De Havilland DH 108

infobox Aircraft
name = de Havilland DH 108
type = experimental
manufacturer = de Havilland



caption = The first DH 108 built – "TG283". The torpedo-shaped objects on the wing tips are containers for anti-spin parachutes.
designer = John Frost
first flight = 15 May avyear|1946
introduced =Experimental programme only
retired =
status =Cancelled
primary user = Royal Aircraft Establishment
more users =
produced = 1946–1947
number built = Three
unit cost =
variants with their own articles = The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, closely resembling the layout of the wartime German Messerschmitt Me 163 "Komet" rocket-powered point-defense interceptor. Initially designed to evaluate swept wing handling characteristics at low and high subsonic speeds for the proposed early tailless design of the Comet airliner, three examples of the DH 108 were built to the Air Ministry specifications E.1/45 and E.11/45. With the adoption of a conventional tail for the Comet, the aircraft were used instead to investigate swept wing handling up to supersonic speeds. All three prototypes were lost in fatal crashes.

Design and development

Employing the main fuselage section and engine of the de Havilland Vampire mated to a longer fuselage with a single tail fin and swept wings, the de Havilland DH 108 was proposed in 1944 as a test "mule" for the DH 106 Comet which had initially considered a tailless, swept-wing concept. [Davies and Birtles 1999, p. 10.] Despite the Comet design taking on more conventional features, the value of testing the unique configuration to provide basic data for the DH.110 Jackson 1962, p. 428.] spurred de Havilland to continue development of the DH 108. Selecting two airframes from the English Electric Vampire F 1 production line, the new aircraft had unmistakable similarities to its fighter origins, especially in the original forward fuselage which retained the nose, cockpit and other components of the Vampire. The Ministry of Supply named the DH 108 the "Swallow", a name that was never officially adopted by the company. [ Winchester 2005, p. 78.]

The new metal wing incorporating a 43˚ sweepback was approximately 15% greater in area than the standard Vampire wing. Control was based on the conventional rudder in combination with elevons that were part elevator and ailerons, fitted outboard of the split trailing edge flaps. Although the Vampire fuselage was retained, as development continued, a revised nose and streamlined, reinforced canopy were incorporated. Jackson 1962, p. 429.]

Testing

The first DH 108 prototype, "TG283," utilising the Vampire fuselage and a 43° swept wing, flew on 15 May 1946. Designed to investigate low-speed handling, it was capable of only 280 mph (451 km/h). De Havilland Chief Test Pilot Geoffrey de Havilland Jr., son of de Havilland company owner-designer Geoffrey de Havilland, gave a display flight in the DH 108 during the 1946 Society of British Aircraft Constructors (SBAC) airshow at Radlett. [ Watkins 1996, p. 39.] In later low-speed testing designed to clear the rear fuselage at high angles of attack, the first prototype was fitted with longer Sea Vampire landing gear. [ Watkins 1996, p. 42.]

The second, high-speed prototype, "TG306," with a 45° swept wing incorporating automatic leading-edge Handley Page slats and powered by a de Havilland Goblin 3 turbojet, flew soon after in June 1946. Modifications to the design included a more streamlined, longer nose and a smaller canopy (framed by a strengthened metal fairing) facilitated by lowering the pilot's seat. While being used to evaluate handling characteristics at high-speed, on 27 September 1946 "TG306" suffered a catastrophic structural failure that occurred in a dive from 10,000 ft (3,050 m) at Mach 0.9 and crashed in the Thames Estuary. The pilot, Geoffrey de Havilland Jr., was killed in the accident. Early wind tunnel testing had pointed to potentially dangerous flight behaviours, but pitch oscillation at high-speed had been unexpected. The subsequent accident investigation centred on a structural failure that occurred as air built up at Mach 0.9, pitching the aircraft into a shock stall that placed tremendous loads on the fuselage and wings. The main spar cracked at the roots with the wings immediately folding backwards. Watkins 1996, p. 40.]

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 lb (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.

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 "back up" for the attempt before it fatally crashed. On 12 April 1948, "VW120" established a new World Air Speed Record of 974.02 km/h (604.98 mph) on a 100 km (62 mi) circuit. Then, on 9 September 1948, John Derry exceeded the speed of sound in a shallow dive from 12,195 m (40,000) ft to 9,145 m (30,000) ft.

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. Winchester 2005, p. 79.] It was destroyed on 15 February 1950 in a fatal crash near Brickhill, Buckinghamshire, killing its test pilot, Squadron Leader Stuart Muller-Rowland. Accident investigation pointed to a faulty oxygen system that incapacitated the pilot. Winchester 2005, p. 79.]

Finally, on 1 May 1950 during stall tests, the first prototype was lost in a crash at Hartley Wintney, killing the pilot, George E.C. Genders. In all, 480 flights had been made by the three Swallows.

Legacy

The DH108 established a number of "firsts" for British aircraft: it was the first British swept-winged jet aircraft and the first British tailless jet aircraft; it was the first British aircraft to exceed Mach 1, one of the first jet-powered aircraft in the world to achieve this landmark speed. The XP-86 (the prototype for the F-86 Sabre) had also broken the sound barrier in a test flight on 26 April 1948. [ Bowman 2004, p. 12. ] Two of the aircraft which earlier had exceeded the speed of sound, the Bell X-1 and the Douglas Skyrocket, were both rocket-powered.

Operators

;UK
*Royal Aircraft Establishment

pecifications (DH 108 "VW120": third prototype)

aircraft specifications
plane or copter?= plane
jet or prop?= jet
ref=
crew= one, pilot
capacity=
length main= 26 ft 10 in
length alt= 8.17 m
span main= 39 ft 0 in
span alt= 11.89 m
height main= 14 ft 0 in
height alt= 4.27 m
area main= 327.86 ft²
area alt= 30.47 m²
airfoil=
empty weight main=
empty weight alt=
loaded weight main= 8,940 lb
loaded weight alt= 4,064 kg
useful load main=
useful load alt=
max takeoff weight main=
max takeoff weight alt=
more general=

engine (jet)= de Havilland Goblin-4
type of jet=turbojet
number of jets=1
thrust main= 3,738 lbf
thrust alt= 16.67 kN
thrust original=
afterburning thrust main=
afterburning thrust alt=

max speed main= 580 kn
max speed alt= 677 mph, 1,090 km/h
cruise speed main=
cruise speed alt=
never exceed speed main=
never exceed speed alt=
stall speed main=
stall speed alt=
range main= 634 NM
range alt= 730 mi, 1,175 km
ceiling main= 35,425 ft
ceiling alt= 10,800 m
climb rate main=
climb rate alt=
loading main= 27 lb/ft²
loading alt= 133 kg/m²
thrust/weight= 0.42
power/mass main=
power/mass alt=
more performance=
armament= 1x 50 mm anti-bomber cannon w/ 220 rounds, 4x 30 mm cannon w/ 350 r.p.g. Underwing racks for rockets and/or 5,000 lbs of bombs
avionics=

ee also

aircontent
related=
* de Havilland Vampire

similar aircraft=
* Douglas X-3
* Leduc 0.21/0.22
* Nord 1402 Gerfaut 1A
* Nord Griffon
* Northrop XP-56 "Black Bullet"
* Northrop XP-79
* Northrop X-4 Bantam
* Sud-Est Bradoudeur
* Sud-Est SE.212 Durandal

lists=

see also=

References

Notes

Bibliography

* Bowman, Martin, "F-86 Sabre" (Combat Legend). London: Airlife, 2004. ISBN 1-84037-411-X.
* Davies, R.E.G. and Philip J. Birtles. "Comet: The World's First Jet Airliner." McLean, Virginia: Paladwr Press, 1999. ISBN 1-888962-14-3.
* Jackson, A.J. "De Havilland Aircraft Since 1915". London, Putnam, 1962. No ISBN.
* McPhee, Andrew. [http://www.unrealaircraft.com/wings/dh108.php "Weird Wings - de Havilland DH.108."] "Unreal Aircraft.". Retrieved: 4 September 2005.
* Watkins, David. "De Havilland Vampire: The Complete History." Thrupp, Stroud, UK: Budding Books, 1996. ISBN 1-84015-023-8.
* Winchester, Jim. "Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft". Kent, UK: Grange Books plc., 2005. ISBN 1-84013-309-2.

External links

* [http://tanks45.tripod.com/Jets45/Histories/DH108/DH108.htm Description of the three aircraft at Jets45]
* [http://www.bowbrickhill.com/dehavillandcrash.html The Brickhill crash of "VW120"]
* [http://www.britishaircraft.co.uk/aircraftpage.php?ID=475 British Aircraft Directory entry]