Dunne D.6
Encyclopedia
The Dunne D.6 was one of J. W. Dunne's sweptwing tailless aircraft designed to have automatic stability, flying about 1911. It was a single seat, single engined pusher
Pusher configuration
In a craft with a pusher configuration the propeller are mounted behind their respective engine. According to Bill Gunston, a "pusher propeller" is one mounted behind engine so that drive shaft is in compression...
monoplane with the Dunne-Capper glider and its powered version as antecedents, and was developed into the Dunne D.7.
Design and development
Although J. W. Dunne is best known for his inherently stable tailless biplanes like the D.5 and D.8Dunne D.8
The Dunne D.8 of 1912 was one of a series of tailless swept wing biplanes, designed by J. W. Dunne to have inherent stability. One of the few built was the only Dunne aircraft to fly, albeit very briefly, with the Royal Flying Corps . Others were used by the US Signal Corps and United States Navy...
, he also developed a series of inherently stable monoplanes. He had submitted a monoplane design to the War Office
War Office
The War Office was a department of the British Government, responsible for the administration of the British Army between the 17th century and 1964, when its functions were transferred to the Ministry of Defence...
in 1905 before he joined the Balloon/Aircraft Factory
School of Ballooning
The School of Ballooning was a training and test centre for British Army experiments with balloons and airships. It was established at Chatham in Kent in 1888. The School moved to Stanhope Lines, Aldershot in 1890 when a balloon section and depot were formed as permanent units of the Royal...
at Farnborough
Farnborough Airfield
Farnborough Airport or TAG London Farnborough Airport is an airport situated in Farnborough, Rushmoor, Hampshire, England...
, though they rejected it. In 1907, employed by the Balloon Factory and encouraged by its head Colonel John Capper
John Capper
Major-General Sir John Edward Capper KCB KCVO was a senior officer of the British Army during the late nineteenth and early twentieth century who served on the North-West Frontier of British India, in South Africa and during the First World War, where he was instrumental in the development of the...
who also contributed to the engineering, Dunne built a parasol winged monoplane glider known as the Dunne-Capper glider.
All Dunne's tailless aircraft had swept wings with marked washout
Washout (aviation)
Washout refers to a feature of wing design to deliberately reduce the lift distribution across the span of the wing of an aircraft. The wing is designed so that angle of incidence is higher at the wing roots and decreases across the span, becoming lowest at the wing tip...
(reduction of angle of incidence
Angle of incidence
Angle of incidence is a measure of deviation of something from "straight on", for example:* in the approach of a ray to a surface, or* the angle at which the wing or horizontal tail of an airplane is installed on the fuselage, measured relative to the axis of the fuselage.-Optics:In geometric...
) at the tips. Since sweepback placed the tips well behind the centre of gravity, they provided longitudinal (pitch) stability in just the same way as a conventional tailplane, mounted at lower incidence than the wing. Both the D.5 and the monoplanes had wing camber
Camber (aerodynamics)
Camber, in aeronautics and aeronautical engineering, is the asymmetry between the top and the bottom surfaces of an aerofoil. An aerofoil that is not cambered is called a symmetric aerofoil...
which increased outwards, though the wing profiles varied differently. The biplanes gained yaw stability from fixed panels between the wings at the tips, but the monoplanes used down-turned wingtips instead. The glider mounted this wing above a pair of transverse A-frames, linked by longitudinal members that supported the pilot's arms; he controlled the aircraft by moving his weight.
Several of Dunne's aircraft from his Balloon Factory period were tested at Blair Atholl
Blair Atholl
Blair Atholl is a small town in Perthshire, Scotland, built about the confluence of the Rivers Tilt and Garry in one of the few areas of flat land in the midst of the Grampian Mountains. The Gaelic place-name Blair, from blàr, 'field, plain', refers to this location...
in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
to maintain secrecy, and it seems the Dunne-Capper glider was one of these. Piloted by Capper, these tests were not successful. This glider had been built with the intention of adding an engine, but this was not done until early in 1911, when a 60 hp (45 kW) Green
Green Engine Co
The Green Engine Co was an early British aero engine manufacturer. It was founded by Gustavus Green in Bexhill to produce engines of his design during the first two decades of the 20th century. Actual manufacturing was carried out at the Aster Engineering Company of Wembley...
was added in a pusher configuration. The wing now had wingtip elevons for control, though because of the down-turned tips these also provided some rudder-like forces. This version of the Dunne-Capper monoplane was tested at Larkhill
Larkhill
Larkhill is a garrison town in the civil parish of Durrington, Wiltshire, England. It is a short distance west of Durrington village proper and north of the prehistoric monument of Stonehenge. It is about north of Salisbury....
on Salisbury Plain
Salisbury Plain
Salisbury Plain is a chalk plateau in central southern England covering . It is part of the Southern England Chalk Formation and largely lies within the county of Wiltshire, with a little in Hampshire. The plain is famous for its rich archaeology, including Stonehenge, one of England's best known...
in January 1911 but failed to take off. As a result, a third A-frame was added to the structure supporting engine and pilot. The earlier undercarriage with two wheels on the rear A-frame and skids at the front was replaced by one with two pairs of wheels at the back and two more wheels at the front. It is not known if this version was more successful.
The D.6, major parts of which were built by Short Bothers, used a similar wing with a very different structure supporting it, the engine, pilot and undercarriage. The wing was straight edged, tapering from a central chord of 6 ft 3 in (1.91 m) to 5 ft 0 in (1.52 m) at the tips. The leading edge was swept at 35°. The A-frames with kingposts
King post
A king post is a central vertical supporting post used in architectural, bridge, or aircraft design applications.-Architecture:...
on the centreline were replaced with a pair of rectangular frames which extended above and below the wings, linked at the bottom by two transverse members. These frames served as double kingposts from which each wing was wire braced above and below. A substantial undercarriage structure was mounted at the bottom of the frames, comprising a long pair of skids which extended from the pusher propeller line well forward beyond the nacelle and curving strongly upwards. Each skid was multiply braced to its frame and inwards to the nacelle; the pair were joined by a cross strut near the forward tip. Both carried a pair of wheels and, at the rear, an articulated and sprung extension to absorb landing shocks.
The nacelle that carried the pilot's seat and the engine behind him was no more than an open wooden framework. The same Green engine was used as before, driving a two bladed, 7 ft 3 in (2.21 m) diameter propeller. A tall, rectangular radiator was placed longitudinally above the wing, positioned to raise the centre of gravity as high as possible. A pair of levers, one for each hand, controlled the aircraft.
This aircraft was tested at Eastchurch airfield on the Isle of Sheppey
Isle of Sheppey
The Isle of Sheppey is an island off the northern coast of Kent, England in the Thames Estuary, some to the east of London. It has an area of . The island forms part of the local government district of Swale...
in June 1911, flown by Dunne. It seems to have been hard to fly, for other tried but failed to master it. Nonetheless, Col Capper was sufficiently interested to order a version of it, designated the Dunne D.7 or D.7 Auto Safety. This was very similar to the D.6, but had a 1 ft (305 mm) shorter span and a 50 hp (37 kW) 7-cylinder Gnome rotary engine. It first appeared, not quite ready for flight, at the Olympia
Olympia, London
Olympia is an exhibition centre and conference centre in West Kensington, on the boundary between The Royal Borough of Kensington & Chelsea and Hammersmith & Fulham, London, W14 8UX, England. It opened in the 19th century and was originally known as the National Agricultural Hall.Opened in 1886,...
Aero Show in March 1911 and was on test with the D.6 at Eastchurch that June. Dunne was pleased with the improved performance. In January 1912 Dunne demonstrated the D.7 to members of the Royal Aeronautical Society
Royal Aeronautical Society
The Royal Aeronautical Society, also known as the RAeS, is a multidisciplinary professional institution dedicated to the global aerospace community.-Function:...
, writing a note whilst flying hands off at 60 mph.
During 1912 the D.6 was modified into a two seater, the Dunne D.7 bis, with a 70 hp (52 kW) Gnome to cope with the increased load. It had the shorter span wing of the D.7, but a centrally mounted surface was added to improve pitch control. This aircraft was successfully flown at Villacoublay in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
by either Dunne or N. S. Percival in April 1913.