THE WINNING MACHINE in the England to Australia race of 1934 was the Comet Grosvenor House, piloted by C. W. A. Scott and Captain T. Campbell Black at 176.8 miles an hour flying time or at 160 miles an hour elapsed time. The aircraft was originally powered by two special high-compression Gipsy Six R engines, each developing 220 horse-power at 2,350 revolutions at sea level.
THE De Havilland Comet, or D.H.88, is a high-speed long-range racing aircraft or mail carrier. When this type of aircraft was introduced in 1934 for the England to Australia race (see the chapter “The Influence of Air Racing”) it incorporated features that were new to British designs. From its inception the aircraft proved a success, winning the race for which it was designed. Since that time and as recently as March 1938 (see the chapter “Flying in New Zealand”) numerous high-speed flights have been made in Comet aircraft and many long-distance records stand to the credit of this type.
The aircraft is a twin-engined low-wing monoplane. Retractable undercarriage units are provided which draw up into the engine nacelles. The engines originally fitted to the Comet were De Havilland Gipsy Six of a specially tuned type. These engines may be said to have been the forerunners of the Gipsy Six Series II engines (see the chapter “The Gipsy Designs”) which were fitted in the Comets that made some of the more recent long-distance flights.
Two seats are provided in the fuselage aft of the wings and are fitted with an enclosing cover. Short trailing edge flaps are provided between the fuselage and the engine nacelles. To retract, the wheels move directly backwards and upwards.
The wings of the Comet taper towards their tips and have a stressed skin covering on a wooden framework. Plywood covering is used for the wings, which have a final layer of fabric. Similarly the fuselage is a wooden frame covered with plywood. The retractable undercarriage units are operated by a screw jack controlled from the cockpit by a continuous cable. Wheel brakes are provided.
The special Gipsy Six R engines developed 220 horse-power each at 2,350 revolutions a minute at sea level. The petrol tanks have a total capacity of 255 gallons. This supply is carried in two petrol tanks in the forepart of the fuselage and in a small tank behind the cockpit. Engine oil is carried in the engine nacelles. The engines were fitted with automatically operated two-position variable-pitch airscrews.
The main difference between the special Gipsy Six engines and the standard Gipsy Six Series I engine was in the increased compression ratio. The span of the main plane is 44 feet; the overall length of the aircraft 29 feet and the overall height 9 feet. The maximum permissible all-up weight of the Comet is 5,550 lb. This includes an allowance of 400 lb. for the crew and their parachutes.
The maximum speed of the aeroplane with full load is 225 miles an hour at sea level, and the cruising speed about 200 miles an hour at 10,000 feet. At this height and speed the maximum range of the aircraft is 2,950 miles; at full throttle at 10,000 feet and at a speed of 220 miles an hour the range is 2,550 miles. The initial rate of climb is 1,100 feet a minute and the time taken to climb to 10,000 feet is 13 minutes. Both these figures are obtained with the airscrew set to fine pitch.
The take-off run is about 450 yards and the landing run about 350 yards, with a load of 5,000 lb. The ceiling of the Comet is 21,000 feet and the absolute ceiling on one engine is 4,000 feet. The normal stalling speed of the aircraft with the flaps in use is 78 miles an hour, but with a light load this is reduced to 63 miles an hour.