Top speed 114 km/h Length 212 m First flight June 23, 1921 | Range 483 km Engine type Sunbeam Cossack Manufacturer Short Brothers | |
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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 the First World War, intended for long-range patrol duties over the North Sea. Four similar airships were originally ordered by the Admiralty, but orders for three of these (R39, R40 and R41) were cancelled after the armistice with Germany and R.38, the lead ship of the class, was sold to the United States Navy in October 1919 before completion. On 23 August 1921, R-38 was destroyed by a structural failure while in flight over the city of Hull. It crashed into the Humber estuary, killing 44 out of the 49 crew aboard. At the time of its first flight it was the world's largest airship. Its destruction was the first of the great airship disasters, followed by the US airship Roma in 1922 (34 dead), the French Dixmude in 1923 (52 dead), the British R101 in 1930 (48 dead), the USS Akron in 1933 (73 dead), and the German Hindenburg in 1937 (36 dead).
Contents
Design and development
The R38 class was designed to meet an Admiralty requirement of June 1918 for an airship capable of patrolling for six days at ranges of up to 300 miles from home base and altitudes of up to 22,000 ft (6,700 m). A heavy load of armaments was specified, to allow the airship to be used to escort surface vessels. Design work was carried out by an Admiralty team led by Constructor-Commander C. I. R. Campbell, of the Royal Corps of Navy Constructors. The construction contract was awarded to Short Brothers in September 1918 but cancelled on 31 January 1919 before work had been started. It was then re-ordered on 17 February: on the same day Oswald Short was informed that the Cardington, Bedfordshire works, recently built as a specialised airship production facility, was to be nationalised. Construction of R38 started at Cardington in February 1919. It was intended to follow R.38 with orders for three airships of the same class: R39, identical to R38, to be built by Armstrong-Whitworth and two others R40 and R41, of a design variant with the length reduced to 690 ft (210.31 m) due to the limited size of existing manufacturing sheds.
Later in 1919, several airship orders were cancelled as a peacetime economy measure, including the three R38 class ships. In a further round of cutbacks, the cancellation of the unfinished R38 also appeared imminent, but before this actually happened the project was offered to the United States.
The hull contained 14 hydrogen-filled gasbags. The 13-sided mainframes were 49 ft (15 m) apart and were made up of diamond-shaped trusses connected by 13 main and 12 secondary longitudinal girders and a trapezoidal keel. There were two secondary ring frames between each pair of mainframes. The forward-mounted control car was directly attached to the hull. The cruciform tail surfaces were unbraced cantilevers and carried aerodynamically balanced elevators and rudders. The six Sunbeam Cossack engines, each driving a two-bladed pusher propeller, were housed in individual cars arranged as three pairs: one pair aft of the control car. one pair amidships and the third pair aft.
Sale to United States
The United States Navy had decided that it wanted to add rigid airships to its fleet and originally hoped to get two Zeppelins as part of war reparations, but these had been 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 R38 had been cancelled, the possibility of buying it was investigated. An agreement was reached in October 1919 for its purchase for £300,000, and work on the airship was resumed.
Operational history
The airship was to be given a curtailed series of tests before being handed over to the U.S. Navy, who would fly it across the Atlantic. J. E. M. Pritchard, the officer in charge of flight testing, proposed to carry out 100 hours of flight testing, including flights in rough weather, followed by 50 more flown by an American crew before crossing the Atlantic. However the Air Ministry ruled that 50 hours would be sufficient.
The R38 made its first flight on 23–24 June 1921, when it flew registered as R-38 but bearing the US serial number ZR-2; the seven-hour flight revealed problems with over-balance of the control surfaces. With the balance area of the top rudder reduced, a second test flight was carried out on 17–18 July. The control balance problem remained, and on return to Cardington all the control surfaces were reduced in area. On 17–18 July a third flight was made, during which the airship was flown from Cardington to Howden and then out over the North Sea, where the speed was increased to 58 mph (93 km/h), causing the ship to begin hunting over a range of around 500 ft (150 m). The highly experienced Pritchard took over the controls from the American coxswain and reduced the oscillation, but several girders in the vicinity of the midship engine cars had already failed. R.38 returned to Howden at reduced speed and work on reinforcing these girders was carried out and completed by 30 July at Howden. There were increasing doubts being expressed about the design, including some made by Air Commodore E. 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 its fourth flight, which had an intended destination of RNAS Pulham in Norfolk, where it could be moored to a mast: a facility unavailable at Howden. In the event, mooring proved impossible because of low cloud and so the airship returned out to sea for the night. The next day, after a brief speed trial during which a speed of 71.9 mph (115.7 km/h) was reached, a series of turning trials was started at a speed of 62.7 mph (100.9 km/h) and an altitude of 2,500 ft (760 m). At 17:37, while close offshore near Hull and watched by thousands of spectators, the structure failed amidships. Eyewitnesses reported seeing creases down the envelope and then both ends drooped. This was followed by a fire in the front section followed by an explosion which broke windows over a large area. The remains 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 who survived were in the tail section. A memorial was erected at Hull, Yorkshire.
There were three official enquiries into the disaster. The first, chaired by Air Vice-Marshal Sir John Salmond and composed mainly of RAF personnel, was convened on 27 August. Its remit was to consider the general circumstances of the accident, and although it came to the conclusion that the structure had failed while extreme control forces were being exerted it was considered necessary to carry out a more detailed technical inquiry into the airship's design. The report also criticized the system by which a single authority was responsible both for the airship's construction and for inspection of the work, and given the great differences between R38 and previous British designs, held that the design should have been subjected to a more thorough scrutiny.
The Admiralty held a second inquiry into the history of the design of the airship and its construction up to the point where it was taken over from the Admiralty by the Air Ministry. In contrast to the previous inquiry, this concluded that the design did not incorporate any new features which affected the airship's strength, and further maintained that "there was at the time no body in existence which could have been called in to advise on the structural strength of R. 38."
The technical Committee of Enquiry, chaired by Mervyn O'Gorman, 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, as this was not part of the committee's remit.
Specifications (R38/ZR-2)
Data from Flight, 9 June 1921, p. 388 [1]
General characteristics
Performance
Armament