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Causes of the R101 Disaster

The wreck of R101 near Allonne [Z434/4]
The wreck of R101 near Allonne [Z434/4]

Bedfordshire and Luton Archives and Records Service has copies of the thirteen day public inquiry into the loss of the R101 held between 28th October and 5th December 1930 at the Institution of Civil Engineers at Great George Street, Westminster before Sir John Simon, Lieutenant-Colonel J. T. C. Moore-Brabazon and Professor C. E. Inglis. The word-for-word transcription of proceedings is available in the Bedfordshire and Luton Archives and Records Service Searchroom.

Sir Maurice J. Dean, who was involved in the trials of R101 wrote an article for the May 1966 edition The Air Force Department Society Journal. A copy of this article is available in the Bedfordshire and Luton Archives and Records Service Searchroom [CRT160/215]. He quoted the findings of the inquiry as follows:

“The reconstruction of the first phase would therefore be somewhat as follows: Assume that vessel had become somewhat heavy and was being buffeted in the wind so that so that her nose was sometimes above and sometimes below the line of horizontal flight. If she had been raised by a buffet, the elevator would be put down by the coxswain who had just come on duty to check and counteract this movement. The coxswain, not yet having got the “feel” of the ship thoroughly, might put his elevator rather more down than was necessary, or keep it down longer than was exactly right. The vessel’s nose would drop. If when her nose is inclined downwards she gets a strong buffet of wind above her nose it will push her nose further down. If she was already heavy from loss of gas – especially if a rent had occurred in a gas-bag which involved progressively rapid deflation – the descent is emphasised. The ship is now on her downward track in the first phase. The coxswain will begin to put his elevator up, and in order to get the ship out of her first dive, has put it up harder. None the less she does not come out of her first dive as rapidly as she should, because she is losing more gas all the time. The slowness of her recovery would give sufficient warning of the crisis. This gives the explanation of the course of events which is most consistent with the evidence, and at certain points is the only explanation which readily presents itself in accordance with the facts. At other points it is no doubt possible to assume certain variations in the data. For example, the final dive might have been assisted by another buffet of wind, and the exact relation between the angle of the elevator and the amount of gas lost can never be ascertained by any process of reconstruction”.

“How the vessel began to lose gas can never be definitely ascertained. The weather was exceptionally bad; the gas-bags were hard up against padded projections, some of which may have begun to wear the fabric; the bumpiness of the wind and the pitching of the ship would intensify the strain; the earlier flights had indicated the possibility of leakage through chafing, or, if the vessel rolled through an unusually large angle, through intermittent opening of the gas valves. But it seems very probable that the more serious and sudden loss of gas which followed was connected with a specific misfortune such as the ripping of the fore part of the envelope. Something of this sort had happened on a previous occasion and no amount of care could secure that it would never happen again. If a rip had begun in the fore part of the envelope it would tend to develop into a larger tear which would both check the speed of the R101 through the air and expose the gas-bags to additional strain. This seems the most probable explanation of a further loss of gas in increasing quantity and suddenness. But whatever the precise circumstances may have been, the explanation that the disaster was caused by a substantial loss of gas in very bumpy weather holds the field. This is the unanimous view of all the three members of the Court of Inquiry”.

Sir Maurice in his article opined that in correcting the first dive R101 entered one of the forward gas bags was torn on the structure of the shop. Sir Maurice claimed that it was not unusual for airships to experience sudden dives, having experienced one himself on one of the R101’s sister ship, R100’s trial flights. This would send hydrogen gas rushing to the aft part of the airship. This would encourage the nose, now heavier than air, to aim towards the ground and the second dive would be unstoppable, particularly since the airship was then within twice its length from the ground. The public inquiry considered this theory but, in the end, did not choose it, opting for a more general statement.

It was the fire following the crash which killed so many of the passengers and crew. This might have begun by sparks caused by friction on impact igniting the 500,000 cubic feet of hydrogen. Another possibility is that some electrical short circuit in the wiring inside the balloon caused by the crash ignited the gas.

At the public inquiry the finger was pointed at Secretary of State for Air, Lord Thomson, for rushing and curtailing R101’s test flights so that he could fly to India in time for an Imperial Conference. Arriving in style by airship at such an important event could not but boost government funding for the airship programme, both civil and military. The captain of R100 stated that had it not been for the Imperial Conference he felt sure that more test flights of R101 would have been undertaken. Certainly the test flight programme was far shorter than desirable. If Lord Thomson did unduly curtail R101’s testing he paid for it with his life.

Lord Thomson [Z434/4]
Lord Thomson [Z434/4]