The Comet, 1952
The first jet airliner to enter commercial service was the de Havilland Comet, operated by the British Overseas Airways Corporation (BOAC). It carried its first fare-paying passengers on 2 May 1952 on a route from London to Johannesburg, with several stops on the way. That was well before 1967, which saw a different milestone, the unveiling of the Boeing 747.
The Comet was a remarkable design. Built by the British company de Havilland, it first flew in July 1949. It had four jet engines buried in the wing roots, a smooth, streamlined shape, and a pressurised cabin that allowed it to cruise high above weather. It carried a small number of passengers, fewer than 50, and was faster and much quieter and smoother than the piston-engined aircraft passengers were used to. Airlines and the public were enthusiastic, and orders came from several countries.
Early success
For about two years, the Comet looked like the future. Flights were popular, and the aircraft gave Britain a lead in civil aviation that American manufacturers had not yet matched. Cabins were seen as luxurious, with the experience described as free of the vibration that came with propellers. Routes expanded to include destinations in Asia and Africa.
The accidents
In 1953 and 1954 the picture changed. Several Comets were lost in accidents.
- In May 1953 a BOAC Comet broke up in the air after leaving Calcutta. At first the cause was thought to be severe weather.
- In January 1954 another BOAC Comet crashed into the sea near the island of Elba in the Mediterranean, with the loss of everyone on board.
- In April 1954 a Comet operated by South African Airways crashed into the sea off Naples soon after leaving Rome.
After the Elba accident, Comets were temporarily grounded, then returned to service after modifications that addressed what were thought at the time to be possible causes. The April 1954 loss made clear that something more basic was wrong, and the whole fleet was grounded again.
Finding the cause: metal fatigue
The investigation was led by the Royal Aircraft Establishment at Farnborough. Wreckage from the sea near Elba was recovered, and engineers reconstructed much of it. A crucial test was also carried out on a complete fuselage, which was placed in a large water tank and repeatedly pressurised and depressurised to simulate many flights.
The test failed in a way that matched the accidents. A crack started at a corner of one of the aircraft’s windows, in a cutout for a radio direction-finding aerial, and spread until the fuselage tore open. The cause was metal fatigue. Each flight pressurised the cabin, then released the pressure on landing, which flexed the skin. Stresses were concentrated at the sharp corners of the windows. Over time, small cracks formed at these points and then grew.
A public inquiry later accepted the finding that fatigue failure of the cabin structure was the most probable cause. Engineers have also noted that, at the time, the understanding of fatigue in pressurised structures was less developed than it is today, and the design had not been tested for so many pressure cycles.
What changed
The consequences went well beyond the Comet:
- Aircraft windows were redesigned with rounded corners rather than square, to avoid concentrating stress.
- Designers began to build in “fail-safe” structures, in which a crack in one part would not lead to total failure and could be found by inspection.
- Manufacturers carried out fatigue testing on full-scale airframes as a standard part of design.
- Accident investigators gained confidence in rebuilding wreckage to find causes, a technique that later became standard practice.
The same logic came up again many years later in other investigations. When the Apollo 204 review board examined the 1967 spacecraft fire, it was part of the same tradition of detailed technical inquiry, though the circumstances were quite different.
The Comet’s second career
De Havilland redesigned the aircraft. The Comet 4, which first flew in 1958, was larger, had more powerful engines and a strengthened structure. BOAC began the first scheduled transatlantic jet service with it on 4 October 1958, a few weeks before Pan American started flights with the Boeing 707. It flew for many years with airlines in several countries.
The Comet’s airframe also formed the basis of the Nimrod, a maritime patrol aircraft that served with the Royal Air Force for decades. So the type’s story did not end with the accidents.
The lasting effect
The Comet gets credit for being first but also for paying a heavy price for it. The American manufacturers that came next, including Boeing and Douglas, had the advantage of seeing the Comet’s mistakes. The Boeing 707, which became the commercial standard for the late 1950s, benefited from the new knowledge about fatigue. Each later generation of jets, up to the 747 and the supersonic Concorde airliner, built on lessons of this kind.
The title of this article describes the first jet airliner entering service. The accurate date for that is 1952, and the story that follows is one of rapid promise, accidents and a safer industry.