De Havilland Comet Prototype at Hatfield
The aircraft was designed to carry 36 passengers in comfort in special reclining "Slumberseats" and at high speed. It was powered by four H.2 Ghost 50 Mk.1 turbojets each of which produced 5,050 lbf thrust. It was a clean, low-drag design which many design elements that were fairly uncommon at the time, including a swept-wing leading edge, integral wing fuel tanks and a tricycle undercarriage, and of course it jet engines which allowed it to fly faster than any other airliner of it time. The aircraft was flown by a crew of 4 which included 2 pilots, a navigator and a flight engineer. Inside the cabin there was a galley for the preparation of hot and cold food, a bar, separate male and female toilets and enough space for the provision of safety equipment including life rafts and life vests for everyone onboard.
The construction of the aircraft used a high proportion of alloys, plastics, and other materials new to civil aviation. The reasons for this being high cabin pressure and fast operating speeds, which were unprecedented in commercial aviation at the time, as well as the need to reduce the weight of the aircraft to accommodate limited the amount thrust generated by the early turbojet engines. The Comet's thin metal skin was composed of advanced new alloys and was both riveted and chemically bonded, which saved weight and reduced the risk of fatigue cracks spreading from the rivets. The skin of the aircraft was at the time highly experimental and it allowed the aircraft operate in extreme heat and cold at high speeds. As part of routine operating procedures the skin of the aircraft had to be checked by the operators of the aircraft.
Cutaway diagram of a De Havilland Comet 1
Early flight testing went extremely well for a aircraft that different from passenger planes that had gone before it and within a few months later the Aircraft appeared at September 1949's Farnborough Air show. After leaving the show the prototype started a long series of tests and trial flights which were aimed at studying the characteristics of the engines, fuel consumption and the flying times over the main commercial air routes of the time. During this process the first prototype was joined by a second prototype to speed up the testing process. During the tests the two aircraft made several non-stop flights on the old Empire routes. Between January 1951 and September 1952 a total of ten of this revolutionary aircraft were delivered to BOAC, and at first were used to familiarise pilots with the new type of aircraft.
The first commercial flight took place 2nd May 1952 with the introduction of the first regular jet passenger service from London to Johannesburg using a Comet 1. This was quickly followed by a regular service from London to Tokyo which cut the flying time in half. So successful were these flights that interest in the aircraft started to mount and soon orders were place by other companies. The French UAT company, Canadian Pacffic and Air France commissioned various models of longer range and able to carry up to 40 passengers from De Havilland. These became known as the Comet 1A and in total 10 aircraft were completed in this version. Soon there were talk of more versions, the Comet 2 with an even larger passenger capacity and the Comet 3 which was further lengthened from the Comet 2 which drew orders from Pan American Airlines and Air India.
BOAC De Havilland Comet 1 at Heathrow Airport in May 1952
The first ever accident occurred to a Comet 1 occurred during takeoff at Karachi, Pakistan on 3 March 1953 and involved a Canadian Pacific Airlines Comet 1A, this accident was blamed on Pilot error due to trying to climb the aircraft too steeply. Then on 2nd May 1953 (G-ALYV) a Comet 1 crashed at Calcutta while climbing after take off killing all 43 people onboard the plane. At the time this accident was also put down air traffic and flight procedures. At the time it was just considered as the inevitable part of the development of a revolutionary aircraft, that was until two similar crashes occurred shortly after. The first of these crashes was on 10th January 1954 (G-ALYP) crashed near the island of Elba killing 35 people and then the second on the 8th April 1954 (G-ALYY) near Stromboli killing another 21 people. This grounded the whole fleet of Comets and started one of the longest technical investigations carried out in commercial aviation to find the cause of the crash.
The first De Havilland Comet 1A to crash in January 1953
The initial expert investigation of the grounded Comet fleet failed to reveal any mechanical or structural defects with the aircraft, but such was the magnitude of the accidents and loss of confidence in jet travel that the cause had to be found. This lead to extensive flying trials with one of the Canadian Comet 1A's together with water tank pressure testing of one of the Comet 1's at Farnborough together with microscopic examinations of the remains of the salvaged wreck G-ALYY which was recovered from the sea bed near Elba. This eventually correctly pinpointed the failure of one of the corners of the rear ADF window caused by the metal fatigue due to the repeated pressurisation cycles. This in turn was probably partly due to the fact the skin of the aircraft had to be thin in order to reduce weight because of the relatively poor performance of the engines compared to those of today. The final report on the accidents concluded that the aircraft had been developed with the knowledge of the day and it was clear that still much to be learnt about the metallurgical aspects of aircraft design.
After the accidents the aircraft was redesigned using the knowledge gained from the experiments done to determine the fatal losses of the airframes of the Comet 1's the completed Comet 2 rebuilt and strengthened as was the single Comet 3. Rather than to end the line altogether De Havilland, realising it was a structural problem rather than a design problem, went on to produce a new version of the Comet, known as the Comet 4. Like all the the aircraft that followed the Comet 1's it had more powerful Rolls Royce Avon engines which could produce 10,500 ldf thrust each, nearly twice as much as the original engines. This not only allowed the skin of the aircraft to be thicker but also meant the aircraft could hold more passengers and fuel which allowed it to at last cross the Atlantic. This version of the aircraft made its first flight 27th April 1958 and showing confidence in the design BOAC ordered 19 aircraft to be used on the North Atlantic route.
Prior to the introduction of the BOAC Comet 4's the older Comets were being put to good use on trial flights and test flights. With the only Comet 3 becoming the first jet airliner to circumnavigate the globe in February 1957, setting a record for the passage between Perth and Sydney with an average speed 5001 mph. Then on the 4th October 1959 that two Comet 4's operated the worlds first transatlantic jet airliner service between London and New York, with one aircraft taking off from London at the same time as the other left New York. Shortly after this the Comets took over all BOAC's London to New York flights, and later routes to Ceylon, Australia, Tokyo, Johannesburg. As time went on the 19 aircraft were used on more and more routes and during their first two years in service they flew 27,000,000 miles and carried 327,000 passengers with a total flying time of 68,000 hours.
The success of the Comet 4's especially at high attitude airfields in hot climates resulted in order from around the world for different versions of the aircraft. With the Comet 4A being ordered by Capital Airlines with a reduced cruising altitude to operate on short and medium range flights in America, but once these order were cancelled the aircraft attached the interest of BEAC who ordered a stretched version of the Comet 4 known as the Comet 4B which could hold up to 101 passengers, nearly tripling the seating capacity of the original Comet 1's. These were were used on flights throughout Europe, Middle East and the Soviet Union . Again the interest drew more interest from overseas and the Comet 4C was produced with the same seating capacity as the 4B but with a longer range. By May 1960 De Havilland had orders for over 50 aircraft in the Comet 4 range, as well as orders for aircraft for the RAF.
Dan Air London De Havilland Comet 4C
De Havilland Comet 4 Cockpit
De Havilland Comet 4 Flight Engineers deck
The cabin of a Dan Air London De Havilland Comet 4C
By the early 1970's the Comets started to appear on the second hand market. Slowly flights by the major airlines came to a halt with the last Comet scheduled service out of Heathrow being flown on 11th November 1972 by Sudan Airways. And when the last Airtours Comet landed at Gatwick from Paris on 31st October 1973, Dan Air London became the last operator of the type. They had been slowly buying all the reaming Comet 4's in service during the 1960's and 70's. At the time the airline needed to replace it ageing piston fleet and saw the Comet 4's as a relatively cheap second hand aircraft which had a lot flying hours left on the airframes. This situation had arisen because the major airlines that had originally first brought the Comet 4s had quite quickly replaced them with more modern types. To make sure it had enough spares the company also brought Comets for scrap and dismantled them for parts from overseas airlines, which allowed them to fly on until 1980.
The last flight undertaken by a Comet 4B (G-APYD) was on 1st November 1979 and it was flown to Science Museum site at Wroughton by Joe Wright and his copilot Bryn Wayt from Gatwick. This left just Dan Air's final Comet 4C's flying with G-BDIW making the last commercial flight on 9th November 1980 after being chartered by a group of enthusiasts. With the demise of the last Comet 4, someone at Dan-Air calculated that during the fleet's life, the legendary Comet had flown a total of some 238,000 hours in Dan-Air service, which equated to a distance of 94,500,000 miles!
Thankfully there exists a number of Comets that have been preserved including one that is still able to move under its own power around the world that will allow generations to come to see what early jet passenger flight was like in the 1950's and 60's.
Footnote - Previous to the first flight of the Comet other piston engine based aircraft had been converted in the UK to use and test fly jet engines. The first hybrid piston/jet airline to fly in the UK was the Avro Nene-Lancastrian which first flew on 14 August 1946 and flew the first international all-jet passenger flight from London to Paris on 23 November 1946 with its two piston engines turned off. This was followed by a pure jet conversion of the a Vickers Viking (Type 618), again with Rolls Royce Nene Engines, which first took to the air on 6th April 1948. On the 39th anniversary of Bleriot's crossing of the Channel, on 25th July 251948, the Viking loaded with passengers left London Heathrow and flew to Villacoublay, Paris, in 34 min 7 sec, less than half the regular scheduled time and was the first, albeit experimental jet airliner.
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