Boulton Paul Defiant

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The Boulton Paul Defiant's a plane from an original design: two-seater fighter, he has a hydraulic turret turns 360 °, equipped with two pairs of Browning machine guns 0.303 caliber 7.7 mm. The plane seems to have a strong firepower, and its driver is fully discharged worries firing. However, it has no weapons on the front. The concentration of four machine guns in the turret can be placed in the awkward position if it is damaged or if the mitraillleur is affected.  

Like almost all British aircraft, it is powered by the Rolls-Royce Merlin, a V-12 liquid-cooled 27-liter engine, which develops about 1,000 CVs in the first version, Mark I, and a little over 1,200 hp in the second version (Mark II). The tower alone weighs 200 kg. In running request, with full tanks and ammo, The Defiant makes over 800 kg to a Hurricane equipped with similar motor. Slower than routine seekers (most extreme speed lower than 500 km / h cruising speed to 400 km / h), and less maneuverable, the Defiant can not par with a Messerschmitt.

Designed in 1935 (Boulton Paul had already developed the turret), the first prototype (without turret) takes the air on August 11, 1937. The design and manufacturing take considerable delay. The second prototype (with turret), steals in May 1939 and the production aircraft first flew on July 30, 1939. It is noted that the performance of the first prototype are significantly degraded by the weight and drag of the turret. Delivery is made in December 1939. The Defiant will equip the 264 Squadron and 141 Squadron.

The design of the aircraft is quite thin, and his silhouette reminiscent of Hurricane. This is probably why the Defiant winner of the first fighting over Dunkirk: German pilots, mistaking him for a conventional fighter, discover too late that the Defiant can fire back. But they quickly learn to identify and take advantage of weaknesses, including its vulnerability to the frontal attack. The losses then become unbearable. As an interceptor of day, the appliance is removed from service shortly after the Battle of Britain, and becomes night fighter until the arrival of Mosquito Beaufighter.Il and then doing a remarkable job during the Blitz, the during the winter of 40-41, with the Squadron 256. the Defiant will be subsequently used for sea rescue, training, pulling targets. A copy will serve until 1948 at Martin-Baker ejection seat for the tests, the ejection seat naturally taking the place of the turret.

Defiant cease production in February 1943: 1,064 copies anront built: 713 212 Mark I and Mark II (from February 1941), which must be added some Defiant equipped with a radar (Mark IA).

The turret fighter was probably not an absurd idea. In 1937, the Defiant is more modern and faster than some conventional devices RAF as the Gloster Gladiator biplane. But when he reaches the stage of production at the end of 1939, it should be compared to the Spitfire and can in no way compete on equal terms with the Messerschmitt. The plane itself was not without qualities. In choisisant apply to single-engine fighter experience of the motorized turret, gained with the Overstand bomber, Boulton Paul thought equip the RAF an interceptor considerable firepower. In fact, the machine had proved vulnerable, unable to fire from the front, and was to be placed necessarily below the opponent while the preceding order to attain it.

The Defiant Boulton Paul, however, allows to get into the mass production of hydraulic turrets, which will equip later many bombers, the Halifax first, then more American aircraft, the B24 for the RAF.

The turret, fully autonomous (it has its own hydraulic pump) is surrounded in the front and rear, retractable spoilers, controlled by hydraulic cylinders. To increase the range, the masts of the radio antenna are located on the belly of the machine, and retract when the landing gear down. In all-metal construction, the Boulton Paul is also a modern aircraft. The turret is autonomous, and can be assembled and disassembled in minutes. The first turret Boulton Paul, mounted on the Overstrand bomber of 1930 were driven by compressed air: they could not work long continuously, because after a few minutes, the compressed air tanks were empty and had to be reloaded again by a compressor. The new model is hydraulic-electric: it comprises two separate pumps and two circuits, the first which ensures the movement of the machine guns and the second movement of the turret. The pumps are driven by electric motors 24 volts.

Resistors are provided for heating the pump and motors, and other incorporated in the hydraulic circuit. Everything is designed to ensure reliable operation at low temperatures encountered at high altitude but nothing has been devised for the gunner, which as on all aircraft of the time, should take a hot combination. An outlet is provided for supplying the combination, as well as the oxygen supply. An electrical switch prohibits firing when the propeller or airplane structures are in the range. Relatively light, the new turret Boulton Paul are designed around the Bowning 0303 machine gun team RAF since the 1920s.

It is surprising persistence to the end of the war the rifle caliber. It is in fact in the last few months appears on airplanes British gauge zero point 5 is 12.5mm, universally used by the USAAF, while arming and protecting hunters had evolved: 20 mm cannons, light armor, thick plexiglass to protect the driver, self-sealing fuel tanks. The 0303 has a great shooting speed (1200 strokes / minute) and a high muzzle velocity, but the size is probably a little inadequate, especially as the scope of the Bowning 0303 low (1000 m in theory, likely 500 m in practice). Browning 0.50, the firing rate is slightly lower, the advantage of a theoretical range of 7000 m, with a piercing ammunition power beyond measure. However, adoption of 0.50 would have induced many difficulties, which it was not possible to provide an immediate response. It was mass-produce munitions, provide for the supply of spare parts, and change the turrets. The machine gun 0.50 is indeed much heavier (about 30 kg against 10 kg) also with heavier ammunition (against 48 g 11 g). The increased weight would inevitably have led to rebuild the turrets, and to change the structure of aircraft to support those burdened turrets.

What should have been the Defiant to be less vulnerable? No doubt a more powerful armament forward to complete the turret. More power also, ie two engines. Curiously, this turret fighter was built, not by Boulton Paul, but Bristol. It was the Beaufighter Mark V, Twin hunting and anti-submarine fight, with two 20 mm guns in the front, a Boulton Paul turret with 2 pairs of Browning machine guns, on which Hercules engines origin (without radial valves) were replaced by Rolls-Royce Merlin. It seems that the turret has spawned a detrimental aerodynamic drag performance. The production was not continued and the Beaufighter Mark V existed in duplicate affected early 1942 to 29 Squadron.



Specifications :  
Crew : 2
Length: 10.770 m
Height: 3.450 m
Wing span: 11.99 m
Wing area: 23.230 m²
Leermasse: 2849 kg
Maximum take-off mass: 3821 kg
Engine: a V12 engine Rolls-Royce Merlin XX with 1280 hp
Max speed: 504 km / h
Service of Ceilling: 9250 m
Range: 748 km
Armament: Four 7.7mm Browning MGs

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