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The de Havilland Comet changed aviation for good

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Re: The de Havilland Comet changed aviation for good

#41

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, ...)…

Air friction goes up with velocity squared, so a small decrease in speed gives you a relatively large savings in fuel. It's just too expensive to fly fast.

There's a sweet spot where fuel savings, customer satisfaction, and capital costs meet, and it's at a much lower speed than engineers are capable of producing.

Re: The de Havilland Comet changed aviation for good

#42
post #39
post #33

Earlier quoted context omitted.

I've often argued that the root cause for loss of empire, was the best and brightest of a generation was left on Flanders fields. The best and brightest of the ruling class at the time was simple used up as cannon fodder, its also the cause for the decline of the aristocracy too.

And this was why postwar Germany lost its scientific and technical advantage and is now a ruined backwater - wait, no. Germany not only lost technicians and an aristocracy in WW1 and 2 but murdered those of its Jewish population that were not able to escape. Survivors defected to the US like Von Braun. The loss of empire was after WW2 not WW1, and partly due to the US insisting (Suez) and partly because it became mor…

I agree with your assessment, pjc50. All major European nations lost most of their privileged/gifted young men in WW1 and WW2, not just UK.

Re: The de Havilland Comet changed aviation for good

#43
post #9
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.

OK, I get it. Thanks :) They are very cool looking.

FWIW, other turbojet airliners had larger intakes. E.g Tu-104 (which, coincidentally, was propped by Comet's fall, becoming the only jet airliner in service for a couple of years):

http://i.imgur.com/L4KLas2.jpg

Re: The de Havilland Comet changed aviation for good

#44
post #7

Such a wasted opportunity. Around the same time, the UK was throwing away its leadership in computing too. Weirdly, both ended up in Seattle.

Classic case of first mover disadvantage. Their failures helped Boeing learn some tough lessons about metal stress, and Boeing got many aspects of the fuselage of their first jet liner so right they're still used on the latest generation of the 737 which will finish in the top two biggest selling aircraft this year. Of course, us Brits learned tough lessons of a different kind with the Concorde: no matter how brillia…

Airbus is one of the companies that will be hit hard by brexit. Arguably the single market is what made Airbus possible to begin with.

Re: The de Havilland Comet changed aviation for good

#45
post #27

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 c…

Could be worse, at least jet fuel isn't hydrazine. It is possible to extinguish a small fire with jet fuel. Don't try this at home.

F16's carry hydrazine as emergency fuel to maintain control in case of loss of power.

Re: The de Havilland Comet changed aviation for good

#47

Earlier quoted context omitted.

Classic case of first mover disadvantage. Their failures helped Boeing learn some tough lessons about metal stress, and Boeing got many aspects of the fuselage of their first jet liner so right they're still used on the latest generation of the 737 which will finish in the top two biggest selling aircraft this year. Of course, us Brits learned tough lessons of a different kind with the Concorde: no matter how brillia…

Airbus is one of the companies that will be hit hard by brexit. Arguably the single market is what made Airbus possible to begin with.

Airbus is based largely in France and Germany. BAE will likely suffer more as a contractor.

Re: The de Havilland Comet changed aviation for good

#48
post #7

Such a wasted opportunity. Around the same time, the UK was throwing away its leadership in computing too. Weirdly, both ended up in Seattle.

You might be interested in James Hamilton-Paterson's book, "Empire of the Clouds", which is about the glory days and subsequent decline of Britain's aviation industry.

Amazon link: https://www.amazon.com/Empire-Clouds-Britains-Aircraft-Ruled...

It's been a while since I read it, but one of the factors he talks about is echoed in the article, about the airplane being built "by engineers" -- it's an improvement on being built by marketers, of course, but it's only part of the right answer. Hamilton-Paterson's book talks about British aviation engineers' deafness to important feedback from pilots, and the additional role the British class system played. Engineers were mostly educated people from good schools, and pilots were mostly farm-boys who'd been recruited by a desperate nation during the war and then advanced professionally in their RAF service. When conflicts between them percolated up to managers, who were also educated men from good schools, the engineers tended to carry the day, whether or not they were right.

The portion of the article where the pilots talked about the lack of force-feedback on the new hydraulic controls, leading to several over-rotation accidents on take-off, reminded me forcefully of this -- obviously I don't know about that issue specifically, but it's exactly the kind of thing that might have come up in flight testing where test-pilot concerns might have been ignored.

The other piece of British aviation decline is government priorities -- aviation innovation is expensive and not profitable in the short term, so the UK decided to hedge their bets by becoming junior partners with Europe. British engineering and technology remains excellent, but it's not leading. Instead, the UK focused on financial services.

The contrast with France is particularly striking. Unlike the US, France was similarly ravaged by war, but the French government basically decided that aviation was a national priority, and supported it accordingly. Today, they are senior partners of European aerospace, and even have a large independent jet manufacturer, Dassault.

Re: The de Havilland Comet changed aviation for good

#49
post #47

Earlier quoted context omitted.

Airbus is one of the companies that will be hit hard by brexit. Arguably the single market is what made Airbus possible to begin with.

Airbus is based largely in France and Germany. BAE will likely suffer more as a contractor.

http://www.airbus.com/company/worldwide-presence/airbus-in-u...

Re: The de Havilland Comet changed aviation for good

#50

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…

In the past couple of years I've been updating my CAD skills, one of the most fascinating discoveries for me was how fillets and rounds distribute the stresses that affect sharp corners. First-year engineering stuff, sure, but pretty amazing to learn what a difference even the smallest details can make.
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