R101 was one of a pair of British rigid airships completed in 1929 as part of the Imperial Airship Scheme, a British government programme to develop civil airships capable of service on long-distance routes within the British Empire. It was designed and built by an Air Ministry–appointed team and was effectively in competition with the government-funded but privately designed and built R100. When built, it was the world's largest flying craft at in length, later enlarged to 777 feet (237 m), and at that size it was not surpassed by another hydrogen-filled rigid airship until the LZ 129 Hindenburg was launched seven years later.
After trial flights and subsequent modifications to increase lifting capacity, which included lengthening the ship by to add another gasbag,"R101". Airship Heritage Trust via Airshipsonline.com. Retrieved: 23 July 2008. the R101 crashed in France during its maiden overseas voyage on 5 October 1930, killing 48 of the 54 people on board.Report of the R101 Inquiry 1931, p. 7. Among the passengers killed were Lord Thomson, the Air Minister who had initiated the programme, senior government officials, and almost all the dirigible's designers from the Royal Airship Works.
The crash of R101 effectively ended British airship development, and it was one of the worst airship accidents of the 1930s. The loss of 48 lives was more than the 36 killed in the better-known Hindenburg disaster of 1937, though fewer than the 52 killed in the French military Dixmude in 1923 and the 73 killed when the USS Akron crashed in the Atlantic Ocean off the coast of New Jersey in 1933.
Background
R101 was built as part of a British government initiative to develop airships to provide passenger and mail transport from Britain to the most distant parts of the British Empire, including India, Australia and Canada, since the distances were then too great for heavier-than-air aircraft. The Burney Scheme of 1922 had proposed a civil airship development programme to be carried out by a specially established subsidiary of Vickers with the support of the British government. The scheme drew support from the Air Ministry, which sought more airships and a base in India. The Admiralty added that it would forgo some light cruisers of which it was very short. However, Prime Minister Lloyd George's government decided it could not afford to support the Burney Scheme.Higham 1961, pp. 283–84.
When the 1923 general election brought Ramsay MacDonald’s Labour administration to power, the new Air Minister, Lord Thomson, formulated the Imperial Airship Scheme in place of the Burney Scheme.Masefield 1982, p. 30. It called for the building of two experimental airships: one, R101, to be designed and constructed under the direction of the Air Ministry, and the other, R100, to be built by a Vickers subsidiary, the Airship Guarantee Company, under a fixed-price contract. They were nicknamed the "Socialist Airship" and the "Capitalist Airship", respectively.Philpott, Ian: The Royal Air Force – Volume 2: An Encyclopedia of the Inter-War Years, pp. 4–9.
In addition to the building of the two airships, the Imperial Airship Scheme involved the establishment of the necessary infrastructure for airship operations; for example, the mooring masts used at Cardington, Ismalia, Karachi and Montreal had to be designed and built, and the meteorological forecasting network extended and improved.Sprigg 1931, p. 128.
Specifications for the airships were drawn up by an Air Ministry committee, whose members included Squadron Leader Reginald Colmore and Lieutenant-Colonel V.C. Richmond,Masefield 1982, p. 454. both of whom had extensive experience with airships, most of them non-rigid. They called for airships of not less than five million cubic feet (140,000 m³) capacity and a fixed structural weight not to exceed 90 tons, giving a "disposable lift" of nearly 62 tons. With the necessary allowance of about 20 tons for the service load consisting of a crew of approximately 40, as well as stores and water ballast, this allowed a possible fuel and passenger load of 42 tons. Accommodation for 100 passengers and tankage for 57 hours' flight was to be provided, and a sustainable cruise speed of and maximum speed of were called for.Report of the R101 Inquiry 1931, p. 14. In wartime, the airships would be expected to carry 200 troops or possibly five parasite fighter aircraft.
Vickers' design team was led by Barnes Wallis, who had extensive experience of rigid airship design and later became famous for the geodetic framework of the Wellington bomber and for the bouncing bomb. His principal assistant (the "Chief Calculator"), Nevil Shute Norway, later well known as the novelist Nevil Shute, later gave his account of the design and construction of the two airships in his 1954 autobiography, Slide Rule: Autobiography of an Engineer. Shute Norway's book characterises R100 as a pragmatic and conservative design, and R101 as extravagant and overambitious, but one purpose of having two design teams was to test different approaches, with R101 deliberately intended to extend the limits of existing technology.Masefield 1982, p. 111. Shute Norway later admitted that many of his criticisms of the R101 team were unjustified.Masefield 1982, pp. 204–05, fn.
An extremely optimistic timetable was drawn up, with construction of the government-built R101 to begin in July 1925 and be complete by the following July, with a trial flight to India planned for January 1927.Masefield 1982, p. 51. In the event, the extensive experimentation that was necessary delayed the start of construction of R101 until early 1927. R100 was also delayed, and neither flew until late 1929.
Design and development
The entire airship programme was under the direction of the Director of Airship Development, Group Captain Peregrine Fellowes, with Colmore acting as his deputy. Lieutenant-Colonel Richmond was appointed Director of Design: later he was credited as "Assistant Director of Airship Development (Technical)"Flight 10 October 1930, p. 1126. with Squadron Leader Michael Rope as his assistant. The Director for Flying and Training, responsible for all operational matters for both airships, was Major G.H. Scott, who had developed the design of the mooring masts that were to be built. Work was based at the Royal Airship Works at Cardington, Bedfordshire, which had been built by Short Brothers during the First World War and had been employed by the Admiralty to copy and improve on the latest German designs from captured rigid airships. The Works had been nationalised in 1919, but after the loss of the R38 (then in the process of being transferred to the US as ZR2), naval airship development was stopped and it had been placed on a care and maintenance basis.
R101 was to be built only after completion of an extensive research and test programme by the National Physical Laboratory (NPL). As part of this programme, the Air Ministry funded the costs of refurbishing and flying R33 in order to gather data about structural loads and the airflow around a large airship. This data was also made available to Vickers;"Written Answers." Hansard, 3 May 1926. both airships had the same elongated tear-drop shape, unlike previous designs. Hilda Lyon, who was responsible for the aerodynamic development, found that this shape produced the minimum amount of drag. Safety was a primary concern and this would have an important influence on the choice of engines.
An early decision had been made to construct the primary structure largely from stainless steel rather than lightweight alloys such as duralumin. The design of the primary structure was shared between Cardington and the aircraft manufacturer Boulton and Paul, who had extensive experience in the use of steel and had developed innovative techniques for forming steel strip into structural sections. Working to an outline design prepared with the help of data supplied by the NPL, the stress calculations were performed by Cardington. This information was then supplied to J.D. North and his team at Boulton and Paul, who designed the metalwork."Division of the Design Work." Flight, 29 November 1928. The individual girders were fabricated by Boulton and Paul in Norwich, and transported to Cardington where they were bolted together. This scheme for a prefabricated structure entailed demanding manufacturing tolerances and was entirely successful, as the ease with which R101 was eventually extended bears witness. Before any contracts for the metalwork were signed, an entire bay consisting of a pair of the 15-sided transverse ring frames and the connecting longitudinal girders was assembled at Cardington. After the assembly had passed loading tests, the individual girders were then tested to destruction. The structure of the airframe was innovative: the ring-shaped transverse frames of previous airships had been braced by radial wires meeting at a central hub, but no such bracing was used in R101, the frames being stiff enough in themselves."His Majesty's Airship R100: The construction of R101."Flight (supplement), 29 November 1928, p. 88. However, this resulted in the structure extending further into the envelope, thereby limiting the size of the gasbags.
The specifications drawn up in 1924 by the Committee for the Safety of Airships had based weight estimates on the then-existing rules for airframe strengths. However, the Air Ministry Inspectorate introduced a new set of rules for airship safety standards in late 1924 and compliance with these as-yet unformulated rules had been explicitly mentioned in the individual specifications for each airship.Masefield 1982, p. 457. These new rules called for all lifting loads to be transmitted directly to the transverse frames rather than being taken via the longitudinal girders.Morpurgo 1982, pp. 132–33. The intention behind this ruling was to enable the stressing of the framework to be fully calculated, rather than relying on empirically accumulated data, as was contemporary practice at the Zeppelin design office. Apart from the implications for the airframe weight, one effect of these regulations was to force both teams to contrive a new system of harnessing the gasbags. R101's patented "parachute" gasbag harnessing, designed by Michael Rope, proved less than satisfactory, permitting the bags to surge unduly, particularly in rough weather.Report of the R101 Inquiry 1931, pp. 39–40. This caused the gasbags to chafe against the structure, tearing holes in the fabric. Another effect was that both R100 and R101 had a relatively small number of longitudinal girders in order to simplify the stress calculations.
R101 used pre-doped linen panels for much of its covering, rather than lacing undoped fabric into place and then applying dope to shrink it. In order to reduce the area of unsupported fabric in the covering, the design alternated the main longitudinals with non-structural "reefing booms" mounted on kingposts which were adjustable using screw-jacks in order to tension the covering.Masefield 1982, p. 470. The pre-doped fabric proved unsatisfactory from the start, with panels splitting because of humidity changes before the airship had even left its shed.Report of the R101 Inquiry 1931, p. 31.