Re: Footnote on the DH Comet

Date:         07 Oct 97 14:10:19 
From:         Marc Schaeffer <marcmsc@geocities.com>
Organization: None
References:   1 2
Followups:    1
Next article
View raw article
  or MIME structure

Walter E. Shepherd wrote:
> If my hazy memory serves me right, there was another factor beyond metal
> fatigue which was contributory to the series of Comet disasters which I have
> not seen mentioned in the recent thread in this newsgroup. Maintenance...
> ground crews used to unpressurised propeller driven (i.e., low altitude)
> aircraft with not much of a future (i.e., the short life expectancies typical
> of combat aircraft) would drill holes at the end of fatigue cracks to keep
> them from propagating further rather than to take the time to replace a skin
> panel.

This is exact. This procedure is well described in the accident report
of YP. However COHEN states in his report that this procedure was
approved by DH and authorities and could not be blamed for the crashes.
Since this report was issued in 1955 it reflects the experience and
know-how of this deacde, of course today we are smarter. 40 years of
experience count, especially in an area which growed that fast in the
last 40 years ...

> This was SOP for workers (and a whole industry) who had gained prior
> experience and training during the hectic pace of the war years.
>
> If my memory is correct, the early Comet fleet reached a point where it was
> riddled with small cracks terminated with little round holes. Most were along
> the window line at the high stress points of the fuselage... so there was in
> effect a perforated line waiting for the right moment to unzip the upper half
> of the fuselage from the lower half. That moment came for several of the early
> Comets at a most inconvienient time and place.

There is no mention of this in the COHEN report. So I doubt that this
was the case. Don't forget that the YP accident investigation was the
most conscientious which was done ... until TWA800. At the time W.
Churchill told investigators to clarify the Comet crashes at ANY costs.
The reputation of the UK a/c constructors was in jeopardy.

> I mention this recollection because I believe that the current generation of
> aviation industry workers, trained under totally different circumstances,
> might not have the perspective to understand how such disasters can arise. I
> have seen sentiments here in this newsgroup laying the blame at the feet of
> the designers, at the feet of the UK aviation industry... etc, etc. I think no
> one need be chastised... the disaster was simply a lingering after effect of a
> disaster filled war... a war that also brought about the  huge growth of the
> aircraft industry. In the seeds of miracle, also lie the seeds of disaster.

I fully agree. The guys at DH were pioneers with all known advantages
and disadvantages.

Note that the sections of the COHEN report which I mention in this post
are not yet on the web, they will follow ...

Rgds,
...........................................................
Marc Schaeffer, Luxembourg // mailto:marcmsc@geocities.com
---->>>>> De Havilland COMET homepage <<<<<----
WWW  http://www.geocities.com/CapeCanaveral/Lab/8803/