« Computing: Filtering Forged Junk Mail Bounces with Procmail | Main | Gnome-o-gram: Tipping Point »

Monday, October 20, 2008

Reading List: De Havilland Comet

Darling, Kev. De Havilland Comet. North Branch, MN: Specialty Press, 2001. ISBN 978-1-58007-036-2.
If the Boeing 377 was the epitome and eventual sunset of the piston powered airliner, the De Havilland Comet was the dawn, or perhaps the false dawn, of the jet age. As World War II was winding down, the British Government convened a commission to explore how the advances in aviation during the war could be translated into commercial aircraft in the postwar era, and how the British aviation industry could transition from military production to a leadership position in postwar aviation. Among the projects proposed, the most daring was the “Type 4”, which eventually became the De Havilland Comet. Powered by British-invented turbojet engines, it would be a swept-wing, four engine aircraft with a cruising speed in excess of 500 miles per hour and a stage length of 1500 miles. Despite these daunting technological leaps, the British aviation industry rose to the challenge, and in July 1949, the prototype De Havilland Comet took to the air. After extensive testing, the Comet entered revenue service in May 1952, the first commercial jet-powered passenger service. Surely the jet age was dawning, and Britannia would rule it.

And then disaster struck. First, three aircraft were lost due to the Comet's tetchy handling qualities and cockpit crews' unfamiliarity with the need to maintain speed in takeoff and landing with swept-wing aircraft. Another Comet was lost with all on board flying into a tropical storm in India. Analysis of the wreckage indicated that metal fatigue cracks at the corners of the square windows may have contributed to the structural failures, but this was not considered the definitive cause of the crash and Comets were permitted to continue to fly. Next, a Comet departed Rome and disintegrated in mid-air above the island of Elba, killing all on board. BOAC (the operator of the Comet in question) grounded their fleet voluntarily pending an investigation, but then reinstated flights 10 weeks later, as no probable cause had been determined for the earlier crashes. Just three days later, another BOAC aircraft, also departing Rome, disintegrated in the air near Naples, with no survivors. The British Civil Aviation Authority withdrew the Permit to Fly for the Comet, grounding all of the aircraft in operation.

Assiduous investigation determined that the flaw in the Comet had nothing to do with its breakthrough jet propulsion, or the performance it permitted, but rather structural failure due to metal fatigue, which started at the aerial covers at the top of the fuselage, then disastrously propagated to cracks originating at the square corners of the windows in the passenger cabin. Reinforcement of the weak points of the fuselage and replacement of the square windows with oval ones completely solved this problem, but only after precious time had been lost and, with it, the Comet's chance to define the jet age.

The subsequent Comets were a great success. The Comet 2 served with distinction with the Royal Air Force in a variety of capacities, and the Comet 4 became the flagship of numerous airlines around the globe. On October 4th, 1958, a Comet 4 inaugurated transatlantic jet passenger service, but just 22 days before the entry into service of the Boeing 707. The 707, with much greater passenger capacity (I remember the first time I saw one—I drew in my breath and said “It's so big”—the 747 actually had less impact on me than the 707 compared to earlier prop airliners) rapidly supplanted the Comet on high traffic city pairs.

But the Comet lived on. In the aftermarket, it was the jet fleet leader of numerous airlines, and the flagship of British airtour operator Dan-Air. The Comet 4 was the basis for the Nimrod marine patrol aircraft, which has served with the Royal Air Force since 1971 and remains in service today. With lifetime extensions, it is entirely possible that Nimrod aircraft will remain on patrol a century after its progenitor, the Comet, first took to the air.

This thorough, well-written, and lavishly illustrated (8 pages in colour) book provides comprehensive coverage of the Comet and Nimrod programmes, from concept through development, test, entry into service, tragedy, recovery, and eventual success (short-lived for the Comet 4, continuing for its Nimrod offspring).

Posted at October 20, 2008 02:20