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Bristol MF / Bullfinch


Bullfinch Mk.1


Captain Frank Barnwell designed the MF as an all-metal parasol-wing monoplane that could be flown as the MFA single-seat fighter or MFB two-seat reconnaissance plane. The latter had an extra fuselage section behind the cockpit for the gunner’s position and, below this on a short cabane arrangement, a cantilever second wing. In April 1921 the Air Ministry ordered three prototypes with wooden wings. Bristol proposed the name Pegasus, but this did not conform with current British practise and the two MFAs became Bullfinch Mk Is while the sole MFB became the two-seat Bullfinch Mk II.

By March 1922, when the name Bullfinch was officially adopted, the decision had been taken to complete two of the prototypes as single-seaters, these being delivered in April 1923. Armed with two 7.7mm Vickers machine guns, the Bullfinch single-seaters were flown experimentally by the RAF and were found to offer a relatively good performance on the 425hp of a Bristol Jupiter III radial, but no production order was forthcoming.


Bullfinch II

The Mk II was first flown on 15 February 1924 and delivered in March 1924. The Bullfinch II differed from the single-seat model primarily in having a 91.4cm section housing a self-contained gunner's cockpit inserted in the fuselage immediately aft of the pilot's cockpit and beneath which was attached a cantilever lower wing, the resultant shift of the centre of pressure compensating for the change in the CG. The only other change consisted of the repositioning of the main undercarriage members farther aft. The rear cockpit was fitted with a Scarff-mounted 7.7mm Lewis gun, and structural weight was increased by 145kg. The 425hp Jupiter III engine was insufficiently powerful to cater for the additional 400kg of the two-seater in fully loaded condition and the performance of the Bullfinch II suffered.
Both variants were fully evaluated, but no orders followed.

Principal versions - Bullfinch Mk I (single-seat fighter prototype) and Bullfinch Mk II (two-seat reconnaissance prototype).

Bullfinch Mk.I
Engine: one 450-hp (336-kW) Bristol Jupiter III radial
Maximum speed 135 mph (217 km/h) at 15,000 ft (4,570 m)
Srvice ceiling 22,000 ft (6,705 m)
Endurance 4 hours 0 minutes.
Empty weight 2,175 lb (987 kg)
Maximum take-off weight 3.205 lb (1,454 kg).
Wing span 38 ft 5 in (11.71 m)
Length 24 ft 5 in (7.44 m)
Height 10 ft 9 in (3.27 m)
Wing area 267.0 sq ft (24.80 sq.m).
Armament: two 0.303-in (7.7-mm) fixed machine guns.

Bullfinch Mk.II

Engine: 425hp Jupiter III
Take-off weight: 1854 kg / 4087 lb
Empty weight: 1132 kg / 2496 lb
Wingspan: 11.71 m / 38 ft 5 in
Length: 8.38 m / 27 ft 6 in
Height: 3.28 m / 10 ft 9 in
Wing area: 36.32 sq.m / 390.94 sq ft
Max. speed: 193 km/h / 120 mph



Bristol Bullfinch I



Bristol Bullfinch II



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