His Majesty's Airship No. 1 was designed and built by Vickers, Sons and Maxim at their works in Barrow-in-Furness, Lancashire, England, as an aerial scout airship for the Royal Navy. It was the first British rigid airship to be built, and was constructed in a direct attempt to compete with the German airship programme. Often referred to as "Mayfly", a nickname given to it by the lower deck (i.e. the non-commissioned component of a naval ship's crew), in public records it is designated 'HMA Hermione because the naval contingent at Barrow were attached to HMS Hermione, a cruiser moored locally preparing to act as its tender.Jarret, P., (ed.) (2002) Pioneer Aircraft; Early Aviation before 1914. London: Putnam. , p. 41
When it was moved from its shed in Cavendish Dock to conduct full trials on 24 September 1911 it broke in two before it could attempt its first flight as a result of being subject to strong winds."Airship Breaks in Half" Popular Mechanics, December 1911, p. 773. Although Mayfly never flew, its brief career provided valuable training and experimental data for British airship crews and designers.HMA No. 1 "The Mayfly" The Airship Heritage Trust. Retrieved on 1 March 2009.
Background In July 1908 Captain Reginald Bacon, the Royal Navy's Director of Naval Ordnance, recommended that the Navy should acquire an airship that would compete with the success of the early German rigid airships built by Count Ferdinand von Zeppelin. The British Government agreed that a sum of £35,000 (£ million today) "should be allocated to the Admiralty for the building of a dirigible balloon", and in March 1909 the armament firm of Vickers, Sons and Maxim advised that they could construct the ship for £28,000 (£ million today), not including the goldbeater's skin gas bags and outer cover, for which the Admiralty was required to provide contractors, and that they would erect a constructional shed at their own expense in return for a 10-year monopoly on airship construction, similar to the submarine agreement they already had with the Crown. The contract was awarded to Vickers on 7 May 1909, with design responsibility divided between Lieutenant N.F. Usborne at the Admiralty and C.G. Robertson of Vickers; however, the 10-year monopoly clause was refused.
Design Mayfly was intended to be an aerial scout, and was similar in design to contemporary Zeppelins, but with some major differences. At length and in diameter, it was longer than the contemporary LZ 6 and had a 50% larger volume, giving a correspondingly greater lift. His Majesty's Airship No. 1 was more commonly known as the "Mayfly", or simply referred to as "No. 1."Higham 1961, p. 40 In official records HMA No. 1 is often referred to by the name of the tender in which the crew was quartered, HMS Hermione, or the "Hermione Airship".Mowthorp, 1995, p. 125 The name Mayfly originated as a nickname originated by the sailors assigned to it. HMA No. 1 was essentially an experimental design and was therefore to be built as cheaply as possible.Higham 1961, p. 42
Zeppelins of the time had a useful load of around 10,000 lb (4,500 kg) and were capable of flying at .Robinson 1973, p. 330 The Vickers design was intended to be moorable on water, carry wireless equipment, be capable of for 24 hours, have a ceiling of , and carry a crew of 20 in comfort. The mooring was to be to a mooring mast, a practice that the British were the first to adopt as standard, and Mayfly was the first rigid airship to be fitted with the mooring equipment in the nose of the ship.
Before construction began an experimental section was constructed. This used a variety of construction techniques: one end used hollow timber spars, the centre frame used a combination of timber and aluminium, while the other end used aluminium only. Although wood proved the most satisfactory, the Admiralty preferred metal.Higham 1961, p. 43. In late 1909 duralumin became available, and it was decided to use this new alloy, which would allow a considerable weight saving while also forming a stronger structure.Robinson 1974, p. 148 The use of Duralumin preceded its use by Zeppelin by four years. Development of HMA No. 1 involved essentially inventing the technology necessary and considerable experimentation in materials and manufacturing techniques was required before the final manufacturing processes were decided upon.Higham 1961, p. 45 The hull was made up of 40 twelve-sided transverse frames spaced apart: some of which were cross-braced by wires, dividing the structure into 17 bays of irregular length, varying from 12.5 ft to 37.5 ft (3.8 m to 11.4 m). The frames were connected by 12 longitudinal girders and a triangular section keel below the main structure.Robinson 1974, p. 147 The hull shape was based on work by the American aerodynamicist Albert Zahm, and its head resistance was claimed to be 40% of that of contemporary Zeppelins. A fully streamlined shape had been proposed, but was rejected by the Admiralty as being too difficult to construct. It was not until 1918 that a truly streamlined airship, the R80, was designed.Mowthorp 1995, p. 143
Experiments were also carried out to determine the most suitable material for the outer cover, resulting in the choice of a treated silk. The covering of the upper half was additionally treated to reduce heat absorption by adding aluminium powder to the coating. This resulted in the underside of the ship being primrose yellow and the top aluminium coloured.Higham 1961, p. 44 The control surfaces, based on a design by Short Brothers and adopted after experiments by the National Physical Laboratory, consisted of quadruple rudders and triple elevators attached to the trailing edges of the cruciform tail surfaces, supplemented by forward mounted triplane elevators and small triple rudders behind the aft gondola.
The two gondolas were constructed of mahogany using the Consuta process to make them watertight so that the craft could be operated off water.Robinson 193, p Each contained a Wolseley 160 hp water-cooled V-8 piston engine, that in the front gondola drove a pair of 11 ft 10 in (3.61 m) diameter four-bladed propellers mounted on outriggers and geared to rotate at half engine speed. The rear engine drove a single two-bladed propeller mounted at the rear of the gondola. Equipment to recover water from the exhaust gases was fitted to replace the weight of fuel as it was consumed and so avoid the necessity to vent lifting gas.Robinson 1973, pp. 147–150 Considerable mistakes were made due to inexperience, Admiralty requirements, and in devices such as water recovery systems for engine exhaust.Higham 1961, p. 47
Construction and trials The construction shed which also doubled as a hangar, was designed by Vickers and built from the wall of Cavendish Dock at their "Naval Construction Yard" in Barrow, out to piles driven into the basin floor. It contained a float on which construction of the airship took place and which could be taken out of the shed together with the airship. Beginning in 1909, the work was due to be completed in August that year and the ship delivered two months later, but in June trouble occurred with driving the piles into the floor of the dock. Consequently, the shed was not completed until June 1910, at which point the actual construction of could begin. A screen was erected in the dock together with a newly designed -high floating mooring mast that was capable of withstanding a steady pull of 80 tons (81 tonnes). A large safety margin had been allowed; the maximum load the ship would exert on the mast was calculated to be approximately 4 tons (4 tonnes) in a wind of .
In preparation for the completion of Mayfly, crew training commenced on 25 February 1910, covering important skills such as working the rubber fabric (carried out at Messrs Short Brothers works, Battersea, London), instructions in petrol engines at Vickers works, and instruction in signals, aeronautics and meteorology.
An entry in Handbook for noted that: Two crews were used to look after the ship whilst out, as the work was new. They lived on board the airship and suffered no discomfort at all although no provision had been made for cooking or smoking on board. At night the temperature of the living space was a little above that of the outside air, but as the ship proved quite free from draughts in the keel and the cabin, it was anticipated that with suitable clothing, no trouble would be experienced from the cold.
The Admiralty's officer responsible for the design of , Lieutenant N.F. Usborne, was selected as captain.Lieutenant N.F. Usborne Usborne family tree. Retrieved on 1 March 2009.
The finished Mayfly was the largest airship yet constructed.
Static trials Static trials inside the shed began on 13 February 1911. The motors were run and controls operated, but outdoor trials could not be carried out until the weather moderated.
On Monday 22 May 1911 Mayfly was removed from the shed for handling and mooring trials. It was towed stern first from its very narrow shed, then gradually swung out of Cavendish Dock and attached to a mooring mast mounted on a pontoon. While moored, nine officers remained on board (having quarters in the keel and telephone communication between the cars) to conduct engine trials, but these were cut short due to radiator problems. On the following day it was subjected to winds of , and during the two nights it was out of the shed, searchlights were trained on it so that its movement could be observed. Mayfly showed no signs of rising, and it was discovered from calculations that the removal of fixtures weighing some three tons would be necessary to enable it to become airborne. It was decided to return it to the shed, where with all ballast, fuel and some equipment removed it floated for approximately five hours with both gondolas around out of the water. During this time the engineers were able to perform trim trials. It was obvious that drastic modifications to reduce weight must be made if HMA No. 1 was ever to fly.
The most drastic of the modifications was the removal of the external keel which resulted in both weakening and distorting the airship's framework.Mowthorp 1995, p. 124 Hartley Pratt, a draughtsman working in another department at Vickers, calculated that this would be disastrous, but his warnings were ignored. Pratt subsequently left the company, but was re-hired to lead the design of the next British airship, the No. 9r which was ordered from Vickers in 1913.Pugh Barnes Wallis Dambuster p 6 quoting Official History of Vickers Other changes included deleting the forward elevators and the water recovery apparatus. The positions of the gondolas was also reversed, the heavier forward gondola being moved to the aft position.Higham 1961, p. 49 Also removed were the cabin and accommodations for the crew while in port. So extreme were the attempts to reduce weight that holes were drilled in engine control levers.Higham 1961, p. 50 The changes resulted in the Mayfly having a disposable lift of 3.21 tons.Robinson 1974, pp. 149–150 With the massive alterations Captain Murray Suter under pressure from the Admiralty solicitor was forced to provisionally accept No. 1 with the provision that she be flown.Higham 1961, p. 51
Final outing