C.Barnes Short Aircraft since 1900 (Putnam)
The Short N.1B Shirl
The story of how the first carrier-borne torpedo-aeroplane, the Sopwith Cuckoo, came into existence has been well told elsewhere, and it is only necessary to recall here that the R.N.A.S. might never have had such a weapon after Commodore Murray Sueter’s posting to the Mediterranean in January 1917, had not work on the prototype been revived six months later at the instigation of Wing Commander Arthur Longmore, who noticed it, set aside half-finished, during a visit to the Sopwith works. The Cuckoo proved to be an excellent aeroplane, its main drawback being that its 1,000-lb Mark IX torpedo was not powerful enough to be effective against large warships. The Admiralty therefore called, in the autumn of 1917, for a generally similar single-seat aeroplane to carry a Mark VIII torpedo weighing 1,423 lb, with a warhead 50 per cent larger than the Mark IX’s; the requirements were embodied in specification N.1B (which was revised as RAF XXII after April 1918), and since deck-landing was not yet operationally practicable, because of delays in completing the new carriers Argus and Eagle, ditching gear and jettisonable wheels were specified, so that the returning aircraft could be salvaged if unable to reach a shore base after launching its missile. Tenders were submitted by two firms, Blackburn and Short Bros, and each received a contract for three prototypes to be powered by the Rolls-Royce Eagle VIII engine of 385 hp.
The Short proposal, later named Shirl, was a simple, solid, two-bay biplane; its fuselage was covered throughout with plywood to resist the effects of temporary immersion, and the wings and tail-unit were similar in construction to those of Oswald Short’s previous design, the N.2B, with four ailerons, cord trailing edges and folding gear; the wings were of equal span, with square tips and neither stagger nor sweep-back. The engine was neatly cowled, with a frontal honeycomb radiator, and the landing chassis was arranged for release after take-off. At first this was a simple expendable two-wheeled cross-axle arrangement, and in this form the first prototype Shirl (S.421, N110) was flown at Grain on 27 May, 1918, by John Parker, climbing to 10,000 ft with full load in 21 minutes; next day the test was repeated with a four-bladed airscrew but found inferior, so the original two-blader was refitted on 29 May. A few days later he delivered it by air to Martlesham Heath, carrying a dummy Mark VIII torpedo; five minutes after take-off the petrol-pump drive sheared and he had to make a hurried forced landing, but the trouble was quickly rectified and he was able to take off again; he then found that the throttle control adjustment had been displaced during the repair and that he was unable to close it. As he was determined not to abandon the delivery flight, he stayed on his course and prevented the engine from overspeeding by maintaining a steady climb; this resulted in his arrival over Martlesham at a height of 12,000 ft, from which he executed a masterly ‘deadstick’ landing with the ignition switched off.
On completion of its official tests, with a temporary restriction of the engine to 345 hp, the first Shirl was returned to Rochester for modifications, including incorporation of a small amount of sweep-back to counteract tail heaviness when flotation bags were installed in the rear fuselage. At the same time a new landing chassis was fitted to permit either normal landing or ditching to be selected, irrespective of when the torpedo was launched. The revised chassis comprised two separate units, each with a tubular skid carrying a pair of wheels on a short cross-axle, a large flotation bag which could be inflated rapidly from a compressed-air bottle and a small hydrovane at the forward end of the skid. The axles were rubber-sprung and could be jettisoned for deck-landing or ditching, and the skids were carried by inclined struts from the bottom longerons and from the wing spars below the inner interplane struts. This arrangement allowed the torpedo to be launched without affecting the landing-gear configuration, although jury struts had to be rigged before the wings could be folded. N110 was completed in this form on 1 July, 1918, and underwent satisfactory ditching trials at Grain. The second Shirl (S.422, N111), built to the same overall standard, but with larger ailerons and a fixed tailplane, was dispatched to Grain from Rochester on 8 July; it was urgently needed for trials at the Torpedo Aeroplane School at East Fortune, near Dunbar, and Parker hoped to be able to fly it there immediately after a preliminary test flight at Grain. Unfortunately his first brief handling trial showed N111 to be considerably more tail-heavy than expected, but a rapid consultation with Oswald Short indicated that an increase of tailplane incidence by 4 degrees would put matters right; the tailplane was removed at noon, new fittings were made in the Grain workshops and by four o’clock Parker was ready for a second flight, before which he took on a full load of fuel; he found longitudinal control satisfactory, so flew straight on to arrive at East Fortune 4 1/2 hours later. He cruised most of the 400 miles at 13,000 ft, his only instruments being radiator thermometer, engine tachometer, altimeter, cross-level, fore-and-aft level, an air-speed indicator that did not indicate and a small compass which had not been swung; but he found the Shirl a remarkably stable and untiring machine to fly and arrived with plenty of fuel in reserve, which proved the aerodynamic efficiency of the design.
At East Fortune the Shirl took part in operational torpedo trials along with the Blackburn Blackburd, but in spite of their higher power and weight-lifting ability, both lacked the agility of the Sopwith Cuckoo in taking evasive action after an attack. After these trials N111 went to Martlesham for performance testing on 24 August, 1918, and was flown at a gross weight of over 6,000 lb; although its performance was excellent, it was criticised for not having a tailplane incidence adjuster like N110; consequently N111 was found to be tail-heavy with the torpedo and nose-heavy without it. The third Shirl (S.423, N112) was not completed till 11 December and was delivered to Gosport early in 1919, being flown back to Eastchurch by Parker on 28 March in a hailstorm; thereafter it was flown at various weights to assess its potential as a civil mail-carrier; for this role a large plywood container of half a ton capacity was slung from the torpedo rack; on 1 April it failed to take-off at 7,400 lb, but three days later it climbed to 5,000 ft in 25 minutes at 6,762 lb. It had a revised tailplane adjuster and a new chassis which dispensed with the underwing struts, so that no jury struts were needed for wing folding. Shorts had been invited to quote for a batch of 20 Shirls in February 1919 and promised delivery in April, but the order was not confirmed, and a production contract already awarded to Blackburn for 100 Shirls was also cancelled in favour of more Cuckoos.
The Shirl’s stability, fuel economy and weight-lifting ability made it an attractive proposition for an attempt to win the Daily Mail’s £10,000 prize for the first non-stop crossing of the North Atlantic, first offered in 1914 and revived in March 1919. It was proposed to convert N112 into a two-seater for this purpose, and a few retouched photographs were issued by Short Brothers to show it as such, but the conversion was never made because the Air Ministry refused to lend it for this purpose, although they offered to make an engine available. Thereupon Short Brothers decided to sponsor the flight as a private venture and built a special variant of the Shirl, S.538, with increased wing area and an external fuel tank giving a still-air range of 3,200 miles, the total tankage being 435 gallons of petrol, 30 gallons of oil and 18 gallons of water. This was sufficient for an east-west flight against the prevailing summer headwinds, and it was planned to start from The Curragh, near Kildare in Ireland, where three square miles of level turf could provide a long unobstructed take-off path in any direction. S.538, nicknamed the Shamrock, was completed at Rochester at the end of March, with three-bay wings of 62 ft 2 in span and a large cylindrical fuel tank slung from the torpedo-rack attachment points; its low-compression Rolls-Royce Eagle VIII engine (No. 5058) was a short-term loan from Air Ministry stocks already held for the F.3 flying-boats being built at Rochester. The Shamrock was unregistered, but its fuselage and wing struts were painted white, with roundels on the khaki-doped wings, the Union Jack emblazoned on the fin and rudder and the maker’s name and address prominently displayed on the fuselage sides; in addition to its crew of two, it carried their food, electrically heated clothing, lighting, maps, sextant, long-range W/T and direction-finding radio; to save weight it used a plain cross-axle chassis of the type initially fitted to the first Shirl; it also had a very large two-bladed airscrew whose pitch was coarse enough to prevent the engine exceeding its most economic cruising rpm; this limited it to 1,400 rpm on the ground, and was one of the reasons for choosing The Curragh as the starting-point. The pilot for the Atlantic flight was Major J. C. P. Wood and his navigator was Capt C. C. Wyllie; substantial support was given by C. C. Wakefield & Co, proprietors of Castrol engine oil. Parker made four preliminary test flights in the Shamrock, the first (of four minutes) on 8 April, when it was found to be tail-heavy, and the second next day, when he climbed to 9,000 ft in 28 minutes with 200 gallons of fuel and Major Wood as passenger.
On 18 April, 1919, at a gross weight of8,400 lb, the Shamrock took off from Eastchurch at 3.15 pm to fly to The Curragh, and was accompanied by Parker flying N112. The two aircraft flew at 3,500 ft and passed over Holyhead at 7.20 pm, but 12 miles out to sea the Shamrock’s engine stopped and, finding that he could not restart it, Major Wood turned back in an attempt to reach land by gliding; he nearly succeeded, but had to ditch about a mile off Anglesey. Wood and Wyllie were both rescued by H.M.S. Paisley, and Parker managed to land his Shirl in a very small field, but broke the airscrew and some chassis struts against a stone boundary wall. The Shamrock floated well, and was in the water for 22 hours before it could be towed into Holyhead and beached; it was taken back to Rochester for inspection and repair, and the cause of the engine stoppage was found to be an air-lock in the fuel transfer system. It was hoped to make a further attempt, but the effects of a whole day’s immersion in sea-water were too serious for a quick overhaul, and in July the prize was won by Alcock and Brown in a Vickers Vimy, as everyone knows. Meanwhile, the Shamrock’s, radiator and engine had been borrowed for temporary installation in the second N.2B seaplane N67, as already recorded. So the Shamrock was abandoned, but the Shirl N112 was repaired and again test-flown by Parker at Eastchurch for 40 minutes on 28 July, 1919, before final delivery to the R.A.F. Twenty years later, when Short Brothers established their new factory at Belfast, Sqn Ldr J. C. P. Wood had become Officer Commanding R.A.F. Station Aldergrove; as the senior R.A.F. officer in Northern Ireland, it was his duty to attend official ceremonies, including the Opening of Parliament at Stormont, in full ‘plumage’, but he was known everywhere by his nickname ‘Atlantic Jim’.
Shirl - Span 52 ft (15-85 m); length 35 ft (10-66 m); area 791 sq ft (73-5 m2); empty weight 3,300 lb (1,497 kg); normal all-up weight 5,950 lb (2,700 kg); max speed 92 mph (148 km/h); normal duration 6-5 hr; max overload weight 6,762 lb (3,065 kg) associated with 85 mph (137 km/h) and duration 10 hr.
Shamrock - Span 62 ft 2 in (18-95 m); length 35 ft (10-66 m); area 1,015 sq ft (94 3 m2); empty weight 3,962 lb (1,798 kg); max weight 8,400 lb (3,810 kg); duration 40 hr at 80 mph (129 km/h).
F.Manson British Bomber Since 1914 (Putnam)
If a significant shortcoming existed in the Cuckoo's concept it was that it was only able to carry the 1,086 lb Mark IX torpedo, a weapon that was not thought capable o f sinking any ship larger than a light - that is, unarmoured - cruiser. The Admiralty's decision to adopt landplane torpedo aircraft coincided with plans to complete two through-deck aircraft carriers in 1918, HMS Argus and Eagle (*)
Air Board Specification N.1B of April 1917 covered a number of naval requirements in single-engine, single-seat aircraft, one of which was to be a torpedo carrier, intended in due course to replace the Cuckoo. The Specification outlining the requirements for the latter was amended several times, and in October 1917 called for the aircraft to be capable of carrying the Mark VIII torpedo, a 1,436 lb weapon that possessed a warhead 50 per cent larger than that of the Mark IX. Both Short Bros and Blackburn submitted tenders, and each company was invited to build three prototypes.
Little time was allowed before the first prototypes were required for preliminary Service evaluation, and both manufacturers made tremendous efforts to meet the deadline set for the end of April 1918. The Short aircraft, named the Shirl (N110-N112), was of simple configuration, owing much to Oswald Short's N.2B seaplane, but with the single cockpit situated in much the same position as the observer's cockpit in the earlier aircraft. As permitted in the Contracts, power was provided by the 375hp Rolls-Royce Eagle VIII driving a two-blade propeller and being neatly cow led with frontal radiator.
The broad-chord wings of equal span and with square tips were rigged without stagger, being foldable and with ailerons on upper and lower wings. An unusual requirement, partly occasioned by delays in the completion of HMS Eagle, was that the wheel landing gear was to be jettisonable so as to simplify ditching if the need arose, and flotation gear was to be provided to increase the chances of salvaging the aircraft from the sea.
When first flown by John Parker at the Isle of Grain on 27 May 1918, the first Shirl, N110, was fitted with a simple two-wheel undercarriage with V-struts and cross-axle, this being necessary to meet the test deadline, and when the aircraft was delivered to Martlesham Heath a few days later it carried a dummy Mark VIII torpedo which of course could not have been released with such an undercarriage. During the early tests the aircraft was found to be severely tail-heavy, and this appeared to be rectified by introducing wings with sweepback when N110 returned to Rochester. At about this time the original undercarriage was replaced by twin-wheel units, each pair of wheels being provided with a skid and attached to the lower wing by a pair of V-struts, thereby eliminating the cross-axle. A large inflatable flotation bag could be carried within each undercarriage structure.
The second Shirl, N111, was delivered to Grain on 8 July and subsequently took part in torpedo dropping trials at East Fortune alongside the Blackburn Blackburd. It then went to Martlesham for Service performance and handling evaluation trials in August. In these, however, despite meeting the general performance and load requirements, the Shirl attracted criticism on account of sluggish handling characteristics, lacking the manoeuvrability of the Cuckoo, particularly during evasive action after releasing its torpedo. It was also found that, while carrying the torpedo, the aircraft was still excessively tail-heavy, and that, after releasing the torpedo, it became nose-heavy.
The third Shirl, N112, did not fly until December 1918 when, with the War over, the urgency for a new torpedo aircraft had largely disappeared, and official interest in the Shirl (and the Blackburn Blackburd) gave place to further production orders for the established Sopwith Cuckoo.
(*) HMS Argus, 15,775 tons, had been begun in 1914 as a liner, Conte Rosso, for an Italian shipping company, but came to be launched in 1917 with a full-length flight deck, and was indeed completed in 1918. HMS Eagle, 22,600 tons, had been begun in 1913 as a dreadnought battleship, Almirante Cochrane for Chile; she was launched in 1918 but did not achieve full service with the Royal Navy until 1923. HMS Furious, 22,000 tons, the only other ship with a true flight deck, was eventually completed in 1917 with a flight deck forward of the superstructure (she had been laid down as a light battle cruiser in 1915); in 1917-18 an after deck was added, and between 1921 and 1925 she was fully converted to a flush-deck carrier).
Type: Single-engine, single-seat, two-bay biplane torpedo bomber.
Admiralty Specification: N I B (later RAF Type XXII).
Manufacturer: Short Brothers, Rochester, Kent.
Powerplant: One 375hp Rolls-Royce Eagle VIII twelve-cylinder, water-cooled, in-line engine driving two-blade propeller.
Dimensions: Span, 52ft 0in; length, 35ft 0in; height, 13ft 3in; wing area, 791 sq ft.
Weights (360hp Eagle VIII): Tare, 3,319 lb; all-up, 5,512 lb (with torpedo).
Performance (360hp Eagle VIII; with torpedo): Max speed, 93 mph at 6,500ft; climb to 6,500ft, 17 min 30 sec; service ceiling, 10.000ft; endurance, 3 3/4 hr.
Armament: One 1,423 lb 18in Mark VIII torpedo. No gun armament.
Prototypes: Three, N110-N112. N110 first flown at Grain by John Parker on 27 May 1918. No production
P.Lewis British Bomber since 1914 (Putnam)
A requirement was formulated at the close of 1917 for a single-seat torpedo-carrying aircraft able to launch the 1,400 lb. Mk. VIII torpedo, a heavier weapon than that borne by the Cuckoo. Two firms - Blackburn and Short - built prototypes, three of each being ordered.
The Short answer to the single-seat torpedo-carrying requirement was the Shirl, N110 being the first prototype flown initially in mid-1918 by John Lankester Parker. The Shirl was far more conventional in appearance than the Blackburd. Two-bay, folding, equal-span wings were fitted to a slim fuselage, the nose of which housed the 345 h.p. Eagle VIII. In place of the simple V-type undercarriage of N110, N111 - the second Shirl - received a complicated structure incorporating skids, together with swept-back wings; the third prototype - N112 - differed once again in its landing-gear.
Under test, both the Blackburd and the Shirl were found to be inferior to the Cuckoo, and development of each ceased with the war’s end.
H.King Armament of British Aircraft (Putnam)
Shirl. Like its counterpart the Blackburn Blackburd, the Shirl (1918) was a single-seat torpedo-carrier, designed specifically to operate with the 18-in Mk.VIII torpedo. Each of the two crutches was stayed by two inverted V-struts.
Jane's All The World Aircraft 1919
THE SHORT "SHIRL" TORPEDO-CARRIER.
The Short "Shirl" biplane is generally similar to the N2B type seaplane except that a divided wheel and skid chassis is fitted for flying off decks and to allow the stowage of an 18 in. torpedo under the fuselage. The machine is a single-seater, the pilot being situated in rear of the main planes, which are noticeably swept back from the fuselage, and are arranged to fold for stowage on board ship.
Flotation gear in the form of air-bags are carried over the skids and small plane form hydro vanes are fitted to the front of the skids, to prevent turning over when alighting on water.
The machine entered by Messrs. Short Bros, for the trans-Atlantic flight is a modified " Shirl," fitted with somewhat larger wings and tailplane, and an immense petrol tank suspended under the fuselage.
Type of machine Biplane.
Name or type No. of machine "Short Shirl."
Purpose for which intended Torpedo carrying.
Span 52 ft.
Gap, maximum and minimum 6 ft.
Overall length 35 ft. 6 in.
Chord 8 ft. upper; 7 ft. lower plane.
Span of tail 15 ft.
Maximum cross section of body 11 sq. ft.
Engine type and h.p. Rolls Eagle 8, 400 h.p.
Airscrew, diam. 10 ft.
Weight of machine empty 2,850 lbs.
Tank capacity In hours Max. 6 1/2 hours.
Tank capacity in gallons 137 gallons.
Speed low down 99 m.p.h.
Speed at 10,000 feet 97 m.p.h.
To 5,000 feet 13 minutes.
To 10,000 feet 30 minutes.
Disposable load apart from fuel 2,500 lbs. normal
Total weight of machine loaded 5,950 lbs.
Flight, April 10, 1919.
THE TRANSATLANTIC RACE
THE preparations for the great race to be first to cross the Atlantic by air are progressing apace. By way of summary, the Sopwith machine, to be piloted by Mr. H. Hawker, who will have with him as navigator and assistant pilot Capt. Grieve, is already at the starting point in Newfoundland, and is only awaiting favourable weather conditions before making a start. The Martinsyde biplane, with its pilot, Mr. F. P. Raynham, and his navigator, Capt. Morgan, is on its way across, and may, by the time these lines appear in print, have arrived at St. John's. The Fairey machine, up till now the only seaplane entered from this side, is rapidly nearing completion, being, in fact, a standard Fairey 3C type especially adapted for the race. The pilot, as already announced, will be Mr. Sydney Pickles, so well knows to all readers of FLIGHT. The name of the navigator who will accompany him has not yet been disclosed, but will, we understand, be announced shortly. The Short machine entered, and which will be piloted by Major Wood, who will have with him as navigator Capt. Wyllie, has the distinction of being the only entrant which, so far, it is proposed to start from this side, the starting point chosen being Bawnmore, near Limerick, in Ireland. This machine, which has been undergoing severe tests during the last couple of weeks, is to be flown first to Ireland, whence the final start will be made.
As to the probability of one or all of the competitors succeeding in getting across, there is of course, a certain element of luck involved, but arrangements, as announced elsewhere, are being made., by the Air Ministry and Admiralty, to take all possible precautions, and to ensure that, even in cases of engine failure, the occupants should have a very good chance of being picked up by passing vessels.
As interest centres more and more in this race, a few words dealing with the British machines entered will, we feel sure be welcomed by readers of FLIGHT.
The Short Machine
Fundamentally the Short machine entered for the race does not differ greatly from their standard torpedo carrier known as the "Shirl." It is, as will be seen from the general arrangement drawings, a land machine fitted with wheels. In the place between the chassis struts usually occupied by the torpedo in the standard "Shirl" is slung a large cylindrical petrol tank which, should the necessity arise, can be quickly emptied so as to form a float of sufficient buoyancy to keep the machine afloat for a considerable period. In order to be able to carry the extra weight of fuel necessary for the long journey larger wings have been fitted, having three pairs of struts on each side instead of the two pairs fitted on the standard machine. A feature which is unique for this machine is the sweepback of the planes, which is very pronounced. This should form a very good feature by which to identify the Short machine, although from the fact that up to the present she is the only machine entered on which the westward flight will be attempted, she can scarcely be confused with any of the other entrants.
As in the case of the Sopwith machine, the Short is fitted with a Rolls-Royce "Eagle," and the petrol capacity is, we understand, sufficient for a flight of 3,200 miles; in still air, of course. As the distance across is a little under 2,000 miles, this leaves a fair margin for adverse weather conditions, the prevailing winds in this part of the Atlantic being westerly at this time of the year. It will, therefore, be seen that the decision to make the westward flight may not be so dangerous as many are apt to imagine, and certainly considerable time will be saved by avoiding the delay of shipping the machine across before a start can be made.
The cockpits are arranged in the usual fashion in this machine, i.e., in tandem. A directional wireless set will be fitted as well as all the navigation instruments of the usual type. The maximum speed is expected, to be about 95 m.p.h., but flying at cruising speed, and allowing for head winds, the actual speed may be expected to be considerably lower.