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The de Havilland Comet changed aviation for good

bbc.com

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Re: The de Havilland Comet changed aviation for good

#21

Post by Animats »

rwmj wrote: post #16

There is a "square windows" Comet 1A in the http://www.dehavillandmuseum.co.uk/ , next to the northern stretch of the M25. Well worth a day out to this quiet little museum (home of the former De Havilland factory) if you live in or around London.

It's surprising the designers made that mistake. Square inside corners were a known problem in shipbuilding.[1] Welding Journal, 1945: "Another contributing failure to welded ship failures is faulty design and in this category the inclusion of square corners is by far the most common and most detrimental. Occasionally some form of square corner will slip by the designer and and draftsman ... Supervisors should call it to the attention to the drawing room and request it be changed. ... would go a long way to solving our welded ship problems."

Early models of US Liberty ships had that problem, big-time.[2] One broke in half before it got out of the shipyard. About 20% of the fleet experienced a square-corner fracture. Those were rush-job ships, built quickly with square corners to save construction time. It was well known in naval architecture to avoid that. Portholes are usually round.

[1] https://books.google.com/books?id=P1IfAQAAMAAJ&lpg=PA473&ots... [2] https://metallurgyandmaterials.wordpress.com/2015/12/25/libe...

Re: The de Havilland Comet changed aviation for good

#22

Post by aphextron »

phillc73 wrote: post #18

When I read the headline, I was really hoping this article was about the de Havilland DH.88 Comet.[1] That really was a beautiful aeroplane. [1] https://en.wikipedia.org/wiki/De_Havilland_DH.88

Not sure why the downvotes. I thought this as well. The DH.88 absolutely changed aviation in it's own way. The first fully monocoque, aluminum skinned, twin engine, variable pitch prop aircraft ever produced. We are still making aircraft with this same basic design to this day.

Re: The de Havilland Comet changed aviation for good

#23

Post by WalterBright »

The other problem the Comet had was economic. It could only carry 36 passengers. The 707 could carry 140.

The larger number of passengers meant the 707 per-passenger cost made it cheaper to operate. The 707 could do 5 times the work of a piston powered DC-6 at only double the cost. It was a huge money-maker for airlines.

http://generalatomic.com/jetmakers/chapter7.html

Re: The de Havilland Comet changed aviation for good

#24

Post by WalterBright »

The corner of a square hole in a flat plate has 4x the stress of the surrounding material. It's called a "stress riser". If you look at a concrete slab with such an inside corner, there's usually a crack there.

Boeing solved the problem by using rounded windows, and riveting on a forged doubler around the window frame. The skin was also organized so a crack will not propagate far. The success of the latter has shown itself in various incidents where an airliner has lost a panel in flight, but went on to land safely.

Re: The de Havilland Comet changed aviation for good

#25

Post by gaius »

cstross wrote: post #13
justinph wrote: post #4

Earlier quoted context omitted.

They're turbojet engines, not the turbofans that you see today. Turbojets have a smaller intake and the entire thing produces thrust. Unlike today's much more efficient turbofans, where a small turbojet turns the larger fans to produce most of the thrust.

The Nimrod maritime patrol aircraft was a modified Comet airframe: https://en.wikipedia.org/wiki/Hawker_Siddeley_Nimrod In the early 2000s, BAe Systems had a project in train to upgrade them to the MRA4 spec, essentially remanufacturing the existing MRA2/MRA3 Nimrods around a new wing structure that could accommodate RR BR700 turbofans, doubling the aircraft's range: https://en.wikipedia.org/wiki/BAE_Systems_Nimrod_M…

Following the cancellation, the Defence Secretary Liam Fox used the Nimrod MRA4 procurement as an example of the worst of MOD procurement performance

Ah those innocent days, before the QE carriers and the F35 made that look like mere pocket change.

Re: The de Havilland Comet changed aviation for good

#26

Post by rjsw »

gaius wrote: post #25
cstross wrote: post #13

Earlier quoted context omitted.

The Nimrod maritime patrol aircraft was a modified Comet airframe: https://en.wikipedia.org/wiki/Hawker_Siddeley_Nimrod In the early 2000s, BAe Systems had a project in train to upgrade them to the MRA4 spec, essentially remanufacturing the existing MRA2/MRA3 Nimrods around a new wing structure that could accommodate RR BR700 turbofans, doubling the aircraft's range: https://en.wikipedia.org/wiki/BAE_Systems_Nimrod_M…

Following the cancellation, the Defence Secretary Liam Fox used the Nimrod MRA4 procurement as an example of the worst of MOD procurement performance Ah those innocent days, before the QE carriers and the F35 made that look like mere pocket change.

I thought the consensus was that the construction of the carriers had gone really well.

Re: The de Havilland Comet changed aviation for good

#27

Post by tajen »

I like the De Havilland story in how it made the managers look like fools: 2 crashes in bad weather, +1 in good weather, a worldwide suspension of operations, resumed a fortnight later with reassuring words from the management, +1 another crash, then a more serious stress test (which should have been done since the beginning), with negative results, then a bankruptcy... Fortunately, that's what happens to the wrong companies.

Another aircraft story I love is the Tu-144, the copy of the Concorde: "Critical alarms were so routine that pilots had to borrow pillows from passengers to stuff the cockpit siren". The full Wikipedia article is worth reading (or the Mayday episode worth watching), it's a good laugh.

Each time I fly, I internally laugh at how crazy humans are, throwing a can of the most inflammable liquid we can find, at 900km/h. "Play with fire, mum says, ..." and play with fire we do.

Re: The de Havilland Comet changed aviation for good

#28

Post by gaius »

rjsw wrote: post #26
gaius wrote: post #25

Earlier quoted context omitted.

Following the cancellation, the Defence Secretary Liam Fox used the Nimrod MRA4 procurement as an example of the worst of MOD procurement performance Ah those innocent days, before the QE carriers and the F35 made that look like mere pocket change.

I thought the consensus was that the construction of the carriers had gone really well.

They were supposed to have finished their sea trials by now.

Also they were supposed to be convertible to cats & traps at the drop of a hat, which would have allowed the UK to procure a non-BAe fighter to fly off them, couldn't have that...

Re: The de Havilland Comet changed aviation for good

#29

Post by lostlogin »

ak217 wrote: post #14
cdegroot wrote: post #10

My biggest "surprise" always is how little we have progressed if you just look at how the planes look and how fast they fly (6h11m NY->London in 1958, that's pretty much what they do today, not?). It seems like the airline industry got a lot of stuff just right the first time and since then just has been doing performance tweaks (where I take "performance" to be very broad to include things like safety, economy, ...)…

In 1958, the cost of a ticket was about 4x what it is today (adjusted for inflation but not earnings growth), flying was at least 20x less safe in terms of fatal crashes per departure, and consumed at least 4x more fuel per passenger-mile. Those are some impressive performance tweaks.

Those of us with legs suffer at least 4x more - The price has been at least partly compensated for by cramming more people in.

Re: The de Havilland Comet changed aviation for good

#30

Post by phillc73 »

aphextron wrote: post #22
phillc73 wrote: post #18

When I read the headline, I was really hoping this article was about the de Havilland DH.88 Comet.[1] That really was a beautiful aeroplane. [1] https://en.wikipedia.org/wiki/De_Havilland_DH.88

Not sure why the downvotes. I thought this as well. The DH.88 absolutely changed aviation in it's own way. The first fully monocoque, aluminum skinned, twin engine, variable pitch prop aircraft ever produced. We are still making aircraft with this same basic design to this day.

Many of the design elements from the DH.88 can also be found in the DH.98 Mosquito,[1] probably the most successful multi-role aeroplane of WWII.

[1] https://en.wikipedia.org/wiki/De_Havilland_Mosquito

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