Comet Cover-up

[spekesoftly]

Thursday 13/6/02 Channel 4 (U.K.) 21.00 - 22.00 (BST)

Documentary reviewing the early years of the D.H. Comet, the world's first jet passenger airliner, launched in 1952. Includes archive footage and interviews
with two of the test pilots.

[Beeayeate]

Ah, a documentry. I thought you were starting a thread about 51 Sqd.

[Flash2001]

The world's first jet airliner was the Avro Canada Jetliner. It first flew long before the Comet. Didn't sell (And didn't come apart in mid-air)

[ORAC]

Sorry, the Comet beat it by two weeks.

Avro Canada C-102 Jetliner:

The first flight of this four jet aircraft occurred at Malton Airport, Hamilton, Ontario, Canada, on 10 August 1949.

Comet:

First engine test runs of prototype G-5-1 were made on 2nd April 1949 with roll out on 25th July after a complex program of engine tests. Two days (27th July) later the Comet made it's historic maiden flight which lasted 31 minutes. Crew: piloted by de Havilland Chief Test Pilot John Cunningham, John Wilson as co-pilot and the flight test observer was Tony Fairbrother.

[Flash2001]

ORAC

I sit corrected.

I do note that the Avro history site calls the Comet's first flight a mere hop off the runway. Then again that same site says that the DC7 had 72 cylinders per engine. I don't intend to rely on it.

Edited to add useless information

[ORAC]

Not just a hop:

The first prototype was rolled out for engine runs in April 1949. By mid-July all was almost ready. On Wednesday 27th July 1949 the London Press Corps were invited out to Hatfield for the unveiling of a new breed of airliner - all were aware that they were witnessing history in the making. Test pilot John Cunningham and his assistants were making a final series of ground-runs and fast taxi's in preparation for flight.

16

There was the usual hospitality laid on for the Press, and during the briefing they were told that '...the aircraft would fly when it was ready, and not before'. Due to inclement weather, this appeared as if the great moment would be delayed, so the Press Corps all went home!

Towards evening, the weather cleared, John Cunningham told the Tower at Hatfield that he was ready to go.On board also was J. W. Wilson, First Officer, F. T. Reynolds, Flight Engineer, H. Waters, Flight Engineer Electrics, and A. J. Fairbrother, Flight Observer. The warble of the Ghosts at idle changed to a shrill crescendo and at 6.17pm the Comet began to roll, lifting up at take-off speed into a shallow climb.

Thirty minutes later the aircraft was back over Hatfield, Cunningham making a flypast at 100 feet for all the workers who had gathered to watch the return.


http://home.btconnect.com/GMS-ENTERPRISE/first.JPG

Comet 2002 site (http://home.btconnect.com/GMS-ENTERPRISE/choice.html)

And, alas, even for the first in the world, no attempt was made to save it:

Britain entered the jet age of the airliner with build of the first de Havilland DH.106 Comet prototype, manufacturers serial no. 6001, having been ordered during June 1946. Roll-out of the aircraft occurred at Hatfield on 2 April 1949 and its first flight was accomplished on 27 July 1949, being flown by John Cunningham, the aircraft wearing Class B registration G-5-1 and being powered by four de Havilland Ghost 50 Mk.1 engines.

This Comet was used for experimental, research and development work with the manufacturers at Hatfield and was registered as G-ALVG by the UK CAA on 1 September 1949 and handed over to the Ministry of Supply/Aviation on that date. Research work continued through to April 1952. It was displayed at the 1949, (with its original single wheel main undercarriage units), the 1950, (by now in BOAC colours), 1951 and 1952 SBAC displays at Farnborough and the Paris Salon during 1951, arousing much interest throughout the industry.

On 3 April 1952, G-ALVG was allocated to de Havilland Engines for development work on the Ghost engine series. On 30 December 1952 the Comet returned to de Havilland Aircraft, for wing test flying work in conjunction with the proposed Comet 3 series. Development and test work continued and, on 31 July 1953, the aircraft arrived at the Royal Aircraft Establishment, Farnborough, for fatigue testing of its airframe by Structures Department. Its registration was cancelled on 6 November 1953, as being permanently withdrawn from use and, on 24 November 1953, it was officially Struck off Charge.

It was moved into Structures Department at Farnborough, building Q153, on 25 June 1954 and placed within the Cathedral structural test rig for wing fatigue tests. After completion of its tests, around September 1954, having basically been tested to destruction where the wing structure failed, it was removed from the test rig and the remains of the airframe were eventually broken up for scrap.

[spekesoftly]

ORAC,

Just a small point - you mention that G-ALVG was registered on the 1st September 1949 by the UK CAA. Should that not read ARB (Air Registration Board) ?

[Bally Heck]

Article in yesterday's Mail on Sunday (Not that I normally read gutter press) about alleged cover up and deception during the design and build of the Comet. Covered in a Channel 4 documentary on Wednesday.

Channel 4 (http://www.channel4.com/history/microsites/S/secret_history/index.html)

Maybe worth a watch.

[Carruthers]

If the Channel 4 documentary on the Chinook crash is their standard then don't bother.

[maninblack]

I would imagine that their "discovery" is that metal fatigue set in around the square window frame and caused explosive decompression. Isn't it funny how DeHavilland and the investigators discovered this forty years before Channel 4.

Channel 4 also recently discovered that HMS Hood sank after taking a direct hit from a German naval shell in the main armoury; sadly about 50 years after the Admiralty worked that out by asking eye witnesses on other ships about what happened.

Apparently they are going to do a series of documentaries next year about how Channel 4 has just discovered the wheel, how to make fire and that ear wax tastes yukky. ;)

[BBK]

Perhaps we should actually watch the documentary before passing comment on it?

[javelin]

The programme looks at handling problems and two crashes involved in that. It questions why Ghost engines were used instead of more powerful RR engines which were available. This led them down a weight saving path which included thinner skin material. Also they look at why the design of the window surrounds was changed from Re Dux glueing to rivetting to save time in construction - that then led to the fatigue problems.

[llamas]

I have my doubts about a coverup, myself.

However, there is a most interesting coincidence regarding the fate of the Comet.

A certain British novelist wrote a very popular novel in 1948, which had as its storyline the failure of a new British translatlantic airliner in flight due to metal fatigue, which was only pipointed as the cause after several crashes and extensive testing-to-failure at the RAE. The book was made into a very successful motion picture in 1950. All of this pre-dated the first flight of the Comet by at least two years.

The novelist knew whereof he wrote - he had, in his earlier life, worked for Geoffrey de Havilland, been instrumental in the structural design of very large aircraft and gone on to start his own successful aircraft company. He was FRAeS, and was personal friends with Lord Brabazon of Tara, one of the driving forces behind the Comet project.

The writer didn't make this story up out of thin air - he made it up because he knew that metal fatigue was a significant issue in aircraft structures, and would only become more so. While structural design should be based in sound engineering practice, the publication of such a work of popular fiction indicates, to me at least, a suggestion that this was a problem not adequately understood or addressed at the time.

Interesting, what?

llater,

llamas

[Nopax,thanx]

That'd be Nevile Shute's "No Highway", then.....a top tale, well written, and not just of interest to those "in the know".

There is a Comet 1 at the Mosquito museum on the M25 at London Colney...well worth a visit; just have a look at the fuselage structure and see how flimsy it appears, compared with today's pressurised jets; it's a real education.

[Konkordski]

I'm not exactly inspired after hearing the trailer for the Comet programme, with a newsreel voice-over talking about the aircraft breaking up -- the voice-over was taken from the Farnborough airshow (1952 ??) and referred to the Sea Vixen which broke up during its display.

[llamas]

Nopax - that's the one.

At the risk of terminal thread drift - fans of Nevil Shute may be interested to know that his first new book in more than 40 years has just been published. Entitled "The Seafarers", this 90,000-word manuscript was among his unpublished papers at the time of his death in 1960. While it speaks strongly to themes found in later works, it's a very good read in its own right.

Find details at www.papertig.com if you are interested and, no, it's not my business and I don't make a dime from the recommendation.

llater,

llamas

[ORAC]

I understood that the airframes were certified and approved by A.R.B. for the issue of its Certificate of Airworthiness - but that the certificates were then issued by the Ministry of Civil Aviation.

The CAA is presently responsible for maintaining the the UK Register of Civil Aircraft. I am presuming that this function was carried out by the Ministry prior to the CAA's founding in 1972.

The following is the text of part the evidence given in the inquiry into the crash og G-ALYY which explains the procedure. I also include a link to the site, which is excellent.

"Yoke Yoke was granted a Certificate of Registration No. R.3221/1 on the 18th September, 1951 in the name of B.O.A.C. as owners and first flew on the 10th September, 1952. On the 23rd September, 1952 it was certified and approved by A.R.B. for the issue of its Certificate of Airworthiness and this Certificate, No. A.3221, was issued by the Ministry of Civil Aviation on the 30th September, 1952. After approval by A.R.B. on the 21st September, 1953 the Certificate of Airworthiness was renewed on the 23rd September, 1953 and was valid at the time of the accident".

Comet (http://www.geocities.com/CapeCanaveral/Lab/8803/fcogalyy.htm)

[Lou Scannon]

His name was Neville Norway actually. He decided to use the name "Shute" (his mother's maiden name) so that his boss, Mr B. Wallis and his firm, Vickers, wouldn't know that their Chief Calculator on the R100 also wrote novels! He eventually became his own boss when he formed an outfit called "Airspeed".

Try reading "Slide Rule" the autobiography of an engineer.

[spekesoftly]

ORAC,

Thanks for the clarification, and the excellent link.

[basil fawlty]

Square cornered windows caused the structural failure. Absolutely no doubt about that, and there was no cover up for sure. However, it absolutely amazes me that they used square windows on a pressurised airframe. Even 50 years ago the science behind stress concentrations on corners was very well understood. Why did they do it???

[aw ditor]

One of the theories put forward was that BOAC insisted on square windows instead of round or eliptical

[ORAC]

Please read the accident report. In particular:

(b) Criticism of de Havillands' design work

116. Dealing first with the period prior to the commencement of the scheduled passenger service on the 2nd May, 1952, the calculations made by de Havillands were criticised and it was suggested that the tests they carried out were inadequate to guard against the risk of fatigue in the cabin structure. In support of this contention particular reference was made to certain calculations included in paragraph 4 of Part 3 of the R.A.E. Report and to other calculations produced by Sir Arnold Hall in the course of his evidence. It is, however, to be observed that the primary object of de Havillands was to lay the foundation for extensive tests which they regarded as the soundest basis for the development of a project rather than to arrive at a precise assessment of the stress distribution at the corners of the cabin windows.

117. I do not think that they can justly be criticised for this approach to the problem. In arriving, at this conclusion I have been assisted by a Memorandum which has been prepared for me by my Assessors and which confirms the impression I formed from the evidence of the witnesses that de Havillands were proceeding in accordance with what was then regarded as good engineering practice. I am also satisfied that in the then state of knowledge de Havillands cannot be blamed for not making greater use of strain gauges than they actually did or for believing, that the static test that they proposed to apply would, if successful, give the necessary assurance against the risk of fatigue during the working life of the aircraft. The Memorandum to which I have referred is included as paragraphs 118 to 129 of this Report.

QUESTIONS AND ANSWERS
My answers to the questions submitted on behalf of the Attorney-General are as follows:_

Question 1

What was the cause of the accident?

Answer.

The cause of the accident was the structural failure of the pressure cabin brought about by fatigue. See para. 95.

Question 2.

If several factors caused the accident what were such factors and to what extent was each contributory?

Answer.

This does not arise.

Question 3.

Was the accident due to the act or default or negligence of any party or of any person in the employment of that party?

Answer.

The accident was not due to the wrongful act or default or to the negligence of any party or of any person in the employment of any party.

Official accident report of Comet I G-ALYP (http://www.geocities.com/CapeCanaveral/Lab/8803/fcogalyp.htm#rae)

[PaperTiger]

However, it absolutely amazes me that they used square windows on a pressurised airframe. Even 50 years ago the science behind stress concentrations on corners was very well understood. Why did they do it???
Perhaps because there had been (and never were) any problems with the Douglas DC-6, DC-7, Lockheed 1049, Convairliners. I thought the cracks emanated from the astro window anyway, not the cabin windows (I could be wrong).

[ORAC]

The ADF window:

75. By examination of the piece containing the A.D.F. windows and the adjacent pieces (see Figure 12) it was established that it was here that the first fracture of the cabin structure of Yoke Peter occurred. In general terms, it took the form of a split along the top centre of the cabin along a line approximately fore and aft passing through corners of the windows as shown in Figure 17. The direction in which the fracture spread was determined by examination of the lines of separation of the material.

[llamas]

Lou Scannon wrote:

"His name was Neville Norway actually. He decided to use the name "Shute" (his mother's maiden name) so that his boss, Mr B. Wallis and his firm, Vickers, wouldn't know that their Chief Calculator on the R100 also wrote novels! He eventually became his own boss when he formed an outfit called "Airspeed".

Try reading "Slide Rule" the autobiography of an engineer."

His name was Nevil Shute Norway, from which he took his nom-de-plume.

His mother's maiden name was Mary Louisa Gadsden. The name Shute traces back to the Cornish roots of his father, Arthur Hamilton Norway.

llater,

llamas

[Only A Few More Seasons]

It sould have never been built in the first place - front door on the wrong side - an absolute ground engineers nightmare.

I cannot wait till that awful thing that sits like a ghost on 136 at LGW is reduced to kitchen foil and milk bottle tops.

Sorry

[spekesoftly]

Quote:-

"sits like a ghost on 136 at LGW"


Still no improvement on its slot time then ? ;)

[basil fawlty]

PaperTiger,
All of the types you mention with square windows attained far lower altitudes than the Comet, therefore the pressure differential was a lot lower and the stress/strain cycling a lot less. They could use square windows no problem, the Comet could very obviously not.

The British aircraft industry certainly learned a lesson from it though, going from paper thin skins on the Comet to over engineered "brick sh*thouse" designs, i.e VC10, Trident, 1-11......

[411A]

Hmmm...perhaps why these types did not sell well, elsewhere. Except "possibly" the 1-11.
However, sure took the maximum advantage of converting kerosene....into NOISE.

[Jhieminga]

Actually 411A, in my view politics were the main reason for the VC10 and Trident sales figures, or lack of them.

For more info:
A Little VC10derness (http://fly.to/VC10)
Trident Domain (http://www.hs121.org.uk)

[maxtransient]

Obviously, I haven't seen the programme yet - but if it concentrates on the performance issues associated with the operation of the Comet in the early days (leading up to a few particularly nasty accidents when the aircraft failed to complete the lift equation) - a good book to read is "Cone of Silence" by David Beaty.

The book is a very thinly veiled description of the early days of Comet operations and, like'No Highway', was also made into a thoroughly 'stirring' British film.

[PaperTiger]

Quite right basil, I was offering a possible explanation why they did it, not suggesting it was a good idea. Specially since Neville (Shute) Norway had predicted just such a failure in No Highway.

The Trident and VC-10 were commercial failures because they were designed for the specific needs of two airlines (BEA, BOAC) who kept changing their requirements and otherwise d!cking about with the design.

[WebPilot]

I am more than a little worried about the programme tonight - the FT review in it today mentions the 'short lived Comet airliner' 1952 - early 80s? Hardly short lived!

Also it refers as one of the criticisms to "having been developed in only 3 years where 7 years is more normal for most airliners".

To compare the Comet with the B.707, development times seem little different:

Comet: Design work commenced 1946, first flight 1949, entry into service 1952

B.707 Design work commenced 1952, first flight 1954, entry into service 1958

[Shaggy Sheep Driver]

Very well done, I thought. Having Bill Gunston on the program ensured at
least some good sense and deep knowledge, as did having recollections from
pilots and engineers who were there at the time.

Just two gripes: it's all very well saying that the Americans were miles
behind, and there was plenty of time for full pressure tests etc and still
be first into the Jet Airliner business. But that's with the benefit of
hindsight, which is always 20/20.

And I find it hard to believe that a designer of RE Bishop's calibre would
allow a major design change - riveting the window surrounds instead of
'Reduxing' them - without checking what effect the drilling of hundreds of
extra holes would have on the structure.

It was also interesting to note that the prototype (the one with
single-wheel main gear) had leading edge slats, which were deleted on the
production machines. I wonder if that's why the wing leading edge on these
early Comets was wrong shaped, leading to the two 'over rotated' take off
crashes? BTW, did you note the clouds of concrete dust as the prototype took
off? The Hatfield runway was still new then - it was a post war addition.
Only broken up a couple of years ago :~(

I must also take issue with something Bill Gunston said - "they always come
unglued, DH aircraft". He was referring to the period between the end of the
war and the Comet disasters - and I can only think of the DH110 in flight
break-up at Farnborough that fits that bill. I don't think Vampires or
Venoms were prone to it (or indeed the Chippy, though that's DHC) - you have
to go back to the pre-war 'Flamingo' to find a 'weak' DH aeroplane. The
biplanes were strong, and all post-Comet DHs were as well (125, Trident,
146).

SSD

[bean]

A DH108 Experimental aircraft also broke up at very high speed killing Geoffrey de Havilland

[Nopax,thanx]

The 'ungluing' reference possibly meant the Mosquito and suchlike non-metallic DH designs as well...they were well ahead of their time in "Composite" technology, but the Mossie's structural problems (Casein Glue, etc) were a hot issue at the time, too.

[treadigraph]

Interesting programme, well presented I thought; as you say having Bill Gunston, John Cunningham etc, certainly added an authoritative element to the programme, unlike some that I've seen which seem to be mostly supposition by ignorant sensationalists.

I think as Mike Ramsden was quoting Bishop about the rivetting rather than Redux that it must be fact and unlikely to be a case of Chinese whispers! Though I take your point...

DH also had the Albatross break its back pre-war... I'd take issue with the idea that DH had no experience with large passenger aircraft as the Albatross and Flamingo fitted that bill. The public could be excused for thinking that the Mosqutio was the largest aicraft they'd built up to that point.

I didn't think the take-off accident was due to over-rotation, the film they showed of the one sinking back seemed if anything to have under-rotated - it seemed a very flat take off - a later shot showed one taking off with the nose well up. Thoughts anyone?

Didn't BOAC also lose one which was deemed to have been due to a screw backing out and jamming the attitide indicator, leading to too high a rate of climb and a stall? Just wondered if that was actually one of the three accidents referred to last night, as I'd always thought two had pranged due to structural failure. As I recall the three were near Elba, near Stromboli and somewhere in India. The stuck attitude indiactor might have been later on a IV though...

Cheers

[bean]

The Aircraft seen in the programme which appeared to be under rotating was definitely the prototype possibly on a pre first flight hop. The crash at Rome & the Canadian Pacific crash both involved the aircraft failing to become airborne in a very nose high attitude. The stuck attitude indicator accident occured to a BEA IVB At Ankara in 1961

[Shaggy Sheep Driver]

I think the one lost to the attitude indicator screw was a BEA Comet 4. It was certainly much later than than the Comet 1 disasters.

I undrstood that the problem with take off on the early Comet 1 was that if the aeroplane was rotated beyond a certain angle, with the mains still on the ground (and it didn't need to be much of an angle) the wing would produce excess drag and insuficient lift, so the aeroplane either wouldn't take off or would not climb away once airbourne and may sink back on. I think this lead to subsequent aeroplanes having to demonstarte 'min speed unstick', to ensure that even if the tail is scraping along the runway, the aeroplane will lift off and climb away safely.

SSD

[InFinRetirement]

Bill Gunston - good. Mike Ramsden - good. The FO's - good. But what has that got to do with the cover-up?

What went on was an absolute disgrace. From the moment that aeroplane was built it was an accident waiting to happen. The corners cut were tantamount to criminal negilence, yet not one of the designers, or directors was bought to book when it was so blatantly obvious that they should have been.

The revelations in written form were an indication of how politicians and men in power can manipulate anything they want to. That they manipulated this aeroplane to early destruction is wicked.

Bishop, as head of design, has had his memory degraded by the programme, and that goes for de Havilland too. And quite rightly judging by the standards they adopted. Especially reducing the skin thickness from 14g down to 20g.

Certainly blaming pilots was obviously the 'easy option'. As used to be the case then. Thank God we have now a responsible body to discover actual cause.

Fortunately, the Comet lived after they went back to the drawing board, and removed all the devious schemes. But sad to say that the 1000 planned only reached 75. If only..................

[411A]

Interesting..
What sort of engine fire protection/extinguishing/shielding did the Comet have?

[PAXboy]

I think the programme did pretty well. It was not too sensationalist, although some of the music was intrusive and intended to set a menacing tone, which was over the top.

Whilst dissapointed to hear of the supression of the fatigue problem, it does not really surprise me. Politics and commerce are a nasty mix!

Could it happen today? I think less so. There would obviously be people who would want to supress such information but we no longer have so many company staff that are 'lifers'. We also have 'this' the Internet. Any one can publish any thing at any time. Any whistleblower in DH would have had more of a problem in getting the news published.

I also agree that politics seriously harmed the VC10, from my reading of Swift, Silent, Superb. However, I think that all prospective purchasers of the VC10, would have tarred it with the same brush as the Comet. Would their pax have believed the sales pitch that Vickers had got it right?

[PaperTiger]

all prospective purchasers of the VC10, would have tarred it with the same brush as the Comet. Would their pax have believed the sales pitch that Vickers had got it right?
Don't know as that follows. The VC10 was many years later and a completely different manufacturer (with a good track record). Even back then I don't think airlines made equipment decisions based on passengers' perceptions. 99% of whom know diddly about what they are flying on, and probably care even less.

[PAXboy]

Sure, I can see that but the publicity of the Comet crashes would have been evident to all. The quantity of pax in those days was very much smaller than now and they would have been well aware of the problems with 'a British aircraft', not knowing that they were different manufacturers.

[PaperTiger]

Didn't seem to bother Braniff, American or Mohawk who ordered the 'British' BAC-111. The 10+ years between the Comet I and the VC10 makes it most unlikely the latter suffered in any way from the former's reputation.

[Shaggy Sheep Driver]

Interesting letter in the 'Guardian' yesterday from two DH designers (AGT Peters
and DR Newman) who were senior members of the 'Comet' team from prototype to
Comet 4. They take Channel 4 to task thus:

1) There was no 'mad race for profit'. DH in those days were just not like
that.

2) The contract for BOAC and BSAA were placed by the airlines themselves,
not the Ministry of Supply. The MoS only bought the first 2 examples.

3) The Ghost engines were the only ones certificated for civilian use at the
time. There was no alternative. The RR Avon was not even civilian-approved
by the time of the groundings, in 1954.

4) Weight reduction is standard procedure in aircraft design. There was
nothing sinister about 'the right engines not being available'.

5) There was no mention of the ARB, the body responsible for public service
certification.

6) The RAE's concerns about fatigue were about wing fatigue, not the
fuselage.

7) there was no mention of the extensive fatigue tests on major airframe
parts undertaken by DH before the prototype flew.

8) Senior people at DH, BOAC, and the ARB are no longer around to defend
themselves against the charges implied by the program.

They also mention that such was the mutual interest in safety that senior
Boeing people came to Hatfield to help after the cabin failure - but the
cynic in me makes me think they may have had their own agenda there...

SSD

[Airways Ed]

As Mike Ramsden has not posted here (yet), I'll pass on these:

Quote from sender of Mike's letter:

"You may have seen, or heard about, a "Secret History" programme on Channel 4 on 13th June. It was entitled "Comet Cover-up" and included interviews with John Cunningham, Ralph Hare, Mike Ramsden and John Wilson - all of whom had been invited to take part in a programme "to celebrate the 50th Anniversary of the Comet's entry to passenger service". The final production purported to show a sinister plot on the part of DH to get the Comet into service regardless of adequate testing.

"Mike Ramsden has written the following letter for as wide as possible circulation to put the record straight. It was sent to me via the DH Tech School Old Boys Association email list. I don't know how or where Mike Ramsden intends to get it published but I thought you all might be interested.

"Tony Fairbrother was told that the programme's producer was changed late on in production, which may account for the change in slant. I can't imagine those interviewed were aware how their comments were going to be used! Dick Bishop can't have been too pleased with what was virtually a character assassination of his father."


Mike's letter:
-----------------------------------------------------------
18 June 2002

Comet Cover-Up

As one of the ex de Havilland people who appeared in the Secret History TV programme about the Comet 1 disasters (Channel 4, 13 June) I would like the truth to be known.

Disasters they were, as we shall not forget. But to accuse de
Havilland and its chief designer R. E. Bishop of avoiding fatigue tests is outrageous. "Secret letters" are cited in support of this allegation. Secret letters from whom, dated when, saying what exactly? Can we have copies? Fleeting glimpses of old files containing the word "fatigue", accompanied by doom-laden music and voice commentary, do not prove anything.

In 1952-53 we built two full-scale test sections of the Comet 1 fuselage including windows, and tested them in the Hatfield water tank. They were intended to prove singIe-overload bursting strength arid repeated-load fatigue strength.
Professional structural engineering opinion at the time was that fatigue strength could be demonstrated by "static" strength. Thus we pumped up one test section to twice normal working pressure (P). If it had failed at less than 2P, which it didn't, we would have been back to the drawing board. We believed we had demonstrated the Comet 1's fatigue and static strength.

Chief designer R.E. Bishop went further. He said "show me 2.5P". We did that too. He then ordered a fatigue test: 16,000 repeat loadings of 1.25P. That test, a world first, went beyond the call of airworthiness requirements. Bishop went even further and ordered the repeat-loading of individual windows to 2P. As an apprentice in the structural test department in 1949 I remember these tests personally. My job was to polish the windows each morning with "Ajax" to see whether any loss of thickness
from window-cleaning in airline service would affect the transparency's strength. Far-fetched, but a measure of Bishop's conscientiousness.

I explained all this in filmed interviews with the Channel 4 programme makers, Steve Ruggi and David Coward. Too technical and boring, perhaps. They edited it all out. But to state as fact that de Havilland refused to fatigue-rest the Comet 1 is just wilful untruthfulness. It makes you wonder how much you can believe of any Channel 4 documentary.

Yes, the Comet 1 windows failed catastrophically from fatigue. No
excuses. But there were reasons - reasons which were established and published by the inquiry and which advanced the science of structural design, inspection and testing.
The Comet 1 windows failed because the production window-cutout reinforcing plates were riveted - and very poorly riveted - instead of being glued (Reduxed) as in the test section. And the test section may have been toughened by the 2.5P load applied to it before the 16,000 x I 25P fatigue cycles. These were mistakes. But they were honest mistakes, made in the course of pioneering unknown structural territory, and they were exposed by a public inquiry.

Bishop accepted responsibility, even though a lesser man would have blamed the production or structures departments, or both. -
Engineers who try to do things which have never been done before will get some things wrong, but besmirching their reputations by representing their honest mistakes as conspiracies is just cheap.

The TV programme makers and editors concerned got much else wrong, too much to elaborate here and some of it ridiculous - for example, that the Comet 1's skin thickness was determined by the choice of de Havilland Ghost rather than Rolls-Royce Avon engines.

Incidentally, Principal films told me and the de Havilland colleagues
who appeared in the programme (and lent personal film, photos and documents) that it was to celebrate the 50th anniversary of jet transport. Was that an honest mistake?

J.M. (Mike) Ramsden

[Lemmon_drop_kid]

When I was about 19-20 'old Frank' told me that they had problems fitting the old square comet windows. He went on to tell me that a fitter (who later became an unpopular foreman) used to have a crow bar hidden under the bench, and used to 'spring' the windows into the fuse.

[treadigraph]

See that Mike Ramsden's letter has been published in "Aeroplane" this month (early August, September Issue) and also John Maynard's (who was also at DH at the time) column at the back of the magazine has a dig at the programme team.