Bristol Blenheim

https://en.wikipedia.org/wiki/Bristol_Blenheim

The Bristol Blenheim is a British light bomber aircraft designed and built by
the Bristol Aeroplane Company (Bristol) which was used extensively in the first
two years and in some cases throughout the Second World War. The aircraft was
developed as Type 142, a civil airliner, in response to a challenge from Lord
Rothermere to produce the fastest commercial aircraft in Europe. The Type 142
first flew in April 1935, and the Air Ministry, impressed by its performance,
ordered a modified design as the Type 142M for the Royal Air Force (RAF) as a
bomber. Deliveries of the newly named Blenheim to RAF squadrons commenced on 10
March 1937.

A development of the Type 142M was the Type 149 which Bristol named the
Bolingbroke, retrospectively changed by the Air Ministry to Blenheim Mk IV and
the Type 142M to the Blenheim Mk I. Fairchild Canada built the Type 149 under
licence as the Bolingbroke. Blenheims Mk I and the Mk IV were adapted as
fighters by the addition of a gun pack of four Browning .303 machine guns in the
bomb bay. The Mk IV was used as a long range fighter and as a maritime patrol
aircraft; both aircraft were used a bomber/gunnery trainers.

The Blenheim was one of the first British aircraft with an all-metal
stressed-skin construction, retractable landing gear, flaps, a powered gun
turret and variable-pitch propellers. The Mk I was faster than most fighters in
the late 1930s but the advance in development of monoplane fighters made all
bombers more vulnerable particularly if flown in daylight, though it proved
successful as a night fighter. The Blenheim was effective as a bomber but many
were shot down. Both Blenheim types were used by overseas operators, being
licence built in Yugoslavia and Finland.

The Blenheim typically carried a crew of three – pilot, navigator/bombardier and
wireless (radio) operator/air gunner. The pilot's quarters on the left side of
the nose were so cramped that the control yoke obscured all flight instruments
while engine instruments eliminated the forward view on landings. Most secondary
instruments were arranged along the left side of the cockpit, essential items
such as the propeller pitch control were actually placed behind the pilot where
they had to be operated by feel alone. The navigator/bombardier was seated
alongside the pilot, and made use of a sliding/folding seat whilst performing
the bomb aiming role. Dual flight controls could be installed. The wireless
operator/air gunner was housed aft of the wing alongside the aircraft's dorsal
gun turret.

Armament comprised a single forward-firing .303 in (7.7 mm) Browning machine gun
outboard of the port engine and a .303 in (7.7 mm) Lewis Gun in a
semi-retracting Bristol Type B Mk I dorsal turret firing to the rear. From 1939
onwards, the Lewis gun was replaced by the more modern .303 in (7.7 mm) Vickers
VGO machine gun of the same calibre. A 1,000 lb (450 kg) bomb load could be
carried in the internal bomb bay set into the center section of the fuselage.
Like most contemporary British aircraft, the bomb bay doors were kept closed
with bungee cords and opened under the weight of the released bombs. Because
there was no way to predict how long it would take for the bombs to force the
doors open, bombing accuracy was consequently poor. The bomb bay could be loaded
using a hand-operated winch incorporated into the fuselage.

To achieve its relatively high speed, the Blenheim used a very small fuselage
cross-section, with its upper front glazing all at one angle in the form of a
"stepless cockpit" that used no separate windscreen panels for the pilot, a
notable feature of a substantial majority of German bomber designs, first
conceived during the war years. Both fixed and sliding window panels were
present, along with a transparent sliding roof. Other onboard equipment included
a radio, cameras, navigation systems, electric lighting, oxygen apparatus, and
stowage for parachutes and clothing


Role
Light bomber / fighter

Manufacturer
Bristol Aeroplane Company

Designer
Frank Barnwell

First flight
12 April 1935

Introduction
1937

Retired
1944 (United Kingdom)
1958 (Finland)

Primary users
Royal Air Force
Royal Canadian Air Force
Finnish Air Force
Royal Yugoslav Air Force

Number built
4,422

Variants
Bristol Beaufort
Bristol Fairchild Bolingbroke

Blenheim units operated throughout the Battle of Britain, often taking heavy
casualties, although they were never accorded the publicity of the fighter
squadrons. From July to December 1940, Blenheims raided German-occupied
airfields both in daylight and at night. Although most of these raids were
unproductive, there were some successes; on 1 August five out of twelve
Blenheims sent to attack Haamstede and Evere (Brussels) were able to bomb,
destroying or heavily damaging three Bf 109s of II./JG 27 and apparently killing
a Staffelkapitän identified as Hauptmann Albrecht von Ankum-Frank. Two other
109s were claimed by Blenheim gunners. Another successful raid on Haamstede was
made by a single Blenheim on 7 August which destroyed one 109 of 4./JG 54,
heavily damaged another and caused lighter damage to four more.

There were also some missions which produced an almost 100% casualty rate
amongst the Blenheims. One such operation was mounted on 13 August 1940 against
a Luftwaffe airfield near Aalborg in north-western Denmark by twelve aircraft of
82 Squadron. One Blenheim returned early (the pilot was later charged and due to
appear before a court martial, but was killed on another operation); the other
eleven, which reached Denmark, were shot down, five by flak and six by Bf 109s.
Blenheim units had also been formed to carry out long-range strategic
reconnaissance missions over Germany and German-occupied territories. In this
role, the Blenheims once again proved to be too slow and vulnerable against
Luftwaffe fighters and they took constant casualties.

The Bristol Blenheim was used by both Bomber and Fighter Commands. Some two
hundred Mk I bombers were modified into Mk IF long-range fighters with 600
(Auxiliary Air Force) Squadron, based at Hendon, the first squadron to take
delivery in September 1938. By 1939, at least seven squadrons were operating
these twin-engined fighters and within a few months, some sixty squadrons had
experience of the type. The Mk IF proved to be slower and less nimble than
expected, and by June 1940, daylight Blenheim losses were to cause concern for
Fighter Command. It was decided that the Mk IF would be relegated mainly to
night fighter duties where No. 23 Squadron RAF, which had already operated the
type under nighttime conditions, had better success.

Specifications (Blenheim Mk IV)

General characteristics
Crew: three
Length: 42 ft 7 in (12.98 m)
Wingspan: 56 ft 4 in (17.17 m)
Height: 9 ft 10 in (3.0 m)
Wing area: 469 ft2 (43.6 m2)
Empty weight: 9,790 lb (4,450 kg)
Loaded weight: 14,400 lb (6,545 kg)
Powerplant: 2 × Bristol Mercury XV radial engine, 920 hp (690 kW) each
Propellers: Three-bladed Hamilton Standard propeller

Performance
Maximum speed: 266 mph (231 kn, 428 km/h at 11,800 ft (3,597 m))
Cruise speed: 198 mph (172.25 kn, 319 km/h)
Range: 1,460 mi (1,270 nmi, 2,351 km)
Service ceiling: 27,260 ft (8,310 m)
Wing loading: 30.7 lb/ft² (150 kg/m²)
Power/mass: 0.13 hp/lb (.21 kW/kg)
Climb to 6,500 feet (2,000 m): 4 min 10 sec

Armament

Guns:
1 × .303 in (7.7 mm) Browning machine gun in port wing
1 or 2 × .303 in (7.7 mm) Browning guns in rear-firing under-nose blister or
Nash & Thomson FN.54 turret
2 × .303 in (7.7 mm) Browning guns in dorsal turret

Bombs:

1200 lb (540 kg) 4 × 250 lb (113 kg) bombs or
2 × 500 lb (227 kg) bombs internally and 8 × 40 lb (18 kg) bombs externally



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