Bristol Beaufort

The Bristol Beaufort (manufacturer designation Type 152) is a British twin-engined torpedo bomber designed by the Bristol Aeroplane Company, and developed from experience gained designing and building the earlier Blenheim light bomber. At least 1,180 Beauforts were built by Bristol and other British manufacturers.

Beauforts first saw service with Royal Air Force Coastal Command and then the Royal Navy Fleet Air Arm from 1940. They were used as torpedo bombers, conventional bombers and mine-layers until 1942, when they were removed from active service and were then used as trainer aircraft until being declared obsolete in 1945. Beauforts also saw considerable action in the Mediterranean; Beaufort squadrons based in Egypt and on Malta helped interdict Axis shipping supplying Rommel's Deutsches Afrikakorps in North Africa.

Although it was designed as a torpedo-bomber, the Beaufort was more often used as a medium day bomber. The Beaufort also flew more hours in training than on operational missions and more were lost through accidents and mechanical failures than were lost to enemy fire. The Beaufort was adapted as a long-range heavy fighter variant called the Beaufighter which proved to be very successful, and many Beaufort units eventually converted to the Beaufighter.

The Australian government's Department of Aircraft Production (DAP) also manufactured variants of the Beaufort. These are often known collectively as the DAP Beaufort. More than 700 Australian-built Beauforts saw service with the Royal Australian Air Force in the South West Pacific theatre, where they were used until the end of the war.

Design and development

Origins

The Beaufort came from Bristol's submission to meet Air Ministry Specifications M.I5/35 and G.24/35 for a land-based, twin-engined torpedo-bomber and a general reconnaissance aircraft. With a production order following under Specification 10/36, the Bristol Type 152 was given the name Beaufort after the Duke of Beaufort, whose ancestral home was nearby in Gloucestershire. The competing torpedo bomber entry from Blackburn was also ordered as the Blackburn Botha; in an unprecedented step, both designs were ordered straight off the drawing board, an indication of how urgently the RAF needed a new torpedo bomber. The wing centre section was inserted into the centre fuselage and the nacelle structure was an integral part of the ribs, to which the main undercarriage was attached. Transport joints were used on the fuselage and wings: this allowed sub-contractors to manufacture the Beaufort in easily transportable sections and was to be important when Australian production got under way.

The results of high level bombing tests carried out at Boscombe Down at an altitude of and an airspeed of showed that the Beaufort was, in the words of the test pilot, "an exceptionally poor bombing platform, being subject to an excessive and continuous roll, which made determination of drift particularly difficult". After 1941, British Beauforts were fitted with semi-circular plates on the trailing edges of the upper wing behind the engine nacelles to smooth airflow and improve directional stability.

As Blenheim production took priority and engine overheating problems continued, production was delayed; the bomber was first flown in October 1938 and should have been available almost immediately, it was not until November 1939 that production started in earnest. Several of the first production Beauforts were engaged in working-up trials and final service entry began in January 1940 with 22 Squadron of RAF Coastal Command.

British Beauforts

thumb|A new late-production Beaufort Mk.II at the [[Filton factory. ASV yagi aerials are under the nose and wings and the new DF loop is fitted. Muzzles of additional Vickers GO are visible in the front upper nose.]]

A total of 1,013 Taurus powered Mark Is were produced and a number of changes were introduced into the line. The original curved perspex bomb aimers' nose panels were replaced by flat, non-distorting panels from the 10th production aircraft. Successive Marks of the Bristol Taurus engine were installed: starting with the Taurus III, the more reliable Taurus IIs were used whenever possible. Initially Beauforts with the Taurus II engines were designated Beaufort Mk.II, while those with other Taurus Marks continued to be Beaufort Mk.Is. Finally all Taurus-engined Beauforts became Mk.Is with the introduction of the Pratt & Whitney Twin-Wasp-powered Beaufort Mk.II. The Taurus Mk.IIs were modified to Mk.IIa, which later became the Taurus Mk.VI. All of these versions produced . The final marks of Taurus engines used were the more powerful XII and XVIs. The Taurus engines drove de Havilland Type DH5/19 constant speed propellers.

As Beaufort units entered service, it was found that the defensive armament was inadequate and extra Vickers GO machine guns were fitted; two on a gimbal mounting in the forward nose and single guns on pivots on either beam. A remotely controlled Browning machine gun was fitted, firing to the rear under the nose. Housed in a clear blown transparency, it was found to be of little use and most operational units soon discarded them.

Fairey-Youngman pneumatic dive brakes were fitted to the wing trailing edges of several Beaufort IIs. After adverse reports from pilots these were locked shut. It was found that the curved alloy extensions on the trailing edges improved the flight characteristics and similar panels were fitted on all later production Beauforts.

When it became apparent that the Taurus engines had problems, planning commenced to re-engine the aircraft with Pratt & Whitney R-1830 Twin-Wasp radials, which were of similar diameter and slightly lighter, driving Hamilton Standard bracket-type variable-pitch propellers. There was no guaranteed supply of the Twin Wasp and production reverted to the Taurus-engined Mark Is after 165 Beaufort Mark IIs had been built, starting with AW244, which first flew in September 1941. Performance with the Twin-Wasps was marginally improved: maximum speed went up from and the service ceiling increased from . Normal range was reduced from .