From R. S. KING
With reference to John Lindop’s letter ‘Pilot in peril’ (16 May), I
designed the Concorde windscreen and I was in the office when the in-service
failure of the BAC 1-11 windscreen occurred and still feel the relief that
no lives were lost.
Yes, of course internal pressure can be prevented from blowing out by
filling the hole with a plug. We managed to think of that. In fact we thought
perhaps a curved screen would carry pressure like a membrane, but pilots,
quite rightly, insist on being able to see out very well; so for that sort
of aircraft it had to be optically flat to quite a high order.
Then we read the airworthiness requirements and saw that we also had
to stop a 4-pound bird coming into the aircraft rapidly (at cruise speeds
up to 8000 feet altitude). There aren’t many ways of doing that so we chose
the lightest and most effective way and fitted the hole with a panel again
supported at its edges.
So we had to judge whether to mount the windscreen from the inside or
outside, but the airline maintenance people said that they would rather
remove the windscreen from the outside because, should the electrical de-Icing
(another requirement) fail, they didn’t want the aircraft delayed for hours
and hours while they dismantled the glare shield and the insulation blankets
and the instrument panel and the wiring and some of the controls and some
other stuff we shove in for all sorts of good reasons, to get it out. In
fact removing the windscreen is a very handy way into the cockpit for some
work. And the customer is often right.
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We did our best to meet a bewildering variety of conflicting requirements.
We thought, honestly, we deserved some marks for our designs. After all
they meet their specifications daily and in the case of the BAC 1-11, have
done this for over 25 years. We have taken note and will try to do even
better.
R. S. King Pucklechurch, Bristol
