The R.38 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. Airships of this class were 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 (R.39, R.40 and R.41) 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 24 August 1921, R.38 (designated ZR-2 by the USN) suffered a structural failure whilst in flight over the city of Hull. It crashed into the Humber Estuary, killing 44 out of the 49 crew aboard and one black cat named Snowball."Snowball". Cats in the Navy, Naval Institute Press, Annapolis, Maryland, 2022, p.152. "Entry includes considerable details about the ship, flight, and crash." 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 Italian-built US semi-rigid airship Roma in 1922 (34 dead), the French Dixmude in 1923 (52 dead), the USS Shenandoah in 1925 (14 dead), the British R101 in 1930 (48 dead), the in 1933 (73 dead), the USS Macon in 1935 (2 dead), and the German Hindenburg in 1937 (36 dead).

Design and development The R.38 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.Swinfield 2012, p. 78 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.Higham 1961, pp. 204–205. Construction of R.38 started at Cardington in February 1919. It was intended to follow R.38 with orders for three airships of the same class: R.39, identical to R.38, to be built by Armstrong-Whitworth, and two others, R.40 and R.41, of a design variant with the length reduced to 690 ft (210.31 m) due to the limited size of existing manufacturing sheds.Higham 1961, p. 207. The Armistice coupled with the assignment of airships from the admiralty to the Royal Air Force and a decision to nationalize the Shorts airship plant into the Royal Airship Works confused the matter of whom was responsible for what. Constructor-Commander Campbell became both Manager and Chief Designer of the Royal Airship Works.Jamison 1994, p. 57.

Later in 1919, several airship orders were cancelled as a peacetime economy measure, including the three planned R.38 class ships. In a further round of cutbacks, the cancellation of the unfinished R.38 also appeared imminent, but, before this actually happened, the project was offered to the United States. The United States Navy demanded significant changes in the airship including modification to the bow in order to allow mooring to a mast, access to the mast from the keel and the addition of weight to the stern to ensure balance.Douglas H. Robinson, and Charles L. Keller. "Up Ship!": U.S. Navy Rigid Airships 1919–1935. Annapolis, Maryland: Naval Institute Press, 1982, p. 34

The hull contained 14 hydrogen-filled gasbags. The 13-sided mainframes were 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.Robinson 1973, pp. 168–169

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 1919Swanborough, G. and Bowers, P. M. United States Navy Aircraft since 1912 (2nd ed.), p. 587. London: Putnam, 1976. . in actions connected with the scuttling of the German fleet at Scapa Flow. An order was placed with the Zeppelin company for a new craft, to be paid for by the Germans (which became USS Los Angeles), and, to go with it, they also planned to build one in the United States (which became USS Shenandoah). With the news of the impending termination of R.38s construction, the possibility of taking over the project was investigated. An agreement was reached in October 1919 for its purchase for £300,000,Robinson 1973, p. 169 and work on the airship was resumed. As work progressed the US Navy began checking the documentation given them by the British. Following significant girder failures during testing Commander Jerome Hunsacker and Charles Burgess raised questions over the strength of R.38. Burgess concluded that "This investigation indicates that the transverses of the R.38 are only just strong enough, and have no factor of safety.Douglas H. Robinson, and Charles L. Keller (1982). "Up Ship!": U.S. Navy Rigid Airships 1919–1935. Annapolis, Maryland: Naval Institute Press. p. 35.

Operational history

The airship was to be given a curtailed series of tests before being handed over to the U.S. Navy, who were to 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.Jamison 1994, p. 77 The commander of the Howden Detachment Commander Maxfield disagreed and urged that the test of R.38 be completed in one day. Air Commodore Edward Maitland as the man most responsible for testing the R.38 was appalled and disagreed. He protested the abbreviated test schedule. He was told to not provide advice unless asked.Jamison 1994, p. 78 The Air Ministry ruled that 50 hours would be sufficient.Robinson 1974, p. 170 The decision had been made in ignorance by officials unfamiliar with airships as well as the knowledgeable officers who were reluctant to release an airship of unproven strength, egged on by an eagerness to return to America by Commander Maxfield.Jamison 1994, p. 79

The R.38 made its first flight on 23–24 June 1921, when it flew registered as R.38 but bearing the US designation 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 , causing the ship to begin hunting over a range of around . 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. The control surfaces were still over balanced. More importantly girders of intermediate frame 7b as well as longitudinal Girder F had failed in one place, while frame 7a and longitudinal F' each had failed in two locations.Douglas H. Robinson, and Charles L. Keller. "Up Ship!": U.S. Navy Rigid Airships 1919–1935. Annapolis, Maryland: Naval Institute Press, 1982, p. 39 R.38 returned to Howden at reduced speed.Higham 1961, p. 221

Work on reinforcing the buckled 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. Maitland urged that all future speed trials be conducted at higher altitude as was the practice of the Germans while testing the fragile Zeppelins upon which the R.38 design was based.Douglas H. Robinson, and Charles L. Keller. "Up Ship!": U.S. Navy Rigid Airships 1919–1935. Annapolis, Maryland: Naval Institute Press, 1982, p. 40 There was considerable concern expressed by Admiral Griffen, the chief of the Bureau of Steam Engineering. Burgess at the Bureau of Construction and Repair was also concerned.Douglas H. Robinson, and Charles L. Keller. "Up Ship!": U.S. Navy Rigid Airships 1919–1935. Annapolis, Maryland: Naval Institute Press, 1982, p. 41 Starr Truscott of the Bureau of Construction and Repairs believed that the negative endorsements of Admirals Griffin and Taylor would suffice to extend trials for the ZR-2 (R.38) but he was soon proven wrong. Admiral Taylor endorsed Commander Maxfield's optimistic report of July 20. Truscott later came to accept that decision writing "We must accept ship as per British practice, i.e., if acceptable to Air Ministry it must be to us. Question of starting flight is up to people in England."Douglas H. Robinson, and Charles L. Keller. "Up Ship!": U.S. Navy Rigid Airships 1919–1935. Annapolis, Maryland: Naval Institute Press, 1982, p. 42

Fatal crash