 It is 6pm on the 8th of April 1954, Campino Airport in Rome, and South African Airways Flight 201 prepares for takeoff. The plane, the crew are operating is a de Havilland Comet. It represents the cutting edge in aviation and is the world's first commercial jet plane. It is relatively new, at only one year and seven months old. The plane is under the command of Captain Wilhelm K. Mostert. The destination is Johannesburg, South Africa. But air journeys of the time involve multiple stop-offs, and 201 is no different. Originating from London, the flight has one more stop-off in Cairo en route, including crew. The aircraft this evening has 21 lives aboard. The plane is cleared for takeoff and the captain takes power at 1832 and climbs rapidly towards its cruising height of 11,000 metres. During its ascent, at 1907, the aircraft contacts Cairo on the long-range high-frequency radio to report an estimated time of arrival of 2102. This would be the last message from 201 as just five minutes later, the aircraft experienced a rapid decompression. The plane disintegrated, killing all on board. The event would be the third of such a fatal loss of a comet in just over 12 months. The mystery of the dramatic and quick loss of South African airways Flight 201 and the previous two accidents would highlight a fatal flaw in one of the world's most advanced and newest forms of air travel and shake the British aero industry to its core. A comet would not take to the skies in commercial service for nearly another four years, severely hampering the public's image of the aircraft. I'm rating the de Havilland Comet events here eight on my disaster scale and here nine on my historical legacy scale. Welcome to Plain Difficult, where we look into disasters and interesting events in history. Crowds gather around a new and striking aircraft at the 1949 Farmer Air Show. The plane is a departure from the usual fare of propeller-driven World War II related aircraft. The new creation from the Havilland, a company famed by its wartime creation, the wooden-framed mosquito, marked the cutting edge of passenger transport. It's easy to think that a jet plane for travel is nothing particularly impressive, but for the late 1940s such an aircraft was almost unthinkable, as just a few years earlier jet-powered fighter planes had only just managed to take part in World War II towards its closing stages. At the time passenger flights were noisy and uncomfortable experiences due to the vibrations emitted from the piston propeller driveline. Little did those observing the future of travel in 1949 know that the aircraft before them would be a ticking time bomb for any who travelled aboard. But our story starts a few years earlier than the optimistic launch of the Comet in war-torn 1943. Between 1942 and 1943 Lord Brabazon of Tara headed a committee to investigate the future of the British Empire's airliner market following World War II. The committee was conducted in two parts, and during the second in 1943 multiple future aircraft were specified, one of which was the Type 4 jet-powered passenger airliner. The concept for a fully jet-powered airliner was personally pursued by de Havilland founder Geoffrey de Havilland. The company was awarded a development and production contract under the designation Type 106. In 1946 a team was set up to design the new aircraft under the leadership of engineer Ronald Bishop of Mosquito fame. During the development phase the Type 106 went through some radical designs. Although originally intended to take just 24 passengers, changes in specifications from the UK's national carrier and potential main customer for the aircraft, BOAC, led to the design needing to accommodate 36. Because of the changes, a more conventional 20 degree swept wing design with unswept tail surfaces was settled upon. Married to an enlarged fuselage, this final design was named the Comet. It was to be an all metal low wing cantilever monoplane powered by four jet engines buried within the wings. The form of the aircraft was low drag and something very different from other airliners of the time. The fuselage was constructed of thin aluminium, which was both riveted and chemically bonded together. And this helped to save weight of the aircraft overall. The crew and passenger areas were pressurised. This mixed with rapid temperature changes and a cruising speed of 460mph meant that the fuselage had to deal with high stress levels. And because of this, the aircraft needed to be extensively tested. Between 1947 and 1948, the Havelins stress tested at Hatfield Aerodrome, small components with large assemblies in a number of different test rigs. De-compression chambers were used to test large sections of the fuselage, involving testing to component failure to get an idea of what the new plane could take. Testing moved to conducting structural studies with a water tank that could be configured to increase pressures gradually to enable individual failure point discovery. Entire sections of the fuselage were also rapidly pressurised to 2.75 pounds per square inch over pressure and depressurised through more than 16,000 cycles in order to simulate tens of thousands of operating hours. The same was done to the windows and frames. All of these yielded satisfactory results. When you look at the comet, something different but not necessarily obvious can be seen. And that is the window shape. When compared to a modern aircraft, the DH-106 had square cutouts for viewing ports. The first prototype's maiden flight out of Hatfield Aerodrome took place on the 27th of July 1949 and lasted just over 30 minutes. The first aircraft was registered as Gulf Alpha Lima Victor Gulf and was the very same aircraft used to wow the crowds at Farnborough the same year. The first production aircraft was lent to BOAC in 1951 for testing and training purposes. And on the 2nd of May 1952, as part of BOAC's route-proving trials became the world's first paying passenger jetliner on a flight from London to Johannesburg. The comet was about 50% faster than their piston-powered contemporaries. And the first year of service proved the aircraft to be very profitable for BOAC. In total 12, the first type would be delivered to customers. But although initially looking good, the journey of the comet would take a rough turn. On the 26th of October 1952, Comet suffered its first loss of whole incident. When a BOAC flight departing Rome's Campino Airport failed to become airborne and ran into rough ground at the end of the runway. However, the next crash involving a comet would sadly be fatal. On the 3rd of March 1953, a new Canadian Pacific Airlines Comet 1A failed to become airborne while attempting a night take-off at Karachi, Pakistan on a delivery flight to Australia. The aircraft plunged into a dry drainage canal and collided with an embankment killing all five crew and six passengers on board. Next came the bloodiest 12 months for the comet. The first of three structural failures of the aircraft took place on the 2nd of May 1953 when BOAC Flight 783 crashed just six minutes after take-off from Calcutta, India killing all 43 on board. Although overstressed at the fuselage was concluded by the inquiry into the accident the ultimate cause was attributed to extreme turbulence and pilot error by overcompensating. The concept of metal fatigue was not on the cards and thus the comet was allowed to continue working in passenger service. It would be less than a year that another total loss would occur within the comet fleet. A comet registered as Gulf Alpha Lima Yankee Papa was being operated as BOAC Flight 781 on a journey from Kalang Airport Singapore to London Heathrow. On the start of its last leg, 781 had 35 on board including its six crew. The crew had just over 15,000 hours of flight time and by any standard as most World War 2 veterans were highly experienced. Whilst the plane was in Rome it was inspected by Jerry Ball, part of his pre-flight check he is to look for incidental damage. Not seeing anything to worry about, Ball's team give the OK for the comet to resume its flight. Flight 781 departed from Rome at 10.31am on the 10th of January 1954. At about 10.50 the comet's captain was in contact with another BOAC flight an Argonaut. The conversation was about the weather but suddenly mid-sentence Captain Alan Gibson went silent and Flight 781 was seen by witnesses falling into the sea. Needless to say investigators were now confronted with two strange occurrences involving the comet and set out to find the cause of such a dramatic loss of aircraft. Initial recovery efforts found 15 bodies, some personal effects and some smaller wreckage pieces. To try and find the cause of the crash, autopsies were undertaken on the recovered bodies. These gave a small glimpse into the cause of the crash. Many had ruptured lungs and fractured skulls and other respiratory injuries hinting at a rapid decompression event. Initially a bomb was thought to have been the cause but investigators couldn't conclude until the wreckage was inspected but another competing theory was that of an engine explosion. In the meantime the fleet was grounded. During this time all remaining comets received a modification to their engines where the turbine ring was encased with an armour plate to contain a possible disintegration of the turbine disk. But a problem arose of how to recover the wreckage as it was plunged into the Mediterranean Sea. It wouldn't be until August 1954 that Flight 781 would be found and returned to the surface for shipping back to the UK. Long before the eventual recovery BOAC wanted their expensive jetliner fleet back into the air and the company pressured the British government and on the 23rd of March just 10 weeks after the crash this was achieved. Just a few weeks after the resumption of services on the 8th of April 1954 South African Airways Flight 201 would be lost departing Rome in almost identical circumstances with three losses of aircraft due to suspected fuselage, explosive decompression, the Royal Aircraft Establishment set about investigating the cause of the disasters. After the 8th of April crash both Flight 781 and 207 were investigated as part of a joint inquiry headed up by Sir Arnold Hall. The report would take over a year to come out but this time would be invested in stress testing the aircraft way beyond what the designers had envisioned. Unlike 781, 201 was deemed unrecoverable but the similarity of the accident meant that if investigators could determine the cause for one then it would likely be the cause for the other. The recovery 781 was completed in August 1954 with around 70% of the airframe reclaimed from the seabed. The wreckage was reconstructed allowing investigators to visualize potential hints for structural failure. The initial thoughts of an engine explosion after the loss of 201 now seemed to be pretty unlikely as the South African Airways plane had received the armoured ring modification to its engines. Seeking to find out the cause a comet had to be structurally tested to find weak points in its fuselage and in order to facilitate this BOAC donated one of its comets Gulf Alpha Lima Yankee Uniform for testing to failure. The aircraft was placed inside a large water tank. The tank was filled and water was pumped into the airplane to simulate flight conditions. By pumping water into the fuselage and then pumping it out again a simulation of takeoff and landings was created with the pressurizing and depressurizing of the cabin. The use of water instead of air allowed investigators to see where potential stress fractures would occur as when air is compressed it can release energy in a way similar to a bomb, virtually destroying any evidence. The donated plane before testing began in June 1954 had experienced roughly 1230 pressurized flights. The fuselage would last another 1830 test flights in the water tank before structural failure occurred. In total the plane including its previous service record had experienced approximately 3060 pressurization cycles. The results of the structural failure were worrying for the entire comet fleet. It was found that stress fractures originated from the front of the fuselage around the window edges but even more worrying was that due to algae growing around the stress fractures it was discovered that the fractures had been gradually growing over multiple pressure cycles. This was around the same time as more pieces of 7-8-1 came in for examination. They were from the area around the wingspan and consisted of two square windows which were used to house the aerials for the aircraft's automatic direction finding equipment. With the evidence from the test tank on the actual wreckage investigators were able to piece together the failure point for cutouts made in a thin fuselage metal for the square windows. Investigators compared the results from the tank test to 7-8-1 which had over 1200 pressurization and 201 which had received 900 pressurization cycles and concluded that both aircraft would have experienced micro stress fractures during their working life. As each time the cabin was pressurized the corners of the windows become fatigued as the stress was concentrated on the corners and wasn't spread evenly across the opening. After hundreds and thousands of cycles the frame would start to crack and continue to weaken the whole structure of the plane. The testing during the design of the comet was found to be inadequate for the actual stresses loaded on the structure. The findings on both the BOAC and South African Airways crashes were published on the 1st of February 1955. The comet design was subsequently revised making improvements to the already in development comet 2 and one main obvious difference could be seen, the windows. This and also an increase in metal thickness and increased structural support. Additionally larger wings and a longer fuselage were incorporated and this meant that the aircraft was now far better. But the damage to the brand was already done. All outstanding orders for the comet from airlines around the world were cancelled. The type would remain grounded from commercial services until 1958 when the aircraft would take to the skies once again. A trickle of orders would come in eventually with two more revisions being released. The aircraft would be retired in 1997 far outlasting the company that had built it. But its legacy would endure way beyond its working life. Both the De Havilland competitors Boeing and Douglas learnt from the mistakes from the comet. Even admitting in private that if De Havilland had not experienced the comet's pressurisation problems first then it would have happened to them. But ironically it would be Boeing with their much less futuristic and pod mounted engine 707 introduced in 1958 that would eventually rule the commercial skies. Leaving the comet as a bold but flawed footnote in aviation. This is the Planetary Foot Production and all videos on the channel are created by Commons Attribution Share Like Licensed. Planetary Foot videos are produced by me, John, in the currently sunny southeastern corner of London, UK. Help the channel grow by liking, commenting and subscribing. Check out my Twitter for all sorts of photos, nods and sods as well as hints on future videos. I've got Patreon and YouTube membership so check them out if you fancy supporting the channel financially. And all that's left to say is thank you for watching.