It has been pointed out that one of the photos of R E Bishop is in fact Mr Miles Thomas, the head of BOAC at the time. Please accept our sincere apologies for the error. We hope that it does not detract from the enjoyment of the video itself.
Great video, what a shame the Comet had such problems, we might all be flying around in de Havilland airliners now instead of Boeings. Cutting edge technology always has its issues.
The Comet wasn’t very advanced aerodynamically to be honest, but not for lack of experimenting by DH on the DH108 swallow. In the end, DH felt that all the systems work that had to be done to make the Comet reliable and efficient were more important. And to say there is nothing revolutionary about the Comet is not true. The Comet slashed flying times wherever it went. . The Comet introduced hydraulic controls to airliners with multiple system redundancy, high pressure refuelling, adding inert gases into the fuel system to minimise chance of explosions along with the first airliner designed to fly at altitudes of over 40,000 feet. Obviously this proved its undoing and many lessons were learned and shared. But none of this was forseeable - the concept of metal fatigue was still developing and the Comet investigations developed many test procedures we now take for granted. But aircraft with potential design flaws have been built since, the L188 Electra, the DC10 , B737 Max to name but a few. DH worked around the clock to identify the issues and then take appropriate action. The DH 106 Comet 4 gave approx 25 years of and was used as the basis for the Nimrod aircraft which flew for another 30 years
Unfortunately DH paid the price of being the pioneer in many ways. Not just with the structural issues but also with the concept of how future generations would travel. The Comet did cause quite a sedate revolution when it entered service with flying times to distant and exotic location slashed in half. It pioneered the quieter and smoother jet travel experience. Passengers felt calm and relaxed. But being early to the market meant the Comet 1 was designed a pretty feeble jet engine. That meant a narrow cabin designed around 4 abreast seating (5 at a squeeze) meant that De Havilland was on the back foot when the B707 and DC8 came along with 6 abreast seating and pylon engines which could be adapted very quickly to new jet engines and technology. DH did follow up the Comet with the Trident which was 6 abreast and cutting edge in the case of the its wing design and avionics. In fact the wing design of the Trident was so good that the Germans were determined to have this Hatfield expertise in Airbus. Thus, the West German Government helped fund Hawker Siddley’s involvement in Airbus when the UK Govt withdrew from the Airbus project. And that’s why Britain remains Airbus Europes wing design and production centre - even though that’s no longer at Hatfield
@@michduncg The de Havilland Comet Disaster is the worst engineering failure in commercial aviation history and a truly shameful and humiliating chapter in British aviation history. The real tragedy of the Comet Disaster was that it could have been easily prevented if de Haviland had not cut corners and followed well-known and understood industry standards for the design and construction of pressurized cabins made from riveted aluminum alloys. de Havilland simply lacked the experience and technology to build a large all-metal pressurized airliner, the company was still building jet aircraft primarily from wood and linen fabric.
@@WilhelmKarsten We feel we can shed some light on some common myths & misunderstandings. That's correct of course, at the time the Comet wasn't particularly dangerous. It was also definitely not the worst aircraft engineering disaster in aviation history obviously. The Comet's engines, right from the first prototype were demonstrated to have enough power even for high altitude / hot airport operation. No incidents were caused by lack of power. Obviously the Comet's engine position & inlet position had some distinct advantages at the time & of course pylon mounted podded engines have some problems including excessive induced drag. The Comet engine inlet design was not a fatal flaw & didn't cause any incidents. Examples of all Comets mks including some Comet 1 airframes continued flying with certification at some point after 1954. Flying carried on until 1997. Losses comparisons. How things were in those days. DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Boeing 307 70% Boeing 247 48% Boeing 707 . 20% Boeing 377 19% MD DC-8 15% Lockheed Electra Turboprop 29% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Convair CV-880 (ff 1959) 27% Convair CV-990 (ff 1961) 35% Of course De Havilland had prior experience building many all metal construction airframe aircraft & thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland. That is of course correct, Comets flew until 1997 & the original Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953, Nimrod aircraft were in service until 2011. Indeed it is the case that the Nimrod was not withdrawn due to structure problems or other airframe issues, it was entirely due to a significant wing upgrade snag & resultant basic economics & an end of line sale happening at Bow-wing (see b-47 wing folding incidents for info) at the same time. The world's first pressurised cabin aircraft was of course an Engineering Division USD-9A, a modified British design Airco DH.9A built under license in the US & was of course the first aircraft to fly with a pressurized cockpit module. This was during a joint US / UK research project in the 1920s. Yes, that's true, De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The Comet was the first airliner where stress due to pressurisation significantly exceeded flying load stress for a full length passenger cabin fuselage. We agree, that's correct, the DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first all metal construction airliner during the 1920s. In all cases other earlier pressurised aircraft were larger, needed thicker fuselage skins due to flying stresses alone & had much lower pressurisation differential pressure or were military aircraft with relatively small heavily built pressurised capsules. Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. Later alloys had very similar properties. The skin thickness used for the Comet was used for similar size later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small. Without doubt De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet. Obviously the DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's highest combined nuclear, aerospace & defence sectors per capita activity. Of course anyone currently flying on a wide body airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines designed & built in the UK. That's correct, the investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Indeed it is the case that ripstop provision was included. Claimed incidents did not involve cracks starting from passenger cabin window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents. Obviously De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet. It is in fact true to say that the way airliners were built changed everywhere, including in the US, after the Comet incidents. We hope this helps, obviously. Cheers indeed of course as always etc. 👍
The real tragedy of the Comet Disaster was that it could have been easily prevented if de Haviland had simply followed well-known and understood industry standards for the design and construction of pressurized cabins made from riveted aluminum alloys
@sandervanderkammen9230 We feel we can shed some light on some common myths & misunderstandings. That's correct of course, at the time the Comet wasn't particularly dangerous. It was also definitely not the worst aircraft engineering disaster in aviation history obviously. The Comet's engines, right from the first prototype were demonstrated to have enough power even for high altitude / hot airport operation. No incidents were caused by lack of power. Obviously the Comet's engine position & inlet position had some distinct advantages at the time & of course pylon mounted podded engines have some problems including excessive induced drag. The Comet engine inlet design was not a fatal flaw & didn't cause any incidents. Examples of all Comets mks including some Comet 1 airframes continued flying with certification at some point after 1954. Flying carried on until 1997. Losses comparisons. How things were in those days. DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Boeing 307 70% Boeing 247 48% Boeing 707 . 20% Boeing 377 19% MD DC-8 15% Lockheed Electra Turboprop 29% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Convair CV-880 (ff 1959) 27% Convair CV-990 (ff 1961) 35% Of course De Havilland had prior experience building many all metal construction airframe aircraft & thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland. That is of course correct, Comets flew until 1997 & the original Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953, Nimrod aircraft were in service until 2011. Indeed it is the case that the Nimrod was not withdrawn due to structure problems or other airframe issues, it was entirely due to a significant wing upgrade snag & resultant basic economics & an end of line sale happening at Bow-wing (see b-47 wing folding incidents for info) at the same time. The world's first pressurised cabin aircraft was of course an Engineering Division USD-9A, a modified British design Airco DH.9A built under license in the US & was of course the first aircraft to fly with a pressurized cockpit module. This was during a joint US / UK research project in the 1920s. Yes, that's true, De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The Comet was the first airliner where stress due to pressurisation significantly exceeded flying load stress for a full length passenger cabin fuselage. We agree, that's correct, the DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first all metal construction airliner during the 1920s. In all cases other earlier pressurised aircraft were larger, needed thicker fuselage skins due to flying stresses alone & had much lower pressurisation differential pressure or were military aircraft with relatively small heavily built pressurised capsules. Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. Later alloys had very similar properties. The skin thickness used for the Comet was used for similar size later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small. Without doubt De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet. Obviously the DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's highest combined nuclear, aerospace & defence sectors per capita activity. Of course anyone currently flying on a wide body airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines designed & built in the UK. That's correct, the investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Indeed it is the case that ripstop provision was included. Claimed incidents did not involve cracks starting from passenger cabin window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents. Obviously De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet. It is in fact true to say that the way airliners were built changed everywhere, including in the US, after the Comet incidents. We hope this helps, obviously. Cheers indeed of course as always etc. 👍
The best reports indicate the simple truth is that De Haviland didn't add redundancy in the event their life span calculations were wrong(the 707 had tear strips added specifically to make a fatigue failure destroying the fuselage impossible) and the calculations used full average pressure load across the whole aircraft (not accounting for small stress points like window corners or joints, OR brief spikes in strain caused by weather or a sudden ascent/descent) which gave an inaccurate picture. This was made worse by the fact that the initial test aircraft they used to get the number was both extremely carefully built(no defects, whole manufacturing process closely watched, best metal around) so it overpreformed compared to an average aircraft, AND due to them using it in a prior overpressure test they accidentally hardened the metal and caused the plastic seals to fuse, making the frame stronger and covering stress points without them knowing. The test aircraft lasted 18,000 cycles before developing serious fatigue. The plane was rated to last 10,000 cycles before it was to be retired. The second Comet to breakup lasted 900 cycles. Modern planes last 75-80,000 cycles on average, though some go longer(The Aloha plane that failed was 90,200). Understanding of metal fatigue was also just generally worse at the time. It's not 100% consistent, aluminum has a pretty big margin of error. The oldest planes in the fleet(excluding the test plane) were over 8,000 cycles. One of the ones that crashed was 900. The 707 and DC-8 likely would have made many of the same mistakes(perhaps not all, but some) if not for the Comet's failure. Pressured aircraft only dated back 20 years and had only been popular for 5. Jet aircraft dated back less than 5 years when the Comet started production and they were the first on that scale. It was the late 40s-early 50s. Some things just weren't known yet
Every report on the Comet says "It wasn't the square windows", well if they really had no impact on the structural failure why has there never been a square window seen on any airliner since? I am a big de Havilland fan and know the story well but that plausible contribution to the structures failure always seems to be dismissed.
The Comet windows weren’t completely square, they had quite rounded corners. The cracks were found to start at rivet holes close to the window frames, not the corner of the windows. These rivet holes themselves weren’t meant be there originally. The prototypes had their window frames attached to the fuselage with Redux bonding. This method of installation was found to be too cumbersome for large scale production The Comet had a circular fuselage of quite a tight diameter so a square window wasn’t unusual and other pressurised airliners of the day also featured square windows. Later jetliners would have a ‘double bubble shape’ fuselage with flatter sides which allowed the taller oblong windows we are all familiar with today. Modern jetliners like the A321 feature straight tops and bottoms with generous radius curvers on the corner.
@@michduncg It's a completely moot point as wreckage recovered from the sea confirmed that the passenger windows were not involved in the catastrophic in-flight structural failures... square windows theory has been completely debunked as a red herring. The actual cause is a far more imbarrassing tale of incompetence and criminal negligence. The orgin of the fatal cracks were in the Crown sheets that were only half as thick as they needed to be and made from AL2014B and completely unsuitable alloy that was too brittle. The Comet lacked proper overlapping Rip-stop doubler joints and the fuselage frame hoops and stringers were too weak and spaced too far apart to prevent cracks from joining up with adjacent panels. The quality of the riveted fastenings were also found to substandard for pressurized cabins and of poor quality overall, no other manufacturers used the primitive methods used by de Havilland on their pressurized cabins.
@@WilhelmKarsten We feel we can shed some light on some common myths & misunderstandings. That's correct of course, at the time the Comet wasn't particularly dangerous. It was also definitely not the worst aircraft engineering disaster in aviation history obviously. The Comet's engines, right from the first prototype were demonstrated to have enough power even for high altitude / hot airport operation. No incidents were caused by lack of power. Obviously the Comet's engine position & inlet position had some distinct advantages at the time & of course pylon mounted podded engines have some problems including excessive induced drag. The Comet engine inlet design was not a fatal flaw & didn't cause any incidents. Examples of all Comets mks including some Comet 1 airframes continued flying with certification at some point after 1954. Flying carried on until 1997. Losses comparisons. How things were in those days. DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Boeing 307 70% Boeing 247 48% Boeing 707 . 20% Boeing 377 19% MD DC-8 15% Lockheed Electra Turboprop 29% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Convair CV-880 (ff 1959) 27% Convair CV-990 (ff 1961) 35% Of course De Havilland had prior experience building many all metal construction airframe aircraft & thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland. That is of course correct, Comets flew until 1997 & the original Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953, Nimrod aircraft were in service until 2011. Indeed it is the case that the Nimrod was not withdrawn due to structure problems or other airframe issues, it was entirely due to a significant wing upgrade snag & resultant basic economics & an end of line sale happening at Bow-wing (see b-47 wing folding incidents for info) at the same time. The world's first pressurised cabin aircraft was of course an Engineering Division USD-9A, a modified British design Airco DH.9A built under license in the US & was of course the first aircraft to fly with a pressurized cockpit module. This was during a joint US / UK research project in the 1920s. Yes, that's true, De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The Comet was the first airliner where stress due to pressurisation significantly exceeded flying load stress for a full length passenger cabin fuselage. We agree, that's correct, the DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first all metal construction airliner during the 1920s. In all cases other earlier pressurised aircraft were larger, needed thicker fuselage skins due to flying stresses alone & had much lower pressurisation differential pressure or were military aircraft with relatively small heavily built pressurised capsules. Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. Later alloys had very similar properties. The skin thickness used for the Comet was used for similar size later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small. Without doubt De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet. Obviously the DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's highest combined nuclear, aerospace & defence sectors per capita activity. Of course anyone currently flying on a wide body airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines designed & built in the UK. That's correct, the investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Indeed it is the case that ripstop provision was included. Claimed incidents did not involve cracks starting from passenger cabin window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents. Obviously De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet. It is in fact true to say that the way airliners were built changed everywhere, including in the US, after the Comet incidents. We hope this helps, obviously. Cheers indeed of course as always etc. 👍
It has been pointed out that one of the photos of R E Bishop is in fact Mr Miles Thomas, the head of BOAC at the time. Please accept our sincere apologies for the error. We hope that it does not detract from the enjoyment of the video itself.
I was 2 when my family flew to Australia in a Comet. I still have a small booklet given to children by BOAC for the flight.
Thanks.
Great video, what a shame the Comet had such problems, we might all be flying around in de Havilland airliners now instead of Boeings. Cutting edge technology always has its issues.
There was nothing cutting edge about the Comet, de Havilland simply lacked the experience to build it.
The Comet wasn’t very advanced aerodynamically to be honest, but not for lack of experimenting by DH on the DH108 swallow. In the end, DH felt that all the systems work that had to be done to make the Comet reliable and efficient were more important. And to say there is nothing revolutionary about the Comet is not true. The Comet slashed flying times wherever it went. . The Comet introduced hydraulic controls to airliners with multiple system redundancy, high pressure refuelling, adding inert gases into the fuel system to minimise chance of explosions along with the first airliner designed to fly at altitudes of over 40,000 feet. Obviously this proved its undoing and many lessons were learned and shared. But none of this was forseeable - the concept of metal fatigue was still developing and the Comet investigations developed many test procedures we now take for granted. But aircraft with potential design flaws have been built since, the L188 Electra, the DC10 , B737 Max to name but a few. DH worked around the clock to identify the issues and then take appropriate action. The DH 106 Comet 4 gave approx 25 years of and was used as the basis for the Nimrod aircraft which flew for another 30 years
Unfortunately DH paid the price of being the pioneer in many ways. Not just with the structural issues but also with the concept of how future generations would travel. The Comet did cause quite a sedate revolution when it entered service with flying times to distant and exotic location slashed in half. It pioneered the quieter and smoother jet travel experience. Passengers felt calm and relaxed. But being early to the market meant the Comet 1 was designed a pretty feeble jet engine. That meant a narrow cabin designed around 4 abreast seating (5 at a squeeze) meant that De Havilland was on the back foot when the B707 and DC8 came along with 6 abreast seating and pylon engines which could be adapted very quickly to new jet engines and technology. DH did follow up the Comet with the Trident which was 6 abreast and cutting edge in the case of the its wing design and avionics. In fact the wing design of the Trident was so good that the Germans were determined to have this Hatfield expertise in Airbus. Thus, the West German Government helped fund Hawker Siddley’s involvement in Airbus when the UK Govt withdrew from the Airbus project. And that’s why Britain remains Airbus Europes wing design and production centre - even though that’s no longer at Hatfield
@@michduncg The de Havilland Comet Disaster is the worst engineering failure in commercial aviation history and a truly shameful and humiliating chapter in British aviation history.
The real tragedy of the Comet Disaster was that it could have been easily prevented if de Haviland had not cut corners and followed well-known and understood industry standards for the design and construction of pressurized cabins made from riveted aluminum alloys.
de Havilland simply lacked the experience and technology to build a large all-metal pressurized airliner, the company was still building jet aircraft primarily from wood and linen fabric.
@@WilhelmKarsten
We feel we can shed some light on some common myths & misunderstandings.
That's correct of course, at the time the Comet wasn't particularly dangerous. It was also definitely not the worst aircraft engineering disaster in aviation history obviously.
The Comet's engines, right from the first prototype were demonstrated to have enough power even for high altitude / hot airport operation. No incidents were caused by lack of power.
Obviously the Comet's engine position & inlet position had some distinct advantages at the time & of course pylon mounted podded engines have some problems including excessive induced drag. The Comet engine inlet design was not a fatal flaw & didn't cause any incidents.
Examples of all Comets mks including some Comet 1 airframes continued flying with certification at some point after 1954. Flying carried on until 1997.
Losses comparisons.
How things were in those days.
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Boeing 307 70%
Boeing 247 48%
Boeing 707 . 20%
Boeing 377 19%
MD DC-8 15%
Lockheed Electra Turboprop 29%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Convair CV-880 (ff 1959) 27%
Convair CV-990 (ff 1961) 35%
Of course De Havilland had prior experience building many all metal construction airframe aircraft & thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland.
That is of course correct, Comets flew until 1997 & the original Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953, Nimrod aircraft were in service until 2011. Indeed it is the case that the Nimrod was not withdrawn due to structure problems or other airframe issues, it was entirely due to a significant wing upgrade snag & resultant basic economics & an end of line sale happening at Bow-wing (see b-47 wing folding incidents for info) at the same time.
The world's first pressurised cabin aircraft was of course an Engineering Division USD-9A, a modified British design Airco DH.9A built under license in the US & was of course the first aircraft to fly with a pressurized cockpit module. This was during a joint US / UK research project in the 1920s.
Yes, that's true, De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The Comet was the first airliner where stress due to pressurisation significantly exceeded flying load stress for a full length passenger cabin fuselage.
We agree, that's correct, the DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first all metal construction airliner during the 1920s.
In all cases other earlier pressurised aircraft were larger, needed thicker fuselage skins due to flying stresses alone & had much lower pressurisation differential pressure or were military aircraft with relatively small heavily built pressurised capsules.
Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. Later alloys had very similar properties. The skin thickness used for the Comet was used for similar size later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small.
Without doubt De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet.
Obviously the DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's highest combined nuclear, aerospace & defence sectors per capita activity. Of course anyone currently flying on a wide body airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines designed & built in the UK.
That's correct, the investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Indeed it is the case that ripstop provision was included. Claimed incidents did not involve cracks starting from passenger cabin window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents.
Obviously De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet.
It is in fact true to say that the way airliners were built changed everywhere, including in the US, after the Comet incidents.
We hope this helps, obviously.
Cheers indeed of course as always etc.
👍
. . .... ... ..... . ..... ..... ..
The real tragedy of the Comet Disaster was that it could have been easily prevented if de Haviland had simply followed well-known and understood industry standards for the design and construction of pressurized cabins made from riveted aluminum alloys
@sandervanderkammen9230
We feel we can shed some light on some common myths & misunderstandings.
That's correct of course, at the time the Comet wasn't particularly dangerous. It was also definitely not the worst aircraft engineering disaster in aviation history obviously.
The Comet's engines, right from the first prototype were demonstrated to have enough power even for high altitude / hot airport operation. No incidents were caused by lack of power.
Obviously the Comet's engine position & inlet position had some distinct advantages at the time & of course pylon mounted podded engines have some problems including excessive induced drag. The Comet engine inlet design was not a fatal flaw & didn't cause any incidents.
Examples of all Comets mks including some Comet 1 airframes continued flying with certification at some point after 1954. Flying carried on until 1997.
Losses comparisons.
How things were in those days.
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Boeing 307 70%
Boeing 247 48%
Boeing 707 . 20%
Boeing 377 19%
MD DC-8 15%
Lockheed Electra Turboprop 29%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Convair CV-880 (ff 1959) 27%
Convair CV-990 (ff 1961) 35%
Of course De Havilland had prior experience building many all metal construction airframe aircraft & thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland.
That is of course correct, Comets flew until 1997 & the original Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953, Nimrod aircraft were in service until 2011. Indeed it is the case that the Nimrod was not withdrawn due to structure problems or other airframe issues, it was entirely due to a significant wing upgrade snag & resultant basic economics & an end of line sale happening at Bow-wing (see b-47 wing folding incidents for info) at the same time.
The world's first pressurised cabin aircraft was of course an Engineering Division USD-9A, a modified British design Airco DH.9A built under license in the US & was of course the first aircraft to fly with a pressurized cockpit module. This was during a joint US / UK research project in the 1920s.
Yes, that's true, De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The Comet was the first airliner where stress due to pressurisation significantly exceeded flying load stress for a full length passenger cabin fuselage.
We agree, that's correct, the DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first all metal construction airliner during the 1920s.
In all cases other earlier pressurised aircraft were larger, needed thicker fuselage skins due to flying stresses alone & had much lower pressurisation differential pressure or were military aircraft with relatively small heavily built pressurised capsules.
Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. Later alloys had very similar properties. The skin thickness used for the Comet was used for similar size later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small.
Without doubt De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet.
Obviously the DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's highest combined nuclear, aerospace & defence sectors per capita activity. Of course anyone currently flying on a wide body airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines designed & built in the UK.
That's correct, the investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Indeed it is the case that ripstop provision was included. Claimed incidents did not involve cracks starting from passenger cabin window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents.
Obviously De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet.
It is in fact true to say that the way airliners were built changed everywhere, including in the US, after the Comet incidents.
We hope this helps, obviously.
Cheers indeed of course as always etc.
👍
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The best reports indicate the simple truth is that De Haviland didn't add redundancy in the event their life span calculations were wrong(the 707 had tear strips added specifically to make a fatigue failure destroying the fuselage impossible) and the calculations used full average pressure load across the whole aircraft (not accounting for small stress points like window corners or joints, OR brief spikes in strain caused by weather or a sudden ascent/descent) which gave an inaccurate picture. This was made worse by the fact that the initial test aircraft they used to get the number was both extremely carefully built(no defects, whole manufacturing process closely watched, best metal around) so it overpreformed compared to an average aircraft, AND due to them using it in a prior overpressure test they accidentally hardened the metal and caused the plastic seals to fuse, making the frame stronger and covering stress points without them knowing.
The test aircraft lasted 18,000 cycles before developing serious fatigue. The plane was rated to last 10,000 cycles before it was to be retired. The second Comet to breakup lasted 900 cycles. Modern planes last 75-80,000 cycles on average, though some go longer(The Aloha plane that failed was 90,200). Understanding of metal fatigue was also just generally worse at the time. It's not 100% consistent, aluminum has a pretty big margin of error. The oldest planes in the fleet(excluding the test plane) were over 8,000 cycles. One of the ones that crashed was 900.
The 707 and DC-8 likely would have made many of the same mistakes(perhaps not all, but some) if not for the Comet's failure. Pressured aircraft only dated back 20 years and had only been popular for 5. Jet aircraft dated back less than 5 years when the Comet started production and they were the first on that scale. It was the late 40s-early 50s. Some things just weren't known yet
Thanks :)
Every report on the Comet says "It wasn't the square windows", well if they really had no impact on the structural failure why has there never been a square window seen on any airliner since?
I am a big de Havilland fan and know the story well but that plausible contribution to the structures failure always seems to be dismissed.
The Comet windows weren’t completely square, they had quite rounded corners. The cracks were found to start at rivet holes close to the window frames, not the corner of the windows. These rivet holes themselves weren’t meant be there originally. The prototypes had their window frames attached to the fuselage with Redux bonding. This method of installation was found to be too cumbersome for large scale production The Comet had a circular fuselage of quite a tight diameter so a square window wasn’t unusual and other pressurised airliners of the day also featured square windows. Later jetliners would have a ‘double bubble shape’ fuselage with flatter sides which allowed the taller oblong windows we are all familiar with today. Modern jetliners like the A321 feature straight tops and bottoms with generous radius curvers on the corner.
@@michduncg It's a completely moot point as wreckage recovered from the sea confirmed that the passenger windows were not involved in the catastrophic in-flight structural failures... square windows theory has been completely debunked as a red herring.
The actual cause is a far more imbarrassing tale of incompetence and criminal negligence.
The orgin of the fatal cracks were in the Crown sheets that were only half as thick as they needed to be and made from AL2014B and completely unsuitable alloy that was too brittle.
The Comet lacked proper overlapping Rip-stop doubler joints and the fuselage frame hoops and stringers were too weak and spaced too far apart to prevent cracks from joining up with adjacent panels.
The quality of the riveted fastenings were also found to substandard for pressurized cabins and of poor quality overall, no other manufacturers used the primitive methods used by de Havilland on their pressurized cabins.
@@WilhelmKarsten
We feel we can shed some light on some common myths & misunderstandings.
That's correct of course, at the time the Comet wasn't particularly dangerous. It was also definitely not the worst aircraft engineering disaster in aviation history obviously.
The Comet's engines, right from the first prototype were demonstrated to have enough power even for high altitude / hot airport operation. No incidents were caused by lack of power.
Obviously the Comet's engine position & inlet position had some distinct advantages at the time & of course pylon mounted podded engines have some problems including excessive induced drag. The Comet engine inlet design was not a fatal flaw & didn't cause any incidents.
Examples of all Comets mks including some Comet 1 airframes continued flying with certification at some point after 1954. Flying carried on until 1997.
Losses comparisons.
How things were in those days.
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Boeing 307 70%
Boeing 247 48%
Boeing 707 . 20%
Boeing 377 19%
MD DC-8 15%
Lockheed Electra Turboprop 29%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Convair CV-880 (ff 1959) 27%
Convair CV-990 (ff 1961) 35%
Of course De Havilland had prior experience building many all metal construction airframe aircraft & thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland.
That is of course correct, Comets flew until 1997 & the original Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953, Nimrod aircraft were in service until 2011. Indeed it is the case that the Nimrod was not withdrawn due to structure problems or other airframe issues, it was entirely due to a significant wing upgrade snag & resultant basic economics & an end of line sale happening at Bow-wing (see b-47 wing folding incidents for info) at the same time.
The world's first pressurised cabin aircraft was of course an Engineering Division USD-9A, a modified British design Airco DH.9A built under license in the US & was of course the first aircraft to fly with a pressurized cockpit module. This was during a joint US / UK research project in the 1920s.
Yes, that's true, De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The Comet was the first airliner where stress due to pressurisation significantly exceeded flying load stress for a full length passenger cabin fuselage.
We agree, that's correct, the DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first all metal construction airliner during the 1920s.
In all cases other earlier pressurised aircraft were larger, needed thicker fuselage skins due to flying stresses alone & had much lower pressurisation differential pressure or were military aircraft with relatively small heavily built pressurised capsules.
Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. Later alloys had very similar properties. The skin thickness used for the Comet was used for similar size later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small.
Without doubt De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet.
Obviously the DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's highest combined nuclear, aerospace & defence sectors per capita activity. Of course anyone currently flying on a wide body airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines designed & built in the UK.
That's correct, the investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Indeed it is the case that ripstop provision was included. Claimed incidents did not involve cracks starting from passenger cabin window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents.
Obviously De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet.
It is in fact true to say that the way airliners were built changed everywhere, including in the US, after the Comet incidents.
We hope this helps, obviously.
Cheers indeed of course as always etc.
👍
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