Service and commercial uses of large aircraft that operate from water
A FOUR-ENGINED TWIN-TANDEM BIPLANE, the ShortSingapore III of 1934. This is a four-engined reconnaissance and coastal patrol flying boat. The span of the upper plane is 90 feet and that of the lower plane 76 feet. The length is 64 ft. 2 in., the height 23 ft. 7 in. and the wing area 1,834 square feet. The four Rolls-Royce Kestrel twelve-cylinder water-cooled engines are mounted in tandem pairs. The maximum speed at 2,000 feet is 145 miles an hour, the cruising speed 105 miles an hour and the range 1,000 miles.
THE flying boat is the air equivalent of the ocean liner. This does not mean that multi-engined land aircraft and floatplanes are not used for crossing large stretches of water. The flying boat, however, is able, in addition, to ride on the surface of the water for long periods and to operate in a similar way to marine craft.
Although passengers on civil air lines are not yet expected to live entirely on board flying boats, Royal Air Force crews can undertake extended cruises without the necessity of finding living and sleeping accommodation elsewhere.
Passenger accommodation in the Short Empire flying boat is roomier than that hitherto provided in passenger aircraft. This is partly accounted for by the inherent design of the hull, which provides more space than the fuselage of a landplane. A landplane’s fuselage is merely a girder connecting wings and tail. To reduce resistance, its cross-section is kept as small as possible. Clearance for airscrews can be obtained from the undercarriage. A flying boat’s hull, on the other hand, in addition to acting as a girder, must provide the buoyancy and stability required when at rest or when moving slowly on the water, the planing surface and stability required when planing, and the necessary clearance between the lowest part of the airscrew disk and the highest wave of water that may be expected to be thrown up in ordinary conditions.
Thus, to accommodate passengers, the landplane’s fuselage has to be expanded from the structural minimum, whereas the flying boat’s hull already offers ample space. This advantage is more pronounced in the cantilever design than in flying boats whose wing is mounted on a centre section and strut braced.
On the water the flying boat is a power-driven craft which must give right of way to sailing craft. In flight it must conform to the regulations applicable to heavier-than-air aircraft.
Because they have to operate as marine craft when on the surface, flying boats must carry equipment for this purpose. Some of the special items carried are bollards, loading level, anchor and chain, bilge pump and hose, boat-hook, collapsible dinghy, drogues, fog bell, marine distress signals, refuelling pump and hoses, mooring lights, towing gear and slinging gear.
Minor running maintenance can be carried out on board, and most British Service flying boats are equipped for the purpose. During operations far from their normal bases some flying boats carry a spare airscrew, a spare engine, engine ladders and engine-slinging derricks to enable them to change an engine without recourse to external help.
Yet, although they are specialized marine aircraft, flying boats must ordinarily be considered as shore-based; and it is just as essential to provide flying boats with adequate bases as to provide ships with efficient harbours.
For a thorough examination of the hull, flying boats must be removed from the water. Normally this means bringing them ashore. On shore, work on the flying boat can be carried out in the same way as with aircraft of any type.
The earliest method of handling a flying boat between land and water was to support its hull on a heavy wooden cradle fitted with iron wheels. To support the flying boat evenly over a sufficient part of its length and breadth, the cradle was built to conform to the shape of the under surface of the hull.
The modern method, however, is to use rubber-tyred wheels mounted on legs. These legs are attached at points where the aircraft’s structure is designed to take the weight of the flying boat.
Both methods require handling parties — men who must wade into the water to remove the auxiliary landing gear or place it correctly in position —and a slipway, inclined at a reasonable angle, with a power winch and cable for hauling up or lowering.
A third method of removing flying boats from the water — by means of a floating dock — is much less common. This method, first developed in Great Britain, is now used also in the United States and elsewhere. The flying boat is floated on to the partly submerged dock; water ballast is then pumped out of the dock until it rises and supports the flying boat clear of the surface.
Germany uses as tenders ships equipped with catapults for commercial ocean-going flying boats (see the chapter “Catapults for Aircraft”). The maintenance of Imperial Airways’ flying boat fleet is carried out at the company’s base at Hythe, near Southampton (see the chapter on “Aircraft Maintenance”).
Although Service flying boat operations are conducted in accordance with the changing needs cf Service requirements and not with the precision-like regularity of a commercial air line, the maintenance of R.A.F. flying boats is extremely good.
Until late in 1937 the squadrons of Royal Air Force flying boats were known as Flying Boat Squadrons. Their classification was then changed to General Reconnaissance Squadrons. This new classification suggests the work on which they are commonly engaged. Their normal duties are concerned with the patrolling of the air above coastal and trunk waterways, and with the carrying out of long-distance oversea reconnaissance.
Modern flying boats, using up-to-date methods of sweeping the sea surface, can discover an approaching fleet many hundreds of miles out to sea, and give warning of its approach many hours before the ships could sight the land towards which they were heading. The usual method of sweeping is to send squadrons of flying boats from several bases. Each flying boat flies singly along one of a series of parallel lines, all of which cover a wide stretch of ocean. At a predetermined distance the flying boats turn left or right and then return along another series of parallel lines over a second stretch of ocean. In this way a vast area of sea can be swept in remarkably short time.
During this work flying boats must operate without wireless; otherwise their approach would be discovered by the hostile fleet, who would launch fighters (see the chapter on “The Fleet Air Arm”) to attack the flying boats before the flying boats sighted the fleet. Thus Service flying boat crews must be able to navigate accurately without radio aids to fix position; each flying boat must be a self-contained unit operating by dead reckoning and celestial navigation.
FLUCTUATIONS OF DESIGN are indicated in the adjoining diagram, which shows the weights of representative flying boats from 1919 to 1938. The heaviest of these aircraft was the Short Sarafand of 1935, with a weight of 64,310 lb., or nearly 29 tons The maximum permissible loaded weight was about 32 tons.
No doubt this was the main reason why the principal R.A.F. school of navigation was for many years a flying boat school. The navigational ability of the personnel of the R.A.F. flying boat squadrons is excellent. Their problem is not always the relatively simple one of making a direct journey from one port to another, but often the more complicated one of travelling for hundreds of miles to a point marked x on the ocean, then changing course, once, twice or many times, before returning to their original base, or perhaps some other base. During this time the flying boats’ crews have no means of checking their position except from their own calculations of course, distance flown and position. Yet they carry out their work with great accuracy; and it is important that they should, for any considerable error in their navigation would make it impossible to fix the position of an advancing fleet with the precision required for staff purposes.
Service flying boats are used also for patrols designed to provide for the safety of merchant ships. A flying boat squadron was sent from England to the Mediterranean for the antisubmarine piracy control in the earlier stages of the Spanish Civil War.
Another of the duties is reinforcement. The ability of the flying boat to use any stretch of reasonably sheltered water with the minimum of prearranged assistance makes it invaluable for this purpose. In America, for example, during exercises, flying boats have reinforced the Hawaiian Islands within twenty-four hours, instead of the four days required by surface vessels.
On December 8-9, 1937, twenty-two hours after they had left San Diego (California), fourteen U.S. Navy flying boats, carrying ninety-eight officers and men, alighted at Coco Solo (Panama Canal Zone) 3,080 miles away.
Flying boats were not able to supersede landplanes for commercial air services until satisfactory methods of all-metal construction were evolved and flying boats became large enough to have a high reliability factor in open sea use. The second consideration had to await, first, the development of engines of sufficient power and then the growth in air traffic to make the use of large flying boats worth while. These conditions were reached only after some fifteen years of regular commercial air services.
Experimental African Service
A factor which then impelled the use of flying boats on the British trunk air routes was the nature of the territory which the routes followed. On parts of these routes the cost of construction and — even more important — the cost of maintenance of land aerodromes are high, whereas the country offers natural facilities for marine aircraft.
The late Captain Thomas A. Gladstone, A.F.C., began in 1921 to explore the possibilities of marine aircraft on the route between Khartoum and the African lakes. In 1926-1927 he ran an experimental floatplane service for North Sea Aerial & General Transport, Ltd., between Khartoum and Kisumu (Kenya). Although this pioneer service was before its time, it pointed the way to the possibilities of the use of marine aircraft on the All-Red Route through Africa. The route to Australia was one over which marine aircraft could operate with ease. Those who know the monsoon conditions in India and Burma are aware how ground that is fit for landing can, within a few minutes, be converted into a swamp. The use of marine-type aircraft is a logical way of overcoming such difficulties of climate and country.
Many believe that the future will see the largest types of aircraft in the marine class. The unlimited length of run frequently afforded on the water, as compared with the land, and the absence of obstructions are sound reasons for the belief that land aircraft will be restricted to sizes substantially smaller than those of the largest marine aircraft.
Thus it appears likely that trans-ocean air travel and travel over the great waterways of the world are likely to produce flying boats of steadily increasing size, with corresponding increases in speed, range and carrying capacity. The non-stop journey between Southampton and New York will become an indispensable factor in the design of some commercial flying boats.
SUPERMARINE WALRUS AMPHIBIAN, shown with wings folded. This type of aircraft is used by the Fleet Air Arm and by the Royal Australian Air Force. In Australia it is known as the Seagull V. It is a single-engined pusher biplane for naval reconnaissance, fleet spotting, training and photography. The span is 45 ft. 10 in. and the width folded 17 ft. II in. ; the length is 37 ft. 7 in. The Bristol Pegasus VI engines gives the aircraft a maximum speed at sea level of 124 miles an hour. The cruising speed at 3.50p feet is 95 miles an hour.
The large flying boat is costly to buy and to maintain. It is therefore a type of aircraft which is at present used extensively only by the greater nations. The smaller nations have been content with floatplanes. Yet the flying boat is today only at the beginning of its development. Increasing use commercially will push that development forward more rapidly than in the past. This may make it essential for some of the smaller nations with maritime interests to pay more attention to the flying boat. With an ever-increasing market opening for this particular type of aircraft, it may be surmised that the prosperity of the flying-boat manufacturer will develop in the same way as that of the builder of steamships during the Victorian era.
The earliest flying boats were built of plywood; to save weight some of them incorporated partial fabric covering on the hulls. This period was followed by the production of boat-built, hulls in which mahogany planking was laid on in diagonal skins and copper fastened, with oiled fabric between the skins. This type of hull had elastic properties which were considered useful to absorb shock on the water. A variant of this type of construction was the “Consuta” plywood, invented and used by S. E. Saunders, Ltd., in which the plywood was first sewn into large sheets.
The introduction of the all-metal hull followed; but wings were still fabric-covered, and wooden members were still commonly used in their internal construction. Next came metal internal construction for the wings, with the retention of fabric covering. This has given place to the real all-metal flying boat in which hull, internal structure and wing covering are of metal, with perhaps the exception of the coverings of some of the air control surfaces.
Of the British flying boats designed and built after the war of 1914-18, the first were the Vickers Vikings of 1919. The Vickers Viking was a single-engined commercial amphibian pusher biplane, accommodating pilot and four passengers. It had a 360 horse-power Rolls-Royce Eagle VIII engine. Other models had a 275 horse-power Rolls-Royce Falcon engine or a 450 horsepower Napier Lion engine.
In 1919-20 appeared the Supermarine Channel type, a single-engined commercial biplane carrying pilot and three passengers. It had a 160 horse-power Beardmore engine. The 1920 Supermarine Sea King, with a similar engine, was a single-engined pusher biplane for naval patrol. To the same year belonged the Saunders Kittiwake, an experimental twin-engined tractor amphibian biplane seating pilot, mechanic and six passengers, and the Gosport G.9, a triplane for ten passengers and a crew of three. The Gosport G.9 had one pusher and two tractor Rolls-Royce Condor engines.
The Vickers Valentia of 1922 was a twin-engined biplane with Rolls-Royce Condor engines. The Supermarine Sea Eagle of 1923, with Rolls-Royce Eagle Series IX engine, was a commercial six-seater pusher amphibian biplane.
The Supermarine Seagull Mark III of 1924 was a single-engined three-seater deck-landing fleet spotter amphibian tractor biplane. It had a 450 horse-power Napier Lion engine. The Supermarine Swan, forerunner of the Southampton (see below), was a twin-engined commercial tractor amphibian biplane for twelve passengers and a crew of two. It had Rolls-Royce Eagle IX or Napier Lion engines.
Other 1924 examples were the Fairey Atalanta, a four-engined twin-tandem biplane, with 700 horse-power Rolls-Royce Condor engines, the Short Stellite (Cockle), a twin-engined high-wing tractor monoplane, with Blackburn engines, and the Short F.5. The English Electric Co. produced the P.5 Cork, a twin-engined tractor biplane with Rolls-Royce Eagle or Napier Lion engines, and the Kingston, a development of the Cork. Mark I of the Kingston had a wooden hull; Marks II and III had an all-metal hull.
EMPIRE FLYING BOAT CORSAIR being launched at Hamble, on the eastern shore of Southampton Water. The Short Empire Flying Boat is a high-wing cantilever monoplane accommodating twenty-four passengers by day and sixteen by night, in addition to baggage and l| tons of mail. Each of the four Bristol Pegasus X.C. nine-cylinder radial air-cooled engines has a normal horse-power of 740. The maximum speed of the standard boat is 200 miles an hour at 5,500 feet and the cruising speed 164 miles an hour. The range in still air is 810 miles.
In 1925 appeared the Fairey Titania, sister to the Atalanta (see above), the English Electric Co.’s Ayr, a single-engined tractor biplane, and two Supermarine models. The Supermarine Scarab was a single-engined four-seater bomber amphibian pusher biplane, with a Rolls-Royce Eagle IX or Napier Lion engine. The Supermarine Southampton was a twin-engined reconnaissance tractor biplane, with Napier Lion engines.
Two Supermarines were produced in 1927-28 — the Solent, a three-engined tractor biplane with Armstrong Siddeley Jaguar engines, and the Twin Lynx Amphibian, a seven-seater twin-engined tractor biplane with Armstrong Siddeley Lynx engines.
The Short Calcutta appeared in 1928. This was a three-engined commercial tractor biplane, with Bristol Jupiter IX engines. In 1929 Blackburn produced the Iris II, a three-engined tractor reconnaissance biplane with 670 horsepower Rolls-Royce Condor engines, and the Sydney, a three-engined tractor reconnaissance and coastal patrol monoplane. The Sydney had 525 horse-power Rolls-Royce Kestrel engines.
The Supermarine three-engined civil monoplane of 1930 was a tractor, with lateral stabilizers; it had Bristol Jupiter XI engines. The contemporary Blackburn Iris III was a three-engined tractor reconnaissance biplane with Rolls-Royce Condor engines. The Short K.F.1 of 1931 was a three-engined tractor biplane with Rolls-Royce Buzzard engines. Other Short models were the Rangoon, the Kent and the Singapore II (see the chapter on the Short Brothers). The Blackburn Experimental Iris IV was fitted for experimental purposes with Armstrong Siddeley 800 horse-power Leopard engines. The Supermarine Southampton Mark X was a three-engined tractor biplane, with Armstrong Siddeley Panther engines.
Air Yacht of 1932
Accommodating fifteen passengers, the Supermarine Air Yacht of 1932 was a three-engined civil tractor monoplane. It had Armstrong Siddeley Panther II A engines. The Saunders-Roe Saro Cloud and Cutty Sark of 1932-33 and the Saro London of 1934-35 are described in the chapter on Saunders-Roe Aircraft.
The Supermarine Southampton Mark II of 1933 was a four- or five-seater twin-engined bombing and naval reconnaissance tractor biplane. It originally had Napier Lion Series V engines; later, Rolls-Royce Kestrels were substituted. The Blackburn Perth was a three-engined reconnaissance and coastal patrol tractor biplane, with Rolls-Royce Buzzard engines. The Short Scipio was a four-engined fifteen-passenger commercial tractor biplane. It was fitted with Bristol Jupiter XF.BM engines. The Supermarine Scapa of 1934 was a twin-engined tractor biplane for reconnaissance and bombing, torpedo transport, training and navigational instruction. It had Rolls-Royce Kestrel III MS engines.
In 1934 appeared the Short Singapore III four-engined twin-tandem biplane; it had Rolls-Royce Kestrel engines. In the following year appeared the Short R.6/28 Sarafand (see the chapter on the Short Brothers) and the Short R.24/31 Knuckleduster. The Knuckleduster was a twin-engined high-wing general purpose tractor monoplane fitted with Rolls-Royce Goshawk VIII engines. The Vickers Supermarine Stranraer was a twin-engined eight-seater tractor biplane for reconnaissance, bombing, torpedo transport, training and navigational instruction.
The standard Short Empire Flying Boat of 1936 was a four-engined twenty-four-passenger tractor monoplane, fitted with Bristol Pegasus Xc engines. The Vickers Supermarine Walrus appeared in 1937. This is a single engined six-seater pusher amphibian biplane for naval reconnaissance, fleet spotting, training and photography. The 1938 Short Maia, part of the Short-Mayo composite aircraft, is described in the chapter on the Short-Mayo composite aircraft.
The Short R.2-33 Sunderland is a four-engined tractor monoplane, with Bristol Pegasus XXII engines. It is the military version of the Short Empire Flying Boat.
THE BLACKBURN PERTH of 1933 was a three-engined reconnaissance and coastal patrol tractor biplane. It was fitted with three 825 horse-power Rolls-Royce Buzzard II MS engines. The aircraft’s span was 97 feet, its length 70 feet and its height 25 ft. 5 in. The maximum speed was 115 knots and the maximum range 1,500 sea miles. Service ceiling was 1 1,500 feet.