De Havilland Comet

De Havilland DH 106 Comet is a four-engine passenger jet designed by de Havilland in the late 1940s. The world’s first jet airliner.

The history of the first airliner began back in 1943, when a special committee was formed in the Cabinet of Ministers of Great Britain, which was to determine the appearance of the country’s air transportation after the Second World War. One of the recommendations of this commission was the idea of ​​creating an aircraft capable of crossing the Atlantic, transporting about 1 ton of cargo and flying at a cruising speed of about 640 km / h. The first point was clear – the planes were supposed to fly to the USA, the second point could also be implemented, but the speed raised questions. The indicator of 640 km / h was not only exceeding the cruising speeds of any other aircraft at that time, but also exceeding the maximum permissible speeds of the then civilian aircraft. For example, Lockheed Constellation flew at a speed of 547 km / h and was considered one of the best aircraft of the time.

It was obvious that piston aircraft could not be the solution to this problem. But the British company De Havilland nevertheless set about fulfilling the order, deciding to use jet engines as a power plant. This decision faced serious skepticism: the first jet engines of that time consumed a lot of fuel and were very unreliable, they barely started to be used in the military sphere and civilian air transportation with their help seemed a very distant prospect. However, a project that received the Type 106 index in early 1945 was officially initiated.

The first problem of the project was the actual lack of a power plant. In the world at that time there was not a single manufacturer capable of creating a jet engine with sufficient flight and economic characteristics. In the beginning, I had to tighten the requirements: it was supposed to create a small plane for regional lines, capable of transporting only 6 people. Later, the aircraft was increased and its capacity increased to 24. Financial risks also continued to grow, but soon the aircraft became interesting to customers: British Overseas Airways Corporation (BOAC) ordered 25 aircraft, although a little later the contract was reduced to 14.

The aircraft continued to change during the development process. In 1946, the BOAC demanded that its capacity be increased to 36 seats. A further increase in the aircraft and its complication led to the fact that de Havilland abandoned a number of major innovations (some versions suggested the tailless option): the aircraft was supposed to have a low stern-shaped wing and the classic tail wing tail for that time, while the fuselage was significantly larger original options: the cabin was supposed to accommodate 36 passengers, 4 seats in a row with one aisle. The Halford H.1 Goblin engines originally planned for installation were not powerful enough for the enlarged aircraft and were planned to be replaced with Rolls-Royce Avon. However, these engines were too complex and their tests dragged on. As a result, the new Halford H.2 Ghost began to be put on planes. In December 1947, Type 106 received the official name DH 106 Comet.

Since the DH 106 was a new type of aircraft, an updated and more rigorous certification test scheme was developed for it. In the period from 1947 to 1948, active research was conducted. Sealed cabin models were tested in a special pressure chamber and pools. It was assumed that the fuselage resource will be 40 thousand hours of operation.

The first prototype was assembled in 1949 and in July made its first flight, which lasted about half an hour. The aircraft was first shown at the Farnborough Air Show that year. The second prototype took off in 1950. Representatives of BOAC, as well as the Australian Qantas, who also planned to purchase new liners, took part in the testing process.

Features

DH 106 Comet is an all-metal monoplane with a low-lying wing. Power plant: four de Havilland Ghost turbojet engines, however, starting with the Comet 2 model, the modernized Rolls-Royce Avon engines began to be installed on aircraft. The engines were arranged in pairs and were recessed into the wing near the center section. Such an arrangement made it possible to protect engines from external damage and somewhat simplified maintenance, although it complicated the design and made the aircraft heavier, the design even used reservation elements that were supposed to prevent the destruction of the wing in case of engine destruction (subsequently, because of this, these schemes were abandoned )

The aircraft fuselage was very large for the jet car of that time and was overall close to the Boeing 737-100 model, which appeared only in the late 1960s. At the same time, the capacity of the first aircraft was only 36 people. The reason for this was the introduction of a large number of elements necessary to reduce vibration, noise and improve passenger comfort. This later yielded results, de Havilland Comet was very comfortable, especially when compared with the then piston aircraft.

The crew of the aircraft most often consisted of four people: two pilots, a flight engineer and a navigator/telecom operator. Avionics had many systems close to its counterparts at Lockheed Constellation, however, de Havilland developed many completely new airborne systems for the aircraft, which were later actively licensed and used on first-generation American and French jetliners.

Operation

The first production aircraft began to fly in early 1951 and was transferred to a special unit of the BOAC airline, created to operate these aircraft. During the year, several more machines were assembled, which completed the tests and were transferred to the customer. In September 1952, de Havilland Comet entered the line. By the summer of 1953, flights on Comets became a real hit after members of the British royal family made a familiarization flight on one of the planes. New jetliners provided passengers with an extraordinary level of flight comfort, compared to piston models, their cruising speed reached 740 km / h, which at that time seemed incredible and, on average, was half as much as its counterparts (the average speeds of the then aircraft were 500-550 km / h).

By then, BOAC had developed the first special long-haul flight from London to Tokyo. The trip involved 9 intermediate landings and took about 36 hours. Earlier, on a similar flight, Argonaut piston aircraft were used and the journey lasted 86 hours, i.e. more than three days. And this is taking into account the good weather. In case of weather difficulties, the advantage of jet aircraft became even more obvious: with their flight altitudes of up to 13 kilometers, comets could fly over storm zones while most piston aircraft had a practical ceiling of 7-8 kilometers and were forced to wait or fly around these zones. The practice of long-distance travel spread and soon Comet began to fly to India, South Africa, and Singapore.

De Havilland culminated in its success. Comet 1 and the upgraded Comet 1A began to be exported to France. Updated Comet 2 with new Rolls-Royce Avon engines were purchased by Air India, Japan Air Lines. Contracts for the purchase of aircraft were signed by airlines from Brazil and the United States, including Pan American, which did not wait for Boeing and Douglas aircraft and placed orders for the updated Comet 3, accommodating up to 76 passengers and capable of flying across the Atlantic. De Havilland Comet became a real revolution and pride of Great Britain. Even the USA and the USSR lagged behind in this direction by at least several years (the Tu-104 began to be operated only in 1956, and the Boeing 707 and Douglas DC-8 arrived only at the end of the decade). However, like all revolutions, this revolution did not manage to avoid casualties.

In 1952 and 1953, two Comets of BOAC and Canadian Pacific Airlines were unable to take off, rolled out of the lanes and collapsed. Several people died. The investigation showed that pilots accustomed to piston airplanes too sharply lifted their nose on takeoff, which led to a sharp decrease in the amount of air entering the engines and a drop in their power. After making some adjustments to the operating rules, as well as upgrading the slats, this problem was resolved.

However, soon, in the same 1953, a new major plane crash occurred. When flying through a storm after taking off from Calcutta airport, the BOAC board crashed in the air. Killed 43 people. Eyewitnesses stated that they saw a burning plane with torn wing consoles. The investigation concluded that the plane crashed in the air from gusts of a gale-force wind.

After only 8 months, in 1954, another BOAC airliner disappeared while flying over the Mediterranean Sea. This time it was not possible to find out the reasons. After several crashes in a row, BOAC decided to suspend the flights of these aircraft. De Havilland began an urgent retrofit program, suggesting that the crash was due to an engine explosion and subsequent glider destruction.

Despite this, confidence in the aircraft remained and other airlines continued to operate them. But that only changed a few months later when the South African Airways Comet, flying from Rome to Cairo on the way to Johannesburg, crashed over the sea near Naples. After that, all DH 106 aircraft were forbidden to fly. The type certificate was temporarily revoked and the De Havilland production line stopped. Prime Minister Winston Churchill demanded clarification of the circumstances of the disasters and an unprecedented in scope investigation began, which was under the direct control of parliament.

The investigation, which lasted several years, showed that the cause of the disasters was the flaws in the fuselage structure. A large number of drills of a thin but durable aluminum fuselage, the use of large square windows, and a number of other solutions were the usual methods of manufacturing aircraft of the time. However, jet comets flew faster and higher than any other aircraft of that time and the structure, especially the fuselage, was subjected to heavy loads and pressure drops. Studies have shown that conventional assembly methods already at the production stage led to the appearance of microdamage, and several incorrect engineering solutions reinforced the influence of the metal fatigue effect on the structural integrity. As a result, the number of micro damages increased exponentially over time, which, in the end, led to the destruction of the aircraft.

De Havilland, however, launched large-scale work to create a new version of the aircraft, which should no longer have been exposed to the described risks. The square portholes were replaced by oval ones, and the fuselage defecation areas were reinforced. But in spite of all efforts, most of the aircraft already released did not fly again. The exploitation of Comets remained banned until 1958.

By that time, the latest and most advanced Comet 4 model was created on the basis of the Comet 3 model. This model has become a new generation, more efficient, more capacious and economical, as well as with a sufficient level of security so that customers would pay attention to it again by signing contracts for several tens of units.

Comet 4 made its first flight in the spring of 1958 and by September received a type certificate. However, time and reputation were lost. Airlines were afraid to buy a plane, and passengers were afraid to fly on it. In addition, by the end of the 1950s, the British monopoly in the market of jet passenger aircraft was completed. The USSR operated its Tu-104, France introduced Sud Aviation Caravelle, and in the USA, the Boeing 707 and Douglas DC-8 entered the market. These aircraft appeared later, walked along the already beaten road and, in many respects, already surpassed the pioneer. A total of 76 Comet 4 airliners were delivered against hundreds of units from competing aircraft. The plans for creating an improved version of Comet 5 did not find the support of the authorities and airlines, the plane was never created. In 1964, production was completed. In total, 114 aircraft of this model were created.

In the 1960s, British airlines began to gradually replace the Comets fleet with new aircraft, especially on transatlantic flights. In addition to the purchased American airliners, second-generation British jets, primarily the long-range Vickers VC10, entered the line.

Two Comet 4C airliners were later returned to De Havilland and, after the company was reorganized and the Hawker Sidelley was created, were converted to prototypes of Hawker Sidelley Nimrod naval patrol aircraft (these aircraft were successfully operated by the Royal Navy until 2011).

The operation of de Havilland Comet aircraft was officially completed in 1997, when the flight of the Comet 4C, which was used as a flying laboratory, ceased.

Heritage

Despite all the problems and disasters associated with Comets, these airliners are considered an absolute revolution in the aviation industry, accelerating the development of the global air transportation market. In addition, the aircraft, ahead of its time, faced serious difficulties, but the experience of its operation allowed aircraft manufacturers in both the UK and other countries to avoid them. First of all, this concerns design errors that led to disasters. If de Havilland had not encountered this disaster, the engineers of Tupolev, Boeing, Douglas and others would probably have faced it.

Specifications

ModificationComet 1Comet 2Comet 3Comet 4
PowerplantHalford H.2 Ghost 50Rolls-Royce Avon Mk 503/504Rolls-Royce Avon Mk 502/521Rolls-Royce Avon Mk 524
Engine thrust4 X 2.24 ts4 X 3.16 ts4 X 4.49 ts4 X 4.79 ts
Maximum number of passengers36 — 4436 — 4458 — 7656 — 81
Practical ceiling13,000 m13,000 m14,000 m13,000 m
Range2,400 km4,200 km4,300 km5,190 km
Maximum take-off weight50 t54 t68 t71 t
Cruising speed740 km /h790 km / h840 km / h840 km / h
Wingspan35 m35 m35 m35 m
Length28 m29.29 m29.29 m33.99 m
Height8.99 m8.99 m8.99 m8.99 m
Graduated from Embry-Riddle Aviation University with a master's degree in aviation science. He began his career as an aviation researcher in local periodicals. Has a pilot license. Now are the author and developer of the Plane Worlds.