Bristol 149 Blenheim IV (and Bolingbroke) | BAE Systems | International

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Bristol 149 Blenheim IV (and Bolingbroke)

The Blenheim IV and the Bollingbroke were the most widely used and extensively produced versions of the Blenheim family of aircraft.
Bristol Blenheim IV V6083 1943 1943 air to air photograph of RAF Bristol Blenheim IV FV-B V6083

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.

 

Bristol 149 Blenheim IV (Bolingbroke) Z7522 Wroughton 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 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

                                                          Blenheim IV                     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

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
Bolingbroke Mk I Two Bristol Mercury VIII, with British equipment 18 built. Two conversions to Mk II (prototype Mk IV) and Mk III (floatplane).
Bolingbroke Mk IV Fitted with anti-icing equipment and US instrumentation, powered by two Bristol Mercury XV, 185 built.
Bolingbroke Mk IVW Variant powered by two 825 hp Pratt & Whitney SB4G Twin Wasp Junior engines. Only 15 built.
Bolingbroke Mk IVC Version with two 900 hp Wright R-1820 Cyclone engines. One built.
Bolingbroke Mk IVT Trainer variant. 350 powered by Mercury XV engines, followed by 107 powered by Mercury XX, giving a total of 457

Survivors

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

www.airmuseum.ca/

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

www.bcam.net/

Bristol Blenheim IV
(BL-200)
Aviation Museum of Central Finland, Tikkakoski, Finland.

www.airforcemuseum.fi/

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

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