Blenheim Mk IF Specifications

Crew: Pilot and air gunner

Powerplant: Two 840 hp Bristol Mercury VIII nine-cylinder air-cooled engines

Span: 56 ft 4 in (17.14 m)

Length: 39 ft 9 in (12.11 m)

Max Speed: 285 mph (460 km/h) at 15,000 ft (4,572 m)

Armament: Four .303 in (7.7 mm) Browning machine guns mounted in a ventral fairing, one .303 in machine gun in hydraulically-operated semi-retractable dorsal turret

Photo Description: A Bristol Blenheim Mk IF of No. 54 Operational Training Unit fitted with an AI Mk III radar antenna in the nose.

The Bristol Blenheim was a British twin-engine long-range light bomber/reconnaissance aircraft used extensively by the Royal Air Force during the early stages of the Second World War. The Blenheim was originally conceived as a civil twin-engine light transport aircraft by Frank Barnwell, Chief Designer at the Bristol Aeroplane Company. The design was known as the Type 135 and attracted the attention of Lord Rothermere, proprietor of the Daily Mail newspaper and a strong proponent of British aviation. Rothermere wanted to recapture the title of fastest civilian aircraft in Europe and challenged the British aviation industry to build him a high-speed aircraft capable of carrying six passengers and two crew members. Bristol decided to develop the Type 135 design further to produce the Type 142 to meet Rothermere’s requirements. The Type 142 was a low-wing cantilever monoplane with an all-metal monocoque fuselage and retractable landing gear. It was powered by two Bristol Mercury VI radial engines. Dubbed Britain First, the aircraft first flew on 12 April 1935 and achieved a top speed of 307 mph (494 km/h), which was higher than that of any RAF fighter then in service. The British Air Ministry quickly became interested and Rothermere donated the aircraft for evaluation as a light bomber. Following successful trials, the Air Ministry issued Specification B.28/35 for a military version with similar performance; the Type 142M. To meet the specified requirements, the wing was raised to create space for a bomb bay and a dorsal turret armed with one .303 in (7.7 mm) Lewis or Vickers K machine gun was added. A second .303 in (7.7 mm) Browning machine gun was mounted in the port wing. The design was complete in September 1935 and an initial order was placed for 150 aircraft. The new bomber was dubbed the Blenheim Mk. I and entered RAF service in March 1937. Another modification led to a long-range heavy fighter version, the Blenheim Mk. IF. About 200 aircraft were fitted with a gun pack under the fuselage, carrying four .303 in (7.7 mm) Browning machine guns.

During the Battle of Britain, the Blenheim was already obsolescent but continued to serve with RAF Bomber Command often taking heavy casualties. Due to its relatively slow speed and light armament, it proved particularly vulnerable to German fighters. Between July and October 1940, units equipped with the Blenheim Mk. IV flew numerous sorties against targets in France and Germany – targeting invasion barges and shipping in Channel ports, raiding German-occupied airfields, and flying long-range reconnaissance patrols. The Blenheim Mk. IF also served with RAF Fighter Command in the night fighter role with some aircraft equipped with Airborne Intercept (AI) Mk. III radar. On the night of 22/23 July 1940 the Fighter Interception Unit (FIU) achieved the first airborne radar intercepted kill in history, shooting down a Dornier Do 17 Z of 2 Staffel, Kampfgeschwader 3. More successes followed and before long the Blenheim proved itself invaluable as a night fighter. The Blenheim was gradually replaced with the faster and better armed Bristol Beaufighter.