DH-106 Comet

De Havilland worked closely with BOAC on specification and costs. As the DH-108 programme unfolded, it became clear that the tailless design had poor stability; the combined elevators and ailerons (“elevons”) were not effective at low speed; and the structure to support such a large, swept wing would compromise payload.

By Summer 1946, the Comet had grown a conventional tail and the wing sweep had been reduced from 40° to 20°. This reduced top speed by 100 mph, but provided increased payload and good low-speed handling.

Detailed design began in November 1946, lead by de Havilland's chief designer, Rod Bishop. It was a monumental challenge: no existing aircraft could carry as much payload so fast and so far, so there was no point of reference. The sheer breadth of achievement is staggering.

Early jet engines were not powerful, therefore the Comet had to be both light and extremely slippery. A great deal of work was done in wind-tunnel research to reduce drag. Characteristically, the engines were incorporated into thin, laminar-flow wings; the thinnest of their size.

For the Mosquito and Vampire, special adhesives had been developed by Dr Norman de Bruyne at the Aero Research Company.

De Havilland were convinced by the use of structural adhesives, which both increased strength and reduced weight compared with conventional mechanical fasteners. New techniques were developed for the Comet, and used extensively in the wings. A special factory was built at Broughton, North Wales, and remains at the cutting edge, designing and manufacturing bonded wings in aluminium and carbon composites for Airbus.

The Comet cruised at 12,200m (40,000 ft), where the temperature is -55°C, and the pressure is 200 millibars. This, combined with military rates of climb and descent, required sophisticated atmospheric control. Traditionally, airliners had used separate heaters and compressors. For these conditions, it would have been too heavy. The solution was to bleed fresh air at high pressure from the engine compressor stage, and hot air from the turbine, via a system of heat exchangers, humidifiers, regulators and silencers.

New metal alloys, fully-powered hydraulics, anti-lock brakes, new fuel and refuelling equipment – these are just some of the innovations that had to be developed by de Havilland and their technical partners. It's even more extraordinary, then, that this totally new kind of aircraft, the world's first jet airliner, was delivered on time, and within budget.