F.Manson British Bomber Since 1914 (Putnam)
Short Type 310
Despite the outstanding, if isolated success achieved by the torpedo-carrying Short 184s at the Dardanelles in August 1915, it was evident that in order for a single-engine aircraft to possess adequate performance while carrying the 1,100 lb 18in torpedo (particularly in hot climates) it was necessary to acquire an engine of more than 300 horsepower, itself weighing scarcely more than the existing 250hp engines. The new Rolls-Royce twelve-cylinder water-cooled powerplant, soon to be named the Eagle, was already approaching the 300hp rating, but production engines were being earmarked for the Handley Page O/100.
At Sunbeam, however, Louis Coatalen was developing a 300hp engine, later named the Cossack, and it was for this engine that Horace and Oswald Short designed new seaplanes, the Type 310A (torpedo-carrier) and the 310B (patrol scout) * - the former being accorded the highest priority owing to increased enemy naval activity in the Mediterranean early in 1916.
* Confusion has existed for many years with regard to the correct designation of the Type 310, resulting from the various systems of referring to the Short seaplanes. The term Type 310 was adopted to identify aircraft powered by the 310hp Sunbeam engine, this being the initial normal power. The rating was soon raised to 320hp (maximum), and eventually came to be regarded as the 'normal' rating. Strictly speaking the aircraft with these more powerful engines should have been referred to as Type 320s, and often were. However, the designation was never sanctioned, and Short's own designation, the Type 310-A4, came to be officially adopted.
In contrast to the earlier Type 184, which carried its torpedo beneath arched float cross-members, the Type 310A incorporated torpedo crutches on the fuselage underside, thereby ensuring that the torpedo was always carried clear of the water. To provide additional float rigidity, a detachable cross-member interconnected the rear ends of the floats when a torpedo was not carried, and extra fixed raked struts gave adequate float rigidity when carrying the torpedo, while allowing the weapon unrestricted fall when released. The front float crossmember was located forward of the torpedo in any case, and therefore remained fixed.
When carrying a torpedo, the Short 310A was invariably flown as a singleseater, the pilot occupying the rear cockpit so as to maintain the aircraft cg within acceptable limits. These crew dispositions were regarded as unsatisfactory as, occupying the front cockpit, the observer was so beset by interplane struts and upper wing that, without a gun mounting, the aircraft was defenceless. To overcome this, later aircraft featured a Lewis gun with Scarff ring level with the upper wing trailing edge; to man the gun, the observer was obliged to stand on his seat with most of his body exposed to the slipstream but at least he possessed an excellent field of fire.
Two prototype Type 310As and two 310Bs had been ordered, and the first two, Nos 8317 and 8318, were first flown by Ronald Kemp in July and August 1916 respectively. (Of the two 310Bs ordered, only No 8319 was completed as such, No 8320 being converted to become an additional Type 310A during manufacture.)
Nos 8317 and 8318 were quickly despatched to RNAS Otranto in Italy for operational torpedo trials, but both aircraft broke up in the air following failures of their rear float attachment. This was rectified in production aircraft by moving the floats further apart, and an additional V-strut was added to brace the float to the lower wing on each side; these struts were disconnected and rotated downwards to allow the wings to be folded. With this modification in place, the aircraft was termed the 310-A4.
A total of 127 Type 310-A4s was built by Short Bros and the Sunbeam Motor Car Company, all carrying N-prefix serial numbers. The first 54 production machines were shipped to Otranto and Malta during the spring of 1917.
Their first operation, however, ended in failure before it even began, when six 310-A4s, having been towed on rafts to Traste Bay, were destroyed by a sudden storm which capsized all the craft moments before the aircraft were due to be disembarked for take off. Their task had been to attack with torpedoes a flotilla of enemy submarines, known to be off Cattaro in the Adriatic. No such target was ever again presented.
The Mediterranean-based seaplanes were employed on long-range patrols, made possible by their six-hour endurance when carrying a pair of 230 lb bombs. No submarine kill by a 310-A4 was ever confirmed, although the pilot of a Kalafrana-based aircraft claimed to have 'probably destroyed' a submarine which had attacked a French warship off Malta on 8 February 1918.
The production of torpedo-carrying seaplanes was ended by the Admiralty late in 1917 when it became evident from trials aboard HMS Furious that year that deck-landing aircraft could operate with greater flexibility a belief that persisted for the remainder of the aerial torpedo's history.
Nevertheless, no fewer than fifty Short Type 310-A4s remained in service with the RAF at the Armistice.
Type: Single-engine, single- or two-seat, two-bay biplane reconnaissance torpedo bomber seaplane.
Manufacturers: Short Bros, Rochester, Rent; The Sunbeam Motor Car Co Ltd, Wolverhampton.
Powerplant: One 310hp (later 320hp) Sunbeam Cossack twelve-cylinder, water-cooled, in-line engine.
Dimensions: Span, 75ft 0in; length, 49ft 9in; height, 17ft 6in; wing area, 810 sq ft.
Weights (320hp Cossack): Tare, 4,933 lb; all-up, 7,014 lb (with 18in torpedo).
Performance (18in torpedo; Cossack): Max speed, 72.5 mph at sea level; climb to 2,000ft, 12 min; ceiling, 3,000ft; endurance, 2 hr.
Armament: One Lewis gun with Scarff ring on wing centresection requiring observer to stand on front cockpit seat to fire gun. Bomb load either one 1,000 lb 18in Mk IX torpedo or two 230 lb bombs. (Flown as single-seater when carrying torpedo.)
Prototypes: Two, Nos 8317 and 8318. No 8317 first flown at Rochester in July 1916, 8318 in August, both by Ronald Kemp.
Production: Total of 125 Short 310As built (excluding prototypes): Short, 75 (N1150-N1159, NT300-N1319, M390-N1409 and N1480-N1504); Sunbeam, 50 (N1360-NT389 and N1690-NT709).
Summary of Service: Short 310As served at RNAS Uembridge (equipping No 253 Sqn, RAF, after August 1918); at RNAS Otranto, Italy (equipping No 263 Sqn, RAF, after September 1918); at RNAS Mudros, Aegean (equipping No 266 Sqn, RAF, after August 1918); at RNAS Kalafrana, Malta (equipping No 268 Sqn. RAF, after August 1918); and at RNAS Killingholme.
O.Thetford Aircraft of the Royal Air Force since 1918 (Putnam)
The Short 320 was the last of a series of seaplanes widely used in the First World War for anti-submarine patrol and naval reconnaissance. It was preceded by the Short 184 (with 225- or 260-h.p. Sunbeam or 250-h.p. Renault engine) and was fitted with a 310- or 320-h.p. Sunbeam engine. Over 300 Short 184s and 50 Short 320s were in service with the R.A.F. in October 1918. Loaded weight, 7,014 lb. Max. speed, 80 m.p.h. Climb, 140 ft./min. Service ceiling, 5,500 ft. Span, 74 ft. 6 in. Length, 45 ft. 9 in. Served with Nos. and 268 Squadrons.
O.Thetford British Naval Aircraft since 1912 (Putnam)
Short 320 Seaplane
The Short 320 was the last of many types of Short seaplane to enter service during the First World War. It was also the largest, since it was designed to combine long range with weight-lifting capacity to carry the new Mk.IX 18-in torpedo of 1,000 lb.
The designation of the Short 320 derived from its 320 hp Sunbeam Cossack engine, though the original version had a Sunbeam of only 310 hp. The prototypes (Nos.8317 and 8318) made their first flights in 1916 and were followed by 75 production aircraft from Shorts and 45 from Sunbeam. At this time the Admiralty was giving increasing attention to the claims of the Mediterranean, where U-boats based in the Adriatic called for more air patrols. As an immediate step, six Short 225s were transferred from Dundee air station to this theatre, and plans were finalised for attacks by torpedo-carrying seaplanes on the Austrian fleet at Pola. It was decided that the new Otranto base should have 12 Short 320s on its strength when these became available and two more were to be established at a torpedo school based in Malta.
The first attack by the Italian-based Short 320s was launched on 2 September 1917, when six aircraft, carrying their 18-in torpedoes, were towed by motor launches to a point 50 miles south of Traste Bay, where they were to take off for a raid on submarines lying off Cattaro. The operation proved abortive; by a great misfortune it was robbed of success by gales and heavy seas which sprang up on 3 September.
For some unexplained reason, no further attacks of this kind were made, though a series of experiments with torpedo drops at Calshot in February 1918 proved very successful. By 31 March 1918 the RNAS had received 110 Short 320s and when the war ended there were 50 still in service: 30 of these were in the Mediterranean. Thereafter, with more interest being shown in the carrier-borne landplane for torpedo work, the Short 320 soon disappeared from the scene. Some of the last remained with No.268 Squadron, which served at Malta until disbanded in October 1919.
RNAS coastal air stations which, following the formation of the RAF, were designated No.229 Squadron (Great Yarmouth), No.240 Squadron (Calshot), No.248 Squadron (Hornsea). No.263 Squadron (Otranto), No.264 Squadron (Suda Bay), No.266 Squadron (Mudros), No.268 (Malta) and No.269 Squadron (Kalafrana).
TECHNICAL DATA (SHORT 320)
Description: Two-seat anti-submarine patrol or single-seat torpedo-carrying seaplane. Wooden structure, fabric covered.
Manufacturers: Short Bros (serialled N1300-1319, N1390-1409 and N1480-1504) and Sunbeam (serialled N1360-1389, N1690-1696 and N1702-1709).
Power Plant: One 310 hp or 320 hp Sunbeam Cossack.
Dimensions: Span, 75 ft. Length, 45 ft 9 in. Height, 17 ft 6 in. Wing area, 810 sq ft.
Weights (with torpedo): Empty, 4,933 lb. Loaded, 7,014 lb.
Performance (with torpedo): Maximum speed, 72 1/2 mph at 1,200 ft. Climb, 12 min to 2,000 ft. Service ceiling, 3,000 ft.
Armament: One free-mounted Lewis machine-gun above front cockpit level with wing. One 18-in torpedo or two 230 lb bombs below the fuselage.
H.King Armament of British Aircraft (Putnam)
Type 320. On this seaplane of 1916 the placing of the massive radiator immediately ahead of the pilot's windscreen, coupled with the presence of a float-bracing cross-tie directly beneath the torpedo-carrier, might have appeared to render the aircraft wholly useless for its intended purpose of dropping an 18-in Mk.IX torpedo. But although the radiator was immovable, and the pilot was committed to making the most of his field of view on either side, the cross-tie between the floats was removable. Before an intended raid by Short 320s on Durazzo harbour, the aircraft were towed out into the Adriatic by Naval launches, and volunteers from the launches swam out to the seaplanes and unbolted the ties. On occasions when the tie was to be removed, the floats were fitted with extra struts, which braced their inner faces.
Although as torpedo-carriers these aircraft achieved no operational success, as had the Type 184, they were used for valuable trials at Calshot early in 1918.
Mostly the Short 320s were used for patrol and bombing, without provision for the torpedo but carrying bombs and a Lewis gun. The bombs were carried in the customary Short fashion under the fuselage, typical loads being two 230-lb or four 112-lb. A standard installation of a Lewis gun was made. This look the form of a Scarff ring-mounting located behind a cut-out in the top wing, the base of the ring being braced to the fuselage by two struts. The observer gunner was in the front seat, and to use the Lewis gun he stood up in his cockpit, being thus exposed to the slipstream.
310-hp Seaplane, Type B. This was the designation applied to the 'North Sea Scout' type of Short seaplane, produced in 1916 as a 'Zeppelin fighter' to carry a 6-pdr Davis recoilless gun, in addition to a Lew is gun for its own defence. The big gun was shackled to a member across the rear cockpit, and fired upward and forward. Accordingly, the centre-section of the top wing was left open, and the radiator was made in two blocks instead of one. The Lewis gun mounting was apparently developed at Grain, where the aircraft was tested.