TechTalk: de Havilland Tiger Moth

The CMF Tiger Moth is prepared for a day of flying by George Serviss at Members' Day 2011.
(Photo by Vic Bentley)
 History of de Havilland
The de Havilland Aircraft Company was a British aviation manufacturer founded in 1920 when Airco, of which Geoffrey de Havilland had been chief designer, was sold. De Havilland then set up a company under his name in September of that year at Stag Lane Aerodrome in Edgware, near London.
De Havilland became known for creating the Moth family of light aircraft; DH51, DH60 Gipsy Moth, DH80 Puss Moth, DH82 Tiger Moth, DH83 Fox Moth and DH87 Hornet Moth, continuing through the twin-engined DH84 Dragon and DH89 Dragon Rapide and on up to the Mosquito, Vampire, Sea Vixen and Comet jet airliner. The company also developed the 4-cylinder Gipsy engine, later developing 6 and 12 cylinder piston engines and jet engines.
History of the Tiger Moth
The original light aircraft that de Havilland developed, the DH60 Moth, was so successful that production was increased from the initial rate of less than one per week to more than three per day. Several different versions were eventually produced along with a number of different engine options. One such version was the metal framed DH60M ‘metal moth.’ This was submitted to the Royal Air Force as a potential primary trainer. Although the Ministry liked the aircraft, they felt that the positioning of the upper wing and fuel tank directly above the front cockpit was not ideal for an instructor wearing a full flying kit and parachute.
De Havilland began work on modifying the airframe of a DH60M. To clear the front cockpit the wings had to be moved forward some 22 inches. This threw the aircraft’s balance out, the centre of gravity now being behind the centre of lift. To remedy this, the wings were swept back by 19 inches, which then created another problem. Taxiing, or a bumpy landing, could cause the lower wingtips to hit the ground. This was cured by slightly increasing the dihedral of the lower wings. To further assist getting in and out of the cockpit, the hinged door panels were deepened. A 120 hp Gipsy III inverted engine was fitted to improve the view over the nose, removing the four upright cylinders of the Gipsy I from the pilot’s line of sight.
In September 1931, a prototype of the modified DH60, the DH60T Tiger Moth, was sent for testing. Pleased with the new aircraft, an order for a production prototype was issued. This flew on October 26 of the same year and was ordered into production for the RAF shortly after. By this stage, the DH60T had undergone so many modifications, de Havilland gave it a new designation – DH82 Tiger Moth.
De Havilland were also pursuing Canadian orders and in March 1937 a meeting was held with the RCAF to agree on details of design changes and by May a set of drawings had arrived from England. New buildings were started, and a British-built DH82A was dismantled and stripped to serve as a master pattern.
The changes required were:
Fuselage. A 2-inch (5-cm) thick foam rubber crash pad was to be fitted around the instruments. A cockpit canopy, dimensionally similar to those already installed by DHC on five British-built DH82As, to be constructed similar to the Fleet 7’s. A cockpit heating system was to be installed consisting of a hot-air muff around the exhaust pipe and suitable ducting. Other detail changes in the cockpit were called for.

Wider walkways were wanted on each lower wing, and plywood leading edges on the lower wings. Hand holds were to be fitted on the lower wingtips. Interplane struts were to be made of steel tubing, and the ailerons were to be mass balanced.
Engine installation. The engine cowls were to be hinged on the aircraft centre-line for improved access. Enlarged filler necks were to be fitted to the fuel and oil tanks and an insulating cover provided for the oil tank.
Undercarriage. Heavier axles were to be installed to take the additional loads imposed by operation on skis.
Work proceeded rapidly and the Canadian prototype, RCAF 237, designated DH82A(Can) to indicate the changes, was first flown on 21 December, 1937.
Further changes included the fitting of wheel brakes and a tailwheel. This required the wheels being moved forward about 9 3/4 in (24.7 cm) to prevent nosing over on brake application, and the front undercarriage members were shortened to do this. American instruments, of smaller size than the original British, were installed which permitted a more logical instrument layout and a reduction in panel size which in turn permitted a reshaping of the coaming between the cockpits to improve the view from the rear cockpit. The ‘cheese cutter’ elevator trim was replaced by trim tabs controlled by a wheel in each cockpit. The elevators were mass balanced to compensate for the weight of the tabs. The RCAF also wanted a new type of cockpit canopy, jettisonable in an emergency. Also included was the fitting of the higher-powered Gipsy Major 1C engine. The modified aircraft, known as the DH82C, was first flown on 12 March, 1940.
The supply of Gipsy Major 1C engines was endangered by possible enemy action, and the 125 hp Menasco D.4 was selected as an alternative; however it was both heavier and less powerful than the Gipsy Major 1C and reduced the aircraft’s performance.
With the 1939 selection of Canada as the main location for the British Commonwealth Air Training Plan (BCATP) pilot training and the anticipated influx of hundreds of thousands of trainee pilots, de Havilland Aircraft of Canada Ltd stepped up local production of the Tiger Moth to supplement those it received from England. Of the 1,747 Canadian Tiger Moths built, 1,553 were the winterized DH82C. August 1945 saw the end of production of the Tiger Moth by which time 9,231 had been built, 8,677 of which were the A or C model.