D.James Westland aircraft since 1915 (Putnam)
During the final months of the 1914-18 War the Air Ministry was already giving thought to its postwar aircraft requirements and preparing some detailed specifications. Among these was RAF Type IIIA for a two-seat fighter-reconnaissance aircraft. It was intended as a replacement for the highly effective Bristol F.2B Fighter - the 'Brisfit' - which was still a comparatively new design having entered service with the Royal Flying Corps in April 1917. The Type IIIA specification called for a much improved performance, particularly in the time-to-height and service ceiling; however, the armament remained the same as the F.2B, being two fixed forward-firing guns and one gun on a Scarff ring mounting in the rear cockpit. The most unfortunate aspect was the preferred use of the ABC Dragonfly engine, a nine-cylinder radial engine designed, like the earlier Wasp which powered the Wagtail, by Granville Bradshaw. The Dragonfly proved to be a disaster in almost every way. It was claimed to produce 340 hp and weigh 600 lb but never, at any stage, delivered more than 295 hp and weighed 656 lb; moreover, it rapidly overheated having what was described as 'probably the worst example of air cooling in a production aircraft engine’. Of most importance was its designed running speed which happened to be the critical torsional vibration frequency of the crankshaft which regularly broke after a few hours running.
It was around the Dragonfly that three manufacturers designed and built prototypes, in various quantities, to meet the Type IIIA requirement. They were the Austin Motor Co which produced the Greyhound, Bristol Aeroplane Co with the Badger and Westland which scaled up its earlier single-seat Wagtail to create the two-seat Weasel.
Designed by Robert Bruce and Arthur Davenport, the Weasel was of similar construction to the Wagtail having a wooden girder type fuselage of rectangular cross-section with spruce longerons and spacer struts, the latter being tapered to fit into square steel cups bolted to the longerons. This structure was internally wire braced. Forward of the front cockpit the fuselage was plywood covered with fabric covering on the remainder; however, a small rectangular area on each side of the observer' cockpit was left uncovered to provide a 'window'. The strut-braced tail unit, which had the Westland-patented variable-incidence tailplane gear, was of similar wire-braced wooden construction and also was fabric covered. The engine mounting ring was carried on an extension of the longerons which was internally wire braced, while the complete nose section of the fuselage had removable metal panels to provide access to the engine and to the fuel and oil tanks. The engine's cylinder heads protruded through holes in the nose cowl and the Dragonfly turned a 9 ft 9 in diameter two-blade fixed-pitch wooden propeller. The fabric-covered two-bay biplane wings were built up around two ash spars with cross-braced drag struts and three-ply cut-out ribs with spruce flanges. The eight interplane struts were of streamline section spruce and, like the four centre-section support struts, were all wire cross-braced. Constant-chord ailerons were fitted to each of the four wings. As in the Wagtail, although the centre-section was smaller in span, there was an angular cut-out in its trailing edge and in that of the lower wings' trailing edge; in addition five ribs were omitted in the centre-section aft of the main spar leaving an uncovered opening above the pilot's cockpit. The two fixed forward-firing synchronised Vickers .303 in machine-guns were carried in troughs in the top of the front fuselage, with provision for one, or two, Lewis guns of similar caliber to be carried on a Scarff ring mounting in the observer's cockpit. Spruce V main undercarriage legs with a cross-axle having enclosed bungee rubber shock absorbers were used with a tailskid. A wind-driven generator was mounted on the port rear main leg. An unusual visual feature of the Weasel was the manner in which the upper and lower wings appeared to be splayed away from each other; in fact, the upper wing had 5 deg dihedral from the flat centre-section while the lower wing had no dihedral. Oxygen bottles with some 3 hours supply for the two crew and electrical heating equipment were carried in the fuselage.
An order for three Weasel prototypes was placed in April 1918 with construction starting almost immediately, but forthcoming events cast their shadows over the work with the first of a number of delays in delivery of the engine. In 'the event the war was ended when the first Weasel, serialled F2912, was flown for the first time by Capt Stuart Keep during late November 1918.
Preliminary flight trials were punctuated by continuous problems with the engine, both on the ground and in the air. One incident, which could have had serious results for Westland, occurred when Stuart Keep was flying the Weasel with Robert Bruce in the observer's cockpit and the engine failed a long way from the aerodrome. Bruce immediately leaned out of the cockpit and cranked the starter magneto which was fitted on the starboard side of the fuselage, but the Dragonfly refused to start. Fortunately, the Weasel had sufficient altitude to glide back to the aerodrome, brushing through the top of the boundary hedge en route to a dead-stick landing. While company trial with this first prototype continued into the early months of 1919, construction of the second and third aircraft proceeded at a steady pace. During May F2912 went to the AEE at Martlesham Heath for 'airframe and Dragonfly motor' tests. These included some handling checks during which the lateral control was criticised. Meanwhile, as a result of the failures of the Dragonfly, it was decided to replace it with a 350 hp Armstrong Siddeley Jaguar II engine, the first airframe to be modified being the third prototype F2914 which went to Martlesham Heath during June 1922. Among airframe modifications was the fitting of horn-balanced ailerons and rudder.
While construction of the second and third Weasels had been proceeding, in August 1919, Westland received an order for a fourth aircraft to be powered by a Jaguar II. By this time all development testing of the disastrous Dragonfly had been abandoned and the production of military aircraft cut to a trickle; thus, Westland was aware that a production order for Weasel was unlikely to be placed. Nevertheless, flying with the four prototypes continued at Yeovil and at Martlesham Heath, at which latter location the Weasels made appearances until November 1924, when F2914, the third prototype was there. During November 1919 F2912, the first prototype, caught fire in the air while allegedly powered by an Armstrong Siddeley Lynx; however, it pilot, Flt Lt A H Orlebar, managed to sideslip to the ground and crash land where the fire was extinguished, the aircraft being written off charge in the following March.
By mid-summer of that year, all the Weasels had been handed over to the Royal Aircraft Establishment at Farnborough where they were being used for flight testing engine and various equipment. Although this work may have appeared mundane compared with operational flying, there was the interest of fitting and flying, in J6577, the exciting new Bristol Jupiter II radial engine which, in September 1921 was the first engine to pass the Air Ministry's type-test by delivering 400 hp at 1,625 rpm. However, there were installation problems, particularly with the Jupiter' valve gear which not only had some teething problems with its push rod which had automatic compensation for cylinder expansion, but also proved vulnerable to icing which topped the engine when tested in climbs to altitude during the winter month. To overcome this latter snag the RAE made some wind-tunnel investigations with a number of different shaped 'helmets' to fit over the Jupiter's exposed cylinder heads, and later test flew the Weasel with this modified cowling. There were moment of glory too, the first on 24 June, 1922, when the Jupiter-powered Weasel appeared in the New Types Park at the third Royal Air Force Pageant at Hendon. However, on 11 July J6577 caught fire in the air while at AEE, crashed and burnt out. F2914 was a 'New Type' at Hendon on 30 June, 1923, but, with F2913, flew at the RAE until written off charge in 1925 and 1924 respectively.
Description: Two-seat biplane fighter. Wood/metal construction with fabric, wood and metal covering.
Accommodation: Pilot and observer/gunner in open cockpits.
Powerplant: One 340 hp ABC Dragonfly nine-cylinder air-cooled normally-aspirated radial engine driving a 9 ft 9 in diameter two-blade wooden propeller (F2912). One 350 hp Armstrong Siddeley Jaguar II fourteen-cylinder two-row normally-aspirated air-cooled radial engine (F2912 and F2914). One 400 hp Bristol Jupiter II nine-cylinder normally-aspirated air-cooled radial engine (F2913 and J6577).
Armament: Two fixed synchronised Vickers .303 in forward-firing machine-gun in troughs in the top of the front fuselage with Aldis and ring-and-bead sights, and one, or two, Lewis .303 in machine-gun on a Scarff mounting in the rear cockpit.
Dimensions: Span 35 ft 6 in; length 24 ft 10 in; height 10 ft 1 in; wing area 36 sq ft.
Weights: Empty 1,626 lb; loaded 3,046 lb.
Performance: Maximum speed 120 mph at sea level; landing speed 56 mph; service ceiling 22,100 ft.
Production: Four Weasel built by Westland Aircraft Work, Yeovil, Somerset, during 1918-19.
H.King Armament of British Aircraft (Putnam)
Weasel. The Weasel was built in 1918 as a specialised two-seat fighter. It had much in common with the Wagtail, including the mounting of the two Vickers guns, though these were somewhat recessed and fired through short troughs. When a Jupiter engine was installed the guns were faired in to the fuselage and fired through longer, deeper troughs. The case chutes were some distance down the fuselage sides. There were Aldis and ring-and-bead sights. The gunner was close behind the pilot and had a Scar ff ring-mounting for twin Lewis guns. Below the ring on each side of the fuselage was a 'window', or uncovered fuselage section.
P.Lewis The British Fighter since 1912 (Putnam)
The Westland designers Bruce and Davenport were responsible for a two-seat fighter reconnaissance biplane which the West Country firm completed towards the end of 1918. Called the Weasel, the machine was of typical two-bay layout but was one of the unlucky types to have the unreliable A.B.C. Dragonfly 1 engine of 320 h.p. Two Vickers guns were provided for the pilot and the observer used a single Lewis on a Scarff ring. The Weasel was quite successful in flight trials but the four built spent their lives in experimental work only.
F.Mason The British Fighter since 1912 (Putnam)
First flown at about the time of the Armistice, the Westland Weasel was one of almost a dozen aircraft whose future - or, more accurately, the lack of it - was compromised by the failure of Granville Bradshaw’s ABC Dragonfly engine.
The two-seat, two-bay Weasel biplane was designed by Robert Bruce and Arthur Davenport during the summer of 1918 in response to the RAF Type IIIA Specification which called for a successor to the Bristol F.2B Fighter which was expected, under wartime conditions, to be due for replacement during 1919-20. Like the Wagtail, the Weasel possessed no dihedral on the lower wings, but pronounced dihedral on the upper planes. The pilot’s cockpit was located below the rear spar of the upper wing, necessitating an inter-spar aperture in the wing centresection above his head for upward view; being well staggered, the lower wing was sufficiently far aft to give the pilot a good view forward and downwards for landing. Generous trailing-edge cutouts were provided on both upper and lower wings which were both fitted with ailerons. The tailplane incidence was adjustable in flight.
Choice of the Dragonfly engine - recommended, it should be said, by the Air Ministry - proved unfortunate, to say the least. Not only was it found to be almost ten per cent heavier than forecast by the manufacturer, but was thirteen per cent down on power. The cylinder finning proved wholly inadequate for cooling, resulting in constant overheating. More serious was the frequent failure of crankshafts (presumably due to fatique) as it was discovered that the engine’s designed running speed coincided with the crankshaft’s critical vibration frequency in torsion.
Three prototype Weasels were ordered on 3 May 1918, and F2912 was flown in November by Capt Stuart Keep. Little or no further flying was done during the next four or five months while alterations were made in the forward fuselage to take account of the unexpectedly heavy engine. F2913 flew in June and F2914 in September.
The first Weasel underwent preliminary trials at Martlesham Heath in May to establish its handling characteristics with the revised c.g., but was destroyed during November in a forced landing following an engine fire; the pilot, Flt Lt Augustus Henry Orlebar afc was unhurt. (Some records suggest that the aircraft was fitted with an Armstrong Siddeley Lynx engine at the time).
After discontinuation of the Dragonfly engine’s development, all efforts to suit the Weasel for an active Service role were abandoned late in 1919. Instead, the two remaining original prototypes were confined to the development of other engines. F2913 was fitted with a Bristol Jupiter IV radial engine in 1921, and continued flying at the RAE until January 1924, being written off charge in October that year.
F2914 also had a long and varied life, suffering but surviving a number of forced landings. In 1920 its fin and rudder were redesigned to incorporate a horn-balanced rudder; beginning in November it underwent some further alteration and emerged in January 1922, powered by a 350hp Armstrong Siddeley Jaguar II two-row radial engine, appearing in this form in the New Types Park at the RAF Hendon Pageant on 24 June, and again at the 1923 Display. A Jaguar III was fitted in November 1923, and F2914 continued flying at Farnborough until 9 April 1925.
A fourth Weasel prototype had been ordered from Westland on 29 August 1919 under the designation Mark II, designed to the new D of R Type 2 Specification. Powered at the outset by a 450hp Cosmos Jupiter II radial, this aircraft, J6577, first flew in March 1920, but in July appeared at Martlesham with a Jaguar II engine. A year later this was replaced by a 436hp Jupiter IV. J6577 differed from the earlier prototypes in being fitted with horn-balanced ailerons.
The fate of this aeroplane is something of a mystery. After appearing in the New Types Park at Hendon in June 1922, it is said that J6577 crashed near Martlesham Heath following a fire in the air, and was burned out. Several records, however, show that this aircraft was flying at Martlesham in 1923, and the accompanying Air Ministry photograph is date-stamped 20 August 1923; moreover the aircraft as depicted appears to be fitted with heat-exchanger muffs on the exhaust pipes of the type developed by Bristol early in 1923.
The data table refers to the Weasel Mk I with Dragonfly engine.
Type: Single-engine, single-seat, two-bay biplane fighter.
Manufacturer: The Westland Aircraft Works, Yeovil, Somerset.
Air Ministry Specifications: RAF Type IIIA of 1918, and D of R Type 2 of 1919.
Powerplant: One 320hp ABC Dragonfly I; also 350hp Armstrong Siddeley Jaguar II, 450hp Cosmos Jupiter II, 436hp Bristol Jupiter IV, and possibly Armstrong Siddeley Lynx.
Dimensions: Span, 35ft 6in; length, 24ft 10in; height, 10ft 1in; wing area, 368 sq ft.
Weights: Tare, 1,867lb; all-up, 3,071lb.
Performance: Max speed 130.5 mph at sea level; climb to 10,000ft, 10 min; ceiling, 20,700ft.
Armament: Two synchronized 0.303in Vickers machine guns on front fuselage decking, and one Lewis gun with Scarff ring on rear cockpit.
Prototypes: Four, F2912-F2914 (Mk Is) and J6577 (Mk II). No production.
W.Green, G.Swanborough The Complete Book of Fighters
WESTLAND WEASEL UK
In April 1918, Westland gained a three-prototype contract for a two-seat fighter-reconnaissance aircraft that was designed to provide a successor to the Bristol F.2b fighter. In configuration, the new fighter, to which the name Weasel was given, closely resembled a scaled-up Wagtail. The pilot was located beneath the trailing edge of the upper wing, with the observer/ gunner close behind, with a single 0.303-in (7,7-mm) Lewis gun on a Scarff ring. Two fixed and synchronised forward-firing Vickers guns of the same calibre were provided for the pilot. The Weasel had a two-spar wooden wing and a wire-braced wooden fuselage, with fabric covering for all but the ply-covered front fuselage. In common with the competing Austin Greyhound and Bristol Badger, the Weasel was powered by the 320 hp ABC Dragonfly nine-cylinder air-cooled radial engine, which (like the ABC Wasp in the Wagtail) proved so unsatisfactory as to rule out any possibility of production, even if the ending of World War I had not removed the urgency from the requirement. Flight testing did not begin until November 1918 and a Weasel went to Martlesham Heath in April the following year, followed by the third prototype in November. Subsequently, two of the Weasels were used for engine development at the RAE Farnborough, one being re- engined with a 385 hp Cosmos Jupiter II nine-cylinder radial and the other with a 350 hp Armstrong Siddeley Jaguar II 14-cylinder radial. A Jupiter II was also used to power a fourth Weasel, which was ordered in August 1919 and delivered in 1920 with full armament, although also used primarily for engine development. The following data refer to the Dragonfly-powered Weasel.
Max speed, 130 mph (210 km/h) at 6,500 ft (1980 m).
Time to 10,000 ft (3 050 m), 10 min.
Service ceiling, 20,700 ft (6310 m).
Empty weight, 1,867 lb (847 kg).
Loaded weight, 3,071 lb (1393 kg).
Span, 35 ft 6 in (10,82 m).
Length, 24 ft 10 in (7,56 m).
Height, 10 ft 1 in (3,07 m).
Wing area, 368 sq ft (34,19 m2).