Boulton Paul Bourges

National origin: United Kingdom
Manufacturer: Boulton & Paul
Designer: John Dudley North
First flight: June 1919
Status: Prototype
Number built: 3

The Boulton & Paul P.7 Bourges was a prototype British twin-engined biplane day bomber built by Boulton & Paul to replace the Airco DH.10. Despite demonstrating excellent performance and manoeuvrability, only three prototypes were built, post World War I cost cutting leading to the DH.10 not being replaced.

Development and design

In 1918, the British Air Ministry drew up specification A.2 (B) for the replacement of the Airco DH.10 medium bomber, despite the fact that the DH.10 Amiens had not yet entered service. In response, J.D North, chief designer of Boulton & Paul's aircraft department designed a twin-engined aircraft, the P.7 Bourges, powered, like most of the types designed to replace the DH.10, by two of the new ABC Dragonfly radial engines. The ABC was ordered off the drawing board by the Ministry and high hopes were held for it. The Bourges was a three-seat, three bay biplane with unstaggered wings of all-wooden construction. Three prototypes were ordered by the Air Ministry.

Delays in delivery of airworthy examples of the Dragonfly lead to the decision to fit the first prototype with the much less powerful (230 hp/172 kW), but reliable Bentley BR2 rotary engine, allowing a first flight as the Bourges Mk IIA in June 1919. It was fitted with Dragonflys in July, becoming the Bourges Mk IA,. Both the Bentley and ABC engined Bourges demonstrated excellent performance and manoeuvrability, being able to be looped and rolled with ease.

The second aircraft was fitted with a gulled upper wing to improve the field of fire for its gunners - the engines moved down to the top of the lower wing. Fitted with Dragonflys, it was designated the Bourges Mk IB. It would crash in 1919 and its structure reused for a different project. The third Bourges was also originally built as a Mk IB, but when Boulton Paul realised that the reliability problems with the Dragonfly could not be cured, it was refitted with BR2s, being redesignated Bourges Mk IIB.

In 1920-21 the third prototype, the Bourges P.7B F2905 was again re-engined, this time with 450 hp (336 kW) Napier Lion engines, and was flown both with the original straight upper wing (Bourges Mk IIIA) and with the gulled wing (Bourges Mk IIIB). While in this form it was superior to the other types planned as DH.10 replacements, the RAF had by this time abandoned the requirement, and the Bourges was used for extensive testing at the Royal Aircraft Establishment, Farnborough continuing in use until 1924.

Specifications (Bourges )

Data from British Aeroplanes 1914-18

General characteristics

Crew: Three
Length: 37 ft 0 in (11.28 m)
Wingspan: 57 ft 4 in (17.48 m)
Height: 12 ft 0 in (3.66 m)
Wing area: 738 ft² (68.6 m²)
Empty weight: 3,820 lb (1,736 kg)
Loaded weight: 6,320 lb (2,873 kg)
Powerplant: 2 x— ABC Dragonfly I 9-cylinder air-cooled radial engine, 320 hp (239 kW) each

Performance

Maximum speed: 123.5 mph (107 kn, 199 km/h) at 6,500 ft (1,980 m)
Endurance: 9¼ hr
Climb to 15,000 ft (4,600 m): 25 min 25 sec
Service ceiling: 20,000 ft (6,100 m)
Wing loading: 8.56 lb/ft² (41.9 kg/m²)
Power/mass: 0.10 hp/lb (0.17 kW/kg)

Armament

Guns: 2 x— .303 in (7.7 mm) Lewis guns each in nose and mid-upper positions
Bombs: 4 x— 230 lb (105 kg) bombs

Related development

Boulton & Paul Bolton
Boulton & Paul Bugle
Boulton Paul Atlantic

Comparable aircraft

Avro 533 Manchester
de Havilland Oxford
Sopwith Cobham
Airco DH.10

Bruce, J.M. British Aeroplanes 1914-18. London:Putnam, 1957.
Lewis, Peter. The British Bomber since 1914. London:Putnam, 1980. ISBN 0-370-30265-6.
Mason, Francis K. The British Bomber since 1914. London:Putnam, 1994. ISBN 0-85177-861-5.

Boulton Paul Bourges Pictures

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Source: WikiPedia