de Havilland Comet




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Specifications

Primary Function:
Crew:
Engines:
Thrust:
Max. Weight:
Seating (typical):
Length:
Wingspan:
Cruise Speed:
Max Speed:
Climb Rate:
Ceiling:
Range:
First Flight:
Year Deployed:
airliner
four
Halford turbojets
4 x 5,000 lbf. ea.
110,000 lbs.
36 - 44 passengers
93 ft.1 in.
114 ft. 11 in.
460 mph
483 mph
2,000 fpm
39,800 feet
1.520 miles
7/27/49
1952




de Havilland Comet

de Havilland Comet

The concept for the de Havilland Comet, officially DH 106 Comet, the world's first jet propelled airliner, originated in 1943 when British aviation experts met to discuss how Great Britain could take the lead in world-wide commercial aviation.

Among the issues discussed was improving passenger comfort. Two of the greatest causes of passenger fatigue were the noise and vibration caused by aircraft piston engines. The piston engines also appeared to have met the limits for which they were capable of producing maximum power.

The use of jet engines, which began development in Great Britain and Germany prior to World War II, were considered as a means to lessen passenger fatigue. Furthermore, they were capable of propelling aircraft at high speeds and altitudes. It was envisioned that, with their advances in jet engine technology, the British could regain the lead from the United States in commercial aviation.

De Havilland aircraft had produced a jet engine powered fighter aircraft that flew prior to the end of World War II. They were the only British company to do so. In February of 1945, the British Ministry of Supply awarded the de Havilland Aircraft Company a contract to produce the world's first jet airliner.

It was understood that the new aircraft would have to fly at high altitudes, where the air is thin, to lessen drag, thus reducing fuel consumption. While the pilot of a jet fighter could breathe using an oxygen mask, this wasn't practical on an airliner. The cabin would need to be pressurized, meaning it would be pumped with air. This posed the problem of stressing the aircraft's structure, during numerous cycles, by successively increasing interior pressure as the plane climbed and reducing pressure when it was descending.

Work on the new jetliner began in 1946. Various aircraft configurations were considered, including tailless. However, stability issues necessitated using a more conventional design. A larger fuselage was necessary to accommodate 36 seats instead of the original 24 seat configuration.

Numerous tests were conducted in a decompression chamber and water tank where aircraft components and its fuselage were subject to higher pressures and more cycles than what was anticipated in normal service.

The new de Havilland Comet first took to the sky on July 27, 1949. British Overseas Airline Corp. (BOAC) placed an order for eight of the new jet airliners. After more testing, a de Havilland Comet with BOAC made its first commercial flight from from London to Johannesburg on May 2, 1952.

On October 26, 1952 a BOAC de Havilland Comet flying out of Rome skidded off the runway during takeoff with two injuries and no loss of life. However, the aircraft would never fly again.

On March 3, 1953 a Canadian Pacific Airlines de Havilland Comet was lost taking off from Karachi Pakistan on a flight to Australia. There were no survivors.

Investigations originally concluded that pilot error was the cause of the incidents. However, upon further investigation, it was found that a change in the wing's leading edges and revised pilot instructions would resolve the issue. It seems that the engines of the aircraft were losing power on takeoff due to reduced air pressure at their inlets during high angles of attack.

On May 2, 1953 a BOAC de Havilland Comet disintegrated as it passed through a severe thunderstorm after taking off from Calcutta airport. All 43 passengers and crew on board perished.

On January 10, 1954 a BOAC de Havilland Comet, some 20 minutes out of Rome climbing through 26,000 feet, suddenly broke up and plunged into the Mediterranean Sea. A witness told police, “I heard a roar, very high. Then there was a series of blasts. The next thing I saw was a streak of smoke plunging perpendicularly into the sea.” The plane's crew and 29 passengers were all lost.

BOAC grounded all of their de Havilland Comet aircraft the next day. The British Navy was tasked with finding parts of the aircraft that lay about 500 feet deep. Large pieces of the aircraft's tail and fuselage were recovered and inspected. Investigators concluded that, "there appeared to be no justification for placing special restrictions on the Comet aircraft". Thereafter flights resumed.

On April 8, 1954 a South African Airways de Havilland Comet flying from Rome to Cairo at an altitude of 35,000 feet suddenly plunged into the Mediterranean. Seven crew and fourteen passengers were lost. Immediately thereafter, all de Havilland Comet aircraft were grounded and their Certificate of Airworthiness revoked.

The further testing of all recovered fuselage pieces pointed to metal fatigue. When an entire de Havilland Comet fuselage was tested from ground level to a simulated altitude of 35,000 feet in a water tank, it was found that after 9,000 hours of repeated pressurization and depressurization, the fuselage split due to metal fatigue. The aircraft which were lost when their fuselages could no longer contain high air pressure had exploded like bombs.

There is a common misunderstanding that the square passenger windows of the first de Havilland Comet aircraft were the cause of the accidents. This is because investigations called the Automatic Direction Finder (ADF) panel on the aircraft's fuselage a window. In fact, the shape of the passenger windows was not at fault. Douglas DC-7 and Boeing 377 aircraft all had similar passenger window shapes and even larger sizes than the first de Havilland Comet aircraft.

New de Havilland Comet aircraft were built using lessons learned from the lost aircraft. They were stronger and larger. However, by this time, both Boeing and Douglas had introduced passenger jets which were, faster, had more range, and held more passengers.

Flying the de Havilland Comet

Pushing the throttles forward while taking off in the jet powered de Havilland Comet doesn't result in an immediate push in the back. However, as the engines spool up, the aircraft quickly accelerates to rotation speed with a quick climb following. The nose must be trimmed down slightly during and after takeoff to avoid reducing air pressure to the engine inlets during high angles of attack.

After takeoff, power levels are reduced to provide for the best climb speed to an altitude of 35,000 feet. Once leveled off, steep turns both to the right and left were flown. Although the controls are quite responsive for this size aircraft, they felt somewhat heavy at higher speeds. Upon descending to 15,000 feet, the same maneuvers were tried. The feel was similar, but perhaps a bit more solid.

Flying final presents no problem as reducing throttle and lowering flaps resulted in quick speed reductions with no loss of control. Some gusty winds were experienced while descending towards touch down. The de Havilland Comet handled them easily, sliding solidly down to the threshold, and once over the runway, pointing exactly as commanded. The original de Havilland Comet jets did not have thrust reversing, but did have very effective brakes.

A total of some 114 de Havilland Comet aircraft of all types were produced.

RC de Havilland Comet

RC de Havilland Comet

The RC de Havilland Comet scratch built by master builder Sergio Vergara has a 76 in. wingspan with a length of 64 in.  Construction is all wood and includes retracts, flaps and navigation lights.  Power is by four 3300 Kv motors turning 60mm EDF units.  All up weight is around 5 lbs.




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