Troubled History Of The Comet (BOAC Flight 781 & SAA Flight 201) - DISASTER BREAKDOWN

Troubled History Of The Comet (BOAC Flight 781 & SAA Flight 201) - DISASTER BREAKDOWN

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This is a de Havilland Comet. In aviation this plane is seen as one of the greatest technological leaps of the 20th century. The Comet was the world’s first Jet passenger plane. Not this particular comet this was a later variant of the plane. But the Comet family first took to the skies in the twilight days of the 1940s. As the world entered a new decade the plane was a symbol of British Engineering, a statement that Britain was cementing itself as a mainstay in the aviation industry, leading the way no less.

As the first jet airliner developed behind closed doors, its arrival turned the heads of engineers all over the world. The comet could fly fast, slashing flight times between destinations. The comet could fly higher and provided a greater level of comfort to its passengers.

For half a decade, the comet went unchallenged in the aviation industry. It wasn’t until 1956 when the Soviet Union launched the Tupolev 104 and later with the arrival of the Boeing 707 and DC8 that the plane was met with some kind of competition. For what it all the Comet was worth though, it certainly wasn’t without tragedy.

Breaking into new frontiers in the sky, the arrival of the comet seemed to present more technological hurdles than previously thought. The early days of this plane are marred with multiple accidents that claimed dozens of lives. In this video we’ll look a little deeper into the tragic history of the Comet focusing on a particular accident that signalled the beginning of the end of this iconic aircraft. January 10th, 1954. It was the late morning. British Overseas Airways Corporation Flight 781 has just departed Rome in Italy heading to London.

It’s the final leg of a long flight that originated in Singapore, Rome was actually the flight’s 7th scheduled stopover point. The 35 passengers and crew were looking forward to arriving in London that afternoon. About a third of the flight’s passengers were international students from Asia. They were flying back to school after visiting family abroad. Also on board was BBC reporter Chester Wilmot.

Originally from Australia he joined the flight in Myanmar and was looking forward to being reunited with his family in London. Captain Alan Gibson was commanding Flight 781. At 31 years old he was one of the youngest Captains and pilots at BOAC. He served in the Royal Air Force during the Second World War and was even decorated with a Distinguished Flying Cross.

He transitioned into commercial aviation where he landed a Job as airline captain on the Comet. By this time he had achieved over 6,500 flight hours. His First Officer was 33-year-old John Bury; he was an experienced pilot in his own right at a logged 4,900 flight hours. Sat behind the two men was a younger Engineer, 27-year-old Charles Macdonald. A radio operator also occupied a seat on the Flight Deck, 32-year-old Luke McMahon.

The plane they were flying was not only a de Havilland Comet, but this aircraft registered as G-ALYP was actually the first Comet to begin commercial services. This final leg to London that day was the plane’s 1291st flight. The plane left Rome at 10:31am local time.

After departure, the plane was flying North East over the Mediterranean Sea. As Flight 781 climbed into the sky, the cabin had begun to pressurize. Pressurized airline cabins were still sort of a new thing at the time.

As a turning point in commercial aviation made in the 1940s, some airplanes had them already such as the Douglas DC6 for example. The air inside a plane is sealed inside the fuselage. As a plane climbs and the outside air becomes thinner, so there is a great difference in pressure between the air inside and outside of the aircraft. Air of higher pressure such as that inside of a plane has a natural tendency to want escape to regions of low pressure so an airplane’s skin is pushed from the inside outward. Airliners are built with the structural integrity to withstand this force.

Because of this what actually happens is the skin of an airliner expands slightly. It contracts when a plane descends. There’s actually a term for this, it’s called a Flight Cycle, the cycle of expansion and contraction. Twenty Minutes after take-off just as the passengers were settling into the flight, the flight crew received contact from another BOAC aircraft.

Flying the same Rome to London route as Flight 781 was a BOAC Canadair Argonaut flying at a lower Flight Level, that aircraft had actually left Rome before the comet but will arrive in London long after the comet arrives... Or so that was the plan anyway. The two Captains took part in the popular British Pastime of talking about the weather. The Captain of the Argonaut was listening into Captain Gibson’s radio message when he was abruptly cut off mid-sentence. The final known words from the ill-fated aircraft were “Did you get my-.”... end.

Flight 781 was approaching the Island of Elba just off the Italian West Coast. Local residents on the island soon reported debris falling from the sky. British Overseas Airways Corporation Flight 781 had suffered a catastrophic failure and crashed into the Mediterranean sea just off the South coast of Elba. From witnessing the falling airplane wreckage a group of local fishermen scrambled to their boats and they were the first to arrive at the scene of disaster on the waters.

They found no sign of life. All they found was wreckage, luggage and other personal belongings, a wedding dress was even found in the water, one passenger was keeping it as a present for his fiancé. The bodies in the sea confirmed the worst, all 35 people onboard Flight 781 were killed. News quickly circulated back to London and an investigation team was mobilized to Italy to try and uncover what had actually brought this plane down.

For air crash investigators in the 1950s their work was extremely difficult and arduous, not helped by the fact the crash occurred over water with wreckage strewn over a great area. There were no flight recorders or similar ATC recordings. At that point they only had eyewitness testimonies and whatever they could grab from the sea to work with. Investigators were left stunned; they had no idea what they were looking at. From what they could deduce they figured an inflight breakup had occurred. But without many leads, they turned to the bodies of the deceased for clues.

Post Mortem results would get investigators moving in the right direction. It appeared that the though many of the passengers’ injuries differed in many aspects, bone fractures in varying areas of the body or what have you, there was an underlying trend in the injuries. Most passengers had suffered skull fractures but the cause of death of many passengers was determined not to be of impact with the water or from bone injuries, but rather from ruptured lungs. This was a clear sign to investigators that a great air pressure difference killed the passengers. It was evident that a sudden decompression had occurred. At that moment of catastrophe the passengers lungs expanded, much like that of an airplane at a similarly high altitude like we discussed earlier.

Their lungs ruptured from this expansion. They were dead before they hit the water. It would take many weeks for significant wreckage to be recovered from the sea. But as time went on investigators were able to attribute many smaller fragments of wreckage to the upper fuselage. Analysis of the recovered items eventually revealed a shocking timeline of an inflight breakup.

The skin of the plane was ripped from the fuselage, fragments of which impacted on the Horizontal Stabilizers. The opening in the aircraft meant the high pressure air inside could escape to the outside, people and debris from the interior were blown out and impacted with other parts of the plane, which resulted in the injuries that were found by investigators. Also the violent nature of this blow out had sent fragments from the cabin into the tail section. The airframe weakened; the tail section detached from the rest of the plane.

This was followed by failure of the wingtips. Rupturing of the fuel tanks resulted in a fire as the wreckage fell to the water below. Something that was observed by those on Elba.

And finally the nose section including the cockpit separated. Now that investigators now understood there was an inflight breakup, they still needed to find out why it happened. Until further information could be gathered, BOAC grounded the Comet, as did Air France. Though it should be noted that this wasn’t an official grounding, air carriers weren’t forced to do this.

So although it wasn’t known at this point why this happened, this didn’t stop investigators looking into possible theories. This wasn’t the first time a de Havilland Comet was in the news for tragic reasons. Structural failure induced by turbulence, poor weather and even lack of forced feedback on the flight controls were factors in the demise of a BOAC Comet in India the previous year. A 1953 document puts the crash of BOAC Flight 783 down to structural failure of the air frame and recommended that a review of the aircraft’s structure and pilot flight controls be done, and necessary modifications be made to prevent further structural failure events.

The crash nearby Elba was the second inflight structural failure event of a Comet. The British government of the day organized a salvage operation of the wreckage, the likes of which had never really been conducted before in aviation. Wreckage that was retrieved was brought to a framing device and fragments were painstakingly fitted back into position, this gave investigators a better view of the plane. So what could have caused this loss of pressure, was still the big question facing investigators. The possibility of an explosive device was ruled out after no evidence of explosives could be found. Other theories were considered, and interest turned to the plane’s engines.

The Comet was powered by four de Havilland manufactured engines, originally, they were known as the Halford H-2 engine, but they’re more commonly known by their final name, the Ghost. The de Havilland Ghost 50 engines were actually concealed within the wing structure as opposed to the mounted engine design that we know today. The plane was designed this way for a reason, the sleek design was there to increase aerodynamic performance and in theory it did reduce drag, however it presented further problems.

Putting your engines here and this close together would mean the structure of the wing would need to be incredibly strong and reinforced as to not cause failure. And this is not even to mention the logistical nightmare of having to perform maintenance or replace an engine with this design. Naturally, it was speculated that a failure in the engines had somehow contributed to the explosive decompression. An uncontained engine failure with fragments fracturing the skin of the plane, could easily explain the decompression.

Whilst the planes were grounded, examinations, modifications and repairs were carried out on the comet’s engines, with focus being the engine turbines. Around 60 changes were made to the plane, in a highly costly endeavor to BOAC and the British Government. As the investigation lingered on, the British Government and BOAC were keen on getting the Comet flying again. The State owned airline was losing a lot of money without their flagship fleet.

With modifications made to the plane’s engines, on March 23rd, 1954, Just ten weeks after the loss of flight 781, BOAC decided it would put the comet back into service, in what would turn out to be a highly questionable move. In a public announcement, BOAC with support from the British Government, exclaimed they were confident and satisfied with the integrity of the Comet. The investigation into flight 781 was still ongoing, investigators had not yet reached a conclusion, it would turn out that this decision would spell further disaster. April 8th, 1954. It has been just 16 days since BOAC relaunched comet services. On behalf of South African Airways, the British Airline flew a Comet service between London and Johannesburg, again with a stopover in Rome.

It was 6 in the evening, after successfully performing the first leg of the journey from London, Flight 201 was preparing for its departure from Rome for the next leg to Cairo in Egypt. The accident comet was examined by the same ground engineer who inspected the lost plane over Elba just three months previously. Like in that case, he found nothing to be amiss with the plane. At just after 6:30pm, South African Airways Flight 201 left Rome heading south.

A South African Flight Crew was commanding the aircraft with Captain William Mostert at the flight controls. As to be expected he reports his climb into the evening sky with to suggest anything was out of the ordinary. A total of 21 passengers and crew were on the aircraft. At just after 7pm the plane was passing West of Naples. The aircraft was continuing its climb to 36,000 feet. Flight 201 made contact via long range radio with controllers in Egypt, where they communicated their expected arrival time.

This was the last radio communication and last known words from the plane. In a shockingly familiar turn of events, flight 201 vanished. Just like the previous accident of Flight 781, this comet had suffered the same structural failure and disintegrated in flight at high altitude. A further 21 people were now dead. Investigators would later find the same injuries on the bodies of the deceased here to that of flight 781.

The news was a further devastating blow to the reputation of the Comet and the British Airliner Manufacturing industry. It was blatantly clear that these planes were unsafe in their current condition, public confidence was shattered. Something was wrong with this plane; the Comet was once again grounded. Now with all of that said, it is time we get down to the bottom of this. What made this plane prone to such failure? There is somewhat of a myth surrounding the comet.

It was to do with the passenger windows on the aircraft, it was said many times even back then that the fact that the comet’s windows were square somehow contributed to failure of the air frame. The idea was that considerable stress was concentrated on the corners of the windows, and that is why airplane windows are rounded in shape today and also why de Havilland fitted circular windows on later Comet models. Ignoring the fact that these windows weren’t actually square, they had rounded corners, this isn’t really true, but it does get us moving in the right direction in that it points towards metal fatigue being the culprit. Now to address the Square Windows issue directly, we need to begin with saying that for however revolutionary the Comet was in its day, it wasn’t necessarily the first high altitude passenger airliner, but it did make a massive leap in terms of altitude, and this is important. Developments throughout the 1940s saw piston propliners pushing service ceilings higher and higher.

The Boeing 377 Stratocruiser for example could actually reach altitudes comparable to airliners today. And some of these planes back then had those Square windows and didn’t seem to have much of a problem with it. They were Squarer than the Comet infact. Large enough square windows that it was actually a trend of the day to fit them with curtains. So this explanation with the Square Windows fails to address why it wasn’t a problem for previous airliners, this isn’t quite the answer were looking for.

So metal fatigue was the Comets big weakness, and that was because the plane was certainly ahead of its time. In the most basic of sense, we simply didn’t know enough about high altitude flying at that time. In the context of the day, engineers at de Havilland wanted to get the most out of their work, airplane manufacturers, as you’d expect want to achieve the best performance they can out of their product, to sell more planes.

So there was this need to push the Comet much higher than any other airliner that came before to increase efficiency. De Havilland understanding this, they designed the Comet with a service ceiling of 42,000 feet in mind. So the way I look at it, there were a further two factors at play in the Comet disasters.

The first is a manufacturing defect. When parts of the Comet were actually being pieced together, the aluminum alloys were riveted into place. The process of which enabled numerous cracks and fractures to take hold on the plane’s skin, before it even set off on its first flight.

This included the areas where the windows were fitted. The second factor was the skin itself. The aluminum alloy used as the plane’s skin was thin, it was so on purpose to keep the plane light. Because of this it just was not as strong as it needed to be to withstand the greater pressure difference at such high altitudes.

The material itself also differed from other previous airliners. Investigators were able to pinpoint the failure of the aircraft structure in the case of flight 781 to the cutouts of two windows positioned on top of the Fuselage. The windows themselves were to assist with the ADF radio navigation instrument. The windows being square, didn’t really have much to do with it, it was how the windows were put there. Think of it this way, the riveting pieced the skin and tiny fractures developed. This probably being where the confusion about plane’s windows came from.

Though failure occurred here, what actually caused the cracking was weak materials and fractures induced by the manufacturing process. Additionally, de Havilland failed to adequately reinforce the fuselage, because the strength needed to withstand the force of this air pressure difference was a huge jump from previous airliners. The Comet was would eventually fail to hold up to it. The Comet involved in the accident at Elba being the first production Comet to actually begin regular commercial flights meant it was easily prone to being the first Comet to fail like this at high altitude.

Every time it climbed and descended, executing one of those Flight Cycles, it flexed the plane’s skin allowing those tiny cracks to grow and weaken the plane further. On that fateful day in 1954, it reached its breaking point. As Flight 781 climbed the air pressure became too great a force for the plane to handle.

In that moment of failure, fractures spread across the aircraft, even accumulating around those passenger windows. The plane shattered and the aircraft was lost. The same thing happened to South African Airways Flight 201. All the way back in the 1950s, investigators were able to solve this mystery by performing a rather elaborate experiment. BOAC had effectively sacrificed one of their Comets to do this. The aircraft registered as G-ALYU, the sister plane to those that were lost, was placed into a large tank that was filled with water.

By increasing and decreasing the water pressure they were able to simulate these Flight Cycles. Knowing the experiment could take months they continuously did this, until... The fuselage opened.

When the results of the experiment were cross-checked with further recovered wreckage, we then knew what was causing these accidents. It had become clear that engineers had vastly over-estimated the lifespan of the Fuselage they had created. Whereas they thought the Comets could perform up to 10,000 flights. In the case of this experiment, the fuselage ruptured in the equivalent of 3,000 flights. Much was learned from Comet.

Our understanding of aviation was changed, the path was paved for safer air travel for decades to come. De Havilland was left with the issue of trying to fix this problem. It was recommended that the material used on the plane be replaced with one of satisfactory strength. A review of other design elements of the Comet was also done. The windows on later Comets were oval in shape, this was actually done for maintenance reasons, they were easier to replace that the larger “squarer” windows.

But to close, what actually became of the Comet in the end. As we mentioned at the very beginning of this video, the Comet was a family of Aircraft. The original Comet became known as the Comet 1, and these were just withdrawn from service in the aftermath of these accidents.

De Havilland had already started development and constructions of the Comet 2 before the two Disasters in the Mediterranean. The subsequent investigation and inquiry stalled the Comet 2’s production until it could be modified. De Havilland eventually started delivering the Comet 2 in 1955. The new plane featured new Rolls Royce Avon Engines, increased fuel capacity and increased wingspan, boosting performance of the plane. The Comet 3 was certainly a one of a kind specimen, literally, only one of them was ever made. The sole Comet 3 was flown around the world on a promotional flight to demonstrate the capabilities of the Comet as well as also being subject to testing of new technologies such as Auto-land.

It’s improvements were integrated in the final version of the plane, the Comet 4. The Comet 4 was the largest of the variants featuring a longer fuselage, newer engines, further increased fuel capacity allowing for increased range capabilities. It could even seat over 100 occupants. The reputation of the De Havilland Comet however never really healed. In the end, despite its technological leaps, only a total of 114 Comets were ever built.

This is in comparison to over twice as many French made Caravelles and about 1000 American Boeing 707s. Even the Soviet Union produced more Tupolev 104s than Britain did the Comet. Although the story of the first Soviet Jetliner is one best saved for another day.

However in a final saving grace to the Comet’s legacy, the overall design of the plane following its revisions was deemed to be absolutely fine. In many ways the Comet joins that rogues gallery of misunderstand aircraft alongside the DC10 perhaps. One must only look to the Comet’s military derivative to see the full potential of the plane.

Manufactured by Hawker Siddeley, the Nimrod served in the British Military for decades as a reliable patrol aircraft and was only ever retired in 2011. But as for the passenger variants. British Airline Dan Air flew the comet right the way into the early 1980s.

The final flight of a passenger Comet took place in September of 1981. Comet registered as G-BDIX was flown to East Fortune in Scotland, the site of the National Museum of Flight where it resides open for the public to enjoy, to this very day. Patreon Outro Hello everyone thank you so much for watching this video. If you enjoyed this video to be sure to leave a like and subscribe so you don’t miss the next one.

Just a reminder in case anyone has missed it, this is actually the last regular Saturday upload as we shift to making some bigger videos. So there won’t be a video next Saturday instead it will probably comes sometime during the week after, its whenever the next video gets done really. And I have something rather special lined for it. I can’t wait to share it with you. It is though, that time of the week where I must take a moment to thank my amazing Patrons over on Patreon for their amazing on-going support to the channel, their names are scrolling on the screen right now. So if your name is on here, big thanks to you.

Shoutouts this week, we have quite a few of them. A thank you to Colin Jones, Gloria Beaumont and T-allen. Big thank you to the highest contributors this week, we’ve got Hamish, Cris Tutt and CatDocTriGeek50, these guys all pledged at the highest tier this week, what total legends.

If you yourself would like to support the channel further, you can join the Disaster Breakdown Patreon from just £1 per month and the link to that will be in the pinned comment below. All Patrons get early access to the next videos 2 days before they go out publicly on YouTube. That is all from me today, have a great weekend and I shall see you, not next weekend but next time. Goodbye!

2023-05-30 21:30

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