Thursday, 7 June 2012

Mitchell’s Amphibian Bomber and an Enigma; The Scarab and the Sheldrake.

Supermarine Sheldrake
Supermarine Scarabs
(images are from paintings by the author)

The Scarab, which first flew on 21 May, 1924, was a powerful fighting machine for its period;  the other Supermarine amphibian at this time, the Sheldrake, was an enigma. 

The Sheldrake
The result of the criticisms of the Supermarine Seagull was that, as early as 1923, an Air Ministry order was placed for an improved version. The resultant aircraft was the Sheldrake whose flying surfaces were virtually identical to those of the Seagull but which had a more efficient boat-like hull very similar to that of the Sea Eagle, if the passenger cabin were discounted. It is surprising that the noisy stabilising screens on either side of the engine were still retained, as was the separation of the pilot from the rest of the crew – which already had been addressed in the Seagull II (see 'Precursors of the Walrus' blog).
Even more surprising was the apparent inactivity around the Sheldrake – perhaps the first flights of the Sea Eagle and of the Sea Lion III, the first production batch of the Seagull IIs, and consideration of the larger flying-boats, the Scylla and the Swan, were important factors here – but, for whatever reasons, its only known public appearance is recorded as late as 1927, at the Hamble Air Pageant. By this time, it was an obsolescent type, as Cozens (see earlier Blogs) said: ‘The writer especially remembers seeing a Sheldrake at the end of the line of aircraft on show at Hamble. This machine, N180, looked very much like an ‘old gaffer’

The Scarab
Meanwhile, a year after the Sheldrake was ordered, the second of our aircraft first flew – the first of a Spanish order for twelve aircraft. There was no prototype for this aircraft and as it was in a great many respects similar to the Sheldrake – the Air Ministry order for the Sheldrake provided most of the design work for the Spanish order – at little extra cost to Supermarine. (And an order for twelve aircraft at this time was quite substantial.)

King Alfonso of Spain was a regular visitor to the Hendon RAF Air Shows and must have had an early appreciation of the new British ‘control without occupation’ tactics whereby air power, not ground forces, was used to control insurgent tribes in areas of the British Empire or in areas mandated to Britain by the League of Nations.
As a result, the Spanish Royal Naval Air Service asked Supermarine for an amphibian to be produced, capable of carrying a bomb load of 454 kilos, as it had been noticed the passenger carrying capacity of the Sea Eagle promised a suitable basis for a design. Supermarine suggested that the plans being drawn for their new Sheldrake would be a more suitable model for the project and, doubtless, Mitchell was already envisaging improvements, particularly in respect of the crew dispositions.
In the new, Scarab, version, the engine was returned to the more familiar pusher configuration as the crew were all now, more conveniently, grouped together in front of the wings, with the navigator/bomb aimer also having a cabin in the hull immediately behind and below his cockpit position.  The fuel tanks were now removed from the hull and placed above the middle section of the top wing. This arrangement provided a reliable gravity feed for the engine and the space not now required in the fuselage was used for twelve 50 lb. bombs which could be dropped via a sealable aperture in the bottom of the hull. Four 100 lb. bombs were also carried under the wings and the total weight of bombs carried amounted to the equivalent of six men. The Scarab also had the crew of three and had to carry a machine-gun, ammunition and a considerable amount of fuel – thus making it an attractive single-engined proposition to its buyers.
The first Scarab made its maiden flight on the 21st of May, 1924, bearing the letters M-NSAA , but whether all twelve, from (M-NSA)A to L, actually saw service is unclear. One of the Scarabs was damaged on acceptance trials when its Spanish pilot hit the side of a Union Castle liner when taking off; and the ship sent to collect them had a cargo lift four inches too small in one dimension, so they had to survive a severe Bay of Biscay storm stowed under tarpaulins as deck cargo. Nevertheless, Scarabs were seen above Barcelona at the 1925 Royal Review of the Spanish forces by King Alfonso and they equipped a seaplane carrier, the Dédalo, a converted merchant vessel which lacked a flush landing deck – the aircraft were lowered into the water or raised from it by crane.  They were based at Carageno from whence they took part in actions against Riff and Jibala insurgents in the Spanish Moroccan campaign, including bombing raids in support of an amphibian  landing at Al Hoceima.
The Moroccan conflict ended soon afterwards in 1926 and so Supermarine publicity ran as follows: "A large number of these machines have been bought by the Spanish Government, and these have been in operation for the past year in Morocco with the most satisfactory results [my italics]."

The Scarab design did not lead to any British orders and the sole Sheldrake was not heard of again but, at least, it had paved the way for the significant order from Spain; and coming soon after the 25 Seagull II aircraft and the three Sea Eagles, it is clear what a valuable asset to the company was its Chief Designer, R.J. Mitchell.

For reference sources see my "Blog Subjects, Sources and References".

Fuller account of the above in my forthcoming 2nd Edition of Schneider Trophy to Spitfire.

No comments:

Post a Comment