"Just Jeepin'" (macintux)
02/12/2019 at 09:15 • Filed to: Planelopnik
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"Just Jeepin'" (macintux)
02/12/2019 at 09:15 • Filed to: Planelopnik | 1
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Haven’t had time to do more than skim this, and I’m sure ttyymmnn has covered this topic, but here’s a recent dive into the first commercial jet airliner and its demise.
http://www.greatdisasters.co.uk/the-de-havilland-comet/
WilliamsSW
> Just Jeepin'
02/12/2019 at 09:36 |
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The most interesting bit to me is at the end. Stresses at sharp corners weren’t well understood, so it’s quite likely that another aircraft manufacturer would have made the same mistake - DeHavilland was punished for being first.
facw
> Just Jeepin'
02/12/2019 at 09:47 |
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Demise might be a bit strong for a plane that was used regularly into the 80s, with some use continuing into the 90s. And of course the Nimrod, which was based on the Comet served until 2011.
Granted, the safety issues definitely caused them to miss their window, they could have sold a lot more planes if not for that, but the Comet also would still have been largely obsolete when the 707 and DC-8 arrived on the scene. The real problem they had was just that aviation technology was just moving so fast in that era. From the commercial debut in 1952, they only had 6 years until the 707 arrived on the scene, 7 for the DC-8 , and only 18 before the 747 completely upended the long haul market.
ttyymmnn
> WilliamsSW
02/12/2019 at 09:49 |
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Yes, Boeing learned a lot from the Comet. Woe to the early adopters.
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WilliamsSW
> ttyymmnn
02/12/2019 at 10:00 |
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“ First mover advantage” is highly overrated.
TheTurbochargedSquirrel
> Just Jeepin'
02/12/2019 at 10:04 |
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They went to pretty serious lengths investigating the failures too. They built a huge water tank to put the fuselage in and then repeatedly pressure cycled it for days on end. Hydraulic jacks were used to load and unload the wings to simulate flight forces. Why pressurize with water in a water tank? Calculations said that pressurizing with air would result in a failure with energy equivalent to detonating a 500lbf bomb in the cabin . The water in the tank was used to counter the weight effect of the water in the fuselage and also as a natural energy absorption method allowing the fuselage to fail without blowing into a million pieces . It’s amazing to see the lengths they went to in the 50s to do something that today would be done using computer simulations.
On a different note integrating the engines into the wings is so much sexier than modern hanging engine designs. It looks so futuristic while hanging engines just look industrial.
Chinny Raccoon
> Just Jeepin'
02/12/2019 at 10:08 |
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Inspiration for the lights on the X-Type of all things.
British Aerospace history is littered with failures grabbed from the jaws of victory.
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WilliamsSW
> TheTurbochargedSquirrel
02/12/2019 at 10:13 |
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That photo of the tank is cool- I’ve never seen it before.
There are a whole bunch of practical reasons why engines hang from pods now instead of being buried in the wing root. Agree that those intakes are very good looking though!
chaozbandit
> Just Jeepin'
02/12/2019 at 10:13 |
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ttyymmnn
> Just Jeepin'
02/12/2019 at 10:16 |
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Yes, the Comet got a mention in the July 27 edition of TDIAH in honor of its maiden flight in 1952. The article you linked had a fascinating Pathé News story about the first flight from London to Johannesburg. I lost track of how many times they had to stop for fuel. A BBC article from back in 1952 described the flight:
The total journey of nearly 7,000 miles is expected to take 23 hours 40 minutes, allowing for five stops at Rome, Beirut, Khartoum, Entebbe and Livingstone.
. . . .
BOAC’s regular flights to Johannesburg on piston-engine Hermes airliners take 27 hours and 55 minutes to reach their destination on a route 1,000 miles shorter than the Comet’s.
Interesting that the Comet only shaved four hours off the trip. But four hours is four hours, I guess. The Hermes four-engine piston airliner mentioned had a range of 2,000 miles, while the Comet 1 managed only 1,500. By the time they got to the Comet 4, range had more than doubled.
The BBC article also said that a round trip ticket for that London-Johannesburg flight was £375, which would be £10,599 today , or $ 13, 654.54 in US dollars. That same flight today, on a British Airways 787 , nonstop, would cost you £1, 534, or a bit under $2,000 US.
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ttyymmnn
> TheTurbochargedSquirrel
02/12/2019 at 10:54 |
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You can thank Boeing for starting to hang the engines under the wing, and it began with the B-47, which basically set the design standard we still use today. It’s another lesson they learned from the Comet.
Placing engines on the wing provides beneficial wing bending relief in flight. The further the engines are away from the fuselage the greater the wing bending relief so engines buried in the wing root provide little relief. Almost all modern large jet airplanes use engines in pods located a significant distance from the wing root for substantial wing bending relief. The pods are in front of the wing to help avoid flutter of the wing which, in turn, allows a much lighter wing structure. Locating the pod below the wing provides each engine with air undisturbed by the fuselage or wing. ( Wiki )
Spamfeller Loves Nazi Clicks
> TheTurbochargedSquirrel
02/12/2019 at 11:07 |
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I actually build systems for FEA, so I can tell you, a disaster like the Comet?
They don’t simulate it on the computers.
I mean, they’ll run FEA on parts, but doing FEA on a complete aircraft is not a reasonable prospect. That’s why NASA went to such insane efforts to recover every single scrap of Columbia and spent so long analyzing every single frame of footage from launch.
FEA also requires absolute known values. If you don’t know the exact values and metallurgy, your FEA’s no good. That’s why NASA also set up a cannon to shoot foam blocks at carbon-carbon leading edges. They had no data, no known values.
Comet investigations as a result, would have been done not too differently from back then, if it were to be introduced and happen today as well. They would have to do the same things to find the failure point (since they didn’t recover enough wreckage to identify it clearly.) And believe me, if they had run the window design from FEA? The entire investigation would change into “why was FEA wrong?”
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facw
> ttyymmnn
02/12/2019 at 12:08 |
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That route does add nearly 1000 miles vs. the great circle route, but I’m sure hitting those British dominated areas was seen as a positive vs. stopping in areas outside the British sphere.
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ttyymmnn
> facw
02/12/2019 at 15:04 |
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Where did you make this map? I was looking to do something similar, but the site I usually use wouldn’t do it, or do it this well. Also, I was watching the old Around The World in 80 Days movie with David Niven. What I was interested to see was how, as Fogg went east from London, there was never a place he stopped that didn’t have an English presence. Except America, of course. It gave a good idea of just how far the old Empire stretched.
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facw
> ttyymmnn
02/12/2019 at 15:34 |
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I used Google Earth Pro:
https://www.google.com/earth/versions/#earth-pro
Just used the ruler tool and then took a screenshot and cropped.
ranwhenparked
> facw
02/12/2019 at 19:50 |
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I mean, 114 commercial examples built over 15 years isn’t exactly a rousing success, but it certainly redeemed itself in military service.