Thursday, August 3, 2017

The Tarrant Tabor

Walter G. Tarrant was a well-known woodworking contractor at Byfleet, Surrey. His company supplied countless structural components to other aircraft manufacturers during WW1. In 1917 Tarrant along with Marcel Lobelle from the nearby company of Martinsyde, and by W H Barling from the Royal Aircraft Factory set about designing and building the world's largest bomber aircraft.

Construction was primarily in wood with conventional biplane strut-braced wings and a monocoque fuselage built up from ply veneers. The monocoque construction gave a large open space within the fuselage. The pilots were situated in the nose, with a partition separating them from the engineer's station and the engine controls mounted on either side of the opening in the partition. The fuel tanks were in the top and sides of the fuselage to maintain the clear internal space.

The original design was to be powered by four 600hp Siddeley Tigers, arranged in tandem pusher/tractor pairs at midgap. It soon became evident, however, that the Tiger would not be ready in the timespan required so in order to maintain a comparable power/weight ratio, Tarrant elected to fit six 450hp Napier Lions instead, at the same time adding an upper, third wing with the same dimensions and structure as those of the bottom wing, transferring the support for what became the central wing's large overhang to the top wing. The two additional Lion tractor engines were mounted directly above the lower pairs.

The intended bomb load was twenty 230 pound bombs carried under the lower wing center section. Diagonal center section struts passed from the upper wing, through the central wing and fuselage meeting on the lower wing. This in effect, created a huge Warren truss of great strength. This structure design would thus have distributed the bomb load to all the wings without compromising the cylindrical fuselage structure.

The fuselage was a finely-streamlined, cigar-shaped structure which carried a biplane tail unit, comprising two tailplanes, the lower of which incorporated a horn-balanced elevator, and the upper a trimming surface operated by handwheel in the pilot's cockpit. A second elevator was mounted in the tailplane gap.
The landing gear was huge, as you can see, with each wheel assembly being attached by struts designed to distribute landing loads equally to the three wings. 

The wingspan was of over 131 ft (40 m), overall height of 37ft 3in compared, for instance, to 20ft 8in of the Bristol Braemar triplane bomber. Loaded weight would have been 44,672 pounds.

Work on the aircraft briefly stopped at the end of the War, when it was no longer needed as a bomber. The design was altered to allow it to be used as a commercial or transport aircraft and construction resumed.
The Tabor was readied for its maiden flight from the Royal Aircraft Establishment at Farnborough on 26 May, 1919. With two pilots and five passengers the plane was taxied around the landing field using only the four lower engines. Satisfied with the behaviour of the aircraft the crew decided to take-off. The tail was off the ground but it was still running on the main wheels, intermittently lifting off.
When the pilots brought both of the upper engines to full power the aircraft pitched forward, causing the aircraft to nose over into the ground and to inflict fatal injuries on both men.

Later analysis suggested that the upper engines were so far above the fuselage that they forced the nose down when full power was applied.

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