Re: Questions about the DH Comet

Date:         08 Sep 97 02:03:50 
From:         Marc Schaeffer <>
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michael piersdorff wrote:

> My understanding of the problem was that most of the in-flight
> breakups were explosive decompressions of the fuselage resulting from
> fatigue failure.

Yes that's corect. The successive cycles let to a cristalline change in
the metal, which was especially strong at the corners of the A.D.F.
hatch. The thin fuselage was another major reason for the breakup. At
the time designers just ignored the intensity of stresses which are
applied to a fuselage at high speed and altitude.

> Successive pressurisation/depressurisation cycles
> (takeoff and landing, respectively) in combination with flight loads
> caused cracks at the corners of the square windows used in the early
> models.

No that's not correct. The YP incident was *not* due to a crack which
started at a window but the crack started at a hatch in the upper part
of the fuselage. To be more precise the crack started at the rear A.D.F
aerial hatches. As a consequence the center fuselage splitted along the
top center line. Where the crack of YY started is unknown since the
fuselage was never recoverd. On the Comet YU, which was used to find out
the reasons of the YP and YY crashes, the cracks started at the forward
escape hatch.

> (snip) The solution,
> of course, was to go to the more or less oval windows one sees today.

The oval windows were an additional security which was incorporated in
the new Comet4

Marc Schaeffer, Luxembourg //
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