Bristol 149 Blenheim IV (and Bolingbroke)

The Type 149 Blenheim IV coastal reconnaissance and bomber that was initially known as the Bolingbroke I and was developed directly from the Bristol Blenheim I / II.  It featured an increased fuel capacity and a longer asymmetric nose with a revised glazing structure.

The Blenheim IV was first flown (K7072) on 24th September 1937 and an initial 134 were ordered against Specification 11/36.

Restored Bristol 149 Blenheim IV (Bolingbroke) Z7522 photographed at Wroughton

Although the type was known as the Blenheim IV in RAF service, the name 'Bolingbroke' was retained and applied to Canadian-built machines for RCAF use.  Production for the RAF comprised 316 by built by Bristol Aeroplane Company, 750 built by AV Roe & Co Ltd at Chadderton and 2,230 built by Rootes Securities in Speke. This gave a UK total production of 3,296 plus 10 that were made in Finland and another 676 in Canada, making a grand total of 3,982 aircraft.  The 10 aircraft that were built under licence in Finland were used extensively by the RAF on operations from the UK, the Middle East and Greece.  

Operational experience led to an increase in defensive armament (as per the detailed in the specification below) and a number of Blenheim IV were also modified as long range fighters (Mk IVF) with an additional pack of 4 forward-firing machine guns mounted under the fuselage.

Bristol 149 Bolingbroke Mk IVT RCAF 9940 under restoration at East Fortune

Production was undertaken by Fairchild Aircraft in Canada, where the type was known as the Bolingbroke. Some 676 were built in a number of variants, the most important of which being the Bolingbroke IV (185 built with US instrumentation and de-icing equipment) and the Bolingbroke IV-T (457 built with 920 hp Mercury XX engines for navigation and gunnery training).

During the war a 'Free French Air Force' was formed at RAF Odiham in Hampshire and they were equipped with a mixture of Blenheims and Westland Lysanders which acted as liaison and observer aircraft.

Blenheims operated throughout the Battle of Britain, often suffering heavy casualties. They also took on strategic low-level bombing roles with targets such as Power Stations and German-occupied french coastal ports.  The aircraft also carried out anti-shipping patrols and it was a Blenheim that sunk the first German U-Boat in March 1940.  With the entry of the Italians into the conflict later that year, 3 Squadrons were equipped with Blenheim IV aircraft to protect the North African ferry routes with many operating from their base on Malta.

After the war Blenheims continued to operate widely at British RAF Bases in Aden, India, Malaysia, Singapore and the Dutch West Indies.  The aircraft was finally retired in the UK during 1944 although in Finland and after being placed in storage in 1948, 5 aircraft were re-activated in 1951 and were used as target tugs until 1956.

Specification