Bristol Blenheim IV V6083 1943
1943 air to air photograph of RAF Bristol Blenheim IV FV-B V6083


The Bristol 149 Blenheim IV coastal reconnaissance and bomber aircraft that was initially known as the Bristol Bolingbroke I and was developed by Bristol Aeroplane Company directly from their Bristol Blenheim I / II. It featured an increased fuel capacity and a longer asymmetric nose with a revised glazing structure.
The Bristol 149 Blenheim IV was first flown (K7072) on 24th September 1937, and an initial 134 were ordered against Specification 11/36.


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


Although the type was known as the Bristol 149 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 Avro Chadderton and 2,230 built by Rootes Securities in Speke. This gave a UK total production of 3,296 plus 10 aircraft that were made in Finland plus another 676 in Canada. This 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 Bristol 149 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
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 Bristol 149 Bolingbroke. Some 676 were built in a number of variants, the most important of which being the Bristol 149 Bolingbroke IV (185 built with US instrumentation and de-icing equipment) and the Bristol 149 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, Hampshire and they were equipped with a mixture of Bristol Blenheims and Westland Lysanders which acted as liaison and observer aircraft.

Bristol 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. Additionally, the aircraft carried out anti-shipping patrols and it was a Bristol 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 Bristol 149 Blenheim IV aircraft to protect the North African ferry routes, with many operating from their base on Malta.
After the war Bristol 149 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. However 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.



                                                 Bristol 149 Blenheim IV      Bristol 149 Bolingbroke IV
Powerplant Two 840 hp Bristol Mercury XV Two 940 hp Bristol Mercury XX
Span 56 ft 4 in
Maximum Weight 15,000 lb 14,400 lb
Capacity  Three crew (pilot, navigator / bomb aimer, gunner). Fixed forward firing Browning gun in port wing, one Lewis gun in dorsal turret.
Additional defensive armament increased by fitting two guns in dorsal turret and two further rearward firing guns in a blister under the nose. Internal bomb load 1,000 lb, plus 320 lb externally. Blenheim IVF carried four additional forward firing Browning machine guns in an under-fuselage pannier. 
Maximum Speed 265 mph
Range 1,950 miles


Variants and number built

Bristol Blenheim IV             
For RAF use: 316 built by Bristol, 750 by Avro and 2,230 by Rootes
Securities. 10 built in Finland under licence. Combined total 3,306
Bristol Bolingbroke Mk I Two Bristol Mercury VIII, with British equipment 18 built. Two conversions to Mk II (prototype Mk IV) and Mk III (floatplane).
Bristol Bolingbroke Mk IV Fitted with anti-icing equipment and US instrumentation, powered by two Bristol Mercury XV, 185 built.
Bristol Bolingbroke Mk IVW
Variant powered by two 825 hp Pratt & Whitney SB4G Twin Wasp Junior engines. Only 15 built.
Bristol Bolingbroke Mk IVC Version with two 900 hp Wright R-1820 Cyclone engines. One built.
Bristol Bolingbroke Mk IVT Trainer variant. 350 powered by Mercury XV engines, followed by 107 powered by Mercury XX, giving a total of 457



Bristol Bolingbroke IV-T      
(RCAF 10001/ L8756)
RAF Museum Hendon, London, United Kingdom
Bristol Bolingbroke Mk IVT (RCAF 9940)
National Museum of Flight, East Fortune, Scotland
Bristol Bolingbroke Mk IVT
(RCAF 9895)
Royal Museum of the Armed Forces and Military History, Brussels
Bristol Bolingbroke IVT
(RCAF 10117 / C-GBLY)
Canadian Warplane Heritage Museum, Hamilton, Ontario, Canada.
Bristol Bolingbroke IVT
(RCAF 9059)
Commonwealth Air Training Plan Museum in Brandon, Manitoba

Bristol Bolingbroke IV
(RCAF 9104)
British Columbia Aviation Museum in Sidney, British Columbia.

Bristol Blenheim IV
Aviation Museum of Central Finland, Tikkakoski, Finland.

Bristol Bolingbroke IVT
(RCAF 10076)
Pima Air & Space Museum, Arizona, USA


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