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WWII Tech Pubs Briefing
Bristol 142M, 149, and 160 Blenheim
Written by
Michael Hyde
A Bristol Blenheim Mk IV of No.139 (Jamaica)
Squadron. On the 12th of May 1940, nine 139 Squadron Blenheims made a
desperate attack on the Maastricht bridges in Belgium in an attempt to
halt the German advance. Seven out of nine were shot down.
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Country of Origin:
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Great Britain
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Manufacturer:
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The Bristol Aeroplane Co. Ltd., Filton, Bristol, Avon, England
(Mark I, IV and V); Valtion Lentokonetehdas, Tampere, Finland (Mark
I and IV); Ikarus A.D., Zemun, Beograd, Yugoslavia (Mark I); Fairchild
Aircraft Ltd., Longueuil, P.Q., Canada (Bolingbroke); A.V.Roe and
Co. Ltd., Chadderton, Lancashire, England (Mark I); Rootes Securities
Ltd., Speke, Liverpool, Lancashire, England (Mark I and IV); Rootes
Securities Ltd., Blythe Bridge, Staffordshire, England (Mark V)
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Major Variants:
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Blenheim Mark I, Blenheim Mark IV, Bolingbroke, Bisley, Blenheim
Mark V
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Role:
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Bomber, Fighter, Night Fighter, Maritime Patrol, Trainer, Reconnaissance,
Target tug.
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Operated by:
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Great Britain, Finland, Turkey, Yugoslavia, Canada, Greece, Rumania,
South Africa, Portugal, Croatia.
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First Flight:
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25 June 1936
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In Service:
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10 March 1937, 114 Squadron RAF, K7036
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Number Built:
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6,229 (plus 80 incomplete)
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Overview
The Bristol Blenheim first flew
in 1935 as a privately-financed fast-civilian-transport demonstrator (Bristol
Type 135) named "Britain First" . It was designed by Frank Barnwell
in 1933. When the RAF heard of its achieved top speed of 307 mph 494
kph - faster than any RAF fighter of that time - they organised
that the Air Ministry issue a Specification (28/35) for a fast light bomber
that was met by the Blenheim I (now designated Bristol Type 142M). The
only significant changes from the type 135 were the provision of a bombardier’s
position and sighting window, and the raising of the wing to a mid-position
to allow room under the spar for the bomb bay.
The Blenheim I was ordered straight
from the plans and the first production aircraft served as the prototype,
completing the flight testing program. The aircraft was of all-metal construction
with twin Bristol Mercury VIII nine-cylinder radial engines. It carried
a crew of three - pilot, navigator/bombardier and gunner/wireless operator,
and was armed with a forward firing Browning .303 in 7.7
mm machine-gun in the wing root and a Vickers .303 in 7.7
mm ‘K’ gun or Lewis gun in a semi-retracting dorsal turret. A 1,000
lb 454 kg bomb load was carried in the internal
bay. The Mark I was used in combat by Britain, Finland, Yugoslavia, Romania
and Greece, and also operated by Turkey and the Croat Air Force. Both
Finland and Yugoslavia manufactured the type under licence.
The Blenheim IV (Bristol Type 149)
was produced to Air Ministry Specification 11/36 as an interim reconnaissance
bomber pending availability of the Bristol Beaufort. To meet this requirement
it had the cockpit lengthened by three feet and the glazing shape changed
to improve pilot visibility. It also had fuel load increased from 278
imp gall 1262 L to 468 imp gall 2125
L and the Bristol Mercury XV engine which was rated at 905 bhp
for take-off. Turret armament was progressively improved to two Vickers
K guns, then twin Browning belt-fed machine guns. When first available
in 1939 it was the fastest bomber in the world. The Blenheim IV saw combat
with British, South Africa and Finnish forces. Some were manufactured
under licence in Finland.
Canada urgently sought modern aircraft
as war approached and in 1937 chose to produce Blenheims under licence
as part of its modernisation process. By the time the agreements had been
made, the Blenheim IV with greater crew visibility and longer range was
soon to be available; an aircraft better suited to Canada’s patrol bomber
requirement. Fairchild retained the name Bolingbroke (the British name
of the prototype) and commenced production with some further local refinements
such as anti-icing boots and dinghy stowage. Later aircraft had American
accessories and instruments fitted. RCAF Bolingbrokes saw combat in the
Aleutians alongside the USAAF, and on the Atlantic seaboard. Later aircraft
were used as trainers within the Empire Air Training Scheme, and as target
tugs.
The Bristol Bisley (Bristol Type
160) was designed as an improved version of the Blenheim IVF to be used
for ground-attack, with a solid nose-cone containing four Browning machine-guns.
The production aircraft were renamed Blenheim V and featured a strengthened
structure, pilot armour, interchangeable nose gun pack or bombardier position,
and Mercury 25 or 30 engines. This variant was used extensively by the
RAF in the Far East and Mediterranean, and was also operated by Portugal
who interned and purchased aircraft that had force-landed on their neutral
territory.
Blenheims participated in many significant
actions in World War II. A RAF 139 Squadron Blenheim IV flew the first
combat sortie over Germany when it photographed part of the German fleet
in Schillig Roads on 3 September 1939; a Mark IF was the first aircraft
to obtain a kill at night with airborne radar; and Blenheims were at the
forefront of the air campaigns in France and the Netherlands in 1940,
North Africa in 1940 and 41, the Balkans and Greece in 1941, and in Malaya
and Burma in 1942; and they fought on both the southern and northern regions
of the Eastern Front in Romanian and Finnish service respectively.
Blenheims suffered terrible losses
in 1940 as the principal attack bomber flying against the well-protected
ports where shipping was being assembled for "Sealion" - the
German invasion of Britain.
Although obsolete for combat operations
by late 1943, many hundreds of Blenheims and Bolingbrokes continued in
service as trainers and target tugs until the war’s end.
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Variants
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Type
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Number Built
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Remarks
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Bristol type 142
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1
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Private venture financed by Lord Rothermere to promote British
aviation. A low-winged monoplane of all-metal construction with
two 850 hp Bristol Mercury VIII radial engines and retractable main
wheels. Achieved a top speed of 307 mph.
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Type 142M Blenheim I
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1,351 plus 24 incomplete
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The first production aircraft (K7033) served as the prototype.
Wing raised to mid-position to allow space for the bomb bay. One
Browning .303 in 7.7 mm machine-gun,
a turret-mounted Lewis gun and a glazed nose with bombardier position
were fitted. Also licenced production in Finland and Yugoslavia.
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Blenheim IF
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unknown. 1,375 gun packs made
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Fighter conversions of Mk I aircraft. A pack with four .303 in
7.7 mm Browning machine guns was fitted
to the bomb-bay. Some night-fighter conversions with A.I.Mk III
air-borne radar.
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Blenheim II
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1
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Reconnaissance conversion of Mk I aircraft. Fuel tankage increased
to 468 imp gall 2125 L and strengthened
undercarriage.
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Blenheim III
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0
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Proposed interim version with Mk IV long nose, but smaller Mk I
fuel tankage.
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Type 149 Blenheim IV
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3,307 plus 5 incomplete
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Nose extended by three feet, glazing scalloped on the pilot-side
for visibility, fuel increased to 468 imp gall 2125
L. Also licenced production in Finland.
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Blenheim IVF
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unknown. 1,375 gun packs made
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Fighter conversions of Mk IV aircraft. A pack with four .303 in
7.7 mm Browning machine guns was fitted
to the bomb-bay, or some with two 20mm Hispano cannon as a trial
fitting.
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Type 160 Bisley
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2
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Solid nose cone with four Browning guns, pilot armour, fully-traversable
dorsal turret and Mercury XVI engines.
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Blenheim V
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942
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Final production model with interchangeable nose-gun pack or bombardier
position, Mercury 25 or 30 engines, strengthened structure and rear-firing
chin guns, and R.1154 radios for tropical service.
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Fairchild Bolingbroke I
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18
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Blenheim IVs built in Canada by the Fairchild Aircraft Company
to Bristol standards with imported components.
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Bolingbroke II
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1
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Converted Bolingbroke I fitted with American equipment and instruments.
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Bolingbroke III
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1
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Converted Bolingbroke I with Edo floats. Later reconverted to land-plane
configuration.
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Bolingbroke IV
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151
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First Canadian production version. All Fairchild-built to American
standards as trialled in the Bolingbroke II. Also with wing de-icing
and interchangeable wheel or ski landing gear.
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Bolingbroke IV-W
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15
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Converted Bolingbroke IV with Pratt and Whitney Twin Wasp junior
(SB4G) engines in anticipation of Bristol engines not being available
from Britain.
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Bolingbroke IV-C
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1
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Converted Bolingbroke IV with Wright Cyclone G3B engines to trial
performance with 93 octane gasoline
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Bolingbroke IV-T
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457 plus 51 incomplete
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The final production version of the Bolingbroke IV completed as
navigational and gunnery trainers, with either Mercury XV or XX
engines.
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Specifications
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Model
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Blenheim I
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Blenheim IV
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Bolingbroke IV
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Bisley
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Blenheim V
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Dimensions
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Span
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56 ft 4 in
17.17 m
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56 ft 4 in
17.17 m
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56 ft 4 in
17.17 m
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56 ft 1 in
17.09 m
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56 ft 1 in
17.09 m
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Length
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39 ft 9 in
12.12 m
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42 ft 9 in
13.03 m
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42 ft 9 in
13.03 m
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43 ft 4 in
13.21 m
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43 ft 11 in
13.39 m
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Height (prop vertical)
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12 ft 10 in
3.91 m
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12 ft 10 in
3.91 m
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12 ft 10 in
3.91 m
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12 ft 10 in
3.91 m
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12 ft 10 in
3.91 m
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Wing area
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469 sq ft
43.6 sq m
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469 sq ft
43.6 sq m
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469 sq ft
43.6 sq m
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469 sq ft
43.6 sq m
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469 sq ft
43.6 sq m
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Powerplant
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Type
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Mercury VIII
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Mercury XV
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Mercury XV
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Mercury XVI
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Mercury 25 or 30
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Cubic Capacity
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-
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-
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-
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-
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-
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Cylinders
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9
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9
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9
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-
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-
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Horsepower
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840
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905 (Take-off)
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905 (Take-off)
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950
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950
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Weights (note - these
figures vary for individual aircraft, and are often not directly
comparable)
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Weight (maximum takeoff)
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12,500 lb
5682 kg
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15,000 lb
6818 kg
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14,500 lb
6591 kg
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17,000 lb
7727 kg
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17,000 lb
7727 kg
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Weight empty
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8,100 lb
3682 kg
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9,823 lb
4465 kg
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9,835 lb
4470 kg
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11,000 lb
5000 kg
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11,000 lb
5000 kg
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Useful load
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4,400 lb
2000 kg
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5,177 lb
2353 kg
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4,665 lb
2120 kg
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6,000 lb
2727 kg
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6,000 lb
2727 kg
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Performance
(note - these figures vary for individual
aircraft, and are often not directly comparable)
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Maximum speed
at [height] mph kph
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285 459
[15,000 ft] [4,572 m]
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266 428
[11,800 ft]
[3,597 m]
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288 464
[18,000 ft]
[5,486 m]
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262 422
[?]
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260 419
[?]
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Stalling speed
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>50 mph
>81 kph
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60 mph
96 kph
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-
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-
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-
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Climb initial
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1,350 ft/min
411.5 m/sec
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1,480 ft/min
451.1 m/sec
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1,480 ft/min
451.1 m/sec
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-
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-
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Service ceiling
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27,280 ft
8,315 m
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31,500 ft
9,601 m
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31,500 ft
9,601 m
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31,000 ft
9449 m
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31,000 ft
9449 m
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Range
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1,125 ml
1811 km
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1,460 ml
2351 km
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1,860 ml (max)
2995 km
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1,600 ml
2576 km
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1,600 ml
2576 km
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Armament
(note - extra defensive guns were often added in the field)
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Armament
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2 X .303 in 7.7 mm mg [F models x
6]
1000 lb 454 kg bombs
4 X flares
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2 [later 3] X .303 in 7.7 mm mg [F
models x 7]
1000 lb 454 kg bombs
4 X flares
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2 X .303 in 7.7 mm mg
1000 lb 454 kg bombs
4 X flares
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7 X .303 in 7.7 mm mg
1000 lb 454 kg bombs
4 X flares
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5 X .303 in 7.7 mm mg
1000 lb 454 kg bombs
4 X flares
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