Comet 1 fatigue problems

[evansb]

The take-off angle and rotation speed was a different problem, and were easily resolved. This thred is about fatigue problems.

[johngreen]

A few years ago, the repositioned parts of the roof section including the ADF windows of G-ALYP were on display in the Science Museum as seen in this image. (They are no longer exhibited.)



File:Fuselage of de Havilland Comet Airliner G-ALYP.JPG - Wikimedia Commons



It was a very sobering experience to be looking down on these pieces in such a very mundane and static state and yet not at all difficult to imagine something of the few seconds of utterly catastrophic trauma that surrounded and included them just over the period of my own lifetime ago.

No doubt those that have dealt or deal now with the aftermath of any such events will know well of such reflections...

[A30yoyo]

I've retitled the thread to cover discussion of all the Comet I losses.
I know that De Havilland re-profiled the Comet wing leading edge to improve take-off characteristics, but what was the exact timescale of the introduction of 'V1, V2...rotate'. In the LIFE magazine series of photos of the first Comet 4 transatlantic service from Heathrow the Comets nose is off for several hundred yards before lift-off..was it a characteristic of the Comet 4?
Jet Comet - Hosted by Google
Jet Comet - Hosted by Google
Jet Comet - Hosted by Google
Jet Comet - Hosted by Google
I watched that from the Public Enclosure you can see behind the Comet in the second shot
Finally has the Comet loss off India ever been linked to fatigue rather than extreme turbulence?

[glendalegoon]

dear mr lupton

I seem to not be alone in this.

No. 112: The Comet Failures

and many more.

I guess we would have to ask nevil to be sure. try your ouji board!

[A30yoyo]

Hmmmm....they're still on about cabin windows....the point was that ALL the cut-outs in the pressure cabin had to be re-evaluated , redesigned and produced in thicker more fatigue resistant alloys with rip-stop features...the initial failures had been at an ADF window and an emergency hatch .
I think Pan Am started 707 services only about a month (edit) after the first Comet 4 transatlantic service...you can see a 707 parked discreetly by the fuel tank 'farm' (site now of T5) in the last of the Comet take-off sequence in #24

Here's some more shots from Mark Kauffmans 'Jet Comet' essay for LIFE mag
Jet Comet - Hosted by Google
Jet Comet - Hosted by Google
Jet Comet - Hosted by Google
Jet Comet - Hosted by Google

and these are from the same session but don't come up by searching 'Jet Comet'
BOAC Comet Captain Alabaster, BOAC Chairman Sir Gerard D'Erlanger and BBC's Reg Turnill in there
LIFE - Hosted by Google
LIFE - Hosted by Google
LIFE - Hosted by Google
LIFE - Hosted by Google
LIFE - Hosted by Google
LIFE - Hosted by Google

[Airbanda]

I seem to not be alone in this.

No. 112: The Comet Failures

and many more.

I guess we would have to ask nevil to be sure. try your ouji board!

The linked article is a bit wayward with its facts and I very much doubt the connection to Rudolf. Apart from anything else it's not clear that the poem/book had reached the mass market at time No Highway was written.

Shute was not 'an engineer with De Havilland' by then although his early career in twenties included a spell at their Stag Lane works. He went from there to Vickers and then airships. After working on the R100 and abandonment of the airship programme following loss of R101 he co-founded Airspeed but parted company in late thirties. At the time it was majority owned by shipbuilders Swan Hunter. Only a couple of years later did they sell out to De Havilland leaving Airspeed as a division of the bigger company. After Airspeed he was able to live on his departure compensation and writing earnings until joining the RNVR at start of WW2 to work on various 'secret weapons'.

By 1948 he was again making his living solely as an author. He did though retain contacts at RAE and elsewhere including Professor Sir Alfred Pugsley who was working on fatigue.

No Highway is a good yarn but as much human story about the 'boffin' Mr Honey as about the science etc.

Shute's biographer John Anderson (Parallel Motion published by Paper Tiger in 2011) quotes Shute on the subject:

You think that was my own idea? Look I'm getting a little embarrassed about being hailed a prophet of metal fatigue. It really happened this way. Someone sent me a couple of technical papers by Professor Pugsley and he forecast the whole thing. I thought it was a fascinating idea for a novel so I wrote it. If anyone was the prophet for that book it was the Prof.

His full name was Nevil Shute Norway, professionally in aviation he was Norway. Shute as a given name was taken from further back up the family tree, the family name of his paternal grandmother.

He used it for his early 'hobby' writing so as not to impinge on his professional work with Vickers/R100 etc and it is the name by which he is generally known.

[Allan Lupton]

Some of Mr Lienhard's flights of fancy are just that and I think Airbanda has nailed it pretty well, so can we leave the "No Highway" digression now, please.

[Airbanda]

Request noted

Given this is a thread in History and Nostalgia (as opposed to a professional/technical sub forum) I'd have thought an element of digression was permissible if not inevitable.

But I've no wish to offend, still less get in an argument.

[VX275]

I've been able to read the original series of Farnborough reports covering the Comet accidents and facinating reading they make. The one point that lept out at me that is rarely mentioned is that the cracks around the ADF and other window openings were occuring on the production line as evidenced by the number of stop drilled cracks, including one of the fatal cracks on Yoke Peter. It is obvious that the cracks propogated despite these measures, with some cracks having more than one hole.
The builders recognised that the material was prone to cracking and applied the industry standard preventative action whilst failing to recognise its ineffectivness and the subsequent consequences.

[Blacksheep]

There was a complete Comet 1 fuselage at Farnborough up until the early '80s.

Come up to London Colney if you want to see it again . . .

We have it at the De Havilland Aircraft Museum, along with lots of other De Havilland aircraft and engine examples.

[Stanwell]

Allan Lupton,
Please come up with an interesting contribution then - OK?
See what I'm getting at?

[Allan Lupton]

Quote
See what I'm getting at?

Since you ask, young sir, no I cannot see what you find interesting.

[barit1]

Seminar visual materials

I discovered this University of Washington visual package - good historical review of the science of fatigue:

http://www.aa.washington.edu/courses...n_2-3-2014.pdf

(For me, It took a while to load)

[Discorde]

I seem to recall that the Comet's designer, Ronald Bishop, was reported as difficult to work with and intolerant of criticism or is that an unfair or inaccurate malignment? Is it true that some engineers questioned the light gauge of the aircraft skin and the square window design in a pressurised hull? The increase of stresses at sharp corners had been known about for many years.

[joy ride]

Interesting to note that the Sud Aviation Caravelle had triangular windows and the L1011 Tristar had square ones. I heard a while back that Redux was originally specified to secure the windows, but de H management were not convinced that this method alone was good enough to rely on, and insisted on the addition of rivet plates and rivets, and it was these additions that initiated the cracks.

I am not sure how true this is, but the record of the Cravelle and 1011 suggests that (within limits) the window's shape is arguably less important than its construction.

[Spooky 2]

That was former Mexicana XA-NAS, which worked through various dealers in the US from the 1970s-90s without ever being used. A onetime regular PPRuNe poster was the flight engineer on that last flight from Albuquerque into O'Hare - apparently none of the crew had even been in a Comet before !


I was the FO on this flight and it's true none of us had flown the Comet prior to that day. We did one takeoff and full stop at KABQ before heading off to KORD. BELARG was the FE and we use to keep in touch a little but I'm afraid he had some health issues that prevented his continued participation in this forum. His postings were always excellent by the way. The fellow who flew Capt on the flight passed away last year.

[WHBM]

Originally Posted by Spooky 2

I was the FO on this flight and it's true none of us had flown the Comet prior to that day. We did one takeoff and full stop at KABQ before heading off to KORD. BELARG was the FE and we use to keep in touch a little but I'm afraid he had some health issues that prevented his continued participation in this forum. His postings were always excellent by the way.

I'm sorry to hear of Belarg's problems, we had many a banter here, both serious and humorous. He had a great knowledge of the 707.

[barit1]

Interesting to me:

Douglas DC-2 cabin windows had a small radius in the corners.
DC-3/C-47/C-53 etc. had square corners.
DC-4/C-54 had round windows.
DC-6 & 7 had square corners (first pressurized Douglas ships)

[Genghis the Engineer]

Originally Posted by Discorde

I seem to recall that the Comet's designer, Ronald Bishop, was reported as difficult to work with and intolerant of criticism or is that an unfair or inaccurate malignment? Is it true that some engineers questioned the light gauge of the aircraft skin and the square window design in a pressurised hull? The increase of stresses at sharp corners had been known about for many years.

(1) A great many senior people throughout the history of aviation have been reported as "difficult to work with and intolerant of criticism", hence CRM !

(2) Engineers generally communicate by criticising each other's work - so I'd be amazed if somebody hadn't asked those questions, along with lots of others.


Yes, increased stresses at corners were known. The impact of cyclic stresses in a pressure hull, relatively speaking, weren't however.

G

[joy ride]

One known example was the cargo hold openings on Liberty ships which originally had 90º corners. These initiated cracks, with at least one Liberty breaking into two. Later ones were built with rounded corners.

However, the examples of Caravelle, L1011 and DC6 / 7 do suggest to me that the shape itself is less important than its construction. I believe that Bishop did specify Redux alone, but management demanded a cautious "belt and braces" construction. It is sadly ironic that this cautious approach was what led to the failures.