Secret Files :The Spitfire floatplanes
The German invasion of Norway in April 1940, and the now seemingly unstoppable advance of her armies across Europe began, it seemed likely that any confrontation in the north of Europe would, in all likeliness, be a sea one. The current British naval fighters in service in 1940 were either already or close to becoming obsolete, and certainly no match for the German Messerschmitt Me 109. New fighters such as the excellent Grumman Martlet and the heavily armed, but slower Fairey Fulmar would not enter service until much later in 1940. The Air Ministry and Admiralty had urgent discussions about the problem, and quickly realised that a bespoke modern British single-seat naval fighter would take time to develop, and certainly would not be in production for many months, if not years. They therefore looked at the two main British single-seat fighters, the Hurricane and Spitfire, and wondered on the feasibility of adapting these excellent fighter to become floatplanes, which would extend the naval fighter range and at least be a temporary ‘quick fix’. Versions of the Blackburn Roc and Skua had been conceived to be equipped with floats, and therefore the Blackburn Aircraft Company were ordered to release an existing pair of Roc floats to both Hawker and Supermarine, and to design a ‘bespoke’ pair of floats for the Spitfire.
Should the initial tests with Roc floats be successful, the Navy were told to release 50 sets of Roc floats. Meanwhile, Hawker, who privately doubted that the Hurricane was suitable for a float conversion, suggested that existing Hawker Osprey [an existing naval biplane fighter] floats might be more adaptable for either aircraft, as they were lighter and slimmer than Roc floats. Supermarine tasked Follands of Hamble to convert a Spitfire I, R6722, using Roc floats, and De Havilland were requested to convert one of their propellers to constant speed for the aircraft. The government suddenly had a confusing ‘volte face’ in May 1940, when Hawkers were charged with building 16 Hurricane floatplanes plus 9 reserve aircraft plus an additional 20 sets of Osprey floats. This confusion was exacerbated when on 10 June, Supermarine were officially informed that they should discontinue the Spitfire conversion, although Follands had already completed the job – yet in the same post came official instructions to complete it!
The aircraft had already arrived at No 12 MU, RAF Kirkbride in Cumbria a week earlier for flotation and taxying trials, but it was quickly discovered that the Spitfire/Roc float combination was very unstable on the water, and therefore totally unsuitable. This Spitfire was eventually re-converted to a landplane and upgraded at 39 MU RAF Colerne, Wiltshire to eventually become a Mark V. At the same time as the government was trying to make its mind up, RAE Farnborough had been conducting sea-worthiness trials on scale models for comparison tests between the Hurricane and Spitfire Roc conversions, and irrespective of the suitability of the floats, had found that the Spitfire outperformed the Hurricane, which unlike the Spitfire, would suffer from radiator and flap damage from spray on take-off. By June 1940, the Germans had control of most of Europe, as well as winning in Norway, and the imminent Battle of Britain now meant that fighter production was, by necessity, concentrated on wheeled, and not float fighters. However, the ‘Narvik Nightmare’, as the Mk I floatplane was unkindly nicknamed, was not forgotten. Almost a year later, the Air Ministry awarded Supermarine a contract for – you’ve guessed it – yet another floatplane variant of the Spitfire, this time based on a prototype Mk III, as a ‘high priority’, with Farnborough again tasked to work on float design and model testing.
From June 1941, a variety of float designs and settings were tested on scale models in the RAE water tanks, but all were considered to be inferior to even those of the floats used on the sole Mk I Spitfire, and by the October, the project was again terminated. There was a clause in the Mk III Supermarine contract, however, that allowed Supermarine to convert the Mk III to Mk V standard – the company then submitted a revised proposal for a Spitfire Mk V version, using their OWN float design. Follands were again called upon to convert a Mk V [a Mk VB, W3760]. Learning from the Mk I failures, this aircraft incorporated a ventral stabilising fin, larger rudder and a strengthened wing spar. Being reluctant to allow anything to interfere with current Spitfire production, the Air Ministry was not best pleased, initially, to learn that Supermarine were continuing a project that they considered dead in the water [sic], and even contacted the Americans on the feasibility of converting the Curtiss P-40 into a floatplane fighter! The Americans were concentrating production of the rugged P-40 for their use, as well as for the UK’s Air Forces in North Africa, and for the Soviet Union, who loved the ‘plane. This general malaise and apathy for the idea rumbled on through the winter of 1941 and late summer of 1942, by which time the Mk VB was ready for flight testing. The particular aircraft, W3760, was not considered to have been well made and many niggling faults had been logged – not least of which were the floats themselves which leaked.
After initial flight tests, however, the aircraft was found to have a maximum speed of 317 mph at 18,000ft, and was delivered to the Marine Aircraft Experimental Establishment at Helensburgh and Rhu, Scotland in February 1943 for pre-Service testing. The floats still leaked badly, due to the caulking flexing and cracking during take-off and landing to the extent that they had to be removed and returned to Hamble for repair, causing delays until June 1943 when she underwent full performance trials back in Scotland. Perhaps surprisingly, by then the aircraft showed very similar flight characteristics to the landplane version, impressing the Air Ministry enough to order another two Mk V conversions to be completed – aircraft serial numbers EP754 and EP951, both of which were quickly completed and tested at Helensburgh by August 1943. These two seemed to have a slightly higher performance, given that they had new Rolls-Royce Merlin 46 engines driving four bladed Rotol propellers of a 10ft 9in diameter, which gave them a maximum speed of 331mph at 14,000ft. Germany was resupplying her Cretan garrison and the rest of the Dodecanese area by air from the Greek mainland, and the Allies struggled to have fighters with enough range at this time to engage the Axis transports. It was therefore decided to send the three Spitfire floatplanes to the Mediterranean on operational trials prior to full scale production, presuming that they were successful in the field.
Despatched on the SS Penrith Castle on 6 October 1943, on arrival in theatre were formed into C Flight, 103 MU. The idea was that they would operate remotely in the area, be supplied from a Royal Navy submarine, with the Flight comprising five pilots, fifteen ground crew, two high speed launches and a Supermarine Walrus amphibian! Training started on the Great Bitter Lake in Egypt and problems immediately occurred. The engine torque on take-off caused one float to dip under the water, allowing the salt water to run over the rear fuselage, rendering the water rudders virtually useless. After a very short period of time, this increased salt water corrosion had a dramatic effect on all three airframes, to the extent that W3760 had to have a new rear fuselage transplanted, having been sent from England. In addition to the practical problems, on the logistical side, the supporting submarine idea foundered [sic] as the Navy’s submarine service was already stretched in their normal role in the Mediterranean area. Even so, the initial idea for the Spitfire floatplane made their ‘Airships’ look further afield, from the Mediterranean to the Pacific Theatre – after all, the Japanese were having some success with floatplane variants of their existing land fighters – the Zero-Sen, Hayate and Raiden.
The Air Ministry had toyed with the idea of moving the three Mk V aircraft and the twelve spare sets of floats to the Far East, and there converting another twelve Spitfires to floatplanes for use against the Japanese, but after long internal discussions cancelled the proposal.
The three aircraft were returned to England by the end of summer 1944, and due to the corrosion, were ‘struck off charge’ [scrapped] by the end of the year. After this fiasco, you’d think that the idea of a Spitfire floatplane would have disappeared from any agenda, but no! Supermarine had already been asked in October 1943 for proposals to convert what would have been the latest model, the Mark VIII, to a floatplane variant, but the proposal was changed to utilise the new Mark IX. By May 1944, a Spitfire LFIXB, MJ892, had been fully converted, and the first tests were to be made in Anglesey, at the Saunders-Roe plant in Beaumaris, utilising the relatively quiet area of the Menai Straits. Saunders-Roe were already producing the Supermarine Walrus amphibian there, so were quite used to Supermarine’s working practices and requirements. The first test flight was made on 6 July 1944, and, like the earlier Mk VB’s problems were quickly encountered.
The main test pilot, Mr F C Furlong, noted that not only was this variant reluctant to become airborne, but on take-off the fitted tropical filter ingressed water causing engine cut-outs at critical times. The aircraft also ‘waddled’ from side to side on her floats when taxying, which could be dangerous in an operational situation. It was decided that there was little point in continuing with this aircraft, and she languished at Beaumaris until returned to Follands in August 1945, where she was ‘struck off charge’ the following November. So that was finally the end of the floatplane Spitfire? Not quite! The ‘Super Spitfire’, as the new Mark 21 Griffon engine variant was known, was almost ready for operational use late in 1944 when the Air Ministry asked Supermarine to submit a proposal for….a naval floatplane version! Supermarine reluctantly submitted a paper proposal as requested, but at this late stage of the war the proposal came to nought. Perhaps this was just as well, given the previous problems with the Mk I, Mk V and Mk IX variants, but problems notwithstanding, all work on this radical idea had been done by three Solent area companies – Supermarine, Follands and Saunders-Roe, who used their tried and tested engineering skills, experience and innovation to overcome the task.