Why Britain is not No 1 the comet.

A lesson on not allowing designers to influence engineering.

"The Comet’s designers opted for large, squared-off windows because they looked more attractive than the simpler, round “porthole” style that had been more traditional."

http://www.extremetech.com/extreme/...from-some-of-the-biggest-hardware-screw-ups/3

 

[stockdam]

A lesson on not allowing designers to influence engineering.

Don't agree with you Sirearl. Nobody at that time suspected that this would happen as there was little test data nor real modelling/analysis.

The good thing was that they made it mandatory to do full scale or detailed fatigue tests following this to "prove" new design before it is introduced into service.

Modern fatigue test articles are heavily strain gauged to confirm that the modelling/analysis used is correct. Damage/cracks/flaws are also introduced to see how well the design copes.

 

[vvaannmmaann]

Big news in 1952 obviously.

 

I think the point is that any first year engineering student knows that stress is evenly disperced on a round aperture as opposed to a square one where the stresses acumulate in the corners.

Not enough testing was done on this well known aspect.Leaving britains aircraft industry in tatters,instead of being the worlds No1 producer of jet aircraft.

Style over function rarely wins as exemplified by the Mini and the Fiat 500.

 

[vvaannmmaann]

"I think the point is that any first year engineering student knows that stress is evenly disperced on a round aperture as opposed to a square one where the stresses acumulate in the corners."

But that knowledgre in relation to aircraft window design was only gained with 20/20 hindsight and testing after the crashes.

 

But that knowledgre in relation to aircraft window design was only gained with 20/20 hindsight and testing after the crashes.

So tell me why do ships,submarines and spacecraft have round portholes.?

 

[Subbynet]

"I think the point is that any first year engineering student knows that stress is evenly disperced on a round aperture as opposed to a square one where the stresses acumulate in the corners."

But that knowledgre in relation to aircraft window design was only gained with 20/20 hindsight and testing after the crashes.

Shhhh... Don't talk common sense around Earl. It only makes him angry!

 

[Nuno]

So tell me why do ships,submarines and spacecraft have round portholes.?

He's right you know:

​

 

[vvaannmmaann]

So tell me why do ships,submarines and spacecraft have round portholes.?

I refer the Gentleman to my previous response.

 

I refer the Gentleman to my previous response.

I refer the gentleman to google to verify that the stresses on square windows were common knowledge long before the flying machines became fasionable.

https://www.google.co.uk/search?q=w...s=org.mozilla:en-GB:official&client=firefox-a

 

[Cylon]

I have to agree with Sirearl on this as logic would dictate that the philosophy behind round windows dates back decades before 'The Comet' and no one in their right mind would put square windows on a vehicle of this type.

 

[Nuno]

What about all those square shape windows at the front? The ones the pilot looks out of? If round is so crucial why aren't those all roundy?

​

 

[Cylon]

Think this has to do with side scuttle pressures (not to be confused with a back scuttle which is something totally different).

The smaller surface area of the front part of plane will allow square windows to be used (round would be better though) but in high pressure environments pressure will be concentrated on a corner and could lead to damage in that area as the focal point of that pressure will be far more than normal tolerances.

This would also explain why submarines and planes aren't rectangles and are more a cylindrical/tubular design.

 

[Nuno]

Cheers Cylon, that's interesting.

 

What about all those square shape windows at the front? The ones the pilot looks out of? If round is so crucial why aren't those all roundy?

​

Well you see the engineers in there wisdom decided that it might be a good idea if the pilot could see where he was going.

And being fully aware of the weakness of square windows they made the frames that held them massive ,unlike the comets side windows where the skin thickness was about as thick as a postcard.

The comet may have survived with round windows,but not the combination of an ultra thin skin and square windows allied to a poor installation technique.

 

[Nuno]

Well you see the engineers in there wisdom decided that it might be a good idea if the pilot could see where he was going.

And being fully aware of the weakness of square windows they made the frames that held them massive ,unlike the comets side windows where the skin thickness was about as thick as a postcard.

The comet may have survived with round windows,but not the combination of an ultra thin skin and square windows allied to a poor installation technique.

With all your detailed 20:20 hindsight you weren't one of the fitters on the Comet were you?
Don't blame me guv, were those bleedin' designers guv, I were on me teabreak when it crashed guv. etc etc.
Just asking...

 

[Subbynet]

Don't worry, Earl will be along tomorrow with another anti-britain post. Something like "Britain going to the knackers, Titanic sunk on first voyage!".

 

Don't worry, Earl will be along tomorrow with another anti-britain post. Something like "Britain going to the knackers, Titanic sunk on first voyage!".

Got just the thing for you laddie.

http://www.guardian.co.uk/commentisfree/2013/feb/18/shops-struggle-corporate-power-shopping

 

With all your detailed 20:20 hindsight you weren't one of the fitters on the Comet were you?

Nope just missed it by a wisker, although as an engineer I did work on the aircraft industry back in the good old days of the ARB.

http://discovery.nationalarchives.gov.uk/SearchUI/browse/C6242

 

[FIZIX Agency]

I refer the gentleman to google to verify that the stresses on square windows were common knowledge long before the flying machines became fasionable.

https://www.google.co.uk/search?q=w...s=org.mozilla:en-GB:official&client=firefox-a

It's funny you say that because I saw a documentary on the Comet a number of years ago (not Air Crash Investigation, a more serious one about the evolution of flight) and IIRC it was that accident that highlighted that square windows posed a weakness on aircraft and brought about proper design and engineering regulation on aircraft.

Your link doesn't point out exactly when engineers learned of the weakness, just explains that square portholes have a weakness (I don't have time to check every link).

However, if engineers did know at the time, if the documentary I saw wasn't lying, could it be that the weakness was known in certain applications but wasn't generally known or considered for other applications?

Ultimately though I am pretty sure that the Comet accident was due to technical understanding all round (or lack thereof) and lack of design regulation rather than designer fault.

 

[hmmm]

hmmm

isnt round or triangle always stronger than square?
even the ancients knew this.

what we could ask were the square ones used because "they" thought they would be strong enough for the job in question, rather than knowing?

hmmm