De Havilland CometThe de Havilland Comet was the world's first commercial jet airliner to reach production. Developed and manufactured by de Havilland, it first flew in 1949 and was considered a landmark British aeronautical design. After a successful introduction into commercial service, early Comet models suffered from catastrophic metal fatigue, causing a string of well-publicised accidents.
The Comet was withdrawn temporarily and redesigned. The Comet 4 series subsequently enjoyed a long and productive career of over 30 years, although sales never fully recovered. The Hawker Siddeley Nimrod, the military derivative of the Comet airliner, is still in service. The original decades-old airframes are being rebuilt with new wings and engines to produce the Nimrod MRA 4, expected to serve with Britain's Royal Air Force until the 2020s, more than 70 years after the Comet's first flight.
The Comet is an all-metal low-wing cantilever monoplane powered by four jet engines, approximately the length of a Boeing 737 but carrying fewer people in greater comfort. The earliest Comets had 11 rows of seats with four seats to a row in the 1A configuration used by Air France. BOAC used an even roomier arrangement of 36 seats (each with its own ashtray). The galley could serve hot and cold food and drinks and there was a bar. Other amenities included separate men's and women's washrooms. The passenger cabin was quieter than those of propeller-driven airliners. The Comet's four-man cockpit held two pilots, a flight engineer, and a navigator.
The clean, low-drag design featured many unique or innovative design elements, including a swept leading edge, integral wing fuel tanks and four-wheel bogie main undercarriage units designed by de Havilland. The Comet was also the first pressurised jet-propelled commercial aircraft. For emergencies, life rafts were stored in the wings near the engines and a life vest was stowed under each seat bottom.
Two pairs of de Havilland Ghost 50 Mk1 turbojet engines were buried in the wings close to the fuselage. British designers chose this configuration because it avoided the drag of podded engines and allowed a smaller fin and rudder, since the hazards of asymmetric thrust were reduced. The engines' higher mounting in the wings also reduced the risk of ingestion damage, a major problem for turbine engines. However, these benefits were compromised by increased structural weight and general complexity, including armour for the engine cells (in case of an engine explosion) and a more complicated wing structure. This arrangement also carried higher risk of catastrophic wing failure in case of an engine fire, cited as the main reason the Boeing Aircraft Company chose podded engines in their subsequent jet bomber and airliner designs.
The Comet was originally intended to have two hydrogen peroxide powered de Havilland Sprite booster rockets for takeoff under hot and high conditions from airports such as Khartoum and Nairobi. These were tested on 30 flights, but the Ghosts were apparently powerful enough without them. The later Comet 4 was highly rated for its takeoff performance from high altitude locations such as Mexico City. Its newer AJ.65 Avon engines, low weight (compared to the Boeing 707 and Douglas DC-8), and exceptionally clean design all contributed to its high performance. Early-model Comets required about five or six man-hours of maintenance labour per flight hour, fewer than the propeller-driven planes it replaced.
The Comet's thin metal skin was composed of advanced new alloys (Directorate of Technical Development 564/L.73 and DTD 746C/L90) and was both chemically bonded using the adhesive Redux and riveted, which saved weight and reduced the risk of fatigue cracks spreading from the rivets. When it went into service with BOAC on 2 May 1952, the Comet was the most exhaustively tested airliner in history. For example, a water tank was used to test the entire forward fuselage section for metal fatigue by repeatedly pressurising to 2.75 psi overpressure (11 psi) and depressurising through more than 16,000 cycles, equivalent to about 40,000 hours of airline service. The windows were tested under a pressure of 12 psi, 4.75 psi above the normal service ceiling of 36,000' (10973 m). One window frame survived a massive 100 psi, about 1,250% over the maximum pressure it would encounter in service.
The Comet was withdrawn temporarily and redesigned. The Comet 4 series subsequently enjoyed a long and productive career of over 30 years, although sales never fully recovered. The Hawker Siddeley Nimrod, the military derivative of the Comet airliner, is still in service. The original decades-old airframes are being rebuilt with new wings and engines to produce the Nimrod MRA 4, expected to serve with Britain's Royal Air Force until the 2020s, more than 70 years after the Comet's first flight.
The Comet is an all-metal low-wing cantilever monoplane powered by four jet engines, approximately the length of a Boeing 737 but carrying fewer people in greater comfort. The earliest Comets had 11 rows of seats with four seats to a row in the 1A configuration used by Air France. BOAC used an even roomier arrangement of 36 seats (each with its own ashtray). The galley could serve hot and cold food and drinks and there was a bar. Other amenities included separate men's and women's washrooms. The passenger cabin was quieter than those of propeller-driven airliners. The Comet's four-man cockpit held two pilots, a flight engineer, and a navigator.
The clean, low-drag design featured many unique or innovative design elements, including a swept leading edge, integral wing fuel tanks and four-wheel bogie main undercarriage units designed by de Havilland. The Comet was also the first pressurised jet-propelled commercial aircraft. For emergencies, life rafts were stored in the wings near the engines and a life vest was stowed under each seat bottom.
Two pairs of de Havilland Ghost 50 Mk1 turbojet engines were buried in the wings close to the fuselage. British designers chose this configuration because it avoided the drag of podded engines and allowed a smaller fin and rudder, since the hazards of asymmetric thrust were reduced. The engines' higher mounting in the wings also reduced the risk of ingestion damage, a major problem for turbine engines. However, these benefits were compromised by increased structural weight and general complexity, including armour for the engine cells (in case of an engine explosion) and a more complicated wing structure. This arrangement also carried higher risk of catastrophic wing failure in case of an engine fire, cited as the main reason the Boeing Aircraft Company chose podded engines in their subsequent jet bomber and airliner designs.
The Comet was originally intended to have two hydrogen peroxide powered de Havilland Sprite booster rockets for takeoff under hot and high conditions from airports such as Khartoum and Nairobi. These were tested on 30 flights, but the Ghosts were apparently powerful enough without them. The later Comet 4 was highly rated for its takeoff performance from high altitude locations such as Mexico City. Its newer AJ.65 Avon engines, low weight (compared to the Boeing 707 and Douglas DC-8), and exceptionally clean design all contributed to its high performance. Early-model Comets required about five or six man-hours of maintenance labour per flight hour, fewer than the propeller-driven planes it replaced.
The Comet's thin metal skin was composed of advanced new alloys (Directorate of Technical Development 564/L.73 and DTD 746C/L90) and was both chemically bonded using the adhesive Redux and riveted, which saved weight and reduced the risk of fatigue cracks spreading from the rivets. When it went into service with BOAC on 2 May 1952, the Comet was the most exhaustively tested airliner in history. For example, a water tank was used to test the entire forward fuselage section for metal fatigue by repeatedly pressurising to 2.75 psi overpressure (11 psi) and depressurising through more than 16,000 cycles, equivalent to about 40,000 hours of airline service. The windows were tested under a pressure of 12 psi, 4.75 psi above the normal service ceiling of 36,000' (10973 m). One window frame survived a massive 100 psi, about 1,250% over the maximum pressure it would encounter in service.
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