R101

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 731 ft (223 m) 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 46 ft (14 m) to add another gasbag, the R101 crashed in France during its maiden overseas voyage on 5 October 1930, killing 48 of the 54 people on board. 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.

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.

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. 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.

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.

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, 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.^{[citation needed]} Accommodation for 100 passengers and tankage for 57 hours' flight was to be provided, and a sustainable cruise speed of 63 mph (101 km/h) and maximum speed of 70 mph (110 km/h) were called for. 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. Shute Norway later admitted that many of his criticisms of the R101 team were unjustified.