R-100 and R-101
The airship branch of the Royal Air Force was closed down in 1920–21, and negotiations of various kinds were undertaken with a view to transferring the existing fleet of airships to some outside body, with a view to their commercial operation. In 1922–23, two schemes were put forward by Commander Dennistoun Burney for taking over the factory, plant and existing airships, carrying out a program of research and building a fleet of airships to operate a commercial service to India, in consideration of large Government subsidies.
Ultimately the Government in 1924 decided upon a smaller scheme, the main features; of which were the carrying out by the Air Ministry of a full program of research and experiment and the building of two airships of 5,000,000 cubic feet capacity, one to be built by the Royal Airship Works and the other by a private company. The design and construction of these airships were to be based upon the results of the theoretical and scientific investigations carried out since the disaster to R38, and to comply with rigid requirements as to airworthiness, laid down by the Aeronautical Research Committee, as well as the independent inspection of the Director of Aeronautical Inspection.
The Imperial Airship Scheme was launched in 1924, designed to link Britain with Australia, Canada, South Africa, and India by means of six rigid airships in commercial service along an Imperial Air-Route. To encourage innovation, the British government commissioned two prototypes. One airship (R100) would be built by Vickers Ltd., a private contractor, and the other (R101) by the Royal Airship Works in Cardington, England.
The book prepared by the Air Minister called "Approach towards a System of Imperial Air Communications," was published at the time of the Imperial Conference of 1926. The result which was put in this book of a service of airships all over the world, would need to have, not two but 10 or 20 airships, and the amount of capital required would be at least £10,000,000 or £20,000,000. So that, assuming that these airships were a technical success and that there is nothing wrong with them, raising a sum of at least £10,000,000 to £20,000,000 would be needed before there could be a beginning with a regular commercial service. This sum of £354,000 is simply keeping the staff going for another 12 months.
There had been mishaps with nearly every airship that had been constructed. There was the American "Shenandoah" and the French and the Italian airships. In fact every airship that had been built in the past few years had come to grief with disastrous results to those in them. If anyone had a talk with some of those who went round the world in the "Graf Zeppelin" there would be no demand for seats in these airships.
Undaunted by the R-38 failure in 1921, the United Kingdom built the R-100 and R-101 in 1929. They were both large airships (the R-101 was 131 feet in diameter and 777 feet in length). The original cost estimate was a composite one for the whole airship program, of 1924, but the sum provided for the construction of R101 may be put at approximately £300,000 as of 1930. Owing to the novel and experimental character of the design, the time taken in construction proved materially longer than had originally been estimated, and in consequence, this figure had subsequently to be increased; and in the Air Estimates for 1929 a figure of £527,000 was given for this purpose. The total expenditure on R101 up to 31st March, 1930, including design, construction, power plant, experimental engines, overhead charges, shed and flight trials, running repairs, modifications and maintenance, was approximately £603,500.
By 1930 the Government had spent £2,300,000 on the whole program. Those two ships put together only just cost £900,000. There is no £1,000,000 ship. The figures are certainly rather interesting. The cost of the two ships together was £894,000, research cost £305,000, and then the ground organisation included two of the largest sheds in the world, three mooring masts—one of the great developments due to British enterprise — and, last but not least, an immense amount of knowledge.
The R.100, built by the Airship Guarantee Company, Ltd., had a gas capacity of well over 5,000,000 cubic feet, while R.101, built at Cardington, exceeded this capacity when alterations were completed. The R101, as a government project, had political as well as technical problems. There was pressure to incorporate ideas which could provide substantial technological advances, if successful, but which had never been tried before. The R101 made its first flight on October 14, 1929. After its first few flights, engineers realized that it did not have as much disposable lift as originally anticipated. It was rebuilt so that it could hold additional gas. When completed, the R101 was too heavy and another bay had to be installed for additional lift. It was the largest manufactured object ever to fly and had dining, sleeping, and recreational accommodations for 100 persons.
R.101 was moored out during the whole of November 1929 and confounded the prophets of disaster by successfully riding out storms in which the wind gusted up to 83 miles per hour. During a line squall the airship swung through 135 degrees in a minute under a wind of 35 miles per hour. The maximum force registered by the bow indicator was something over 15 tons, though the airship is designed to withstand a strain of 30 tons at this point. There was no doubt that from a constructional point of view the completed airships definitely disproved many of the gloomy forecasts, ranging from minor defect to utter disaster, which had been made from time to time.
The builders of R101 moved away from traditional airship designs, incorporating many new technologies. R101 was approved in 1924 with great expectations for a commercially operational vehicle by 1926. Design stretched into 1927 with escalating costs as well as pressure from the skeptical press and impatient Parliament to demonstrate results. The R101 design team set out to push the envelope of technology in many ways: by employing diesel engine technology for the first time in a rigid airship; using steel for the first time in airship rib structures; employing newly designed pressure valves on the flotation bags; implementing (unsuccessfully, in that it was not incorporated into the test flights) innovations in outer skin manufacturing; and unsuccessfully attempting to developand implement hollow metal reversible propeller blades.
The R101 was run on heavy oil, and the R100 on petrol. The R100 was also designed for heavy oil, but the engines could not be obtained when she was ready to take the air. Petrol is a great danger to airship work. The Germans used gas. Gas is not so dangerous. When there is a leakage of petrol in an airship it collects at the bottom of the ship and a spark may lead to an explosion, but with a leakage of gas, the gas rises and escapes of its own accord out of the ship. But by far the safer thing is heavy oil. Not only is it safer, but the cost is £5 per ton as compared with £25 per ton in the case of petrol. Moreover, given engines of equal weight, the heavy oil will carry the ship 25 per cent. greater distance. The great difficulty was to get heavy oil engines designed light enough for this particular work. The total weight of the petrol engines (with reversing gears) installed in R100 was 10,424 lbs., while that of the heavy oil engines in R.101 was 23,300 lbs., giving approximate weights per horse-power of 2.9 lbs. and 7.96 lbs.
The R101 team stuck with the intrinsically flawed diesel engines, citing safety concerns. Ironically, the fuel safety hazard concern unwittingly introduced much greater safety risks which reduced flight safety margins for buoyancy and control. The R101 engines were constructed by joining together two four-cylinder Beardmore diesel engines. This arrangement provided less power than anticipated (585 brake horsepower (bhp) actual vs. 700 bhp expected), and at 17 tons the five engines were 6 tons above the design weight. In addition, the diesel engine rotational frequencies (both idling and cruising) excited natural resonant vibrations in piping and structures, resulting in leaks and cracks.
Even when fully filled with hydrogen, R101 provided just under 50 tons of “disposable lift” compared to the 60 tons for which it had been designed. In the end, operational decisions concerning use of the disposable load (manifest of passengers, luggage, carpeting, food, amenities, and fuel) created a very thin margin of safety, a result of a failure in design margin management. During a journey to participate in a Royal Air Force Air Display (air show) in June 1930 (amid flight testing), the R101 showed a disturbing propensity to enter steep nose down postures that were difficult to correct. In addition, test flight crews described her handling properties as heavy and sluggish.
The carrying out of a flight to India by each airship was to be a last stage in flying trials, to be followed by a continuity period of development before commercial operation was undertaken. This meant the design of two airships nearly double the size of any airship yet constructed in the country; and their construction to comply with exacting requirements as to factors of safety and to provide passenger accommodation on a scale never before attempted. As a result of the Imperial Conference of 1926, there was a further requirement imposed of carrying out a flight across the Atlantic to the mooring tower erected by the Canadian Government at Montreal.
The proposed program for 1930 for R.100 consisted of flights to Montreal and back between May and September, and between October and March schedule flights between Cardington and Ismailia. For R.101, a flight to Karachi and back in September or October, then again to Karachi in December or January, after which there were to be mooring trials and experimental flying from Karachi. In 1930, the R101 airship was assigned to take the Secretary of State for Air, Lord Thomson, to India. Lord Thomson had boasted to the press that the R-101 was "safe as a house, except for the millionth chance." The flight to India was meant to showcase the abilities of English airships.
The R101 airship launched on 04 October 1930; it was heavily loaded. During the flight, the R-101 apparently lost hydrogen from one or more gas cells, the cause is not known. The airship lost lift due to the hydrogen leak and crashed outside of Beauvais, France (about forty miles northwest of Paris) during a rainstorm on October 5, 1930. Survivors reported that there was no violent movementupon impact and that the ship bounced slightly and thenleveled. The force of the crash twisted the starboard for-ward engine around on its struts, bringing it into contactwith and igniting hydrogen from the ruptured forward envelope.
Another account suggests that, by an unfortunate circumstance, calcium flares were in the control cab for use during flights across the English Channel. When the craft crashed, these flares were damaged. The exposed flares contacted water from rain and subsequently ignited. The burning flares ignited the hydrogen escaping from R-101's gas cells that ruptured on impact with the ground. The hydrogen exploded. The account does not specify if the explosion was a deflagration or a detonation; multiple flares burning are a strong ignitor so it is possible that a detonation occurred. One unharmed witness claimed to be only a few hundred yards away from the crash, therefore, a flash fire is the most likely combustion phenomenon.
Only six people survived the crash; forty-eight people were killed. This event caused the United Kingdom to turn away from airships. The R-100 was scrapped and no further airship designs were pursued.
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