Boeing B-17 Flying Fortress (USA)

Frustrated in their efforts to acquire a fleet of strategic bombers for service with the Army Air Corps, US Army planners – who were devotees of the theories expounded by Brigadier General William “Billy” Mitchell – inserted the thin end of an important wedge when they ordered a small number of YB-17 prototypes in January 1936, ostensibly for the nation’s defence. Originating as the Boeing Model 299, the prototype was built as a private venture, Boeing gambling heavily on producing a winner that would bring a large military contract. It must have seemed to Boeing that their gamble had failed when, almost at the end of military trials, the Model 299 crashed on take-off. Fortunately investigation proved that the aircraft had been flown with the flying controls locked and safety of the basic design was not suspect.

It was not until 1938 that the USAAC was able to place an order for 39 B-17Bs, the last of this batch entering service in March 1940. These were the first B-17 production aircraft to be equipped with turbo-charged engines, providing a higher maximum speed and much increased service ceiling. Of the B-17Cs that followed, a batch of 20 were supplied to the RAF (designated Fortress I) and used operationally in Europe for evaluation, leading to improved B-17D and B-17E aircraft with self-sealing fuel tanks and revised armament.

The B-17E was truly a Flying Fortress, armed with one 0.30 inch and twelve 0.50-inch machine guns for defence and capable to carry a maximum 17,600 pounds (7,983 kilograms) of bombs.  Most extensively built variant was the B-17G (8680), built by Douglas and Lockheed Vega and the Boeing plant at Seattle. Pratt and Whitney R-1820-97 radial engines and improved turbochargers enabled the B-17G to operate at an altitude of up to 35,000 feet (10,670 metres); and the addition of a chin turret below the nose (containing two 0.50 inch machine guns) provided better air defence against head-on attacks being launched by Luftwaffe fighter pilots in their attempts to reduce the number of Fortresses striking daily at strategic targets deep in German territory.

Special variants included the B-40 with up to 30 machine guns/cannons, which was intended as a B-17 escort, but proved to an operational failure; BQ-7 pilotless aircraft packed with explosives to be deployed against German targets by radio control, which failed due to unreliable control equipment; CB-17 equipped to serve as an Air Sea Rescue aircraft and able to deploy a lifeboat carried beneath the fuselage.

 In Britain, more than anywhere else in the world, the B-17 evokes vivid memories of courageous aircraft who day after day – despite sometimes horrific losses – continued to attack targets in Europe until victory was won. For Boeing, their private-venture gamble paid off: a total of 12,731 Flying Fortresses were built by the Boeing, Douglas and Lockheed team.

Avro 683 Lancaster (UK)

The most famous of all Avro military aircraft and without doubt the most successful heavy night bomber to be deployed over Europe during World War II. The Avro 683 evolved almost accidentally as a result of recurrent failure of the insufficiently developed Rolls Royce Vulture engines installed in the twin-engined Manchester. Owing to delays in the full development of the Vulture engine, the decision was taken in mid-1940 to design a new version of the Manchester with four Rolls Royce Merlin engines. The first conversion made use of about 75% of the Manchester’s parts to and assemblies, the principal change being the provision of a new centre-section of the wing with mountings for Merlin engines. This aeroplane became the first prototype of the Lancaster. A second prototype fitted with Merlin engines and significantly modified in detail was designed, built and flown in just eight months. The first production Lancaster I flew just over five months later, its power plant comprising similar 1280 hp (954 kW) Rolls Royce Merlin XX in-line liquid cooled engines, each driving a three blade constant speed and fully feathering propeller. Because of the possibility of some interruption in Merlin production, the Lancaster II was built with 1650 hp (1229.5 kW) Bristol Hercules VI radial engines. These fears did not materialise, with the result that only 300 Lancaster II were built.

First operational RAF Squadron to be equipped with Lancaster 1s was # 44 Squadron which used them operationally for the first time on 3 March 1942- laying mines in the Heligoland Bight. Defended by ten machine guns and carrying a maximum bomb load of 14000 lb (6350 kg), the Lancaster was – and soon proved itself to be – a formidable weapon in the hands of the RAF, which had by mid-1942 learned a great deal about night bombing operations over Europe. By comparison with contemporary four-engined bombers it was statistically the most effective, dropping 132 tons of bombs for each aircraft lost on operations; the corresponding figures for Halifax and Stirling were 56 and 41 tons respectively. The Lancaster was so right from the beginning that there were few changes in airframe design during its wartime service.

Improved power plants, however, provided steadily improving performance: the Lancaster VII for example with 1620 hp (1207 kW) Merlin 24 engines had a maximum take off weight of 68,000 lb (30844 kg) by comparison with the 50,000 (22680 kg) of the early Is. Bomb load changed considerably; the cavernous bomb bay being designed originally to carry bombs up to 4000 lb with a total bomb load of 14000 lb (6350 kg); it was modified progressively to carry the 22000 lb Grand Slam bomb.

The Lancaster will be remembered for its part in two spectacular operations: the breaching of the Mohne and Eder dams on the night of 16-17 May 1943 by 617 Squadron (led by Wing Commander Guy Gibson); and the sinking of the German battleship, Tirpitz. Its contribution to victory in World War is best measured, however, by the total of 608,612 tons of bombs delivered, which represented two-thirds of the total bomb load dropped by the RAF from the time of its entry into service. A total of 7366 Lancasters were built (including Mk Xs in Canada) and the type remained in front line service with the RAF until 1954. Canada had some photo-reconnaissance Lancasters in service in 1964.

Courtesy of: Jane’s Encyclopedia of Aviation Compiled and Edited by Michael J.H. Taylor; Crescent Books New Books New York 1980