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The Westland Wallace (Flight May 4th 1933)

The Westland Wallace 1933

THE WESTLAND " WALLACE " : This three-quarter front view shows how closely the service machine resembles
the version used on the Houston-Mount Everest flight. The engine is a Bristol " Pegasus."

Originally designed as a private venture known as the " P.V.6 " the version used in the British Royal Air Force has been given the name " Wallace," and is of the class known as " General Purpose." As the class title indicates, machines must be adaptable to a great variety of purposes, and the demands made are by no means easy to meet, as will be realised when we point out that "G.P." machines must have a flight range of at least 5 hr., must be ca pable of carrying a fairly heavy bomb load, must be equipped for taking photographs and for radio communication with ground troops and guns, must carry oxygen apparatus for high flying, must carry fixed and movable machine guns, and must be fitted with dual flying controls. Yet in spite of all these demands the "G.P." machine must have a good performance. Thus, somewhat paradoxically, the design of a general-purpose aeroplane has become very much a specialised task. The Westland Aircraft Works of Yeovil have had exceptional experience in the production of "G.P." machines. and it may be recalled that the "Wapiti" (Bristol "Jupiter" ) has been built in very great numbers (more than 500) for the R.A.F., the R.A.A.F., and the S.A.A.F. The" Wallace " incorporates everything that was found completely satisfactory in the" Wapiti," and a number of improvements besides.

How great an improvement on the "Wapiti" is the "Wallace " can best be indicated by a few figures. The "Wapiti" has a tare weight of 3,180 lb while the weight of the " Wallace " is 3,520 lb. The gross weights are 5300 lb. and 5,750 lb. respectively. The fuel and oil carried is the same in both cases, i.e 105 gallons of petrol and 10 gallons of oil, so that the useful loads (crew. military load and equipment) are comparable. That of the "Wapiti" is 1,213 lb., while the " Wallace " load is 1,323 lb. In other words, the " Wallace " carries about 100 lb. more than the " Wapiti." Thanks to the extra

power of the Bristol " Pegasus" M3 engine (555 b.h.p. as compared with the 460 b.h.p. of the " Jupiter ':.') and the improved aerodynamic design of the" Wallace;" the latest machine has a very much better performance. For example,the maximum speed of the" Wallace " at 5,000 ft. is 161 m.p.h., while that of the " Wapiti " is 139 m.p.h. at the same height. In the matter of climb also, the " Wallace " is very superior. For instance, the time to 10,000 ft . is 8.8 min. The "Wapiti" takes 11.5 min. The service ceiling of the "Wallace" is 22,800 ft. That of the "Wapiti" 19,300 ft.

The photographs, general arrangement drawings, etc., which we publish herewith show the general lines of the "Wallace." It will be seen that there is considerable similarity between it and the " Wapiti," but dimensionally the two differ a good deal. The only thing which they have in common is the wing span and area. The former is 46 ft. 5 in. and the latter 488 sq. ft.

Structurally also the "Wallace" follows tile principle and methods which have been found so successful in the "Wapiti" The machine is an all-metal biplane, and can be supplied equipped with a number of alternative power plants, such as the Bristol " Pegasus, "the Armstrong Siddeley" Jaguar " or " Panther," or the Gnome -Rhone" :Mistral." The Royal Air Force version is, as already stated, fitted with the Bristol " Pegasus "M3.

The fuselage is constructed in the familiar Westland manner, of tubes of approximately square section. Joints <Ire made by flat pitch plates and tubular steel rivets. In the forward portion of the fuselage the structure is of the rigid type, with bracing formed by diagonal tubes, while the rear fuselage portion is braced by swaged rods. This type of construction is extremely simple. and has been found very easy to maintain and repair. The biplane wings are of the staggered, two-bay arrangement, and are of equal span and chord. They have corrugated steel strip spars of box section, and are detachable at top centre-section and fuselage. Ailerons of the Frise type are fitted to upper and lower planes, and Handley Page automatic wing-tip slots are fitted to the upper plane.

The inter-plane struts are of streamline section, and built up steel construction. External bracing is by RAF wire. The tail organs are of duralumin construction. The covering of the front portion of the fuselage is of aluminium, arranged in the form of easily detachable panels. In the "Wapiti" this covering was corrugated for stiffness, but in the "Wallace" a .slightly heavier gauge has been used, and the corrugations are omitted. The rear portion of the fuselage is covered with doped fabric, as is also the wing covering. An undercarriage of the "split" type is fitted, and from some of the views it will be seen that this is of relatively narrow track. It has, however, been found that the stability on the ground is sufficient. The telescopic legs of the undercarriage are of a special Westland patented type, and possess great shock absorbing qualities. The undercarriage wheels are provided with brakes, and these are so arranged that they can be used together or independently. They are operated by toe pedals on the rudder bar, and can be locked on by a hand brake lever in the cockpit. A reduction of 50 per cent in landing run is gained by applying the brakes simultaneously.

The wheels are partly enclosed in "spats." A low-pressure castoring tail wheel takes the place of the old type of tail skid, and in conjunction with the wheel brakes makes manoeuvring on the ground quite easy, and avoids the need for a separate tail trolley.

The "Wallace" can also be produced as a twin-float seaplane, and the fittings on the fuselage are arranged to take either wheel or float type. Skis can also be fitted if the machine is to be used in localities where snow-covered ground or frozen lakes are found. The floats are of duralumin construction . with straight rounded top and stepped vee bottom. Water rudders are fitted to the heels of the floats, and are connected to the rudder bar. At 5,850 lb. gross machine weight, the excess buoyancy is 100 per cent.

The Bristol "Pegasus" engine is fitted in the nose of the fuselage, and is provided with a radial exhaust ring which, in conjunction with the Townend cowling ring, materially decreases the drag of the engine. The petrol tanks are of welded aluminium, anodically treated against corrosion and painted.

The main tank, which is of cylindrical shape, is placed in the fuselage, approximately on the centre of gravity, so that as its contents are consumed the trim of the machine is not altered. The auxiliary petrol tank and the oil tank are placed farther forward in the fuselage. A combination of pressure and gravity petrol feed is employed. The total tank capacity is 131 gallons, and the oil capacity 14 gallons. The oil is cooled by an oil radiator. If the " Wallace " is required for long distance work, a considerable extra quantity of fuel can be carried. In that case the bombs under the lower plane are omitted, and streamline petrol tanks fitted instead, each of 60-gall oil capacity. The range then becomes 1,000 miles.

The pilot's cockpit aft of the top plane is so situated that a very good view is obtained. The deck fairing in front of the pilot, it will be seen, slopes away to the engine, and from the cockpit the upper part of the Townend ring is seen " edge on," so that it does not obstruct the view greatly. The pilot's seat is so arranged that it can be raised and lowered, and the foot bar has an adjustment to enable pilots of different height to be suited.

Particular care has been taken to exclude draught from the cockpit. To relieve as much as possible the pilot during a long flight, provision has been made not only for trimming the machine in a fore and aft sense by means of a trimming tailplane operated by a wheel in the cockpit, but the machine can also be trimmed directionally by a rudder bias gear on the rudder bar.

In the observer's cockpit, close behind that of the pilot, there is a Scarff gun ring for the movable machine gun. The observer's seat is of the "tip-up "type, and the floor can be moved out of the way when the prone bomber's position is used. The field of fire from the rear gun is very wide, and by using the firing steps on each side of the floor, the gunner can fire vertically downwards on either side.

Westland Wallace Fuselage Detail

EASY INSPECTION: "Zip" fasteners are used in the fabric covering of the rear portion of the fuselage.


Parachute and ammunition racks are fitted, and a camera may be mounted on the fuselage floor, behind the cockpit, and operated by remote control. To leave the cockpits as unencumbered as possible, especially with parachute jumping in view, the control cables are taken, in the vicinity of the cockpits, through the inside of the fuselage fairings , i.e., between the primary structure and the outer covering. To trim the machine when no observer is carried, there is a small stowage space just in front of the tail, into which suitable weights can be loaded. The total weight of bombs which can be carried is 500 lb. in normal service. But for special purposes this load can be, and has been, increased to 1,000 lb.

The forward air-cooled gun is, of course, fixed and fires through the airscrew disc, a Constantinesco interrupter gear being fitted. The gun is completely enclosed in the port fuselage fairing, but is within reach of Ěthe pilot for clearing stoppages, etc." An automatic air-cooled gun is normally fitted on the Scarff gun ring in the rear cockpit, but duplicate guns call be mounted if desired .

Westland Wallace Production

THE" WALLACE " IN PRODUCTION: On the right a small section of the works at Yeovil, with fuselages in various stages of construction. On the left a view through the Townend ring which surrounds the" Pegasus " engine.



In conclusion, it may be pointed out that the" Wallace " has, of course, been designed to the load factors laid down by the British Air Ministry, and complies with these factors both for normal flying at a gross weight of 6,300 lb. and for aerobatics at a gross weight of 5,650 lb. The original machine was type-tested at the Aeroplane and Armament Experimental Establishment at Martlesham Heath. so that foreign purchasers may .place orders for the " Wallace " with all the confidence which "passed by Martlesham" engenders.

Westland Wallace General Arrangement

 

WESTLAND WALLACE - Bristol Pegasus M.3
Main Dimensions

  ft ins m
Length o.a 34 2 10.4
Wing span  46 5 14.1
Wing chord  5  9 1.75
Wing area  sq ft. 438 sq ft 45.4
Wheel track 6 10 2.1

Weights etc

  lb kg  
Tare Weight 3520 1595  
Fuel (105 Gallons) 810 367  
Oil  (10 Gallons) 97 44  
Crew - Load & Equipment 1323 604  
Wing Loading 11.75 lb/ft2
Power Loading 10.35 lb/hp

Performance

Top speed. at 5,000 ft 161 m.p.h. (259 kmh.)
Top speed at 10,000 ft. 157 m.p.h. (253 kmh.)
Top speed at 15,000 ft. 150 m.p.h. (242 kmh.)
Stalling speed 60.5 m.p.h. (97 kmh.)
Service ceiling 22,800 ft. (6950 m.).
Absolute ceiling 24,300 ft. (7400 m.)
Time to 5,000 ft. 4 mins
Time to 10,000 ft . 8.8 mins
Time to 15,000 ft. 15.8 mins
Time to 20,000 ft. 28 mins

The performances given above refer to standard atmosphere. The effect of bombs or other equivalent resistances will slightly reduce the performances.


 


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