World War II Database

Contributor: Alan Chanter

ww2dbaseDuring the late 1930s, Richard Palmer of the Vultee Aircraft Division of the Aviation Manufacturing Corporation conceived the original idea of designing four types of aircraft for different military roles, all using the same basic tooling and featuring common wings , aft fuselage and tail assembly. The four designs were given the designations of P-48 single seat fighter, BC-51 basic combat trainer; B-54 advanced Trainer and B.54D (eventually developed as the BT-13) basic trainer.

ww2dbaseThe Model 48 single-seat monoplane fighter, design of which began in 1938, featured a steel-tube metal covered semi-monocoque fuselage (the centre section of which was identical to that of the BC-51and B-54). It had a two spar wing, built on the same jigs as those employed on the low-performance trainers, and a rather unusual symmetrical aerofoil with wingtips and root chord taken from the other three projects. The Model 48 fighter also had fabric-covered hydraulically actuated split flap control surfaces, and the fully retractable undercarriage was the same as that employed on the BC-51 and B-54 trainers.

ww2dbaseWhile the first prototype (Serial NX21755) was under construction it was decided to fit the 1,200 h.p. 14-cylinder Pratt and Whitney R-1830-S4C4-G air cooled radial engine within a long pointed cowling to reduce drag, with its cooling being effected by means of a variable air intake beneath the nose, immediately aft of the airscrew spinner. To accomplish this change the engine and propeller needed to be connected by a lengthened drive shaft. In this form the first prototype (assigned the name Vanguard by the company) was completed and flown for the first time on 9 September 1939.

ww2dbaseFrom the outset the streamlined cowling created serious engine overheating problems and after a few test flights, the variable air intake beneath the nose was fixed in the "open" position and a further air scoop added above the cowling. Simultaneously the rudder area was enlarged to improve stability. At this time, the proposed production version was designated Model 61, but only limited flight testing had been complete when, on May 9, 1940, the prototype collided with a Lockheed Sirius while landing at Vultee airfield, the impact severing one main undercarriage leg. Nevertheless the pilot, Vance Breese, skillfully landed the aeroplane with little additional damage. It was subsequently rebuilt with the orthodox cowling as employed on subsequent machines.

ww2dbaseIt was then concluded that the close fitting cowling and extension-shaft arrangement was not entirely satisfactory. It was heavy and the negligible drag reduction that it offered was insufficient to compensate for the cooling and carburetor ducting problems. Thus, the second prototype, the Model 48X (NX19999) which had flown on February 11, 1940, reverted to the more orthodox engine cowling that had originally been envisaged for the machine. The second prototype also differed by having redesigned compound wings dihedral, modified main undercarriage members, a rearward retracting tail-wheel and provision for twin 0.5 (12.7-mm) machine-guns in the forward fuselage and two 0.3-in (7.62-mm) machine-guns in the wings.

ww2dbaseOn 6 February 1940, Vultee received an order from the Swedish government for 144 aircraft. The Swedish machines were designated Model 48C and a production prototype (NX28300) made a maiden flight on 6 September 1940. This was essentially similar to the Model 48X with the redesigned and enlarged vertical and horizontal tail surfaces as applied to that aircraft at an early flight test stage. The Swedish aircraft were equipped with a R-1830-S3C4-G engine which possessed a similar take-off rating to the S4C4-G engine of the earlier prototypes, but had a superior altitude ratings (1,050 hp at 13,100 ft). These Swedish Vanguards also had two additional 0.3-in (7.62-mm) wing guns. Unfortunately, by the time deliveries were of the fighter were due to commence in September 1941 the US government had placed an embargo on the sale to Sweden and the contract was therefore offered to the British Purchasing committee, who envisaged that the Vanguard could be employed as an advanced trainer in Canada. British serial numbers were allocated to the machines, and at least the first two (BW208 and BW209) were completed in RAF colours. In the event, no Vanguard aircraft were, in fact, accepted by the RAF and the British relinquished the aircraft to China which was selected to receive, under Lend-Lease arrangements, one hundred and twenty-nine of the 144 Vanguard fighters manufactured. The remaining fifteen machines were allocated to the USAAF with the designation P-66 and these aircraft were generally assigned to pursuit training bases on the US west coast (some late U.S. machines had a reduced transparent area aft of the pilots seat).

ww2dbaseVultee completed all Vanguard builds in April 1942 and the Chinese P-66 fighters were duly shipped out to India for onward transmission to China during the second half of 1942, although only 79 machines ever reached the Chinese Air Force, these being used comparatively briefly by the 3rd and 11th Pursuit Groups.

P-66 Vanguard Timeline

SPECIFICATIONS

P-66 Vanguard

Machinery	One Pratt & Whitney R-1830-S3C4-G air-cooled 14-cylinder radial engine rated at 1,200hp
Armament	4x0.3in machine guns, 2x0.5in machine guns
Crew	1
Span	10.97 m
Length	8.66 m
Height	2.87 m
Wing Area	18.30 m²
Weight, Empty	2,374 kg
Weight, Loaded	3,220 kg
Weight, Maximum	3,349 kg
Speed, Maximum	547 km/h
Rate of Climb	12.80 m/s
Service Ceiling	8,595 m
Range, Normal	1,368 km

Photographs