The Engineering Error That Killed 99 Passengers
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- Опубліковано 21 тра 2024
- This plane kept on crashing, it took 3 crashes and 99 lives to finally have it grounded and thoroughly investigated. The investigation revealed a very import engineering law. The de Havilland Comet crashes shone light on the importance of considering fatigue when it comes to structural components that undergo repeated loading and unloading. As a consequence of the failures, the Paris-Erdogan Law was discovered which is widely used today. Without the de Havilland Comet, our understanding of fatigue and fracture would not be at the level that it is today.
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References:
[1] D. R. Jones and M. Ashby, Engineering Materials 1, Elsevier, 2018.
[2] P. A. Withey, "Fatigue Failure of the De Havilland Comet I," Engineering Failure Analysis, vol. 4, no. 2, pp. 147-154, 1997.
[3] J. M. Gere and B. J. Goodno, Mechanics of Materials, Cengage Learning, 2013.
[4] D. Anderson, I. Graham and B. Williams, Flight and Motion, New York: Routledge, 2011. - Наука та технологія
There was another factor not mentioned in this video. The stress tests of the hull were made after an initial test that loaded the structure with much more stress than it would ever experience in real life. This over-stressing caused changes in the material before cracks could grow and then it slowed their growth, when compared to identical structures that were not over-stressed before the cycling began. As in many cases, it is a chain on events, that add up to cause disasters. Every chain link contributed its part: The change from gluing to riveting, the unknowingly invalid stress test results of the partial frame because of material changes in initial over-stressing, the flawed statistical approach. What was not the cause is the design of the windows in the first place. Main causes were technological changes, unknowingly false stress test procedure and the mentioned statistical error.
Yes that's absolutely correct! The overloading was listed in nearly all of the reports/papers that I read about the case. I had that part also included initially but decided to drop it out later on since it needed to go into plasticity and how overloading the metal actually resulted in a severe overestimation of the fatigue life. I felt like this needed a deeper explanation and left it out for another video, possibly a more generic video only on fatigue. Kind of regret saying in the video that "the test was valid", there is a huge asterisk attached to that sentence. This comment deserves a pin, thanks for opening the discussion. Would be great if other viewers also jump in and share their knowledge/opinion of the case. Cheers!
@@TheEngineeringHub I am looking forward for that video. Maybe you should have mentioned it briefly, telling that it will be further discussed in another video. You produce high quality videos that I enjoy a lot. Brings back many memories from decades ago, when I was studying this stuff.
Initial overload - you mean, warm prestressing.
It's worth reading Neville Shute's autobiography 'Slide Rule'
Yes, the Neville Shute who wrote 'no highway' and yes, it was a warning about Comet and metal fatigue.
Shute was fired from de Havilland and gagged using the Official Secrets Act after writing a memo predicting a mid-air breakup due to misuse of rivets, so he emigrated to Australia and wrote the book
Another point not touched on in this video is the lack of training given to production line staff.
Comet was the first pressurised aircraft de Havilland produced, but not the first production pressurised aircraft - the design team closely studied the Lockheed Constellation in order to assess pressurisation and life cycle issues. They _knew_ riveting was problematic and had avoided it. De Havilland management overruled their use of adhesives and welding "because they knew best" (which they didn't) and in the highly stratified British industrial world of the time (complete with an actual "executive dining room" which had silver lunchtime service for free, vs worker canteens where workers paid for everything), engineering/design staff were utterly prohibited from interacting with production line staff
The production staff had never built pressurised aircraft before. They didn't know that punch riveting caused stress cracking AND they were overtightening rivets, which exacerbated the issue (this is why Shute to write his memo). When the designers discovered this stuff (to their abject horror) they were forbidden from instructing production staff about correct ways to rivet on pressurised aircraft and threatened with criminal prosecution under Britain's State secrets acts if they breathed a word about anything. It's in this atmosphere that Shute wrote his book, carefully avoiding mention of cracking starting around rivets when discussing pressure-cycle metal fatigue causing the "reindeer tail" (hint: santa claus) to break off his fictional aircraft (hint: tails aren't pressurised)
This managment incompetence and intransigence was all covered up for years. The windows were de Havilland management's blame deflector, tossing the designers and engineers under a bus to avoid corporate manslaughter charges being laid against the executives and minimising the compensation claims from victim families (had the underwriters found out, de Havilland's liability insurance would have been voided)
The same Dunning-Kruger management 'superiority' attitudes and approaches which caused Comet (and the implosion of the British auto industry) have continued to pervade British society though and are a large factor of the driving force behind Brexit. Repeated lessons simply haven't penetrated the right skulls and "Made in Britain" is frequently still regarded as a warning label to this day due to the tendency to produce great designs with glaring botchups and then toss customers under a bus rather than deal with the issues properly - there's a reason that commonwealth countries which escaped the shackles of the Ottawa agreement usually moved from 80-90% of technology imports being British to having it less than 10% within 5 years
Comet isn't just an engineering disaster investigation story. It's a microcosm of the entire "British problem" that still persists because unlike aviation, the underlying issues have never been addressed and stamped out.
Indeed, that over stressing became the basis of the fatigue analysis industry. Cold working, shot peening, hole filling, forging…all things adding compressive stress around discontinuities in structure before it is flight loaded.
As someone who had a career lifetime in jet engine design, I frequently comment on aerospace issues such as this. In doing so, I have noticed a "fundamental flaw" that often affects contributors on the other side of the pond - and the problem? They exhibit a form of collective and selective amnesia when it comes to problems with aerospace products of US origin, while being very quick to comment critically on similar products from elsewhere. So can I suggest that we consider just a small selection of such problems?
I have already commented on the Lockheed Electra, but that aircraft went into service with a fundamental design flaw, which resulted in two (or was it three?) crashes in 1959-60. It cost Lockheed millions to rectify the problem and no new Electras were sold.
Closer to home, I clearly remember the crash of a DC-10 in France in 1974. That was down to the cargo door latch mechanism not being properly secured. There was a degree of human error but, nevertheless, the original design had a fundamental flaw, which permitted that error.
The crash of a DC-10 at Chicago O'Hare in 1979,was primarily down to a totally unapproved method of installing an engine using a forklift truck. Nevertheless, the design of the engine mounting arrangement was flawed, in that it was unduly sensitive to damage.
Sadly, one of the most publicised failures of US aerospace engineering happened in 1986, with the loss of the 'Challenger'. That was down to the fundamentally flawed design of the O-seals in the SRBs, compounded by a fundamentally flawed decision to launch in unusually cold weather at Cape Canaveral. Tragically, there was also the Columbia disaster in 2003, which could be ascribed to a flaw in the design and/or application of the insulating foam, a lump of which shed and damaged the wing. The problem had been experienced before, but it appears that a calculated risk was taken, with disastrous consequences. As an aside, I would mention that my son, during a visit to the USA, actually met one of the astronauts who was subsequently lost on that mission.
Moving closer to home again, there was the Kegworth disaster in 1989: I happened to drive past the scene two weeks after. The CFM56-3C engines of the B.737-400 went into service with a fundamental design flaw. The new design of fan had only been tested at ground level, not at altitude, where the blades went into a flutter mode. This initiated fatigue cracks, which resulted in a fan blade failure. Again, there was a degree of human error in shutting down the wrong engine, but the root cause was that fundamental flaw.
I have previously mentioned the B.737-Max8 crashes, which were down to a succession of fundamental flaws. The first fundamental flaw was an aircraft being fitted with engines for which the airframe was never originally designed. This changed its flying characteristics, which resulted in Boeing introducing the Maneuvering Characteristics Augmentation System, aka MCAS. .
This system was flawed in itself, resulting in the loss of Lion Air flight 610 and Ethiopian Airlines flight 302, with the loss of 346 lives. There was also a fundamental flaw in Boeing's introduction of MCAS, in that pilots were unaware of the system. There were scurrilous attempts to blame the pilots, but the loss of life was entirely down to Boeing's failures. In some parts of the world, Boeing management would have found themselves behind bars.
I must also mention the failure of a Virgin Orbit satellite launch in January of this year, which was to be the first such launch from the UK. There were immediate and snide remarks on UA-cam by uninformed individuals in the USA, who commented critically on British engineering. However, the technology was all-American: the rocket launcher that failed was designed and built in the USA.
In conclusion of my lengthy piece, I must mention that I have discussed Rolls-Royce's problems with their engines elsewhere, which seem to get extensive coverage in the media in the USA. Yet again, I have the impression that equivalent problems with American engines do not get the same level of coverage. There was, of course, the well-publicised issue with the Trent 1000 engines on the B.787, which resulted in a large number of aircraft being grounded. However, I was not aware of the same level of publicity when United had to ground their whole fleet of B.777s for over a year, because of problems with their P&W engines.
WRT shuttles the fundamental problem was that the orbiter was mounted side saddle where falling ice/foam could hit it and where if anything went wrong with the boosters/main tank there was no escape possible
Neither disaster would have happened if the orbiter was stacked as per the original dyna-saur and shuttle designs. The massive growth was a direct result of USAF demands for large capacity AND single orbit return to base - ironically resulting in a ship the USAF tested and then refused to use again because it was fundamentally unsafe-by-design
I was a structural design engineer on the F14 program for couple of years. One of the few structural issues we had with the Tomcat was the ‘notch’ on the lower centerline designed into the major bulkheads. The notch in the bulkheads were needed for the recess that was there to accommodate weapons mounting. The originally designed pass through had a rectangular shape, machined into the lowest flange and protruding into the lower web area of the fitting. The bulkhead located at the rear of the wing box and near where the tail hook/MLG mounted would develop cracks in the upper corners of the notch during fatigue testing on the dynamic rig. The shape was changed to an arch, but was never completely satisfactory from the analysts’ perspective. It never failed or anything, but was inspected regularly as the fleet aged. Sharp corners, large changes in section area, never work out well.
Every engineer should know that any change in section is a weakness, and the sharper the change the weaker it becomes. That is why tapers and circles ( or parts of circles ) are good and squares are bad
And with the tools and knowledge available, not available to Comet designers, who were using slide rules and perspex models, as well as rig testing, there was still a spate of F15 (not F14) aircraft where the nose and cockpit separated from the aircraft when in flight.
My father worked for Dowty and De Havilland (primarily on hydraulic systems) and was directly involved in the investigations. I still have many photos from the period!
First, fatigue was not the primary cause of the disasters, although it was a consequence. Nor were the square(ish) windows. The problem was a miscalculation about the magnitude of stresses (aka forces) experienced by the fuselage. This was uncovered during the post-crash investigations. Put simply, the fuselage was over-stressed (compared to anticipated loads) and fatigue failure was inevitable. Note that metal fatigue was reasonably well understood by the time the Comet was designed.
The water tank tests were dramatic but substantially a waste of time; the problems were already identified from an analysis of wreckage.
The actual origin point of failure was a redesigned radome cover. The original was found to perform poorly with the installed equipment and was enlarged to compensate. Unfortunately additional bracing to the enlarged dome was not added, which in turn lead to vibration that accelerated wear / fatigue.
The square windows were certainly not wanted by the original designers and yes, that was a management/marketing decision. However, the windows were not the cause. The cracks spread from the radome down towards the port door and then along the side of the aircraft, taking the path of least resistance which happened to be the windows. During stress testing the cracks actually bypassed the windows entirely on several occasions with tears just above the wing root. Indeed the square windows were only replaced because it was easier (and cheaper) to manufacture oval windows.
Although fractures leading from the windows were discovered in grounded aircraft, none were likely to cause a mid-flight disintegration. Rather, by the time the crack had propagated down from the radome, aerodynamic forces were certain to rip the aircraft apart within just a few seconds.
To imply that fatigue was not understood and was the primary cause of the disasters is completely misleading. The fatigue was the consequence of stress miscalculations and it was in the area of stressed fuselage design that most progress was made. Unfortunately, the response to the Comet disaster was to over-strengthen the Comet's airframe far beyond what was necessary; which reduced the economic efficiency of the aircraft.
Boeing enjoyed playing into the disaster for obvious reasons, but quietly went about strengthening their own aircraft (aka the 707). I personally flew the Nimrod (the military derivative) and the aircraft was insanely over-engineered. Sadly there would be Nimrod failures later down the road, but that was due to expediency and rank incompetence in poorly designed modifications.
The hoop stress of a shell is very easily calculated, with both positive and negative pressures on the fuselage. There was much experience with submarine hull design. So what was the error?
Agreed that fatigue failure was quite well understood, that is why ships have port holes.
"The fuselage was simply overstressed"... So the original assumptions of loading were in error? Loading caused by what? Storms?
Thanks for sharing!
Hi David. Good work. I believe the salient factor in changing to oval windows was that they gave an immediate visual impression to non-technical observers that "something big had been changed". It was the minimum "damage control marketing psychology" to launch the comet 4. Imagine the distrust among potential purchasers if they'd left the square windows in. Cheers, P.R.
Thx for sharing to this detail… amazing !!! Today what is key is the scatter factors … analysis 8x life test 5 times life for EASA and 4x FAA and then perform the test upfront such that the test article is leading the fleet in lab and in real life !!
Today
I was lucky enough to fly on many Comets ( 4b's as I recall ) in the 60s on European routes as a kid with my parents ( BEA ). Growing to love flying and travel, I have now at the age of 59 flown on almost every type of commercial aircraft from the late 60s till now, including flying by Concorde to NY from London and back on 4 occasions in the 90s. Also took a 'fun' flight on a DC 3 about 10 years ago. What was my 'fav' aircraft? - obviously, the Concorde, followed by Comet, 707, 747, Tristar, A380, and A350 in that order. I do feel blessed! The ones I hated...........Dassault Mercure, 737, DH Dash 8's and ATRs.
When pushing the technology envelope, success in Engineering almost ALWAYS comes from a long line of failures. Build, break, repeat. Even with computer modeling, this is still critical, as the models are based on what we know, and it's usually what we don't know that kills us.
That's true but breaking is best done during the development phase, without killing people. The problem is that politicians see development breakage as a failure even when it's intentional (to see what actual stress limits are, etc)
The result is fisacos like Japan's original few space launches (everything exactly to spec, but failed horribly) or Starliner
let's not forget that it was Rolls Royce overenthusiastic claims about the RB211 and covering up how badly things were going which spelled the business doom of the L1011
Although taken out of commercial service, the Comet flew on as the updated and modified Hawker Siddeley Nimrod until 2011.
Hi. The last comet 4's to fly passengers were for Denmark's "Danair" about 1980. They then went into the usual "old age" niche of freight only. Cheers, P.R.
In Robert Sterling's 1992 book, "Legend and Legacy: The Story of Boeing and Its People", it was noted that thanks to their extensive experience with large military jets like the B-47 and B-52 that Boeing already knew about the problem and had engineered fatigue crack propagation OUT of the prototype Dash-80 and production 707-series from the start with the extensive use of crack arrestors. Boeing also wisely used a thicker skin that could better accommodate having a recess drilled in for the rivet heads to sit flush for aerodynamic reasons. (Standard aerospace practice at the time.) The Comet used punch riveting on a thin skin to recess the rivet heads by compressing the skin which itself created micro-stresses before the planes even left the factory. The 2nd generation Comet had both elliptical windows and a thicker skin to accommodate standard aerospace riveting.
And still F15's lost their cockpits in flight, and Galaxies needed new wings, and 707's lost engines, and 747 pressure bulkheads fail. The Comets thicker skin was allowable due to engine improvements, and if given a choice would have been used from day one. But then performance and range targets would not have been met. Riveting was a production 'let', the design was originally to be bonded.
Crazy to think about all the structures we rely on today that are built on failures of the past!
Really nice video branching out from your typical topics but keeping that great technical perspective 👍
"The cutting edge of new technology is stained with the blood of those who tried it first", I don't know who coined that phrase but it is never more true than here. Other companies learned a great deal from De Havillands experiences.
Unfair to blame the designers. After the cause in the early Comets the problems were fixed and it went on the be very successful. It was the worlds first commercial jet airliner. Have we learned all the lessons? Well, there’s this thing called the 737 Max that isn’t really a 737 at all… so it appears there are still lessons to learn…
@@ShaunieDale it's also expressed as "All aviation safety standards are built upon tombstones"
In far too many cases, warnings were studiously ignored by "the powers that be" until people died and the result is a mish-mash of patches masquerading as a functional system
Human factors is a _huge_ part of aviation training these days, but it needs to be applied across entire organisations, not just the operational parts.
Thank you for debunking the "Square window" cause argument.
Hmm, not debunked, I’m looking at a picture of the 2 ADF aerial windows, and there are 5 cracks propagating through the corners of those square windows. They are labeled by the investigators “direction of propagation of main failures.”
The confusion arises from people confusing the ADF aerial windows on top of the fuselage, with passenger windows on the side of the fuselage. The ADF windows are nonetheless windows.
i've seen a number of vids on this topic and this is the first one that even mentions hoop stress. all the others emplasised the square windows. +1 i too would like to see a fatigue & fracture vid.
I have seen a documentary which shows an imprint of the failure site displaying shear lips under the microscope. The offending pieces of metal are in the custody of the Science Museum.
The 'square windows' stuff was a distraction tactic by de Havilland management (in conjunction with the British government) to dodge corporate manslaughter charges stemming from rotten assembly practices caused by failing to educate line workers about pressurised designs and additionally overriding the designers' decisions on fixings which had been made for safety reasons - to save money and poo-poohing objections raised about stresses.
De Havilland management were directly responsible for the Comet losses, then threw their engineering/design staff under a bus in order to save their own skins
@@miscbits6399 If the corporate brass put the blame on sguare cornered windows, they should have been all imprisoned.
Even ships have port holes.
@@BasementEngineer It Wasn’t because of the square windows! The cracks Actually started in the forward Cabin Roof! At one of the two ADF Ariel Installations! My late father flew comets for several years!
@@pikachu6031 I agree with you!
My post was to point out that if the corporate brass was willing to blame the crashes on the "rectangular" windows, they should be imprisoned for knowingly implementing problematic air craft design features. After all, they acknowledged that the windows were problematic.
De Haviland paved the way for the rest to follow. But , unfortunately didn't reap the benefits. It was a beautiful plane, just not fully developed when it flew and no one knew that because this was uncharted territory.
Yes we should all take a boat across the Atlantic that takes a week one way because everyone has 3 months vacation lmao, maybe instead of airmail they should have just stuck with Pony Express
The Comet is seen today as an example of how not to build a jet airliner... and a reminder that Britain was decades behind in aircraft technology
@@WilhelmKarsten ~ The US Military Industrial Complex is owned by people who profit from war including all the wars fought for centuries. These people own all the world governments and corporations, wars are planned. The UK lost their Empire because of WW2, in the last 100 years they lost their dominance in industry and manufacturing too. I believe this was all planned. It seems the perpetrators want to remake (or great reset) the world, where Europeans, UK, US and Western Civ will be phased out. But eastern owned governments and corporations will dominate.
@@WilhelmKarsten More an example of how not to manage a company building airliners - a lesson which Boeing has clearly forgotten
Britain wasn't behind in aviation technology at the time. It was decades behind in management attitudes, which were still heavily rooted in classism and largely suspicious of those with actual scientific or engineering qualifications, because they hadn't been to the "right" school, etc
Parachuting in managers who don't know anything about the business they're in (based on social or family ties) is a toxic British and American trait, which has been exacerbated by parachuting in management which only has experience in accounting or sales with little understanding of the underlaying factors
@@alanbrown397 Britain's class system is certainly archaic and backwards but it was decades behind in aircraft technology.
de Havilland was still building biplanes when companies like Boeing, Lockheed and Junkers were building all-metal pressurized aircraft.
In fact de Havilland was still building jets made primarily from wood and fabric when it built the Comet, a jet airliner that also made use of obsolete materials and techniques.
Britain would not have a supersonic aircraft until 1954.
My university lecturer told me they also made a mistake with the initial stress test. They started the first few thousand cycles at a lower pressure, allowing the frame to bed in slowly, a luxury not afforded to the production models.
That's correct and when Neville Shute flagged the issue (and the riveting) they compounded it by overpressurisiing the hull, which work-hardened the thing, making all tests past that point invalid
Shute was driven out of the British aviation industry. His documentation of the fiascos going on inside R101 development are interesting too - showing that Comet wasn't exactly an isolated case but a manifestation of a systemic problem that persists to this day across British industry
The actual failure zone in the recovered wreckage is kept in the Science Museum, South Kensington. I watched a documentary where they obtained an imprint of the shear lips, and the sheer lips showed up very clearly in the microscope. I have a personal interest in the Comet, because when I was an infant, my parents took me on it. We are all still alive.
The comet 4 was still in commercial use into the 1970s. I flew on one on a package holiday to Benidorm.
Please do make a video on fatigue & fracture and plasticity & overloading causing false stress testing!
Pressurised aircraft are still successfully being built with rivets. To say that this method of construction is inherently dangerous is incorrect. The lessons learned include “fail safe” design which is a design method that seeks to prevent long running cracks forming and keeps them localised and the importance of correct hole prep and rivet installation. You can add the importance of proper inspection and maintenance to that.
Great video friend. I would love to see more on Fatigue.
Thanks for your useful information, I really appreciate it 👍
everything is tested to failure. except the bean counter who places more emphasis on corporate profit than human life. 737 max.
True, but corporate structure, not just a single accountant.
That is one of the huge flaws with bean-counters - their insistence on cutting costs to the bone. After that, they start actually cutting the bone as well.
@@davidb6576 But that is the structure of most corporations.
This phenomenon is echoed in reverse as well: The (mostly) titanium Lockheed SR-71 _Blackbird,_ now retired, had much better fatigue longevity than initially anticipated.
Each mission at speed, generating up to 600° F. from aerodynamic heating at flight up to Mach 3, annealed the structure, thus mitigating stress concentrations.
Wow that's great! I never even thought about the heat generated from the air friction at such high speeds before. It makes sense, very interesting!
Darryl Greenamyer assembled an F104 to use for record breaking. In his ultimate record attempt the timing equipment malfunctioned. He was not able to make another attempt because of the heating of the airframe had degraded the metal making another attempt too dangerous
@@truthboomertruthbomber5125 Aluminum is an entirely different metal than Titanium.
@@truthboomertruthbomber5125 ... and, IIRC, failure of the landing gear(s) to deploy, leading to ejection and total loss the plane.
@@brianhiles8164 I think this was on a later flight.
A passenger of the Comet (BOAC Flight 781) that crashed off the Island of Elba was Australian writer and WW2 war correspondent Chester Wilmot.
His book about Tobruk is still a must read for any military history buff.
Chester was also deregistered by blamey for questioning the colour of aussie uniforms and had to leave australia
@@johnwilson455 Hasn't he also quite publicly called Blamey incompetent?
@@GeorgHaeder Yes he did and he ordered aussie soldiers to engage with isolated Japanese garrisons with many useless deaths
@@johnwilson455 I see, I need to get more books about that theatre of operations. Most of my books are about the Battle of the Atlantic and North Africa/Italy.
@@GeorgHaeder you will need to search,for the last 2 1/2 years of the war lots of aussies died in useless battles with the japanese. nothing worth writing about. we were excluded from the Americans offensives..
I am interested in a fatigue video.
Let's get this straight: the "square" windows did not cause the problem. It is a myth that has been comprehensively debunked over the years - and yet it keeps getting regurgitated. The windows were rectangular with sensibly radiused corners,. The failures did not originate from the corners of the windows, but the popular press (ignorant as ever) propagated the myth.
A couple of years ago, I attended an online lecture on the subject, which provided a thorough analysis of the real problem: it was down to the way in which the rivet holes were punched. It has been mentioned by another contributor, but the fuselage test section, upon which the predicted safe flight cycles were based, was over-pressured before being cyclic pressure tested to failure, which misled DeHavilland's engineers.
I cannot remember the details (and cannot find my notes of the lecture), but the over-pressure modified the incipient cracks in the rivet holes in some way, which resulted in the test section failing at a much higher life than the actual airframes.
And what of the "most unsafe/dangerous" label that has been slapped on the Comet 1? What of the Lockheed Electra? And what of the Boeing 737 Max8?
Yes, that's exactly what the video was focused on. The square windows were not the root cause of the crashes.
It was the fact that the holes were punched rather than drilled. Punching the holes resulted in local hardening and a higher likelihood of subsequent cracking than would have been the case with drilled holes.
@@craigfreeman9280 The Electra had a fundamental design problem that potentially put any Electra airframe at risk when it flew. It cost Lockheed millions to redesign and strengthen the wings. As a result of the crashes, the Electra failed commercially, but the Orion is still flying in military service today. The Comet was similarly fixed in its later marks and the Nimrod flew on for years in RAF service.
@The Engineering Hub Yet despite your video and numerous other rebuttals the square window myth still persists.
For your information, I have now found my notes of the lecture that I attended: it was actually 'live', not online. You can find the recording of the lecture on UA-cam: it was given on 29 April 2019 at the University of Bristol, by Professor Paul Withey of the University of Birmingham. Look for 'The DeHavilland Comet Disasters - A Story of Fatigue.'
You are correct, but for a long time, those square windows were given much of the blame, so that is what people remember, and often refuse to let go of.
A very well put together and informative video. Just a couple of minor corrections and observations if I may: My late father flew the Comet 4b for many years with Channel Airways of Stansted England. From him, I know the Comet story very well indeed. All the water tank tests and flight test, conducted with a Comet 1, were conducted after the Elba Comet tragedy and not Before the Comet 1 entered service in 1952. Only the normal flight testing and stress testing was conducted before being presented to the British Board of Trade (now the Civil Aviation Authority CAA) for their approval for a Certificate of Airworthiness! The Actual Problem started in the Cabin Roof, at the sight of the two ADF Ariel housings. The cracks ran forward and aft along the roof and then down to the corner of the square windows. Yes, the square windows was a poor design, but it Was NOT the primary cause. This was in the Riveting Technique employed that caused tiny hairline cracks to develop over a period of time. Note: Once most of YP had been recovered off the coast of Elba, it was flown to RAF Farnborough. After it was re assembled, they noticed in particular, the Cabin Roof Was Missing! De Havilland Aircraft Corporation did Not release a Knowingly unsafe aircraft into service, far from it. And it is important to note that three years of Stringent and Exhaustive ground and flight testing was conducted, after the first flight at Hatfield in 1949, flown by De Havilland’s Chief Test Pilot Group Captain John “Catseyes” Cunningham, just four years after the end of the Second World War! The Comet 1 enjoyed a whole year of fine service before the first, Calcutta crash, exactly a year after the inaugural flight, which was caused by an Inflight Breakup after flying into a severe thunderstorm and not pressurisation problems. After the Elba Comet disaster, there was yet another lost en route. After this crash, ALL Comet 1’s were grounded until the tank tests confirmed the cause. Note: Tank and Unpressurised Flight Testing of a Sole Comet 1 were only conducted after the withdrawal of the type’s Certificate of Airworthiness (C of A). None of these potential design flaws and weaknesses had been known about prior to the Comet’s entry into service. Only After the cause of these terrible tragedies had been established, were all Comet 1’s permanently grounded! The work on the new Comet 2 had been allowed to continue, with redesigned Oval windows, and with a strengthened fuselage. All Comet 2’s subsequently entered service with RAF Transport Command in 1954, none were operated by any civilian airlines. The Comet 3 was a single unit demonstrator, built solely for Marketing Purposes for the up coming Comet 4b and 4c, which entered into Airline Service in 1957. BOAC being the launch customer. The only difference between the two was that the 4c had extended range with integral wing tanks, being slightly slower than the clean wing 4b! The Nimrod was a completely different animal, being built from the ground up, based on the Comet 4c airframe, including new Rolls Royce Spey Turbojets, replacing the RR Avon as used in the Comet 3, 4b and 4c. The Comet 1, 1a and Comet 2’s were all powered by the same Rolls Royce Ghost - Centrifugal Compressor Jet Engine! Hope that straightens out a few Disingenuous Comments and miss understandings regarding De Havilland Aircraft, their Comet’s Design Team, Engineers and the Wonderful and Groundbreaking De Havilland Comet. The World’s FIRST JET AIRLINER!!!
I think you may need to rewatch the video. The video agreed with everything you said. The water tank test were done after the crashes, and the square windows were NOT the main root cause of the problem, exactly like the video says. The problem originated from the ADF window, also what the video says. Not sure what the massive corrections are?
@@TheEngineeringHub Thank you for your reply. You need to specify that these tests were All conducted After the Elba Comet crash. And After the Comet 1’s had all been grounded. Many of the comments are saying that the Comet was a poor design, and that these tests weakened the fuselage structure, resulting in an unsafe aircraft being released into service. This is absolutely incorrect and I think you could stress this in your video (no pun intended). I didn’t mean your video is inaccurate, just some context improvements and inclusions of more background and dates would certainly make it more enjoyable. And stop people from getting hold of the wrong end of the stick!
Thank you Sir. I’ve edited my initial comment for you, as I felt I was a little unfair to you with my introduction. I hope you’ll like my changes to it. Looking forward to some more from you!
We owe Jimmy Stewart a debt of gratitude to finding what was happening! :)
That plane’s visual design with the jets in the wings minus the square windows is the most beautiful ever.
Why minus the square windows?
Best looking passenger jet ever. Connie was best looking propeller engine.
BOAC 781....RIP Crew & Passengers of ALYP.
It could be argued that the 737 MAX is the most dangerous. What is the death count for each?
And by the time the 737 max came to exist Boeing had more than 50 years of jet airliner type design & build experience which makes the 737 max incidents significantly different to what was happening in the 50s.
Thank you so much for detailed explanation. The problem is that some underdeveloped countries are doing deviations in the procedure of periodic fatigue tests. In my opinion, mandatory compliance must be put in place across the globe to establish harmonization of testing SOPs and verification of compliance through audits. Are there ISO Guidelines?
A recent study of parts of the Comet still available, says part of the problem lay with the manufacture of the window frames and the reinforcing doublers at the corners.
The rivet holes for these parts were punched (by machine), not drilled. This led to microscopic cracking around all the holes, which ultimately led to the failures.
The Comet and the Nimrod continued to fly with square windows (in the roof) to the end.
Wrong! All Comet 1’s were permanently grounded after the YP disaster! The Comet 2,3 and 4 had OVAL WINDOWS! The Nimrod only had a few Oval windows!
@@pikachu6031 Look at a plan view of the aircraft. The Navigation windows are just at the rear of the cockpit.
@@everTriumph Yes, I know they were. I don’t really understand what you mean but here’s an explanation to help you: The Two Square Windows, positioned aft of the Cockpit Roof of the DH-106 Comet 1, where there purely for RDF/ADF Equipment. These windows were removed in the subsequent Comet 2’s and Comet 4’s. They also didn’t feature in the Royal Air Force’s BAC Nimrods either. Strangely enough though, one Comet 4, that was owned by the Aeroplane and Armament Experimental Establishment (A&AEE) Based at RAF Boscombe Down in South West England, did feature the two ADF Windows for some reason! Anyway. This was where the first two cracks in the cabin roof started. The third crack started in one of the corners of one of the Square passenger Windows on the port side of the fuselage. In the roof, where the ADF windows were located, one crack ran forward from the forward ADF Window, and the other ran aft, from the Aft ADF Window along the length of the cabin roof. The crack in the corner of the passenger window ran upwards and met the crack in the cabin roof running aft. The cabin roof failed first, followed by the sides of the forward fuselage. The failure of the fuselage was exasperated by the resulting Explosive Decompression, which totally destroyed the fuselage. All this took place in a split second and killed everyone onboard Instantly. Those poor people all suffered broken necks and burst lungs as they were violently ejected from their seats into outer space. The cause of the failure was found to be Cracks, caused by RIVETS in the ADF Aerial windows and the square passenger windows. The Square windows were found to be a poor design and also contributed to the failure of the fuselage. In the Comet 2, the ADF windows in the roof were removed and the passenger windows were replaced with much stronger Oval ones. The MkI Comet’s Fuselage simply wasn’t strong enough to withstand the constant pressurisation and depressurisation cycles. The Comet 2 Fuselage was greatly strengthened and as a result, the Explosive Decompositions that resulted the tragic loss of Three Comet 1’s, never happened again! All of the Comet 2’s were commissioned into RAF Service with RAF Transport Command. Only One Comet Mk3 was produced. This was used primarily as a demonstrator, for the coming DH-106 Comet 4! Hope that helps you out a bit!!
Also interested in a fatique video. Thanks!
This is the nearest to the truth.
The design and testing issue was that fracture mechanics related to cyclic loading and structural fatigue was not all encompassing to say the least. deHaviland did carry out 18,000 repeated loadings on a test airframe (static loading) that "removed any doubt about the fatigue life of the cabin". That's all very fine if the cabin was constructed to the highest levels of integrity. But the cabin (fuselage) was constructed by overlapping sections of plates mostly of thin (22 SWG) by rivetting not reduxed bonding. Any holes drilled and cut countersunk (as they were) for rivetting removes thickness that resists air loading (force/area) and should have at least been dimpled. The original source of the cabin failure was the forward escape hatch (window) forward lower and aft corners where stress raisers on cut countersunk rivet holes (caused burrs by a blunt rose bit) cracking forward to frame 13a and aft to frame 16. The window remained in place but the frame sprung outwards from the bottom two corners. It was concluded that DH did not make use of calculations in an attempt to arrive at a close estimate of stress distribution near the corners of the cabin windows. They used a sample of the fuselage 24-26 ft long by 3 ft wide from which they projected a life of 10,000 pressurised flights. The sample was not holistically represented as it was supported by a stiff bulkhed where many other fuselage panels were not. But what they did or could not legislate for was standard of workmanship and that cut countersinking 22 SWG reduced the skin thickness substantially and the resulting burr stress raiser reduced the safe life by over a half. My background was in establishing the first Def Stan 05-123 Repair Design Office capability in the RAF and was the fixed wing critical repairs liaison engineering officer for all three services working with design authority repair design and stressing departments. The actual reports on G-ALYP (Jan 1954) and G-ALYY (Apr 1954) available still I think from HM Stationery Office .
THE FIRST AND STILL THE MOST BEAUTIFUL COMMERCIAL JET AIRLINE.
THE MOST UNSAFE PLAN EVER BUILT on your thumbnail is a disgraceful trivialization of the issues surrounding this early jetliner.
Relax keyboard warrior
Are there any Comets left in functional condition? Such an historically important aircraft deserves to have a few preserved in aviation museums.
When my uncle was a small aircraft engineer apprentice aged 14, they sent him inside the wing tanks to look for clues why Comet crashed. My grandma said he used to come home green with sickness.
Hi neuralwarp. Me too! Not the comet, but inside a Fokker F27 wing tank to paint it with anti corrosive goo. I protested, but the engineer said it was "a long established tradition since 1750 that in British territories apprentices could be sent up chimneys to clean them, so what's not to love about a sweet-smelling gas tank"?
His gift of the gab got to me, so up I went, but not before obtaining a reversible vacuum cleaner from No. 4 hangar's stores and arranging it to deliver forced air ventilation into the tank. The engineer complained I was holding up the trim-shop. I said I was holding on to my ability to breathe. The union shop steward (the most unloved man in the company), said I was striking a blow for the workers' conditions, and I was allowed to sit at his table at smoko after that, along with all the other stirrers.
My aviation career did not reach lift-off, fell like a comet, and crashed and burned, but I consoled myself by parachuting into academia, where mistakes don't have mortal consequences. Every so often I have a cheap sherry or port of aviation jet-fuel quality to remind me what generations of apprentices have had to endure. Cheers, P.R.
I worked in the Stress office at Hatfield in the late 1970’s. This is generally a good video although there are a couple of things worth mentioning. Firstly it was not cost that decided in favour of rivets rather than Redux bonding of window reinforcing doublers. Order books were full and riveting was simply quicker . The section in the video where you suggest the fatigue sample was not statistically representative rather misses the point. The mistake that was made was that the cabin “over pressure” test specimen which passed and appeared to be undamaged, was subsequently used for the fatigue test. You rightly mention that unknown to the Engineers, the punch riveting process left tiny micro cracks in the surface of the holes. The cabin over pressure test sample had these micro cracks in them and during the test cycles the material strength around the crack tip was increased by the “work hardening” process.
The crack development during subsequent fatigue test was therefore slower than would have been the case on a virgin sample and lead to an over optimistic test result. Ralph Hare was one of the original 9 members of the DH Mosquito design team and a real Gent. In an interview I have seen he lamented his decision to allow Manufacturing to rivet rather than Redux but its important to know that the enquiry found that DH were operating at or beyond the state of knowledge at the time. There are always risks in being “ the first” introducing new technology. When I subsequently moved to work in the car industry at the Rover Group, we were “ fast followers”
Yes, you are absolutely correct. In fact, this was discussed here in the comment section. The statistical error is not the full picture, but I decided not to include the plastic deformations and consequences of that as it may get too complicated for an average person. I know now that I should have gone deeper into that. Cheers, and thanks for the extensive comment
For the most part, very good article. However, pressurization was not a new thing in 1952. The Boeing 307, which came out in 1940, was pressurized, the Lockheed Constellation, which came out in 1947, was pressurized, and the Boeing 377, which came out in 1950, was pressurized, as was the DC6, which came out in 1947. Also, DeHavviland used a thinner than normal skin for a plane that was not only pressurized, but flew at a very high altitude, making the problem all the worse.
The Comet flew higher (and faster) and had a bigger pressure differential (lower outside pressure), hence more stress, than piston engined aircraft. Only military jets at that height then.
@@everTriumphThat's completely false, Junkers Ju-86 was flying pressurized to over 52,000 feet during WW2.
Boeing had more experience with pressurized cabins than any manufacturer in the world.
The Boeing B-47 had a much higher cabin pressure differential (9.8 psi at 40,000 ft.)
de Havilland was still decades behind in aircraft technology.
Gorgeous design lines though
Excellent, thanks for posting this. The Comet could have dominated jet civilian aviation...
Very unlikely
de Havilland was a company in steep decline in the late 1940s... the Comet was a high risk gamble in an effort to save the company from going under... and it backfired spectacularly, completely destroyed the company.
You can see the cockpit section of one at the Canadian air and space museum.
I always thought the Comet is one of the most beautiful passenger jets. Pity it turned out the way it did.
i wish modern airliners had engines integrated into the wings like the comet did, it looked so cool
I agree, the Comet was a beauty! I wonder if they moved away from that practice in order to make it easier to do repairs or full replacement of an engine if necessary 🤔
@@TheEngineeringHub Its a couple of reasons. First I think is safety, if an engine explodes it would probably take out the engine next to it. Second it makes the wing pretty thick which limits performance. Third the spars get very complicated because there are big holes in the middle of your wing and you have to support around them. The B-47 flew in 1947 and Comet in 1949 so Boeing got to get a lot of data on podded engines and I am sure that Boeing studied the Comet. Also well done video.
A podded engine is easier to maintain and change but more importantly it is more sacrificial and less likely to compromise the airframe if it suffers a catastrophic failure in flight.
@@TheEngineeringHub Yes, it makes maintenance and repairs considerable harder when the engines are integrated into wings. What I hate about today's planes is the close together windows. They allow the airlines to move the seats closer together, and I demand ROOM.
On podded engines the attachment arrangement can be designed so that a significantly out of balance podded engine can shear its fixings & drop off leaving the rest of the aircraft to carry on hopefully.
An interesting advantage to podded engines mounted mid wing is the fact that during flight, when the wings are carrying the weight of the fuselage part of the aircraft, the engines are in relatively low wing stressing positions & are acting also as a kind of wing span counter balance & provides wing drag structural stress loading reduction by canceling some of it as the engines push the wing forwards relative to the fuselage which all results in lighter wing structures & over all a useful reduction in the weight of the aircraft.
I think it is more than a little unfair to call the Comet "The most unsafe aircraft ever built", as in your thumbnail. The Comet was a world aviation first, and as such was a very steep learning curve that all future manufacturers took advantage of, without having to do the groundwork. There were 13 fatal crashes and 426 fatalities, but 5 of these were CFITs controlled flight into terrain, 1 was instrument failure, 1 was weather, and 1 was a terrorist bombing. Only 3 of the 13 crashes were due to structural problems.
The first Comet flew commercially in 1952,and later variants continued to fly commercially until 1981, so a 29 year life for the type. Also it continued to fly militarily in it's Nimrod variant until 2011, so 59 years in total.
I thought that the Avro Canada jetliner was the first jet airliner?
Reminds me of No Highway In The Sky with James Stewart and Marlene Dietrich
In 1957, the possibility of a Comet crash was a tension-plot-device in Nevil Shute's novel, "On the Beach".
Let’s not forget that this plane was designed without any computer calculations or simulations it was purely designed by hand and brain power
But hand and brain power are not what decided to use a thinner than standard skin. I bet it was COST CUTTERS.
@@michaelbenardo5695 It was the chief designer. With the thrust and consumption of the infant jet engine weight had to be saved and volume found for fuel to meet the performance goals. Better engines removed the need for the weight saving. Production's lack of faith in Redux bonding altered the original build method to riveting. Whether the bonded design would have had the same, or different problems? Who knows.
Was the Avro Canada jetliner ahead of the Comet?
It was essentially at the same time, first flight of the Avro was a few days after the Comet's first flight. The Avro got cancelled due to military aircraft work taking precedence at the time.
*_Former Boeing Everett... over 1 million rivets are used on aircraft today..._*
All aircraft manufacturers learned from the Comet Disasters. Whenever you make over a million holes in the Aluminum Skins used for aircraft, strict compliance for Safety is not questioned today.
Every rivet has a part number. Every drill-bit used to make holes has a part number. Every jig and fixture used to make holes has a part number. If a hole is drilled off vertical, it becomes elongated. That hole has to be re-drilled with a larger drill-bit, which has a part number. The 'fix' has to be documented.
Many people wonder why rivets are used instead of welding. Rivets allow for expansion when fuselages are pressurized. They allow for thermal expansion. They allow the fuselages to contract as they are de-pressurized. Welding would cause additional stresses over wider areas of Skin. Seams between panels overlap or use double pieces of Aluminum. Sealants are used to fill gaps to keep air pressures within specs.
*_You guessed it... even the Sealants have a part number..._*
The problem was that the Comet wound up using a thinner than standard skin. That is what aircraft manufacturers learned that you just can't do.
@@michaelbenardo5695 Thanks for comment
Ironically the Comet is closely related to the later RAF Nimrod recon aircraft,it was quite a successful plane in its own right.
Erm....
Nimrods _are_ Comets.
Lots of modifications in them (such as the massive canoe fairing) but they're built on what was originally a production Comet airframe
The first 2 nimrods were built using the last 2 commercial comet airframes that were on the production line.
What finally grounded them was the issue that the production line was essentially a "craft build" process and each aircraft produced had unique dimensions requiring individual tweaking of components to fit. By the time the last generation of Nomrods was being built they had to be rewinged - which was done to precise dimensions for the test article, only to find that the newly produced wingsets didn't fit any of the other fuselages.
Faced with rapidly mounting costs for what was supposed to be an easy job the British government cut its losses and took the cheaper option of ordering entirely new-build aircraft
The Nimrod rebuilds could have been salvaged, but would have essentially been a "new" old aircraft for at least twice as much as simply starting over from scratch
(I know the UK is currently using Rivet Joints almost as old as the Nimrods. These are an interim measure until the P8s are ready. It was still cheaper to do this than keep going with the Nimrod airframes)
The Nimrod is a completely different aircraft
@@miscbits6399The Nimrod is a completely different aircraft from the Comet, they share no significant parts or assemblies in common.
If they had just watched Jimmy Stewart in "No Highway in the Sky" (1951) they would have known that fatigue failure was a definite possibility.
The length of time at the cabin or fuselage is pressurized is the difference. On an actual flight, it’s pressurized for longer than it would be for a test.
98.765% of the cause of the potential problem is the change is stress not any steady stress. If it can stand the repeated increase & decrease in stress to to pressurisation cycles then the length of time pressurisation lasts for during 1 cycle becomes largely irrelevant.
The Comets airframe was unsafe and any duration or number of cycles.
These were brand new aircraft suffering from metal fatigue in less than 1 year in service
de Havilland used aluminum skins that were too thin and brittle and Comet 1lacked proper rip-stop doubler joints between panels and the fuselage reinforcement hoops were too weak and spaced too far apart to prevent cracks from joining up with adjacent panels
Ductile materials when cycled and stretched beyond their limits become brittle especially in sub-zero temp conditions and eventualy crack. Lack of understanding in strength of materials was definitely a factor with the Comet design and not just the square windows... otherwise, modern aircraft doors should not be square shaped too. 😊
Many materials do not suffer a ductile-brittle transition - Aluminium is one of them.
Although aircraft doors are squarish the corners have quite a large radius.
@@ShaunieDale
Yep you have a point there 🙂
The trouble with being the first is that you are going into the unknown, experience is hard won...
Didn't stop Boeing from being first, they got it right
@@WilhelmKarsten Boeing learned a great deal from the Comet, nobody had realised that repeated to the great height that comet flew, and being the first pressurised passenger aircraft that metal fatigue was a problem.... Just like pretty much everything else Britain developed the science and Americans made money from it - the yanks really are the cows tail where science and engineering is concerned.
@@chrissmith2114 Junker invented all-metal, pressurized aircraft in 1930... when d-H was still building wood and fabric biplanes like the Dragon Rapid.
Boeing introduced the first pressurized airliner in 1938.
The Junkers Ju-86 was flying pressurized to over 52,000 feet during WW2.
Both the Royal Aircraft Establishment and de Haviland received technical data on metal fatigue in pressurized cabins from the B-29 program during WW2.
Prior to the _Comet Disaster_ thousands of pressurized aircraft were already in service with Lockheed, Junkers, Boeing and Douglas... none suffered any catastrophic in-flight structural failures before or since.
The Boeing B-47 flew faster, higher and with a higher cabin pressure differential (9.8psi)
Nothing was learned from the de Haviland Comet Disaster, the Boeing 707 flew in July 15th 1954, before anyone, not even de Haviland knew what caused the crashes.
You look like a fool right now.
@@WilhelmKarsten
@sandervanderkammen9230
They might like to provide sources for their outlandish & fictitious claims?
They should attempt to understand
Comet 1s flew after 1954.
Comets flew until 1997.
Comet derivatives flew until 2010.
DH construction methods were industry standard practice or were much better & far more advanced.
A Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin large airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
My father’s close friends ,a Swiss national,was on the second one.
The thumbnail leading into this video is out of line. The Comet was a transitional technology well tested and successful until the aircraft accumulated flight cycles where the flaws became apparent. Unfortunately people lost their lives, however the circumstances were no different of design issues that have occurred up until present day passenger aircraft design.
The Popular Science Magazine cover of May 1950 was unfortunately prescient.
Hehe, and now a much more lnteresting case of cyclic failures.
Because of the time that the pressure difference lasted in the test versus real life?
There were insufficiencies with the tests for sure. But the biggest problem was the fact that they only had 1 sample. Each plane is inherently different and naturally some would be strong and some weak. If you test only 1 of something, it is impossible to claim that that is the strength to expect from all other samples. Maybe just by accident you selected a very strong sample and set the bar high for the expectation of the strength for the rest of the samples (basically what happened). When we test to figure out the strength of a material, we do dozens or hundreds of tests to make sure we get a better idea of where the weakest sample lies and then design accordingly.
Steady pressure load application time lengths for the fuselage skin & structure would be unimportant if safe stress levels for the materials are not exceeded.
Dehaviland did not carry out water tank pressure cycling tests on a significant number of large fuselage sections in order to obtain statistical info on cycles life differences data for the Comet 4 design for example, there was no need on such a complex structure things average out and as long as the materials & methods were uniform & adequate all aircraft produced would have similar life expectancy to the single test prototype as specified.
This video has a fair amount of nonsense included.
The Comet was the Pioneer! It made it safe for jet airliners to come.
The only lesson learned from the Comet was that de Haviland should have stuck to building planes out of wood
Comet was the worst engineering failure in the entire history of commercial jet aviation history.
Comet is the only jet airliner to have its airworthiness certification PERMANENTLY REVOKED and it has the highest loss rate and fatalities statistics of any jet airliner
@@sandervanderkammen9230
They should attempt to understand
Comet 1s flew after 1954.
Comets flew until 1997.
Comet derivatives flew until 2010.
Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
@@petemaly8950You are a liar. COMET 1 46% LOSS RATE.
AIRWORTHINESS CERTIFICATION WAS PERMANENTLY REVOKED
They opted to use a very thin metal skin in the early Comets, what could possibly go wrong?
They also punch cut the rivet holes, big mistake.
@@sandervanderkammen9230
They might like to provide sources for their outlandish & fictitious claims?
They should attempt to understand
Comet 1s flew after 1954.
Comets flew until 1997.
Comet derivatives flew until 2010.
DH construction methods were industry standard practice or were much better & far more advanced.
A Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
@@petemaly8950COMET 1 HAS A 46% LOSS RATE
@@petemaly8950Comet 1 had its airworthiness certification permanently revoked
70 years on and we still talk about the Comet, I wonder if in 70 years time we shall be talking about the Boeing 737 Max ?
Interesting video. Id heard it was from fatigue but didnt know much more.
The statistics also have second fault…? There are TWO cycles on each flight? Planes goes up. Planes goes down.
Ground... 45000ft ... Ground. One cycle.
Sorry I could not see that the windows were square in the opening scene but.
Another possible contributing factor could have been thermal cycling / age hardening of aluminum.
Did they test at ambient temp only?
They were pushing boundaries at the time. Boeing can’t use that excuse with the 737Max.
Also, they used a thinner than standard skin, which is unforgivable. Boeing tried to make the pilots relay on stupid computers, which would over-ride what the pilot wanted to do, no matter what.
I dated a girl back in the late fifties, it turned out her Father was on the Comet that went down off Rome, She was a lovely girl who took the tragedy bravely.
I agree with everything except “De Havilland company, we would not enjoy the same reliability and comfort today”, because sooner or later the airline industry would have found out, it is like undermining the human intelligence that they just can’t learn without making mistakes. Nice video anyway.
I agree with you completely, sooner or later we would have figured things out. The comment was meant to give credit to de Havilland for getting out of the comfort zone (piston driven engines) and implement something new and better which forced the whole industry to adapt or else become obsolete. In essence, I think that's true for any discovery/technological advancement. If Newton didn't discover the Law's of Motion someone else would have eventually done it. Thanks for the comment! Cheers!
The only lesson learned from the Comet Disaster was aircraft manufacturers could no longer be trusted to conduct their own crash investigations, the financial stakes became too high in the jet age, de Haviland was pressured to ignore warnings and cover up mistakes.
@@WilhelmKarsten
They might like to provide sources for their outlandish & fictitious claims?
They should attempt to understand
Comet 1s flew after 1954.
Comets flew until 1997.
Comet derivatives flew until 2010.
DH construction methods were industry standard practice or were much better & far more advanced.
A Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
@petemaly8950 *HI Peppa Wiggles!* *Please name a single British company that still makes British jet aircraft in the UK?*
@@TheEngineeringHub For the sake of historical accuracy, it wasn’t DH’s initiative, the initiative derived from the Brabazon Committee. It was unfortunate that the BC selected DH, if one of the British companies that had experience with large metal aircraft construction had the task, likely the result would have been quite different. But that’s only a supposition in hindsight of course.
No one knew about metal fatigue up until the comet was launched. It was only after a few flights that it began to appear. Then once they worked out what it was and why the aircraft manufacturers all over the world took steps to eliminate it from their future aircraft
Nobody knew as much about it as was soon learned, but to say "nobody knew about metal fatigue" is simply not true. The 50s was not the Dark Ages.
That's a completely false narrative, metal fatigue was well-known and understood at the time.
Both the RAE and de Havilland received technical data on metal fatigue in pressurized cabins from the Boeing B-29 program during WW2.
D-H had very little experience building large pressurized aircraft made from riveted aluminum alloys and was still building jet aircraft fuselages primarily from wood and linen fabric
Typical engineering practice (today) would obtain a safe life from the test result by dividing by a safe life factor of 5. So the 18000 cycle test result would be a safe life of 3600 cycles. Maybe this practice was born out of the Comet accidents ?
But also today's planes use a much lower pressurisation (hoop) stress than the Comet. I think the Comet hoop stress was about 20ksi, and as I remember the RAE report wanted to place frames every 10 inches (ridiculous for windows) rather than adopt a hoop stress typical of today's planes ... 12-15 ksi.
Yeah, and those punch rivets ... I wonder what riveting the B707 used ?
I recalled a couple of things from the documentary film (I cannot recall the title). One is that the engineers found the curious embossment of half pound coin on the outer side of fuselage near the tail, which led them to speculate the fuselage failure due to the pressure. Another was that they spoke in a very British depreciation (paraphrase) : "ironically, we the British became the world's first aeroplane crash investigators".
The main thing that is concerning: the engines inside the wings. We have seen the catastrophic effect of uncontained engine failures, puncturing the wings and fuselages as well as severing the cables and pipes in the modern aeroplanes. If that happens to Comets, there's no guarantee that the pilots would be able to safely fly and land the crippled planes. That's why the engines are mounted on the pods to give them extra safety edge.
I think a Nimrod went in because of an uncontrolled engine fire within the wing. It's on UA-cam somewhere.
The shape and size of ghosts (centrifugal turbines not dissimilar to a turbocharger) made them too clumsy to pod. They didnt spin at the very high rpm of axial flow turbines and the stresses were correspondingly less
In-wing engines were realised as potentially problematic but the slab front of a windmilling ghost would have been a major issue. By having the air intake in the wing leading edge the parasitic effects of a dead engine were vastly reduced.
Nimrods took advantage of this by shutting down 2 or 3 engines once on-station to prolong patrol duration
The nimrod fire was a result of poor air-to-air refuelling pipework design and maintenance. An interbank line broke and dumped fuel over a hot exhaust, which ignited. The engines themselves didn't fail - just the 1950s airframe decisions around them
That fire was essentially the end of the line for Nimrod. It was assessed that there was no practical way of making them safe from a repeat event
The government attempted to press on regardless but quickly discovered that no two comrt airframes hand the same dimensions as they were hand-built on wooden frames. Anything measured and built on one airframe wouldn't fit any others - new wings had been constructed for one and replicated via cad engineering, only to discover that they wouldn't attach to the others
That was the point where the project was cancelled. Smashing up the airframes was extreme but prevented any more attempts to throw more money at a black hole
In 1956, what, exactly, is a 'half pound coin'?
Is that 'half pound coin' weight or currency? If weight, I know of no UK coin produced for normal circulation that weighs 1/2 lb. If it is currency, there was never a 10/- coin. The largest currency coin in the UK was the Crown (5/-).
As an aside, I have flown in Comet 2, Comet 4b and Nimrod variants of this aeroplane - all beautiful aircraft.
I'm guessing they didn't include any openings in the section they tested? Huh ok I missed the mark.
The statistical error thing seems possibly incorrect. If the various types of testing & design showed a safe service life of 18000 flight pressurisation cycles for example there is no chance that it would be possible that for some reason some of the aircraft coming out of the production facility could be liable to catastrophic failure at approx 3000 cycles for instance.
Check out the pinned comment; there is a quick explanation. You are right there are reasons why it performed so high. Otherwise it would have to be like a 3-4 sigma event, which is very unlikely
@@TheEngineeringHub
It almost definately wasn't a statistical error thing.
I venture to suggest that none of the aircraft to the design & produced using the methods used would have come out of the factory with a safe life of 18000 cycles or a safe life anywhere near 18000 cycles even if they'd made 10,000 of them.
To be clear -
So it seems for example that the safe life would have been say 1234.56 (+/- a max 12.34% variabillity) cycles maybe & that would have been for every aircraft produced if they didn't deviate from the set design & manufacturing methods, you wouldn't expect to get one now & then come out of the factory that had a safe life of 12,345 cycles & would be expected to disintegrate at around 23,456 cycles (+/- up to 12.34%)
@paulpaul9914 that section that achieved 18 000 cycles was first stress tested above its yield capacity as a part of an allowable stress test. They decided to reuse that section also for the fatigue tests, which was a mistake. Stressing the section above the yield strength caused plastic deformations that halted any crack growth and actually improved the fatigue life. This method of increasing the fatigue life was not known/researched at the time, so they incorrectly concluded that 18 000 was the expected life. If they had pre-stressed all planes before commissioning, then that might have been the actual life, but since they didn't, the results were what they were. In summary, they improved the fatigue life with prior tests without knowing about it.
@@TheEngineeringHubthanks indeed, I know about the excess / high pressure test stress relief issues giving a false fatigue test result for the test fuselage section but all that is not related to any statistical error problem. I still state - there was no statistical error.
@@TheEngineeringHub
Just looked at the statistical error thing which seemed odd, due to that I'm going through the entire video with a fine tooth comb later.
It really was a beautiful airplane.
Not for the 426 people killed, the Comet remains the worst jet airliner in history
@@WilhelmKarsten
@sandervanderkammen9230
They might like to provide sources for their outlandish & fictitious claims?
They should attempt to understand
Comet 1s flew after 1954.
Comets flew until 1997.
Comet derivatives flew until 2010.
DH construction methods were industry standard practice or were much better & far more advanced.
A Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
3:21 It wasn’t just the change in pressure during the cycle but the rate of change. The Comet zoomed to its cruising altitude so quickly that the cabin expanded more quickly than expected. This further increased the stresses especially at the square window corners. Boeing engineers faulted DeHavilland for the square windows.
The Comet had about 1/2 the power to weight ratio of a 737, and I've never heard of anyone accusing the 737 of being a rocket ship, the Comet wasn't "zooming" to altitude. Climbs would have been slow and slogging.
" Boeing engineers faulted DeHavilland" what does that even mean? The British CAA would have done the analysis, Boeing engineers would have read the report(s) produced by the CAA. Boeing engineers didn't get a say in those reports.
@@fantabuloussnuffaluffagus They faulted it by commenting when they saw it perform at Farnborough. Of course they didn’t have any day in it’s specification.
@@fantabuloussnuffaluffagus It zoomed compared to the piston powered passenger aircraft of the time. These other pressurized vessels had stresses equivalent for any particular altitude but over a longer period of time. The comparison of 737s doesn’t apply.
@@fantabuloussnuffaluffagus What do you know about the Hawaiian 737’s loss of a section of the cabin from corrosion? The report that made the most sense to me is that the initial failure down low wasn’t enough for the main section to separate but something caused the rate of decompression to change when the initial failure got plugged!
@@kenjohnson5124 Sense, try making some.
It was a 60kpa while should've been pressurized to 80kpa
Is this correct? A jet aircraft (not sure about this aircraft type) climbs faster than the human ears can cope. So before take off the cabin pressure is dropped. This allows the captain to set a rate of assent for the plane and a different slower rate of assent for the cabin. The point is that before take off the structure is also exposed to higher pressures outside than inside. Maybe this isn't as relevant, but do\did they test for forces pressing in as well as out?
No
The aircraft didn't 'explode' in mid air. They ruptured and broke up.
What a vapid title!
Hi Shane! Yeah, the title is not the best. I am struggling to come up with a good title for the video. I am open to suggestions. Cheers
Aircraft crashes have always & always been due to pilots errors, and never been due to manufacturers defects !
Only according to de Havilland... who had the highest loss rate of any manufacturer in history.
Rather a sad story. The English were the first in this field and acted as pathfinders so that later american planes could take advantage of the knowledge without the financial losses. Much the same thing has happened at other times such as computers, radar, sonar, swept wings and of course rolls royces research in fan jet technology.
I thought d haviland was a Canadian company
@@Richard-zc1cj de Havilland Canada was a subsidiary of the British company which eventually became an independent entity
We have given the Americans far too much data in good faith only for them to flick us the bird, Gas turbine technology, Nuclear bomb research data, supersonic aerodynamic data and even VSTOL technology. I think they got a lot of our radar research data too. Every time we think we have a reciprocal agreement they take our data and then tell us to sod off. They were also responsible for the UK cancelling the P1154 and TSR2 aircraft. They are not our friends.
Unfortunately lots of these lessons have had to be relearnt by many notable companies and organisations
That's a romantic sounding myth, but in the end it's just a myth. Other large aircraft makers had jets on the drawing board in the mid 40's also, but they all understood the engine technology was not there yet, and it would not be technically or economically wise to proceed.
Dehavilland went ahead, encouraged by the brabazon committee, and probably also because they did not have experience building metal aircraft or large aircraft. They made serious design and construction mistakes that experienced American and British large metal aircraft makers would not have made.
So, they weren't trailblazers, and they didn't discover any lessons that others learned from. They just made a lot of mistakes because they were working in an area where they shouldn't have been.
Engineers have the same hidden design flaws in today's manufacturing that they are not using and won't test for because of the increasing use of composite materials. I'm retired and will not give the industry the information that needs attention - so don't ask, but failure modes are going to happen. Company's Don't care or listen to engineers and base any catastrophic failures on sheer numbers of loss versus revenue dollars per flight hours achieved. It's cheaper to pay for the loss and liability of aircraft failure than to worry about it..
Frank Whittle the inventor of the jet engine warned de Havilland about the design yet they just ignored his warning.
Frank Whittle was only the 4th person to successfully demonstrate a jet aircraft engine
@@WilhelmKarsten
Frank Whittle produced & demonstrated for the first time in the world a self contained pure internal combustion turbine jet engine running on liquid fuel that would be capable of being a practical & reliable aircraft engine.
Also & in addition -
They might like to provide sources for their numerous & parrot like outlandish & fictitious claims?
They should attempt to understand
Comet 1s flew after 1954.
Comets flew until 1997.
Comet derivatives flew until 2010.
DH construction methods were industry standard practice or were much better & far more advanced.
A Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
@@petemaly8950FRANK WHITTLE WAS NOT THE FIRST TO ACHIEVE ANYTHING RELATED TO THE JET ENGINE
I wonder why it took 3 crashes nefore action was taken
Greed.
Airliners had a habit of being destroyed during normal service in those days.
A Comparison - for an idea of how things were back then.
Lockheed Electra
US.
*First flew 1957 9 years after the Viscount.*
First US turboprop airliner
4 engine turboprop.
Pressurised passenger cabin.
Of the total of 170 Electras built, as of June 2011, 58 have been written off because of crashes and other accidents.
29% of aircraft in hull loss accidents.
6 fatalities per aircraft.
Hull-losses: 59
Hull-loss accidents: 49
with a total of 1037 fatalities
Criminal occurences (hull-losses ): 1
with a total of 0 fatalities
Hijackings: 6
with a total of 1 fatalities
Survival rate:
12.0% of all occupants survived fatal accidents.
Three aircraft were lost in fatal accidents between February 1959 and March 1960. After the third crash, the FAA limited the Electra's speed until the cause could be determined.[7] After an extensive investigation, two of the crashes (in September 1959 and March 1960) were found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter"
Could cause wing destruction.
The three aircraft accidents did not result in the type being grounded for some unfathomable reason, odd isn't it?
*Vickers Viscount.*
UK.
*First flew 1948 9 years before the Electra.*
4 engine turboprop, 1st turboprop metal construction pressurised passenger cabin airliner in the world.
RR Dart Gas turbine engines.
Pressurised passenger cabin.
445 Built.
131 Hull-loss accidents: 29%
131 with a total of 1521 fatalities
fatalities Survival rate:
3.4 fatalities per aircraft.
11% of all occupants survived fatal accidents
*UK Dehavilland Comet. DH-106*
*Worlds first & most advanced high altitude Jet powered pressurised passenger cabin all metal construction airliner.*
114 Built.
17% Hull loss accidents.
Hull-losses: 25
Hull-loss accidents: 20 with a total of 426 fatalities
3.7 fatalities per aircraft.
Survival rate: 11.4% of all occupants survived fatal accidents.
There actually 6 hull loss accidents in just 2 years of limited service.
Comet 1 had a 46% loss rate and its airworthiness certification was permanently revoked
@@UQRXDde Havilland had a well-known reputation for building aircraft that crashed often.
Great video. Nevil Shute wrote a brilliant book called "No Highway" in 1947 about a mythical aircraft called the Reindeer. Sudden structural failures in flight turned out to be caused by Metal Fatigue. Shame the Comet designers did not read it.
It so closely mirrors the comet fiasco, it’s really quite remarkable. The film was released a year before the comet launch. Having worked for DH and for Vickers, one suspects that he must have had some inside knowledge and doubts about the design.
It’s seems that you’ve forgotten the Boeing 737 Max !
The Boeing 737 Max is a much safer aircraft
The de Haviland Comet had 39 hull loss accidents out of 114 built and only 76 in actual passenger service.
The Boeing 737 Max has just 2 hull losses with 1,340 aircraft in operational service
@@sandervanderkammen9230
100% Garbage video.
& Of course the Comet had 17% accident.airframe losses
The Being 707 had 29% accident airframe losses.
There were no excuses for the Boeing 737, with more than 50 years of type design & build experience producing an aircraft that flew itself into the ground entirely automatically on two occasions is criminal & unforgivable obviously.
@@Peppa_Wiggles23 *GARBAGE PLANE COMET 1 46% LOSS RATE.*
@@Peppa_Wiggles23 *46%*
The 707 didn't really win because of the Comet windows. The failure of the Sud Caravelle should emphasise that
The 707 had a much larger passenger capacity and range than anything else. It made longhaul flights actually practical
Older designs simply were too small and refuelled too often to be commercially viable (which is why flying before the 1960s was a _very_ expensive luxury)
The British made a similar mistake with the Bristol Brabazon - which was HUGE for its time (767 size) but carried a relatively small number of passengers in ocean-liner comfort because it assumed the competition was from ships and luxury, not "time"
Even then, the airlines wanted to fit as many passengers as possible on board to bring the price per seat down - so nobody ordered the thing, despite it being the pathfinder for so much of what we consider "modern" aviation design
A similar British mistake can be seen in the VC10 - the design brief was to produce an aircraft capable of operating from "hot and high" airfields on tbe empire routes, because their runways were too short for 707s
It was a commercial failure because by the time it entered production the problem had largely been solved - by extending the runways in question to handle 707s - at a total cost across ALL airports of less than _one_ VC10, let alone the development costs
BOAC didn't want the aircraft, but was ordered to buy them - orders which came from the same civil servants who had decided the solution would be a short field aircraft and ordered the VC10 development (but didn't foot the bill, leaving Vickers on the hook and bankrupting them despite a number of VC10s being ordered as RAF tankers to help offset their costs)
The reason BOAC didn't want the aircraft? They had already assessed that extending runways would solve the issues and were quietly working with airports to buy land and make it happen
The latest Constellations and DC7s could indeed make long-haul flights without refueling, but their maximum capacity was about 100 passengers, partly due to the fact that you couldn't move the seats closer together - the window locations. Many passengers would have been staring at a blank wall. The first DC8 also was limited that way, but the 707 had those accursed close together windows, allowing many more passengers to be backed in and is one of the reasons I hate modern planes. I like ROOM. And I will trade some speed for it. Even the slowest plane is much faster than the fastest ship.
@@michaelbenardo5695 hence the comments about capacity and cost.
Yes, the piston airliners had greater range than the jets, but they were much smaller, less than half the speed and required a lot of maintenance due to those piston engines
Air New Zealand (TEAL) pilots loved Connies - describing them as the finest three engine aircraft to ply the Pacific
It wasn't at all unusual to have an engine failure on a long flight and 3 engine landings were regarded as routine. Even without failures, each leg required significant downtime with tens of manhours of maintenance required per engine between each flight
That made them _expensive_ (the seating capacity was limited by MTOW rather than windows)
707 was the first passenger jet which solved the range + capacity issue that allowed longhaul flying to become practical. Even with the massive stepchange in costs, flying was still very expensive until the 747 transformed the market entirely
@@miscbits6399 I still hate close together windows. And yes, I remember how the 747, then airline deregulation, dramatically reduced the cost to fly. Suddenly, people who before would consider flying a once-in-a-lifetime thing suddenly could afford to fly over and over and over again.
The Caravelle was medium/short haul. Had a Comet nose. Comet was intended long haul.
The Comet was a sound airliner once it was sorted . I flew in a couple of the Comet 4’s & the flight was a lot smoother ,than Boeing 707 bone shaker crocks I also flew on .
The de Haviland Comet would go on to have an absolutely appalling loss rate and fatalities statistics
@@WilhelmKarsten Not once the teething issues were sorted ,on the new versions there was only the odd smash up now & then ,no worse than any other similar type of aircraft . I few on them & always felt safe ,even ones with many air miles on them .
@@maskedavenger2578 Teething issues?
Comet 1 suffered 6 unexplained hull loss accidents and was grounded, it's airworthiness certification was revoked in 1958 and never returned to revenue passenger service.
Comet required major remedial engineering and redesign, the Comet 4 is a completely different aircraft... it too had issues and would have the highest loss rate of any jet airliner (except for the Comet 1).
@@WilhelmKarsten A minor set back , considering it was the first jet airliner , only a few teething problems . The second versions with the improvements were sound reliable aircraft ,so much so they developed the nimrod that went on to give good service for many years . The USA are jealous of every aircraft the British design or have a part in designing or building . We seen the capers over the Concord & we were streets ahead with the Harrier vertical lift off jet . The Comet & the V C I0 were the best looking & smoothest aircraft of their day , modern versions of them should be built ,to give Airbus & Boeing a run for their money .
@@maskedavenger2578 Is that supposed to be sarcasm? No one can possibly be that delusional?
I have to say that De haviland was a great-looking plane, I love the design and how integrated the engines look. The square Windows do look like a big mistake. Round or oval Windows would have been a much better option structurally.
Bit unfair saying it had a fatal flaw, it was world leading that was pushing the boundaries of technology, metallurgy, the engineers didn’t know they were building the faults into it with square windows, other aircraft manufacturers learnt from these mistakes and then took the lead.
As a pilot, these metric measurements are hurting my brain. Great video though
It's Boeing 737 max now
The 737 Max has an excellent safety record compared to the Comet.
DC 10:💀
DC-10 has an excellent safety record compared to the Comet
Other large aircraft makers had jets on the drawing board in the mid 40's also, but they all understood the engine technology was not there yet, and it would not be technically or economically wise to proceed, and they waited for appropriate engines to appear.
Dehavilland went ahead, encouraged by the Brabazon committee, and probably also because they did not have experience building metal aircraft or large aircraft, so they didn't know better what they were getting in to. They made serious design and construction mistakes that experienced American and British large metal aircraft makers would not have made.
So, they weren't trailblazers, and they didn't discover any lessons that others learned from. Dehavilland just made a lot of mistakes because they were working in an area where they shouldn't have been. A lot of the comments in this section illustrate the errors that were made.
The fuselage skin was too thin to countersink properly for the 1/8 inch diameter rivets (at 1/2 inch pitch), so the outer skin was dimpled into a backing strip along the joints of the skin panels. Originally the dimples were just pressed in which occasionally caused cracks. After the crashes and the detailed investigation, the dimples were formed by a spinning tool and the inspection for cracked dimples was much more strict. The original fuselages were pressure tested to 15 psi before the wings were added. this was supposed to stretch all the high stress areas so that they would be in compression and that was supposed to prevent fatigue. That theory was tragically wrong. But the whole aircraft was designed with very high stress levels, so there were other areas of the Comet 1 which would have caused trouble before the design life of the aircraft. Essentially, the fuel consumption of the D H Ghost Jet engines was too thirsty so the rest of the design was marginal.
☕
Too many holes in the same stress line spell failure, stagger and use adhesive or weld .
de Havilland was still building aircraft primarily from wood and fabric in the late 1940s... a decade or more behind in aircraft technology