed so from the outset -- the only problem was that pressurisation
was still relatively new when that aircraft was designed, and the differential
pressures were pretty high (given the cruise altitude). Also, the number of
cycles was higher than other previous pressurised aircraft were likely to
have encountered, so experience at that time was scarce. The static test
article was tested in a water tank, but not enough, and stress-related fatigue
due to the high number of cycles built up at the corner of one of the apertures
in the fuselage (I think a window above the forward fuselage, which had
sharpish corners -- not good for stress buildup), eventually
leading to failure of the fuselage at that point, followed by explosive
decompression. The Comet IVs were safe, but by that time they'd a bad
reputation, so everybody bought DC-8s and 707s instead. The rest is history.


Mark.
-- 
Mark A. Brown
Department of Computer Science,
Queen Mary & Westfield College,
University of London,
Mile End Road,
London E1 4NS
email: eeyore@uk.ac.qmw.dcs,  Tel: +44 71 975 5220