Flight, July 1926

THE ARMSTRONG-WHITWORTH "ARGOSY”
The Latest Three-Engined Commercial Aeroplane

   THE multi-engined aeroplane is undoubtedly gaining increasing favour as regards commercial work, and, what is more important, its various advantages are being substantiated in actual practice more and more as development progresses. In theory these advantages have always been unquestionable, but there have been, in the past, certain difficulties that have arisen when it came to actual practice - primarily, the problem of perfect balance and control under all conditions, especially when one or other of the engines is cut out.
   These difficulties, however, are today fast disappearing, and we think it can be said that the multi-engined machine is now as practical a proposition as is the single-engined type. This is apparent when it is remembered that the multi-engined machine is now adopted as the standard type for their commercial air services by Imperial Airways, Ltd.
   Last week we were fortunate to be able to witness the trial flights of one of the latest designs in this class of commercial aircraft, i.e., the Armstrong-Whitworth "Argosy," which will be seen in public for the first time at the R.A.F. Display on Saturday. This huge air liner, which has a span of 90 ft. 7 1/2 ins. and has accommodation for 20 passengers, is fitted with three Siddeley "Jaguar" engines, developing a total of nearly 1,200 h.p.
   One of its engines is mounted in the nose of the fuselage, while the remaining two engines are mounted midway between the main planes, one on each side of the fuselage. All three engines drive tractor airscrews. The wing engines, which project slightly beyond the leading edges of the planes, are mounted steel tube nacelles carried by the centre-section interplane struts.
   Upper and lower planes are set a t a dihedral angle, but are not swept back. They are built up in five main sections - centre (the lower unit actually is in two sections, being divided by the fuselage), intermediate and outer. Balanced ailerons are fitted to both top and bottom planes. The large biplane tail, placed comparatively high in relation to the line of thrust, is adjustable as to incidence from the pilot's cockpit.
   The fuselage, of rectangular cross section, is of tubular steel construction (which, by the way, is employed largely throughout the construction of this machine), noteworthy for the fact that welding is conspicuous for its absence. The pilot's cockpit is located high up in the forward portion of the fuselage. Provision is made for two pilots, seated side by side, and seated high up, well in front, as they are, they have an excellent all-round view. Dual control is provided, and the arrangement and equipment of this cockpit is about the best we have had the pleasure of seeing.
   Immediately behind the pilot's cockpit is a space which contains the wireless outfit, while a small window enables one pilot to look back right into the main cabin. Aft of this comes the main passenger cabin, some 30 ft. in length and about 6 ft. high. There is, in fact, an exceptional amount of room for the passengers, who enter the cabin by a door on the port side of the fuselage, and there is no transverse bracing of any kind inside this part of the fuselage.
   The passengers are accommodated in two rows of very comfortable wicker armchairs, with a central gangway. Spacious windows (which can be opened), level with the passengers' heads, extend the entire length of the cabin walls, so that the interior of the cabin is not only very bright and cheerful, but an excellent view of the country below is obtained. Above the seats are racks for hats and light luggage.
   For night flying the cabin is provided with electric light, while on the front wall of the cabin are instruments indicating the speed and altitude of the machine. A lavatory adjoins the main cabin, and another compartment behind is provided for luggage - there being also another space for small packages beneath the pilot's cockpit.
   The total weight of the "Argosy" is nearly 8 tons, of which 2 tons are paying load. Sufficient petrol is carried for a flight of 400 miles. Its top speed is in the neighbourhood of 110 m.p.h. and the normal cruising speed is 90-95 m.p.h.
   The "Argosy" was put through its final trials before going for the Air Ministry tests last week by Capt. F. L. Barnard, the well-known Imperial Airways pilot - who, by the way, is responsible for numerous practical "brain waves" in its design. This huge machine certainly put up an exceptionally good performance. It takes off after a remarkably short run; in fact, it is able to take the air after a run of some 350 yards, and can attain an altitude of 3,000 ft. in five minutes. It flies well and comfortably on only two engines, making right and left turns without difficulty with either wing engine cut out.
   In conclusion, we would like to say from actual experience that it is an exceptionally comfortable machine to fly in there being comparatively little noise, from the engines, inside the cabin, and even with Barnard's remarkable banked turns, we felt entirely at our ease seated in one of the roomy and comfortable chairs. Eventually the "Argosy" will be put into service by Imperial Airways.

Flight, August 1926

THE ARMSTRONG-WHITWORTH "ARGOSY”
Some Constructional Features Described and Illustrated

   THE first of the new three-engined Armstrong-Whitworth "Argosy" passenger-carriers has now been taken over by Imperial Airways, and from what we can gather the machine has created an exceptionally favourable impression at Croydon, where usually critics have no difficulty in discovering features or peculiarities of machines about which to exercise their wit. A brief general description of the "Argosy," with photographs and general arrangement drawings, was published in our issue of July 1, 1926. Last week we had an opportunity of inspecting one of the "Argosies" in course of construction at the Armstrong Whitworth Aircraft Works at Whitley Aerodrome, near Coventry, and the following notes and illustrations are a result of this visit.
   In order to relieve readers of the necessity for turning back to the July 1 issue of FLIGHT, we are reproducing again this week the three-quarter front view of the machine, from which it will be seen that the "Argosy" is a large biplane of orthodox design, fitted with three Armstrong Siddeley Jaguar engines, and mainly characterised by the considerable forward projection of the fuselage in front of the wings. It is not difficult to realise that with the pilot's cockpit arranged immediately behind the central engine the view in practically all directions is quite exceptionally good, although it seems likely that a pilot may feel somewhat strange in attempting to land this machine for the first time, owing to the fact that as the tail is dropped for a three-point landing, the nose of the machine rises quite considerably, so that the pilot may easily get the feeling that the machine is dropping behind him, and we should imagine that at first there may be a tendency on the part of pilots to land this machine a good deal faster than is necessary, partly because of his somewhat unusual position, and also on account of the very low speed at which the machine is able to keep the air. However, it should not take pilots long to become accustomed to the machine, after which we believe they will soon form a very high opinion of its flying qualities as well as the excellent lay-out of the pilot's cockpit. Constructionally the Armstrong-Whitworth "Argosy" is characterised by a steel tube fuselage and wooden wings, although the centre sections have steel tube spars, for reasons connected with the arrangement of the two wing engines, etc. The fuselage is a plain rectangular section structure, with steel tube longerons and struts braced by tie-rods. The attachment of struts to longerons is of the type shown in one of our sketches, and a feature of the bracing is that the longerons are kept of fairly light gauge and with the main fuselage struts placed relatively wide apart. In order to steady the longerons between supports, hinged auxiliary struts are fitted half-way between the main struts, the diagonal bracing running through the centre of these hinged struts. The arrangement is similar in principle, although different in detail, to that employed in the wing bracing of certain early types of Spad biplane, and still used on almost all Savoia flying-boats. One of our photographs shows an external view of a portion of the cabin in which the arrangement of main and auxiliary struts is shown.
   Ball and socket joints are used fairly extensively in the construction of the "Argosy" and one such joint occurs at the point of attachment of the lower wing spars to the fuselage. This is illustrated by a sketch. Another ball and socket joint occurs at the point where the divided wheel axle meets the inverted pyramid cabane, and is illustrated in a photograph. As regards its shock absorbing portion, the "Argosy" shows the typical large diameter large section coil spring with Oleo damping gear, which has been a feature of Armstrong-Whitworth machines for a number of years. In spite of its size only two wheels are used on the "Argosy," these being Palmer wheels of very large diameter.
   It is quite an impressive sight to stand at the entrance door to the cabin of the "Argosy," and looking along it, the cabin being more of the size and proportions of a tramcar than typical of a flying machine, and. to the engineer at any rate, the first question which comes to mind in looking at this large cabin is, how the weight of all these passengers is transferred to the tubular structure. Fortunately the machine inspected at Coventry had not yet been covered in as regards this part of the structure, and so it was possible to discover the details of what may be termed the cabin suspension. This is in the form of transverse members which stop short just inside the main steel tube structure, to which it is attached by steel brackets sloping down at an angle, as shown in one of our sketches. Longitudinal stringers running between the transverse beams of the floor serve to support the three-ply which forms the floor boards, and thus the weight of the cabin and its occupants is taken direct on to the vertical members of the fuselage structure. The cabin itself is not a complete box of three-ply as is the case, for instance, in the De Havilland "Hercules." It consists mainly of the floor and of a fairly shallow three-ply skirting board rising to the height of a foot or so from the floorboards and serving to protect the fuselage structure against accidental kicks. The cabin walls are for the rest formed of fabric, but a shallow box runs along some distance up the sides and serves as a support for the windows of the cabin.
   The wing construction is on normal lines, but it is worthy of note that in the out-board portions the main spars, which are of spruce, are spindled out to an I-section. At a time when spruce in such lengths is difficult to obtain in good quality, it is perhaps significant that the firm should have insisted upon this somewhat expensive form of spar in preference to taking the line of least resistance and using built-up box section spars. In the centre sections, where local loads are apt to be somewhat heavy, the spars are in the form of circular section steel tubes of generous proportions, and to these are attached the engine mounting struts, the undercarriage struts, and, in the case of the top centre section, the two large gravity petrol tanks.
   A type of engine mounting of somewhat unusual form has been adopted in the "Argosy." The "saucepan" which forms part of all Armstrong Siddeley Jaguar engines, is bolted in the "Argosy" to a sheet steel engine plate which is in turn supported on four short cantilever beams joining the fuselage structure at the four corners. The necessary rigidity of this engine structure is provided by the particular design of the four cantilever beams, which are built up from sheet steel corrugated in a manner shown in our illustrations. These four beams provide their own bracing, so that there is a total absence of any diagonal members, with a consequent gain in the ease with which the back of the engine can be reached.

Flight, March 1929

NEW ARMSTRONG-WHITWORTH "ARGOSIES"
Many Improvements in 1929 Types

   FOR use on the first stage of the new England-India air route which is to come into operation this spring, Armstrong-Whitworth "Argosies" of improved design are being produced, and are now nearing completion at the Whitley works. We are able to give this week photographs of some of the new features of these machines.
   A very interesting innovation is the use of servo-rudders for the lateral controls. The angle of the servo-rudder can be varied by the pilot, and in spite of small forces on the control stick considerable forces may be exerted on the ailerons. Hitherto servo-rudders have been used mainly in connection with the main rudders of an aircraft, and the application of this principle to ailerons is distinctly interesting.
   The use of geared "Jaguar" engines on the new "Argosies" should result in a considerable improvement. This will be particularly noticeable in the case of the take-off, where the extra propeller efficiency of the slower-running airscrews should shorten the run to take off considerably, or alternatively enable the machine to take off with a greater load. The economy at cruising speed will probably also be better, and as it seems likely that the new cowling, with which experiments have been carried out with considerable success, will be fitted on the "Argosies," the overall efficiency of the machine should improve to an extent which appeared outside the sphere of practical realisation but a few years ago. In fact, it is to be expected that the new "Argosies" will come much nearer to "paying their way" than has any three-engined machine of the same power. As the "Jaguar" is reliable in service, the new machines should combine in a remarkable degree the freedom from forced landings, coupled with good operational economy.
   The mounting of the outboard "Jaguar" in the new machines will differ from that previously used, and one of the photographs shows the framework of the mounting. The skeleton of the former indicates that the cowling behind the engine is to be very complete, and used in conjunction with the "ring" should reduce the drag of the outboard engines a great deal. The mounting of the fuselage engine is shown in another photograph. The tubular framework will carry a fireproof bulkhead and a quickly-detachable engine mounting.
   The petrol capacity of the new "Argosies" will be increased to 360 gallons, the fuel being carried in two tanks (one of which is shown in a photograph) of 180 gallons capacity each, slung under the top plane. A petrol gauge will be fitted in the front of each tank so that the pilot can see at any time how much petrol is left. The capacity is estimated to be sufficient for a range of 500 miles.
   The wide-track undercarriage unit is also shown in a photograph. The wheels and tyres are made by the Dunlop Company, and springing is by oil-damped buffers.

Flight, June 1929

BRITISH AIRCRAFT AT OLYMPIA

SIR W.G.ARMSTRONG WHITWORTH AIRCRAFT, LTD.

   THE exhibits of A. V. Roe and Co., Ltd., will, at Olympia, be staged on the same stand as those of Sir W. G. Armstrong Whitworth Aircraft, Ltd., the two firms being now combined. For the sake of alphabetical order, however, the two firms will be dealt with as if they were still entirely separate concerns.
   Sir W. G. Armstrong Whitworth Aircraft, Ltd., will exhibit three complete aircraft: "The "Argosy" commercial triple-engined passenger machine, the "Atlas" Army Co-operation biplane, and the A.W. XIV single-seater fighter. All three machines, it is almost superfluous to state, are fitted with Armstrong-Siddeley "Jaguar" engines.

   The Armstrong Whitworth "Argosy" has been in regular use on the air routes of Imperial Airways, Ltd., for a long period, and has given excellent service both as regards reliability and what the Germans term Rentabilitat, i.e., commercial economy. In fact, it may probably be said that the "Argosy" is one of the most economical commercial aeroplanes in service at the present time, bearing in mind that the type is fitted with three engines and therefore should be, theoretically at least, immune from forced landings away from an aerodrome, owing to its ability to continue flight with one of its three engines out of action. The earlier "Argosies" were fitted with direct-drive "Jaguar" engines. The latest types, delivered to Imperial Airways this year, incorporate a number of improvements, among which not the least important is the fitting of geared instead of direct-drive "Jaguars." Not only does this mean a better propeller efficiency, and, therefore, greater thrust horse-power, but also the ability to carry a greater pay load per horsepower, or, conversely, a greater percentage of power in reserve. Put in another way, with geared engines the ability to continue flight with one of the three engines stopped is improved, and the likelihood of a forced landing should, in the new "Argosies," be reduced almost to vanishing point.
   What adds further to the efficiency of the latest type of "Argosy" is the fitting of "Townend" rings over the engines. This is not the place for a detailed description of this new piece of equipment, but briefly it may be explained that the "Townend ring" is a metal ring, sometimes of aerofoil section and sometimes just of plain sheet metal bent to a camber, fitted around the outside of the cylinder heads of a radial engine. In a measure the "Townend ring" acts in a manner similar to that of the Handley Page automatic wing tip slot in that it causes the air flowing past the engine to converge upon and follow the surfaces of the fuselage or nacelle behind the engine, instead of breaking away to form vortices, as the disturbed air behind a radial engine is otherwise apt to do. This is not a very scientific, nor, we fear, very accurate, explanation, but it will, at least, serve to indicate the raison d'etre of the "Townend ring" which will be found on several of the aircraft exhibited at Olympia this year.
   In the case of the "Argosy," for example, the effect of fitting the "Townend ring" is to reduce by a very large percentage the drag of three radial air-cooled engines, which at once means a greater reserve of power, or surplus of "power available" over "power required." Advantage can, of course, be taken of this in two ways: By saving fuel for a given journey or, by running at the same thrust horsepower, to reduce the duration of the journey by adopting a higher cruising speed. Looked at from any point of view, the fitting of the "Townend ring" spells greater efficiency.
   Other features marking improvement in design are incorporated in the latest type of "Argosy." For example, the ailerons are no longer operated by the pilot direct. Mounted behind the trailing edge of the lower wings, one on each side, is a servo-rudder whose surface is in a vertical plane. These servo-rudders are connected up to the ailerons in such a manner that, when the pilot operates the servo-rudders in one direction, the air forces on them are such as to raise the ailerons on one side and depress those on the other. The direction of operation of the servo-rudders has been so arranged that if the aircraft begins to sideslip, the air forces on the servo-rudders at once cause these to move in the direction desired for getting the aircraft out of the sideslip. This, of course, is a function of usefulness which the ordinary balanced aileron cannot perform.
   Altogether the new "Argosy" is an uncommonly interesting machine, and will be found well worth a visit and inspection. Structurally, the machine to be shown at Olympia will not be found to differ greatly from the old models, which are already well known to readers of FLIGHT. The fuselage is a steel tube structure with bolted joints, while the wings have box spars of corrugated steel strip construction, and steel wing ribs.
   The "Argosy" has a saloon with seating accommodation for 20 passengers, and in this connection it is of interest to note that when the machine carries fuel for a flight of 3 1/2 hours' duration, the pay load is 5,000 lbs. In addition to the saloon, the "Argosy" has two large luggage compartments, one in front of the saloon, i.e., below the pilot's cockpit, and a larger one aft of the saloon.
   The petrol tanks have a capacity of 360 gallons, and are housed in the top plane, whence they provide direct-gravity feed to the engines. As the "Argosy" cruises at a speed of 95 m.p.h. on a fuel consumption of 65 gallons per hour, this tankage gives an endurance of about 5 1/2 hours. With any one of the three engines stopped the "Argosy" will fly easily on the remaining two at an altitude of 2,000 ft.
   The main dimensions of the "Argosy" are: Length o.a., 67 ft.; wing span, 90 ft. 4 in.; wing chord (top), 12 ft.; wing chord (bottom), 10 ft.; overall height, 20 ft.; wing area, 1,874 sq. ft.
   The tare weight is 12,090 lbs., and the gross weight 19,200 lbs. The load carried may be divided as follows :- Fuel and oil, 2,110 lbs. Paying load, 5,000 lbs. Performance figures are not available.
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