When built, it was the world's largest flying craft[3] at 731 ft (223 m) in length, and 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,[4] the R101 crashed in France during its maiden overseas voyage on 5 October 1930, killing 48 of the 54 people on board.

[5] 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 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.

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.

[23] 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.

R101's patented "parachute" gasbag harnessing, designed by Michael Rope, proved less than satisfactory, permitting the bags to surge unduly, particularly in rough weather.

[26] Heavy oil (diesel) engines were specified by the Air Ministry because the airship was intended for use on the India route, where it was thought that high temperatures would make petrol an unacceptable fire hazard because of its low flash point.

These moved an indicator in the engine car to signal the desired throttle setting and also rang a bell to draw attention to the fact that an order had been transmitted.

After a short circuit over Bedford, course was set for London, where it passed over the Palace of Westminster, St Paul's Cathedral and the City, returning to Cardington after a flight lasting five hours 40 minutes.

[44] A second flight lasting nine hours 38 minutes followed on 18 October, with Lord Thomson among the passengers, after which R101 was briefly returned to the shed to enable some modifications to be made to the starting engines.

[46] On 2 November the first night flight was made, slipping the mast at 20:12 before heading south to fly over London and Portsmouth before attempting a speed trial over a 43 mi (69 km) circuit over the Solent and the Isle of Wight.

[49] On 16 November, it had been planned to carry out a demonstration flight for a party of 100 MPs, a scheme that had been suggested by Lord Thomson in the expectation that few would wish to take advantage of the offer; in the event, it was oversubscribed.

During the night, a series of turning trials were made over the Irish Sea, after which the airship was flown south to fly over Dublin (the home town of R101's Captain, Carmichael Irwin) before returning to Cardington via Anglesey and Chester.

The only technical problem encountered during the flight was with the pump for transferring fuel, which broke down several times, although subsequent examination of the engines showed that one was on the point of suffering a failure of a big end bearing.

With the barometric pressure low, R101 lacked sufficient lift to carry 100 passengers, even though all but a bare minimum of fuel was drained off and the ship lightened by removing all unnecessary stores.

The flight was cancelled because of the weather, but not before the politicians had arrived at Cardington: they accordingly embarked and had lunch while the ship rode at the mast, only kept in the air by dynamic lift produced by the 45 mph (72 km/h) wind.

It had been at the mast for less than an hour in a moderate wind when an alarming rippling movement was observed, and shortly afterwards a 140 ft (43 m) split in the cover appeared on the starboard side of the airship.

Airship valves are intended primarily to vent gas automatically if pressure in the cells rises to the point that the bag might rupture; they are also used to adjust lift for handling.

On 3 July, bypassing his immediate superior, McWade wrote a letter to the Director of Aeronautical Inspection, Lieutenant-Colonel H. W. S. Outram, expressing his unwillingness to recommend either an extension to the permit or the granting of the full Certificate of Airworthiness which would be necessary before the airship could fly in the airspace of other countries.

This lasted 16 hours 51 minutes and was undertaken under near-ideal weather conditions; because of the failure of the oil cooler in one engine, it was not possible to carry out full-speed trials.

[70] R101 departed from Cardington on the evening of 4 October 1930 for its intended destination of Karachi, via a refuelling stop at Ismaïlia in Egypt, under the command of Flight Lieutenant Carmichael Irwin.

[73] R101 cast off from the mast at 18:36 GMT to a cheer from the crowd which had gathered to witness the event, gently backed from the tower, and, as another ton of ballast was jettisoned, the engines were opened up to about half power and the airship slowly began to climb away, initially heading northeast to fly over Bedford before making a 180° turn to port to pass north of Cardington.

At 20:01, R101, by now over Potters Bar, made its second report to Cardington, confirming the intention to proceed via London, Paris and Narbonne, but making no mention of the engine problem.

By now the wind had risen to about 44 mph (71 km/h) with strong gusts, but a further meteorological report received shortly after the airship had crossed the coast had been encouraging about weather conditions south of Paris.

R101 was at this point "flying heavy",[citation needed] relying on dynamic lift generated by forward airspeed to maintain altitude, estimated by the Board of Inquiry as at least 1,000 ft (300 m) above the ground.

The only major fracture found in the wreckage was at the rear of the new framework extension but it was considered that this had either occurred on impact or more probably been caused by the intense heat of the subsequent fire.

[69] The airship's competitor, R100, despite a more successful development programme and a satisfactory, although not entirely trouble-free, transatlantic trial flight to Canada and back, was grounded immediately after the R101 crash.

Nevil Shute Norway's autobiography was serialised by the Sunday Graphic on its publication in 1954 and was misleadingly promoted as containing sensational revelations,[99] and the accuracy of his account is a cause of contention among airship historians.

[101] On 27 November 2014, 84 years after the disaster, Baroness Smith of Basildon, together with members of the Airship Heritage Trust, unveiled a memorial plaque to the R101 in St Stephens Hall in the Palace of Westminster.