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De Havilland DH-106 Comet 1 (1949)

De Havilland DH-106 Comet 1 (1949)

The aircraft manufactured by the British de Haviland company was the world's first mass-produced commercial jetliner.

Technology

Keywords

airplane, Comet, aviation, jet engine, passenger carrier, passenger transport, gázturbina, disaster, aviation disaster, accident, air pressure, contemporary era, transportation, invention

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Scenes

DH-106 Comet 1

The de Havilland DH 106 Comet 1, manufactured by the British-owned de Havilland Aircraft Company Limited, was the first mass-produced, turbojet-powered airliner. The maiden flight of the airliner’s prototype was in 1949 and the first scheduled flights of the Comets, operated by the British Overseas Airways Corporation (BOAC), occurred three years later, in 1952.

The aircraft featured several innovative elements, which were new to civil aviation. Since these airliners were popular with the public and their operation also seemed economical, the Comets were set for a bright future; however, the high hopes were never fully realised because of the Comet's accidents. In addition, rival American manufacturers also gained an edge over the de Havilland Aircraft Company.

Construction

  • cockpit
  • fuselage - It consisted of a thin metal skin and had a clean design. The cargo hold was built in the lower deck area.
  • wing - The large, trapezoidal wings were mounted low.
  • jet engine - Two of these engines were buried in each wing root.
  • air intake
  • windows - Originally, these were rectangular but, following the findings of the investigations of the crashes, they were replaced with oval ones.
  • BOAC - The jetliner was used primarily by the British Overseas Airways Corporation.
  • undercarriage
  • elevon
  • flap
  • outlet
  • vertical stabiliser
  • rudder
  • elevator control
  • passenger cabin - This area was pressurised in order to balance the low outside air pressure at high altitudes.

In contrast with other airliners of the time, the Comet had a more spacious passenger cabin with large windows, comfortable seats and tables. It also had a galley (kitchen) for serving hot and cold food, and separate lavatories for men and women.

Much to the passengers’ surprise, the Comet was relatively quiet because of the soundproof passenger cabin and the use of sound baffles in the jet engines. Flights were also smooth and the passengers experienced barely any vibration; these aspects were uncommon for propeller-driven aircrafts. Moreover, the Comet could cover the same distance 50% faster than rival airliners.

Pressure change

  • atmospheric pressure: 100 kPa
  • atmospheric pressure: 19 kPa
  • cabin pressure: 100 kPa
  • cabin pressure: 79 kPa

The comfortable and economical Comets had a clean design, and their first scheduled flights, in 1952, signalled the beginning of a success story. However, serious accidents happened already in their first year of operation.

The first two accidents were caused probably by pilot error but the third one occurred because of a construction flaw. As a result of the latter accident, the Comets were equipped with weather radars and their control yokes were improved by the addition of an artificial feel system (Q-feel system). Sadly enough, more disasters followed in 1954 when two Comets crashed into the Mediterranean Sea killing everyone on board. Consequently, all these airliners were withdrawn immediately from service and their production stopped temporarily.

The wreckage of the planes were retrieved and then thoroughly examined; the fuselage of the plane underwent special pressure tests. It turned out that the disasters were caused by fatigue cracks, which developed around the corners of the rectangular windows because of stress concentration and poorly installed window frames. The rectangular windows were replaced with oval ones and the structure of the fuselage and the wings were also strengthened. The catastrophes of the Comets and the consequent improvements of the planes provided valuable lessons for other aircraft manufacturers as well.

The effect of pressure change on window types

  • rectangular window - Because of the constant pressurisation and depressurisation of the passenger cabin, fatigue cracks developed in the corners of the window frames.
  • rounded window - After the de Havilland crashes, aeroplane designers replaced rectangular aeroplane windows with rounded ones in order to reduce mechanical stress around the window frames.

As we move higher in the atmosphere, air pressure gets lower: at cruising altitude, (about 10,000 m), it is about one fourth or one fifth of the air pressure measured at ground level.

As a result, the higher air pressure within the passenger cabin exerts pressure on the inside of the walls of the cabin. (Although the air pressure in the passenger cabin is not constant, the decrease is insignificant.)

In addition, at a height of 10,000 m, the outside air temperature is about -40 °C, so the outside of the wall of the passenger cabin cools down. However, friction, which occurs because of the high speed of the aeroplane, does exactly the opposite: it heats the outside surface of the plane.

If these factors are taken into account together with the forces acting on the aircraft during take-off and landing, it becomes clear that the airframe and the wings must be as durable as possible to bear extreme forces. Stress around the corners of rectangular window frames was a result of the forces acting on the plane, and these led to the development of fatigue cracks. In the case of oval windows, stress resulting from the change of the passenger cabin's shape is significantly lower.

Animation

  • cockpit
  • fuselage - It consisted of a thin metal skin and had a clean design. The cargo hold was built in the lower deck area.
  • wing - The large, trapezoidal wings were mounted low.
  • jet engine - Two of these engines were buried in each wing root.
  • air intake
  • windows - Originally, these were rectangular but, following the findings of the investigations of the crashes, they were replaced with oval ones.
  • BOAC - The jetliner was used primarily by the British Overseas Airways Corporation.
  • undercarriage
  • elevon
  • flap
  • outlet
  • vertical stabiliser
  • rudder
  • elevator control
  • passenger cabin - This area was pressurised in order to balance the low outside air pressure at high altitudes.

Narration

The de Havilland DH 106 Comet 1, manufactured by the British-owned de Havilland Aircraft Company, was the first mass-produced, turbojet-powered airliner, that is, the first jetliner. This aircraft is therefore considered a milestone in the history of aviation.

The first scheduled flight of the Comet took place in 1952, when the Johannesburg-bound plane took off from London.

The Comet had a clean design and was significantly faster and far more comfortable than other airliners. In addition, it was economical to operate and the aircraft was set for a bright future; however, expectations were never fully realised because of accidents caused by construction flaws.

Even though the de Havilland Aircraft Company corrected the flaws in their planes and helped pave the way for safer civil aviation, the improved Comets could not compete with airliners produced by ambitious American manufacturers.

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