The DH108 established a number of "firsts" for a British aircraft: it was the first British swept-winged jet aircraft and the first British tailless jet aircraft.
The De Havilland Swallow aircraft were evolved to investigate the transonic region near the sound barrier with tailless aircraft.
The Allies reaped a technological windfall with the unconditional surrender of Nazi Germany in May 1945. Both the United States and Great Britain in particular found that their wartime studies of future jet aircraft experienced quantum leaps in performance with the incorporation of the aeronautical knowledge of the personnel technical documents, and aircraft of the Third Reich. During the final half of the Second World War, Britain grappled with the future of passenger flight with the Brabazon Committee's deliberations on the future of commercial aviation. Of the five designs put forth by the Committee, the most advanced was the Type IV design for a jet-powered 100-passenger design. This aircraft would become the De Havilland DH.106 Comet- but the DH.106 started out as a very small, modest adaptation of the Vampire jet fighter as jet-powered mailplane with a six-seat passenger compartment. But with the input of the Brabazon Committee, the DH.106 evolved into a substantially larger aircraft that at one point was a tailless design before taking on the shape now familiar as the Comet.
The first DH 108 prototype, serial number TG283, utilising the Vampire fuselage and a 43° swept wing, flew on 15 May 1946 at RAF Woodbridge. Powered by H-1 Goblin.
Designed by De Havilland engineer Ronald Bishop, what was designated the DH.108 used the fuselage of the De Havilland Vampire jet fighter which was stretched and streamlined combined with a new swept vertical fin and new swept wings. This served to save time and effort and like the Vampire jet fighter, the DH.108 had wing root intakes. Unofficially named "Swallow", the two prototypes received the RAF serials TG283 and TG306. TG283 had a 43-degree swept wing and was intended for low speed testing while TG306 had a 45-degree wing and was assigned to high-speed transonic testing. Initial wind tunnel studies suggested that the Swallow would have lousy stall characteristics, so the first of the two to fly, the low-speed assigned TG283, had fixed wing slats and anti-spin parachutes in fairings on the wingtips. It made its first flight on 15 May 1946 and TG306, the high-speed Swallow, made its first flight a month later and had automatic wing slats but no anti-spin parachutes.
Designed 1945 but the second prototype tragically caused the death if de Havilland Junior on 27 September 1946 in TG306
The test pilot for the DH.108 was the chief test pilot for the company, Geoffrey De Havilland, Jr, the son of the company's founder. After several problem-free test flights it was found that both aircraft lacked the predicted poor stall characteristics and the high speed aircraft, TG306, joined the formal research program on 23 August 1946. By the time De Havilland had safely taken it to 630 mph at altitude with no problems, it was decided he would take TG306 to break the world speed record. On a practice run over the Thames Estuary on 27 September 1946, the aircraft exceeded its structural limits at high speed and broke up, killing Geoffrey De Havilland, Jr, as the aircraft had no ejection seat.
After the loss of the second prototype, VW120 became the third and final prototype based on the newer Vampire F.5 fighter built at Hatfield. It differed from the first test aircraft in that it featured an even more streamlined pointed nose and smaller reinforced canopy (lowering the pilot's seat allowed for a more aerodynamic canopy shape to be employed). Power-boosted elevators had been specified as a means to control the pitch oscillations at the root of the earlier disaster. A more powerful Goblin 4 of 3,738 lbf (16.67 kN) thrust had the potential to push the DH 108 into the supersonic range. VW120 first flew on 24 July 1947 flown by John Cunningham, the wartime nightfighter ace.
New engine, new test pilot new plane
John Cunningham succeeded De Havilland as chief test pilot and took over flying the DH.108. To replace the lost aircraft, a third DH.108 was ordered and received the RAF serial VW120. It featured a more pointed nose, revised canopy and cockpit including a Martin-Baker ejection seat, and a higher thrust Goblin 4 turbo engine than what had powered the first two aircraft.
Considered an important testbed for high-speed flight, VW120 was readied for an attempt at the World Speed Record then held by a Gloster Meteor at 616 mph (991 km/h). The second prototype, TG306, was a "backup" for the attempt before it fatally crashed. On 12 April 1948, VW120 established a new World Air Speed Record of 604.98 mph (974.02 km/h) on a 62-mile (100 km) circuit. Then, on 6 September 1948, John Derry is thought to have probably exceeded the speed of sound in a shallow dive from 40,000 ft (12,195 m) to 30,000 ft (9,145 m). The test pilot Captain Eric "Winkle" Brown, who escaped a crash in 1949, described the DH 108 as "a killer".
In 1949, VW120 put on an aerial display at Farnborough and scored third place in the Society of British Aircraft Constructors Challenge Trophy Air Race before being turned over to the Ministry of Supply and test flown at RAE Farnborough. It was destroyed on 15 February 1950 in a crash near Brickhill, Buckinghamshire, killing its test pilot, Squadron Leader Stuart Muller-Rowland. The accident investigation at the time pointed, not to the aircraft, but to a faulty oxygen system that incapacitated the pilot.
Military Aircraft Monthly International, Volume 9, Issue 12. "A Deadly Swallow: The short sharp story of De Havilland's DH.108" by Nico Braas, p28-32. Link
The first prototype TG 283
The second prototype TG 306
All three aircraft crashed killing their pilots.
TG 283 1/5/1950 G.Genders, (a noted wartime ace and CO of Farnborough’s Aero Flight) Genders stalled the aircraft as planned at 15,000ft, but lost control while recovering and entered a violent inverted spin. Attempting to use the anti-spin parachutes, both units failed, and the aircraft hit the ground close to the local village of Hartley Wintney. Although Genders managed to abandon the stricken machine, there was no time for his parachute to deploy.
TG 306 27/9/1946 G.De Havilland. His intentions were to push the jet to Mach 0.87 in a shallow dive from 10,000ft, followed by a level-speed run at 650mph. Lowering the nose, he soon lost control when the aeroplane began to oscillate along the pitch axis, leading to structural failure in both wings – the starboard mainplane giving way first – and hurling the machine into an incredibly violent outside loop. The wreckage fell into the mudflats at Egypt Bay off Gravesend, Kent. Calculations indicated that prior to breaking up, TG306 had reached a speed of around 580mph, or Mach 0.87, at about 7,000ft – higher than anything obtained before.
VW 120 15/2/1950 J.Muller-Rowland -destroyed in a crash at Brickhill near Bletchley, Buckinghamshire on February 15, 1950. During a high-speed descent from 27,000ft, RAE pilot Sqn Ldr Stewart Muller-Rowland lost control of the aircraft, which broke apart while passing through 10,000ft, somewhat reminiscent of de Havilland Jr’s loss, VW120’s port wing failed.