Bristol Blenheim, part nine, the Blenheim during early 1940

 

The Bristol Blenheim was a twin-engined high-performance all-metal bomber aircraft that was powered by two Bristol Mercury VIII air-cooled radial engines yielding 860 hp each. Each engine drove a three-bladed propeller and were equipped with both manual and electronic engine starters. To make maintenance easier, engine cowlings were designed with a split-segment to facilitate quick engine removal without having to disturb the carburetors. Two fuel tanks, each containing 140 gallons (637 litres) were housed in the central section of the fuselage.

The fuselage employed a light alloy monocoque structure using open section stingers and was built in three sections. The wing was also built in three sections, with the central one bolted and riveted into the fuselage. Outer wings were tapered in chord and thickness. Spars, ribs, skin, flaps and webs were sheeted in Alclad in order to reinforce them. The tail unit was of cantilever monoplane style, employing an all-metal tailplane and fin, with the aerodynamically-balanced rudder and elevators used a metal frame covered with fabric. The undercarriage was hydraulically retracted and had an auxiliary hand-pump for emergency cases. Medium-pressure tyres were employed with pneumatically-actuated differentially control-brakes.

When the Royal Air Force's (RAF) Advanced Air Striking Force (AASF) was deployed to France many Blenheims conducted short range bombing missions against German industrial targets. Many of Blenheim Mk.IV-equipped squadrons were employed during the Phoney War period. 

During the German invasion of Denmark and Norway in April 1940, Blenheims belonging to detachments of Nos. 107 and 110 Squadrons, based in RAF Lossiemouth, Scotland, conducted anti-shipping missions to intercept and bomb German warships en-route to Norwegian ports. These missions were, however, not effective and they did not report any enemy losses. As German troops started to gain foot on Norwegian lands, the aforementioned  squadrons were ordered to change their targets to attack enemy occupied airfields along the Norwegian coast. Luftwaffe fighter interception was unavoidable and, when the Blenheims pressed home their attacks, they suffered high losses. By early May, the Allied presence in Norway was hopeless and both squadrons were rebased to RAF Wattisham, Suffolk, to be prepared for the expected German offensive in central Europe.

Sources:

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

2. Signal Squadron - Aircraft In action 88 - Bristol Blenheim in Action

3. Hall Park Books - Warpaint 26 - Bristol Blenheim

4.Osprey Publishing - Combat Aircraft 5 - Blenheim Squadrons of World War 2

Bristol Blenheim, part eight. The Blenheim goes to war

 

An extended range reconnaissance version of the Blenheim was worked on, named as "Blenheim Mk.II". This was a regular Mk.I with the turret removed and larger fuel tanks. Only one prototype was built as, when tested, performance rates were  only marginally better and the variant was discarded.
Another Mk.III version was also developed which had a longer nose with the steepless cockpit of the Mk.I with a true windscreen in front of the pilot, giving this way, more room for the bomb aimer. This configuration required the nose to be "scooped out" in front of the pilot to keep visibility during take off and landing. This machine was further developed and, together with a newer version of the 905 hp Mercury radial engine and a pair of Browning machine guns (instead of the original Vickers K gun) placed in the turret, led to the Mk.IV variant. 
During the first half of 1939 the first production batch of Mk.IVs were accepted into service with the Royal Air Force (RAF). They lacked, however, outer fuel tanks, due to the urgent demand of the type and were powered by an earlier variant of the Mercury engine. From 1939 until June 1943 (though some sources claim it was until 1944) a total of 3.307 Mk.IVs were manufactured including those manufactured in Finland.

A long-range fighter variant was also developed, the Mk.IF. These machines were fitted with a gun pack containing four .303 in Browning machine guns. 

In September 1939, when the World War 2 broke out, the Blenheim Mk.I was serving with two home-based squadrons and 11 overseas ones in places such as Egypt, Iraq, Aden, India and Singapore. Further bomber squadrons were in the process of converting to the more capable Mk.IV and, by the outbreak of the war, a total of 168 Blenheim Mk.IV were in active service with the RAF. 

On 3rd September 1939, the day when both Britain and France declared war on Germany, a single Mk.IV piloted by Flying Officer Andrew McPherson was the first British airplane to fly over Germany to perform a reconnaissance mission on the Kriegsmarine's (German Navy) facilities in Wilhelmshaven, Lower Saxony. The next morning, fifteen Blenheims belonging to three different squadrons, took off to bomb the ships spotted the previous morning. RAF's Coastal Command also employed the type early on with the stated mission of protecting shipping convoys off the east coast of Britain. 

Sources:

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

2. Hall Park Books - Warpaint 26 - Bristol Blenheim

3.Osprey Publishing - Combat Aircraft 5 - Blenheim Squadrons of World War 2

Bristol Blenheim, part seven. Early Blenheims.

 

In 1933 Frank Barnwell, chief designer of Bristol Aeroplane Company travelled to the United States to gather information about their latest twin-engined, low-wing monoplane airliners. He was particularly interested in the Lockheed Electra Model 12A, and he drawn a design that would match it, employing the Bristol Aquila engine which yielded 500 hp of power, the same amount that the engines of the Electra produced. This design, which was identical to the Electra was named as Type 135 by Bristol. 

One year later, Lord Rothermere, owner of Daily Mail newspaper challenged the British aviation industry to build an airplane capable of carrying six passengers and two crew members at high speeds. This was done to catch the German designs, which at the time, they were breaking many speed records, like the Heinkel He.70. Rothermere wanted not only the prestige of having the fastest passenger airplane in the world, as well as purchase it. 

He became aware of the Type 135 and, on 3rd March 1934 Barnwell issued him with a quote of the specifications and expected performance of the type, with an estimated speed of 240 mph (390 km/h) at 6.500 ft (2.000 m), with the supercharged Bristol Mercury engines instead of the original Aquila ones, as these were shelved, considered outdated. Rothermere considered the design as suitable, however some changes needed to be made to suit it to his requirements and thus, the Type 142 was designed. In late March 1934 Rothermere ordered a single Type 142, for which he payed £18.500.

On 12th April 1935 the Type 142, named as "Britain's First", made its maiden flight at Filton aerodrome, in Gloucestershire. Flight testing showed the type to be faster than the Bristol Bulldog and the Hawker Fury, which were the main fighters of the Royal Air Force (RAF) at the time. The Type 142 achieved a top speed of 307 mph (494 km/h). 

In 1935 British Air Ministry showed interest on the type and on 9th July a conference was held at Bristol's headquarters to deal with the question of converting the Type 142 into a viable medium bomber. 

After that conference, Air Ministry issued Specification B.28/35 which sought for prototypes for a bomber version, with the interim designation of Type 142M (the letter M standing for Military). One important change from the Type 142 and the 142M was the repositioning of the wing, from a low-wing to a mid-wing position, to allow internal space for a bomb load. Other modifications included a bomb-aimer position, a Browning machine-gun at the nose and a semi-retractable turret in the dorsal position.

In September 1935 an initial order for 150 aircraft was placed. The type was ordered directly off the drawing board as the Air Ministry sought a quick expansion and modernization of the RAF. The first aircraft produced, on 25th June 1936 acted as the prototype and the type received the name of Blenheim, after the battle of the War of the Spanish Succession. On 10th March 1937 the first batches were officially delivered to the RAF, being No.114 Squadron the first one to receive the type. Later, on 13th January 1938, the No. 30 Squadron became the first overseas squadron to operate the type and, in early 1939 the Blenheim arrived in India.

Sources:

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

2. Hall Park Books - Warpaint 26 - Bristol Blenheim

3.Osprey Publishing - Combat Aircraft 5 - Blenheim Squadrons of World War 2

Bristol Blenheim, part six, Yugoslav users

 

The Bristol Blenheim was a British light bomber of the Second World War which saw action with many countries all around the world, among them, the former Kingdom of Yugoslavia. 

The Kingdom of Yugoslavia also showed interest in the Blenheim and, just like the Finns did, they also acquired a production license for 50 aircraft which would be produced by Ikarus at their factory in Zemum, close to Belgrade.

In November 1937 two Mk.Is were shipped to serve as patterns and by 1939 Ikarus had completed a around 23 frames, without engines though. The engine supply from the United Kingdom turned to be a serious problem, so one machine, No.29, was fitted with Italian Alfa Romeo 126 radial engine. Eventually, Bristol Mercury engines were obtained from the Polish PZL factory after Germany occupied Poland, so further 14 machines could be completed at Ikarus'. Therefore, a total of 40 Ikarus-built Blenheims Mk.Is were delivered to the Royal Yugoslav Air Force, also known as JKRV. The Yugoslav-built Blenheims were armed with Italian 12,7mm Breda-SAFAT machine guns instead of the original British ones. Some were also up-armed with additional Italian 12,7mm Breda-SAFAT machine guns, which increased its weight and made the aircraft harder to fly.

Back in August 1939 they also requested a supply of Mk.IVs, but Bristol refused it and sent 20 additional Avro-built Mk.Is instead. However, it seems that by early 1941 the production line was set to produce the Mk.IV and around 20 partially completed airframes were found by the Germans when they invaded in April 1941. These tools and frames were later given to Finland. Some sources claim that one machine was completed and even painted, but never flew. As we couldn't confirm nor deny it, we decided to draw it anyway. 

The first unit of the JKRV to employ the Blenheim was the 1st Bomber Regiment in 1938, which was joined later by the 8th Bomber Regiment and, in 1940, the 11th Independent Long Range Reconnaissance Group. Most of the Yugoslav Blenheims were in service when Germany invaded on 6th April 1941. Some were destroyed on ground by Luftwaffe's raids, but many others performed unescorted bombing raids and showed to be very vulnerable to both fighters and anti-air fire. 

However, some successful attacks were made, but, with their bases threatened, many units were forced to evacuate and by 13th April there were few Blenheims available, with some being destroyed by Yugoslav to prevent to fall into German hands. A few, around 20 machines, were captured by the Germans, and after some refurbishment, they were given to the Independent State of Croatia's Air Force. 

It seems that at least one machine was captured at the end of the war by Yugoslav's Partisans and it received Yugoslav Communist markings. Its fate is unknown.

Sources:

1. Hall Park Books - Warpaint 26 - Bristol Blenheim

2. https://en.wikipedia.org/wiki/List_of_Bristol_Blenheim_operators