Flight, January 1927

THE SHORT "CALCUTTA" FLYING-BOAT
Three Bristol "Jupiter" Engines

   As first announced in FLIGHT last week, two new flying-boats are now in course of construction for Imperial Airways at the Rochester works of Short Brothers. At the moment it is not possible to give very full details of these machines, nor to state precisely where they are to be used, but we have obtained permission to publish herewith the general arrangement drawings, from which a good idea of the lines of these machines may be formed. At the same time it is possible to give a brief general description of the main features, a more detailed reference being reserved for some future occasion, when the constructional work on the new boats is somewhat more advanced.
   As we on FLIGHT have for very many years been firm believers in, and have made ourselves the champions of, the seaplane as a factor in Empire communications, it is naturally with very considerable satisfaction that we are now able to place on record the fact that at last Imperial Airways appear to be seriously contemplating the organisation of seaplane routes. Hitherto the only route of this kind has been that between Southampton and the Channel Islands, and a service operated once a week over a route where, in the very nature of things, there cannot be very much traffic is scarcely in keeping with the spirit of British Empire aviation. The solitary flying-boat used on this route has been spending nearly the whole of its time "sitting" on the Itchen, a familiar landmark to those who regularly use the floating bridge between Southampton and Woolston. Doubtless this use of a flying-boat may have provided data as to weathering qualities, hull soakage, etc., but it is scarcely the way to progress in Empire seaplane communications.
   Readers of FLIGHT will be familiar with the pioneer work on Duralumin construction which Short Brothers have been carrying out since the end of the war. Commencing with the famous "Silver Streak," exhibited at the post-war Olympia aero show, this firm has continued to develop a farm of construction totally different, as far as we are aware, from any used by any other firm in the world. Although detail improvements have naturally been evolved during the intervening years, the system remains substantially the same as that used in the "Silver Streak," and this whether the job is a flying-boat hull or an aeroplane fuselage. Without going into too great detail, it may be said that this system consists fundamentally in a stress-resisting "skin" or planking, stiffened against compression loads by longitudinal stringers, which do not, however, run through from nose to stern, as is the case with most other forms of construction, but are interrupted at each of the "rings" or formers that give the fuselage or boat hull its cross-sectional shape. The actual "skin" is in the form of fairly short panels, riveted at each end to the flanges of the "rings" or formers, and in certain localities to the fore and aft members as well. In a fuselage of approximately streamline form this type of construction is simplicity itself, as the rings are of simple shape and the panels of the skin require no "beating." In a shape like a flying-boat hull, where the change from almost flat sides to curved chine and thence to curved planing bottom, calls for reversed curvatures, the problem is not quite so simple, but in the hull of the new "Calcutta" the lines have been simplified to some extent, so that the amount of panel beating required is relatively small. Thus even in a comparatively difficult shape like a flying-boat hull, the Short system of metal construction has a very great deal to recommend it from the point of view of rapid production.
   In the matter of wing construction, also, Short Brothers have been doing some very interesting research and experimental work, with the result that wing spars of Duralumin, of the crinkled strip type, can now be produced rapidly and comparatively cheaply. The plant for producing these spars was described and illustrated in FLIGHT of August 26, 1926, as was also a representative spar (that of the little Short "Mussel" light seaplane). If we add that recently Short Brothers have installed at their Rochester works an extensive plant for anodic treatment of Duralumin to protect it against corrosion, and recall that this firm has its own water tank in which models of hulls, floats, etc., are tested, it will be realized that few firms could be better equipped to tackle the not easy task of producing all-metal flying boats for the Empire air routes.
   As regards the Short "Calcutta" flying-boat, two of which are now coming through the works, the general arrangement drawings will show this to be a large flying-boat of modern design in the matter of hull shape, surmounted by a fairly normal wing structure, and with a somewhat unusual arrangement of its engines. These will be Bristol "Jupiters," and will, it will be seen, be enclosed in streamline nacelles. The front elevation shows the "Calcutta" to be of very clean lines for a three-engined machine. The hull is of the two-step type, and has been developed from extensive work on models in the tank. Tests indicate that the new hull should be of very low resistance, very clean running, and have no tendency to "porpoise." Its constructional detail features may not be described at the moment, but the construction generally follows that of previous Short metal hulls, with such minor improvements as experience has shown to be desirable. Among the advantages of the all-metal hull perhaps one of the most important is that of freedom from water soakage, which may be a serious item in a wooden hull and may amount in some cases to several hundred pounds. Furthermore, it is claimed that the Short form of hull construction actually gives a structure which is lighter, size for size and strength for strength, than a wooden hull, quite apart from the question of water soakage. Long experience with metal hulls and metal floats has shown that the corrosion problems are not as serious as was at one time thought to be the case, and the makers of the "Calcutta" are confident that with reasonable care a Duralumin hull will last for many years, if properly treated during manufacture and subsequently during use.
   The passenger accommodation of the "Calcutta" will be unusually comfortable, and owing to the placing of the lower plane above the hull, and the provision of large windows, the view from the cabin will be practically unobstructed laterally and diagonally downwards. The 15 seats are arranged in three rows of 5 each, and access to the cabin will be by a hatchway that can be reached from a landing stage or from a motor-boat. The cabin is to be heated from the engine exhaust pipes, and a carefully considered ventilation arrangement is provided. Provision is to be made for a small bar in the cabin where light refreshments will be obtainable, this being considered necessary in view of the fact that the machine is designed for a range of over 500 miles. Aft of the cabin is a lavatory, and behind that again a large luggage compartment, which has a separate hatch for loading and unloading.
   The cockpit for the two pilots is in the nose of the hull, with two seats side by side and dual controls. There is ample room for one pilot to step down to the wireless compartment, which is on the starboard side, immediately aft of the pilot's cockpit. The machine is to be equipped with a particularly complete wireless outfit, including transmitting and receiving apparatus, direction-finding outfit of the Bellini-Tosi type, navigation equipment, &c. The control cables to rudder, elevator, &c, run along the top of the hull in a duct so as to be entirely out of the way of the passengers.
   The wing structure is, as already said, of the all-metal type, with the exception of the covering, which is fabric. The spars of corrugated strip construction, and the flanges are laminated so that where local concentrated loads occur they are given an adequate thickness. In order to avoid too sudden changes of section, the laminations have their ends forked and the edges bevelled. The ribs are Duralumin tubes arranged in the form of lattices. Ailerons are fitted to the top plane only.
   The engine installation is shown in the general arrangement drawings. Inside the cowling of the central engine is a Bristol gas starter, which also drives the bilge pump, and, in an emergency, the general purpose generator, so that should the machine be compelled to alight on the sea it would still be able to send out wireless messages. The engines are provided with exhaust ring collectors and long tail pipes in order to reduce as much as possible the noise during flight. The petrol tanks, of which there are two, are housed in the top plane, whence the fuel is supplied by gravity feed to the three engines. Apart from the advantage which such a simple petrol system has in doing away with the necessity for petrol pumps, pressure gauges, etc., with liability to failure and breakdown, the placing of the tanks in the top plane, as far as possible removed from the hull, should make it possible for the passengers to smoke with perfect safety, the more so as the hull itself is of all-metal construction. What this will mean on a long flight of some five hours' duration can readily be imagined.
   From experience with previous machines of somewhat similar type it is confidently expected that the Short "Calcutta" will be very stable, so that the pilot will not be fatigued by flights of long duration. It will be seen that a servo rudder is to be fitted. This rudder is a comparatively new invention, and has but recently been introduced on aircraft in this country. Several of the newer large machines now coming along are, however, to be so equipped, and as far as present experience goes the servo rudder enables a pilot to deal with very large rudder loads indeed. The action of the servo rudder is simple enough. The pilot operates the servo rudder, which in turn operates the main rudder.
   We do not know who first thought of the servo rudder for aircraft, but in Germany Herr Anton Flettner, inventor of the Flettner "rotor," patented such servo rudders for ships several years ago, and it appears probable that he also is the inventor of the servo rudder for aircraft, although it is gathered that considerable research on its use has been carried out at the Royal Aircraft Establishment at Farnborough. In the Short "Calcutta" a monoplane tail and single rudder is used, which is rather unusual for a large three-engined machine. We understand, however, that there is a probability of two smaller rudders being mounted above the tail plane, which may be used to correct any turning moment due to the failure of one of the wing engines.
   The main dimensions and areas of the Short "Calcutta" are indicated on the general arrangement drawings. These may be supplemented by the following brief specification: Weight of machine fully loaded, 19,600 lbs. (8,920 kgs.). Paying load, 3,540 lbs. (1,610 kgs.). Maximum speed fully loaded, 105 knots = 121 m.p.h. (195 km./h.). Landing speed fully loaded, 46 knots = 53 m.p.h. (85-5 km./h.). Maximum range, 545 miles (878 km.).

Flight, February 1928

THE SHORT "CALCUTTA”
Britain's First All-Metal Commercial Flying-Boat

   LAUNCHED at Rochester on Monday of last week, as recorded in FLIGHT, the Short "Calcutta" has been moored in the Medway off the Short works for several days, owing to the gales which prevented bringing her up the slipway and into the works. While this meant a great deal of anxiety on the part of the staff, because of the possibility of the machine dragging her moorings, it also gave an opportunity of testing the seaworthiness qualities of the new machine in an extremely strong wind. Let it be said at once that the "Calcutta" proved equal to the test. Rolling gently from side to side in the strong gusty wind, she rode as easily as a yacht, and in point of fact when one was aboard, as the writer had an opportunity of being for some two hours last week, one had very strongly the impression that one was aboard a yacht at anchor. In the cabin there was quiet, with but the slap-slap of the waves against the metal hull, but a visit "on deck" for the purpose of examining in some detail the mounting and cowling of the central engine very quickly brought home to one the force of the gale. So strong was this that it was necessary, in order to keep from getting blown in, to clutch hold of bracing wires, struts and anything else that offered a hand hold. The wind whistled in wires and struts, the rain beat down unmercifully on the wing fabric and drummed on it and on the metal roof of the cabin. Yet the machine appeared perfectly at home and in her element. If she is as steady in the air she will be a wonderful craft, and there is no reason to doubt that she will.
   Driven below by the weather, we made a tour of inspection of the hull, and a most interesting tour it proved. "Ship-shape and Bristol fashion " is an expression that inevitably comes to mind, and shipshape she certainly was, below as above, the "Bristol" fashion being, perhaps, more noticeable on deck, where the three "Jupiter IX" geared engines in their streamline nacelles gave promise of good air performance. But to return below decks.
   The cabin of the Short "Calcutta" is a very roomy affair. There is about 6 ft. headroom, and the cabin is long and wide and gives an airy impression in spite of the fact that to get 16 seats arranged in the space available there is naturally no room wasted anywhere. Actually, the cabin has seating accommodation for 15 passengers, the sixteenth seat being for the steward who presides over a small galley and buffet just aft of the cabin. In front there is a sliding door communicating with the wireless compartment, which in turn leads to the pilot's cockpit. Aft of the cabin, and on the starboard side, opposite the galley, is a very roomy lavatory with tip-up wash basin. Aft of that again, and communicating with the cabin by a hinged door, is the luggage compartment, which is, as a matter of fact, the entire aft portion of the hull. And amazingly roomy it is with the total absence of any bracing members. Nowhere does one, perhaps, see to better advantage the special type of hull construction developed by Shorts. One can walk right up in the extreme stern to the rudder post (not that it would be advisable to do so during flight, as it might upset the trim), and although the luggage to be carried will naturally be collected and secured as close to the cabin as possible, it is obvious that, should the machine ever be used by a relatively few passengers for a protracted cruise, it would be extremely easy to fit up this aft portion of the hull with bunks, so that one could sleep comfortably on board. The fact that all petrol is some 15 ft. or so away from the cabin roof makes it perfectly safe to smoke in the hull, and half-a-dozen people could live very comfortably on board for long periods.
   The cabin chairs are built of Duralumin tubes, and the extent to which it has been possible to reduce weight in this part of the equipment may be realised when we point out that the weight of a chair frame (without upholstery) is only 2 lbs.! The chairs are arranged with a single row down the port side and a double row down the starboard side, the gangway between them being thus slightly off centre. The upholstery is in the form of air cushions, and another neat idea is that these cushions have been designed as lifebelts, being easily detached from the chairs and put on, a strap being provided for keeping them in place. Thus no extra weight of special lifebelts is incurred.
   Large glass port holes of oval shape give plenty of light in the cabin. Even with the machine moored, and thus with the lower plane fairly low over the water, the cabin is quite light. In flight, the amount of light which comes through the windows is naturally even greater, and the fact that the port holes are below the level of the lower wing gives the passengers an unobstructed view outward and downward.
   The pilot's cockpit is very roomy, and as it is far forward in the hull, the view is particularly good. There are two seats, side by side, the port one being the pilot's, while the starboard seat has removable controls in front of it. Normally, the navigator will be in his wireless cabin, where a seat, table, map shelf, instrument lockers, etc., give comfort for working out a position as well as for sending and receiving messages. The machine is equipped with a Marconi AD.8 set, the range of the transmitting apparatus from the machine to a ground station being, under average conditions, 300-400 miles for C.W. telegraphy, 200-250 miles for telephony, and 240-280 miles for Tonic Train telegraphy. For use when the machine is on the sea, there is an emergency aerial on a telescopic mast attached to the upper wing. In addition to the normal radio equipment, the "Calcutta" carries Bellini-Tosi loops for purposes of direction-finding radio.
   Two hatchways give access to the cabin and luggage compartment respectively, the cabin hatchway being on the port side, forward of the wings, and forming, when open, steps by means of which the passengers can easily get into and out of the cabin. The aft hatchway would also serve as an emergency exit in case, through any mishap, the forward one should be inaccessible.
   For transporting the "Calcutta" on land, a special beaching chassis has been designed, which incorporates two large aero wheels, the struts of which have quick-release attachments to the chine tubes and lower plane spar fittings. To prevent the tubes from sinking, they are provided with bladders, and the outside tubes have, in addition, a special form of quick-locking device so as to facilitate assembly while the machine is on the water. The two inner chassis struts and the halves of the outer chassis struts are permanently bolted to the wheel. The upper ends of the outer struts, however, are separate units, and when putting on the chassis, the two pins of the inner struts are secured first. Then the short upper ends of the outer struts are secured to the spar fittings, and the whole, is secured by the special joints in the outer struts.
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Specification

   As the general arrangement drawings of the Short "Calcutta" were published in a recent issue of FLIGHT we do not propose to reprint them here.
   The main dimensions and areas are: Span of upper plane, 93 ft. (28-35 m.); span of lower plane, 76 ft. 6 in. (23-15 m.); total wing area, including ailerons, 1,825 sq. ft. (170 m2); length, o.a., including servo rudder, 64 ft. 9 in. (19-75 m.); wing chord, 11 ft. 6 in. (3-51 m.). Area of ailerons (total), 150 sq. ft. (13-95 m2); area of tail plane, 112sq. ft. (10-4 m2); area of elevators, 105 sq. ft. (9-76 m.2); area of fin, 56 sq. ft. (5-2 m.2); area of main rudder, 49 sq.ft. (4-55 m2) , area of servo rudder, 7-6 sq. ft. (0-706 m2). Weight of machine empty, 12,600 lb (5,730 kg.); weight fully loaded, 20,200 lb. (9,185 kg.); weight available for load, 7,600 lb. (3,455 kg). The available load may be composed as follows: A crew of three, with baggage, food and water, 768 lb. (319 kg.), and 320 gallons of petrol and 30 gallons of oil, 2,730 lb. (1,241 kg.). Wireless, electrical equipment, instruments, fire extinguishers, cooking and marine equipment account for a weight of 562 lb. (255 kg.), leaving a pay load of 3,540 1b. (1,610 kg.), which is equivalent to 15 passengers with baggage, food and water (at 236 lb. per head). The fuel and oil capacity given does not represent the maximum, as the tanks have been designed to hold 480 gallons of petrol and 45 gallons of oil, so that by sacrificing a certain amount of pay load the range can be correspondingly increased. With the quantities mentioned, the range is 5 1/2 hours, or 500 miles (805 km.), and with full tanks and a smaller pay load the duration is 8-2 hours, and the range 740 miles (1,190 km). The wing loading is 11-05 lb./sq. ft. (54 kg./m.2), and the power loading (at full power) 12-8 lb./h.p. (5-83 kg./h.p.).

Performance

   Although the official performance tests of the "Calcutta" have not yet been carried out, it may be of interest to give the estimated performances. The top speed at sea level is 120 m.p.h. (193 km./h.), and the cruising speed 100 m.p.h. (161 km./h.). The landing speed is 57-5 m.p.h. (93 km./h.). Rate of climb at ground level is 800 ft. /min. (244 m./min.). The service ceiling is 10,000 ft. (3,050 m). The "Wing Power" is 0-863 h.p. per sq. ft. = 9-26 h.p./m2 As the top speed is 193 km. /h., the Everting "High-speed Figure" (metric) is 14, which is an extremely good value for a three-engined flying-boat. The Everting "Distance Figure" at top speed is 4-2, which is also a high value for a machine of this type, As this refers to the top speed, it is not, of course, an optimum value, but as we have no information relating to the power at which the machine cruises most economically, it is not possible to give the maximum value of the "Distance Figure." That it is well above the average seems more than probable.

Flight, July 1928

THE SHORT "CALCUTTA”
Three Bristol "Jupiter IX" Engines

   THE first British all-metal commercial flying-boat to be put in service is the "Calcutta," designed and built by Short Brothers, of Rochester, who have devoted a great deal of work and research to the development of all-metal, and more particularly to all-Duralumin, construction during the last five or six years. The "Calcutta" is a good deal like the Short "Singapore" on which Sir Alan Cobham recently completed his flight around Africa, but with passenger cabin accommodation and three engines instead of two.
   The Boat Hull. - Built entirely of Duralumin, the hull is of the two-step type, but with the rear step faired in so as to reduce resistance. The planing bottom has a fairly pronounced Vee so as to reduce shock on alighting. The construction is the special type developed by Short Brothers, in which the outer plating is in small panels attached to transverse formers by riveting. The fore-and-aft members or stringers do not run through, but are interrupted at the transverse formers and bulkheads.
   The cabin has seating accommodation for 15 passengers, and aft of the cabin is on one side the lavatory with folding wash basin and on the other a buffet and an oil cooker for the preparation of meals during flight. Ahead of the cabin is the pilot's cockpit, with two seats side by side. The wireless compartment is comfortable, with seat, table, shelves, etc., and the machine is equipped for sending and receiving wireless messages over considerable distances.
   Wings. - Except for the fabric covering, the wings are of all-metal construction, Duralumin being the material chiefly used, with a few steel fittings at highly-stressed points. The spars are built up of corrugated webs and flanges of Duralumin, laminated according to the local strength required at any point, and the ribs are lattices of Duralumin tube. Ailerons are fitted to top plane only. Wing tip floats, also of Duralumin construction, give lateral stability on the water.
   Tail. - Duralumin construction with fabric covering. The rudder has a horn balance and a small Servo rudder as well, making the machine very light on the controls.
   Engine Installation. - The three "Jupiter" engines are mounted in the gap between wings. The petrol tanks are in the top plane, and there is no petrol in the hull.

Flight, October 1930

SHORT "CALCUTTA"
(Service Type)

   THE recent history of flying boats produced by Short Brothers of Rochester has shown a rather remarkable mutual effect of service and commercial types. First there was the "Singapore I" service type, with two Rolls-Royce "Condor" engines. This machine was later lent to Sir Alan Cobham for a civilian tour of Africa. As a result of the experience with the "Singapore," the "Calcutta" civil type (three "Jupiters") came into being and proved a great success. Then came the “Singapore II" service type with four Rolls-Royce "F" engines. And now has been launched the "Calcutta" service type with three Bristol "Jupiter IX F" engines, shown in the photographs on this page.
   The "family resemblance" is quite unmistakable, and the service type of "Calcutta" does not differ fundamentally from the civilian version used by Imperial Airways, Ltd., on stages of the London-India route. The internal arrangements are, of course, quite different, the service type of machine being an open sea reconnaissance flying boat. Other alterations as compared with the civilian machine are the gunners' cockpits in the nose of the hull and projecting from the hull sides aft of the wings.

Flight, November 1932

British Aircraft

Short Brothers, Ltd.
Rochester, Kent

   LONG before aeroplanes came into being Short Brothers were aeronautical engineers in that in 1897 they had established their own balloon factory. When the work of Wright Brothers and other experimenters began to become known Short Brothers were quick to realise the tremendous possibilities of heavier-than-air craft, and at once set to work to design and construct. Since those early days (1909 or so) they have never looked back, and to-day Short Brothers are among the most esteemed of British aircraft firms. Twin-float seaplanes were among the first Short machines to be constructed, and ever since then the firm has been closely connected with the development of marine aircraft. Of recent years these have been mostly of the flying-boat type, although other types have also been produced.
   The first commercial flying-boat to make the name of Short famous was the "Calcutta", which was designed and built for work on the Mediterranean section of the Imperial Airways route to Egypt and Cape Town. The "Calcutta" (three Bristol Jupiter XI.F engines) is a 16-passenger all-metal flying-boat, with a hull built of Duralumin and biplane wings having Duralumin spars and ribs, with fabric covering. The crew consists of three, with dual controls in the cockpit.
   The principal "Calcutta" data are :-
   Length o.a. 66 ft. 0 in. (20,1 m.)
   Wing span 93 ft. 0 in. (28,3 m.)
   Wing area 1,825 sq. ft. (170 m'.)
   Tare weight 13,845 lb. (6 300 kg.)
   Fuel 4,050 lb. (1 840 kg.)
   Pay load and crew 4,605 lb. (2 090 kg.)
   Maximum weight 22,500 lb. (10 230 kg.)
   Maximum speed 118 m.p.h. (190 km./h.)
   Cruising speed 97 m.p.h. (156 km./h.)
   Range 650 miles (1 046 km.)