The de Havilland DH.88 Comet is a British two-seat, twin-engined aircraft built by the de Havilland Aircraft Company. It was developed specifically to participate in the 1934 England-Australia MacRobertson Air Race from the United Kingdom to Australia.
Development of the Comet was seen as both a prestige project and an entry into the use of modern techniques. It was designed to meet the specific requirements of the race. It was the first British aircraft to incorporate in one airframe all the elements of the modern high speed aircraft - stressed-skin construction, cantilever monoplane flying surfaces, retractable undercarriage, landing flaps, variable-pitch propellers and an enclosed cockpit.
Three Comets were produced for the race, all for private owners at the discounted price of £5,000 per aircraft. The aircraft underwent a rapid development cycle, performing its maiden flight only six weeks prior to the race. Comet G-ACSS Grosvenor House emerged as the winner. Another two Comets were built after the race. The Comet established many aviation records, both during the race and afterwards, and also took part in further races. Three were bought and evaluated by national governments, typically as mail planes. Two Comets, G-ACSS and G-ACSP, survived while a number of full-scale replicas have also been constructed.
Development
Background: The Great Air Race
During 1933, the MacRobertson Air Race, a multi-stage flight from the United Kingdom to Australia, was being planned for October 1934, to celebrate the 100th anniversary of the Australian State of Victoria. Sponsored by Macpherson Robertson, an Australian confectionery manufacturer, the race would be flown in stages from England to Melbourne.
The new generation of monoplane airliners which were then being developed in America had no rival in Britain at the time, so Geoffrey de Havilland, a British aviation pioneer and founder of aircraft manufacturing firm de Havilland, was determined that, for the sake of national prestige, Britain should put up a serious competitor. While the company board recognised that there would be no prospect of recouping the full investment of producing such a machine, they believed that the project would enhance the company's prestige and also provide experience in the development of fast monoplanes.
They therefore announced in January 1934 that, if three orders could be obtained by 28 February, a specialist racer which could achieve a guaranteed speed of to be named the Comet would be built and sold for £5,000 each, . This price was estimated as being half of the cost of manufacture. Three orders were received by the deadline; one from Jim Mollison, to be flown by him and his wife Amy (better known as Amy Johnson), one from Arthur Edwards, a hotel owner and manager, and the last from motorcar racer Bernard Rubin.
Design phase
Although designed around the requirements for the MacRobertson race, owing to its unusual requirements the Comet did not fit the standard technical specification for a racing aircraft, nevertheless it was classed as a "Special, sub-division (f), Racing or Record". De Havilland paid special attention to the non-stop range necessary for the long official stages. They initially intended to produce a twin-engined two-seat development of the DH.71 experimental monoplane. However, this would have had inadequate performance so the designer, A. E. Hagg, turned to a more innovative design. He chose a cantilever monoplane with enclosed cockpit, retractable undercarriage and flaps. In order to achieve take-off at a reasonable speed and with high all-up weight, combined with a satisfactory high-speed cruise, it would be necessary to fit variable-pitch propellers.