Comments by "Keit Hammleter" (@keithammleter3824) on "When you turn a bomber into the first jetliner - 707" video.

At 2:51 the narrator says airlines couldn't understand the need for jets. Not true. By then they were getting pretty sick of the high maintenance costs and frequent failures inherent in a large 4-engine piston engine airliner. E.g., 4 engines each 28 cylinders means 224 spark plugs to fowl up. Given a typical plug MTBF of around 1000 - 2000 hours that means an engine miss-firing and a fire risk every few flights. The USAF had the same problem, driving them to jets. Changing all plugs after every flight was acceptable in wartime, but not in peace time. Also, jets are smoother and quieter. Aircraft are noisy things, but if you have never flown on a large multiengine piston engine aircraft, you don't know what noise is.
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@Sacto1654 : Utter nonsense. rounded windows had been standard on Boeing pressurised transports for years before the 707 or the Comet disasters. And on the wartime Lockheed Constellation. And the reason is that for sufficient strength the weight is less. There is nothing inherently bad about squared off windows - its a matter of competent engineering. All doors on pressurised airliners are square and they do not fail. This business about Comets and square windows was fluff put out by technically ignorant journalists who figured it was a good story they could sell to equally ignorant public. The Comet 1 had several crashes until permanently grounded for various reasons - faulty engine air intake design, incorrectly specified radio antenna that couldn't take the pressure differential, an inadequate riveting method, etc. All these fatal flaws were due to it being designed and engineered by incompetent inexperienced fools. It wasn't a case of other manufacturers benefitting from the Comet mistakes, it was a case of the Comet designers being too dumb and stupid to use what was already known by others. Finally, there was not A Comet crash investigation, there were about 10 of them (a couple of crashes reinvestigated when more debris was found), with some key findings kept secret until 2015.
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@vincentmaddux2302 The Nimrod looked like a Comet 1, but was completely re-engineered. The Comet actually went through 4 major revisions but of course the Comet 1 crashes made it unsaleable to the public, and thus only the RAAF could be persuaded to take it.
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@GreenBlueWalkthrough : That was the root of all the Comet problems - incorrect rivetting, bad engine air intake design, radio antenna not specified for pressure differential, etc etc, all of which led to the crashes. They were competent to design & engineer unpressurised wooden aircraft, but not large pressurised metal aircraft. It was a bit like someone who built a nice model aircraft out of balsa wood and a 1 cc model engine thinking he now has the experience to build a Cessna 150. One would think that DeHavilland engineers should have had enough ethics to say to management, "Hey, this is above us, you better poach someone from a company that has built pressurised metal aircraft."
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I went to an airshow over 50 years ago, organised by a glider club. There were lots of gliders, Cessnas, and other small single prop aircraft on display, a helicopter giving rides etc. The local airline based at the capital city 150 km away sent over a Fokker F28 (mid sized T-jet airliner) - a brand new one they had recently purchased. It amazed the crowd - pilot threw it around the sky like a dog-fighting fighter jet, though he didn't quite get it upside down. I remember the commentator saying something like "Captain so and so and his co are enjoying themselves with this one-time opportunity - they can't do this with passengers on board - the passengers would vomit and/or black out."
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@obelic71 : You are not wrong re political interference. The Brabazon prototype reportedly flew quite well but it was an aircraft that no airline wanted, due to it being specified by an incompetent government committee led by politician Lord Brabazon who thought air travel was only for the rich and famous who would pay lots of money for luxury and privilige. All governments must appoint committees from time to time to solve problems or recommend decisions, as elected politicians cannot be everywhere and cannot know everything. But post-war British governments seem to have excelled in appointing unnecessary committees (eg Brabazon - the aircraft makers if left to themselves would no doubt had focused on actual market needs as you alluded to) or stuffing committees with people least likely to understand the issues. However, I disagree that British aircraft engineering was world class. Pre-war aircraft were simple and not very large, so British firms could keep up. But during the war, the US developed advanced very large transports and bombers and this experience and funding gave them immense advantages that only very large firms could leverage. The Comet turned out to be a disaster due to bad design and engineering by an incompetent team, pure and simple. They were like an ordinary nurse suddenly taking on brain surgery. It wasn't a disaster because it was the first jet airliner, it wasn't really a disaster due to bringing to market in haste (though a bit less haste might have helped), it was a disaster because multiple fatal defects were built in from the start through sheer ignorance.
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The only thing amazing about the Comet is the multiple fatal flaws designed into it by a totally incompetent set of designers working in a company with zero relevant experience. Boeing learnt nothing from it - they had heaps of relevant experience to draw upon and used quite different construction methods and design features.
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"Many considered its design was weak." That is an enormous understatement. It was designed by an incompetent team and had multiple fatal flaws, as shown by eventual ground testing of a Comet donated by an airline.
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@obelic71 Bad rivetting was not the only problem. They ordered things like radio antennae from the usual supplier but didn't think to specify that they had to withstand pressurisation. So they didn't withstand pressurisation. Two Comets were lost because defective engine air intake design caused unexpected sudden loss of power on climb out.
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@alexander1485 : Much the same thing as far as stresses go - in fact stress is a little bit higher with sides different length to top and bottom. The term "square" in engineering means "at right angles" or "squared up in shape", not always "all sides straight and equal length.".
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@77ice11 : The second part of which of my various posts here? You are repeating a urban myth started by sloppy British journalists writing before all the various reports into the various Comet accidents were made publicly available. I suggest you read up on each of the Comet 1 accidents - each was due to a different cause. Of the 13 Comet 1 accidents, metal fatigue was identified as a factor in only 2. If you check the various large pressurised transports that Boeing and other US manufacturers had sold and were in use before the first Comet was even built, you should quickly realise you have it completely wrong. This urban myth that Boeing learnt from the Comet is based in part that the 707 came several years after the Comet. However, Boeing had pressurised all-metal experience going back to the B-29 bomber, in service during WW2, and with pressurised all metal large airliners in service before the Comet. Boeing did put out marketing that wing-root mounted engines was a bad idea (and it is, from both a structural failure mode and air intake points of view, but has handling advantages), but since they had never ever done such a thing, that in no way implies Boeing learnt from the Comet. Fatal Comet accidents include ADF antenna not specified for pressure and blew out in flight, sudden unexpected loss of power during climb out due to faulty engine air intake design.
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I certainly do not work for Boeing. I am a retired large diesel engine dealer engineer, and before that an electronics engineer based in Australia
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@77ice11 : Your descent into personal terms shows that you are incapable of contributing relevant facts. This was never about British people, nor about British engineers in general. My posts are about specific design flaws in the Comet, and the fact there were multiple and different fatal flaws in the Comet is proof that the particular engineers involved were incompetent. You cannot argue that they were breaking new ground in these flaws, as most related to pressurisation, and pressurisation was not new. ADF antenna (which necessarily must penetrate the hull = they ordered them from their usual supplier but didn't think to specify that they were for a pressurised aircraft; a riveting process unsuitable for a pressurised aircraft was used. Etc etc. Rather than being a case of other manufacturers benefiting from Comet experience, it was a case of the specific Comet designers being ignorant of what was by then well known in the industry, as the company had until then only made unpressurised wooden aircraft, even though such aircraft were by then standard elsewhere. Apart from the lessons learnt by British investigation authorities to lift their game (later investigations changed the findings of the first investigations), there is another important lesson in the Comet for all engineers, British and others - it is unethical to take on a task for which you have no relevant qualifications or experience. people can die if you do.
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@77ice11 It's not disputed that Boeing slipped up badly on 737 MAX - a failure of FMEA. However even the 737 MAX looks very safe compared to the Comet. There have been only 2 fatal losses of 737 MAX compared to 13 fatal losses of the Comet 1. The 737 MAX had a single fatal flaw. The Comet had multiple fatal flaws. The 737 MAX was grounded temporarily and then cleared for further use, and is to continue manufacture, as only a very minor change to airspeed detection was required - the aircraft structure is fundamentally safe. The Comet 1 was ordered permanently grounded and manufacture ceased, as the structure and fittings were not safe - the aircraft needed a complete redesign and a major change in manufacturing process. I don't doubt that less Boeings will be sold to airlines now, as Boeing have damaged their reputation, but that is another issue. You are the one with bad manners and the first and only one to descend into personal terms in this thread. You continue to imply that the Comet designers had no prior knowhow available to them - that was the case only within De Haviland. Your comment about CAD/CAM is irrelevant, as even where it was identified that metal was overstressed in the Comet, it was found to be stressed well beyond limits accepted as standard in the British aircraft industry at the time the Comet was designed. In other words, they failed to correctly apply what was already known. The ADF antenna blow out is not in any way imaginable to be due to not having CAD/CAM, or even someone counting on their fingers. It was simply due to someone in De Haviland ordering antennas from their usual supplier without telling the supplier it was for a pressurised aircraft. If De Haviland had requested pressure withstand capability, their supplier would no doubt have supplied a compliant antenna (probably at extra cost), or informed De Haviland they should go to someone who can. Pressurised aircraft were nothing new at the time.
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@77ice11 : If I am so unconvincing, why are you so upset about it? You can't give facts and just make stuff up. An interesting comparison between the Comet 1 and the 707:- Comet 1: 12 placed in service averaging 40 seats each and killed 411 people. Boeing 707: 865 built averaging 170 seats and killed 3039 people, Thus a seat the Comet 1 was likely to kill 0.85 people. A seat on a 707 was likely to kill 0.02 people. The Comet 1 was41 times as lethal. Actually, its much worse, because each Comet 1 was in service for only a year or 2. Boeing 707's remained in service for up to 20 years or more. No wonder the Comet 1 was the ONLY airliner type to be ordered permanently grounded. With each different Comet crash due to a different cause (one was lost due to tail spar failure, nothing to do with windows, metal fatigue) it is abundently clear the designers were incompetent.
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@77ice11 Of course there were more 707 incidents/accidents. THERE WERE VASTLY MORE 707's IN USE. You are like saying a GM Chevrolet car is mare dangerous than the Rambler, because there are far more Chevys in accidents, ignoring that Chevys outnumber Ramblers by huge numbers. The B707 WAS a far better plane. Another factor is that 707's lasted long enough to be operated by less ideal airlines as second and third hand planes. The Comet 1 operation life was so short and in so few numbers is was never anything than a new aircraft operated by premium airlines with an otherwise excellent safety record. If you are a potential passenger, what matters too you is the probability of the aircraft you fly on killing you, not how many others get killed in the same accident. So what matters to you is deaths per passenger kilometer. On that basis, the lethality of the Comet is stark - it stands alone. If the Comet 1 was any good, any good at all, how come the British government (which had a vested interest in keeping it flying) permanently banned it from passenger service? The Comet 1 is the only western airliner so banned, ever. Even the Douglas DC-10 was allowed to fly after the doors and a couple of minor issues were fixed. As far as I know, there was only one other airliner banned forever from passenger service - that was the Russian "Concordski" TU-144, though it was allowed to operate as a freighter for urgent freight, and it was apparently regarded as too expensive to operate in passenger service anyway, limiting its passenger application to heads of state and top government officials.
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@77ice11 : You are the one who just doesn't get the point. You talk about public data, but you don't understand the data. Sure, various western airliners have been grounded - until the problems were identified and corrected. Then they were cleared to fly again. Of all western airliners, only the Comet 1 was permanently grounded. For instance the Concorde, although another British design aircraft with safety standards well below things like Boeing 747, is not permanently grounded - but it doesn't fly because the 2 airlines that flew it no longer see it as profitable. The Yak-42 was indeed grounded due to a single flaw, but later returned to service. The problems with 737 MAX are clearly embarrassing for Boeing as it is a clear failure of FMEA as I previously wrote, but only one fatal flaw has been identified - that is far and away better than the Comet 1's multiple fatal flaws. The Comet 2, 3, and 4 don't count as no airline put them into wide use, and they had a lot of changes wrt Comet 1. The Nimrod doesn't count - it is a military plane (actually a Comet 4), and the military do lots of things that are necessary but too risky for airlines. It's choice was influenced by political considerations, and using up Comet 4 hulls that could not be sold to any airline. The 737 Deamliner doesn't count because no hull losses or fatalities occurred. This idea that other manufacturers learnt from the Comet 1 mistakes is an urban myth, propagated by sloppy journalism. For the facts, go back and read my previous posts. Boeing 737MAX - returned to service 9 December 2020. Boeing 787 - no fatalities and no losses. The 787's problem were batteries and engines supplied by others - nothing made by Boeing was defective. production limited by the impact of COVID. Concorde - cleared to fly again in 2003 but the operators decided to retire it for commercial reasons. Yak-42 - cleared to fly again October 1984. Still in service. Most Yak-42 incidents not due to any defect in the plane. DC-10 - cleared to flay again 1980, production continued until 1989. DC-6 - grounded 1947 but cleared to fly again 4 months later. Remained in service in small numbers until 1990! Constellation - cleared to fly again, in widespread airline use from 1949 and production continued until 1958. Made obsolete by the 707. It is worth noting that the Constellation, designed in 1943 and used as a military transport during WW2, was the first high altitude (and thus fully pressurised) airliner - giving lie to the urban myth that the much later Comet 1 provided new knowledge against American knowhow.
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@77ice11 : It would be difficult for me to be interviewed for a job at DeHavilland, given I was born in Australia, and have remained there ever since. You live in fantasy land. Various Comet 1's crashed for different reasons: Incorrect radio antenna not designed for pressurisation, engine air intake design faulty leading to sudden unexpected loss of power, faulty riveting, etc. etc. Look it up. None of these design errors have anything to do with American practice before or since. You can't even get your facts right. Comet 4 came out in 1958. The B707 first flew 1957 and its design goes back to 1954. The permanent grounding of the Comet 1 by the British Govt is important - it signifies they had no faith in it. No faith that there were not other as yet undiscovered faults in this aircraft clearly produced by a company incompetent to do so. And they had a huge political and financial incentive to give it every chance they could. Britain was broke then, they were desperate to get export income. Your equating the safety of the 707 with the Comet is utterly ridiculous. In a sense, the Comet 1 was a lesson in how to make a better aircraft - in the limited sense that it told the British authorities that jet transports were beyond DeHavilland and they needed to be watched VERY carefully. More importantly, it taught the British accident investigation authority that they needed to get far more thorough and professional than they were. Indeed, they initially blamed a couple of Comet crashed on pilot error, and later were forced to realise it was not pilot error at all. Claiming pilot error was a cop-out that never solved anything. The forced improvement in British accident investigation, and the lesson taken on in other countries, is the single important lesson from the Comet 1 disaster, applicable to all aircraft types. Perhaps this distinction between poor aircraft and poor accident investigation is too subtle for you. I suggest you thoroughly read and seen to understand sources before you post again. You have plenty of sources and search terms in my previous posts.
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