R38

''R38 redirects here. For the subway cars see either R38 (New York City Subway car), or London Underground R Stock.

The R38 was a British rigid airship that was built for the US Navy as the ZR-2. It was at the time the world's largest airship.

History

The R38 was built at Cardington, Bedfordshire by Short Brothers. The original design was for a North Sea scouting ship and this led to a requirement for high speed, high altitude capability to escape from fighter aircraft and long duration. All of this had to be fitted within the dimensions of the construction shed which led to inevitable conflicts in design. As a result two of the power cars were moved up to the sides of the structure to save height, the number of gas bags was reduced from 16 to 14 and there were fewer girder rings around the envelope. The contract was placed on 31 January 1918 but then cancelled on 31 January 1919 as a peacetime economy measure. The intended program for R38 sister ships, R39, R40 and R41 was cancelled too.

The United States Navy had decided that it wanted to add rigid airships to its fleet and originally intended to get some German Zeppelins as part of the wartime reparations but these were deliberately destroyed by their crews in 1919. An order was placed with the Zeppelin company for a new craft (to be paid for by the Germans) and to go with it they planned to build one in the United States. With the news that the R38 had been cancelled the possibility of buying it was investigated. An agreement was reached in October 1919 for purchase at $2,000,000 and work on the airship recommenced. Changes included a requirement for mast mooring gear, which added a ton to the bows which was then balanced by ballast at the rear. This modification along with the weight savings in the design made a craft that was weak longitudinally. The Germans had made lightweight high altitude Zeppelins towards the end of the war and part of one of these, the L70, had been recovered from the North Sea after it was shot down in August 1918. However it was not realised that the manoeverability of these Zeppelins was deliberately restricted, especially in the rate and tightness of turn, due to the lightweight structure

The R38 made its first flight on 23 June 1921. After some modifications to the rudder and elevators, a second test flight flew on the 17 July to Howden, East Riding of Yorkshire for airworthiness and acceptance trials. Some testing of the re-balanced control surfaces was performed on this flight which resulted in severe pitching. When in the shed at Howden, examination of the structure revealed damage to several of the girders. These were replaced and others were strengthened but there were increasing doubts being expressed about the design including some by Air Commodore E. M. Maitland, the very experienced commander of the Howden base.

While in the shed the opportunity had also been taken to paint the American insignia on the covering. Following a spell of bad weather the airship was finally walked out on the 23 August and in the early morning took off for her fourth flight which had an intended destination of Pulham Market, Norfolk where she could be moored to a mast, a facility lacking at Howden. In the event mooring proved impossible because of low cloud and so the airship returned out to sea with the intention of running some high speed tests and then returning to Howden. The speed runs proved successful and as there was still daylight left it was decided to try some low altitude rudder tests to simulate the effects of the rough weather that could be expected on the Atlantic crossing. At 17:37 15 degrees of rudder was applied over the city of Hull. Eye witnesses reported seeing creases down the envelope and then both ends drooped. This was followed by a fire in the bow and then a large explosion which broke windows over a large area. The airship had failed structurally and fell into the shallow waters of the Humber estuary. Sixteen of the 17 Americans and 28 of the 32 Britons in the crew were killed.

The Committee of Enquiry that was convened to investigate the disaster concluded that no allowance had been made for aerodynamic stresses in the design and that while no loads had been placed on the structure during testing that would not have been met in normal use, the effects of the manoeuvres made had weakened the hull. No blame was attached to anyone, this was not part of the committee's remit.

In the end it seems that with the knowledge of structures and materials at the time the design brief was asking too much. Designing seven hundred feet of interlinked girders covered in linen to withstand largely unknown forces was asking too much when the only calculating tools were books of tables and slide rules.

Specifications

General characteristics

Crew:
Length: 699 feet
Diameter: 85 feet 6 inches
Gas bags 14
Hydrogen capacity: 2,724,000 ft³
Gross lift:
Weights
- Empty:
- Disposable load:
- Including water ballast and crew:
- Fuel, oil and payload:
Powerplant: 6 Sunbeam Cossack III V12 engines

Performance

Maximum speed: 70 mph (design)
Maximum altitude: 22,000 feet (design)
Still air range:
Endurance : 6 days

References

T W Jamison, Icarus over the Humber, Lampada Press, 1994 ISBN 1873811039
Lord Ventry and Eugene Kolesnik, Airship saga: The history of airships seen through the eyes of the men who designed, built, and flew them , 1982, ISBN 0713710012
Manfred Griehl and Joachim Dressel, Zeppelin! The German Airship Story, 1990 ISBN 1-85409-045-3
Ces Mowthorpe, Battlebags: British Airships of the First World War, 1995 ISBN 0905-778-138
Lord Ventry and Eugene Kolesnik, Jane's Pocket Book 7 - Airship Development, 1976 ISBN 0356-04656-7

External links

Airshipsonline - Airship Heritage Trust: R38

Airships of the United Kingdom | Airships | United States Navy airships | British air disasters

Vzducholoď R 38 | R38 | R38 (ZR-2) | Vzducholoď R 38