The Bristol Type 159 bomber in the markings of 83 Squadron, RAF circa 1942-43.
The Bristol Type 159 was designed to Spec B.1/39 for an 'Ideal Bomber' able to cruise at 280mph with a minimum 2,500 mile range at 15,000 feet with 9,000lbs of bombs, four-engine and a maximum weight no greater than 50,000lbs. The Boulton Paul quadruple 20mm cannon turret became the favoured defensive armament. Armstrong Whitworth, Avro, Blackburn, Bristol, Fairey, Gloster, Handley Page, Shorts and Vickers all submitted designs. The Bristol Type 159 carried its bombs (a 15,000lb maximum load) in the inner wing with two bomb cells outboard of the outer engines allowing the two massive quadruple 20mm cannon turrets to be at the centre of gravity. 2,580 gallons of fuel were carried. Four Bristol Hercules would be fitted although the Rolls-Royce Griffon was the second choice. Cruising speed was 282 mph at 15,000 ft, maximum speed 302 mph at same altitude, service ceiling 25,300 ft, 114 ft 6 in span, 80 ft 3in long, 1,800 sq ft wing area and maximum weight 77,860 lbs. In December 1939 two prototypes were ordered from Bristol and Handley Page but in May 1940 work was halted due to other priorities. During final calculations it was found the structure weight grew so much that the fuel and bomb load would be reduced. This also killed the project. The Halifax and Lancaster filled the gap but this huge bomber would have been a mammoth undertaking. It would not have been able to carry the later wartime 'blockbusters' in its wing cells but the eight cannon would have been deadly against night fighters, especially the ventral turret.