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The R38 class (also known as the A class) of rigid airships was designed for Britain's Royal Navy during the final months of World War I, intended for long-range patrol duties over the North Sea.
Four such airships were originally ordered by the Admiralty, but orders for three of them (R39, R40 and R41) were cancelled after the armistice with Germany and work on the lead ship of the class, R38, continued only after the United States Navy had agreed to purchase her.
At the time of her first flight in 1921, she was the world's largest airship.
The American designation ZR-2 was already painted on the hull before its four completed test flights and in preparation for a final trial flight and delivery to Lakehurst.
On 23 August 1921, ZR-2 was destroyed by a structural failure while in flight over the city of Hull and crashed into the Humber estuary, killing 44 out of the 49 crew aboard. This disaster resulted in more deaths than the more famous Hindenburg Disaster that killed 35.
Design, Construction and Flight
The R38 class was designed in response to an Admiralty requirement of June 1918 for an airship capable of six days of patrol, at ranges of up to 300 miles from home base, and at altitudes of up to 22,000 ft. Apart from scouting duties, a heavy load of armament was specified, to allow airship to be used for escort duties for surface vessels.
1919 The contract for R38 was awarded to Short Brothers, followed by orders for three more ships to the same design. Construction of R38 commenced at Cardington, Bedfordshire in February 1919. Certain modifications to the original design had to be made to allow the R38s to be built within the available construction shed. 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.
Later in 1919, several airship orders were cancelled as a peacetime economy measure, including the three R38 class ships on which work had not yet commenced: R39, R40, and R41. In a further round of cutbacks, the cancellation of the unfinished R38 also appeared imminent, but before this was actually carried out, the project was offered to the United States in October.
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 L 70, had been recovered from the North Sea after it was shot down in August 1918. However it was not realised that the manoeuvrability of these Zeppelins was deliberately restricted, especially in the rate and tightness of turn, due to the lightweight structure.
1921 The R38 made its first flight on 23 June where it flew registered as R-38 but with US insignia ZR-2 painted on. It flew to RNAS Howden where the full conversion to American livery was to be made.
After some modifications to the rudder and elevators, a second test flight flew on 17 July to Howden 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 Edward M. Maitland, the very experienced commander of the Howden base.
Following a spell of bad weather the airship was finally walked out on 23 August and in the early morning took off for her fourth flight which had an intended destination of RNAS Pulham, 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, fifteen 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 only American to survive was Rigger Norman C. Walker. The five that survived were in the tail section. A memorial was erected at Hull, Yorkshire.
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.
The Loss of the R38 Court of Inquiry Report - Air Ministry 1921.
The terms of reference of the Court of Inquiry were as follows; - "By command of the Air Council, a Court of Inquiry will assemble at RAF Airship Base, Howden at 10:00 hours on Saturday, August 27th, 1921 to inquire into the circumstances occasioning the loss of HMA R38 on August 24th 1921, and to express an opinion as to the possible causes of the loss"....[More].