06/30/2010. Remarks by Johan Visschedijk: "In the early summer of 1940, with the first production P-40s leaving the assembly line, the Curtiss-Wright Corporation was naturally preoccupied with the desire to maintain their position as the leading American manufacturer of fighter aircraft by producing the P-40s successor.

Several proposals had been made to the USAAC, the most promising being a development of the basic P-40 design featuring the NACA's low-drag laminar-flow airfoil, the Continental XIV-1430-3 inverted V-engine then under development and expected to develop 1,800 hp at 15,000 ft (4,572 m), and a wing-mounted armament of eight 0.5 in (12.7 mm) guns.

This proposal was accepted by the USAAC as the XP-53 (Model 88), and two prototypes were ordered on October 1, 1940. At a conference held six weeks later, however, Curtiss-Wright were informed of the USAAC's desire to obtain a fighter combining laminar-flow wings with the British Merlin engine, and the decision to complete the second XP-53 with this power plant as the XP-60. Provision was to be made for the alternative installation of the Continental engine, and the P-40-type rearward-retracting landing gear was to be replaced by a new inward-retracting landing gear.

90 XP-60 (Ron Myers Collection) APS No. 3535

In order to expedite flight testing, the armament installation, self-sealing fuel tanks and pilot armor were to be eliminated. Modifications were held to a minimum and, ten months later, on September 16, 1941, the XP-60 (Model 90, s/n 41-19508) began taxiing trials, flying for the first time two days later with a British-built Merlin 28. In November it was decided to convert the first XP-53 prototype into a static test airframe for the production P-60, and install the bullet-proof windscreen, self-sealing fuel tanks and six of the 0.5 in (12.7 mm) guns from this aircraft in the XP-60.

The choice of the Merlin engine for other fighters and possible delays in quantity deliveries of the license-built version of this power plant from Packard hid resulted in consideration being given to the installation of a turbocharged Allison V-1710-75 offering 1,425 hp at 25,000 ft (7,620 m), and when, on October 31, 1941, a contract for 1,950 P-60A fighters was approved, the Allison engine was selected on the basis of reliability and availability. In the meantime, flight testing of the XP-60 had not been proceeding entirely smoothly, and on two occasions the aircraft had suffered damage as the result of landing gear failures.

The XP-60 had an empty weight of 7,008 lb (3,179 kg) and a design gross weight of 9,700 lb (4,400kg), and attained a maximum speed of 380 mph (612 kmh) at 20,000 ft (6,096 m), but performance did not comply with the manufacturer's guarantees due to the wing surface not being finished to the degree of smoothness required for the laminar-flow wing and the fact that the engine did not deliver guaranteed output. On November 17, 1941, it was pointed out that the P-60A would be underpowered and that a more powerful engine should be installed or another fighter built in lieu of the P-60A.

95A XP-60A (Bernhard Klein Memorial Collection)

95C XP-60C (Bernhard Klein Memorial Collection)

Work on the P-60A therefore stopped on December 20th, and one XP-60A (Model 95A, s/n 42-79423), one XP-60B (Model 95B, s/n 42-79425) and one XP-60C (Model 95C, s/n 42-79424) should be built. The XP-60A was to have the Allison V-1710-75 engine and a General Electric B-14 turbo- supercharger, the XP-60B was to be similar apart from the installation of a Wright SU-504-2 turbo- supercharger, and the XP-60C was to be fitted with the Chrysler XIV-2220 sixteen-cylinder engine.

On April 1, 1942 Curtiss-Wright submitted a preliminary study on the installation of the Chrysler engine in the XP-60C which indicated that it would be necessary to install several hundred pounds of lead in the tail of the existing airframe for ballast or design a new fuselage. As the status of the XIV-2220 engine was, at this time, somewhat questionable, a decision was held in abeyance, but in August it was proposed that a Pratt and Whitney R-2800 radial replace the Chrysler engine in the XP-60C and, in the following month, this suggestion was agreed to.

In the meantime, the original XP-60 had been returned to Curtiss-Wright for the installation of a Merlin 61 engine. The vertical tail surfaces were enlarged and the aircraft was redesignated XP-60D (Model 90B). Eventually it crashed at Rome Air Depot, New York, on May 6, 1943.

The XP-60A made its initial ground run during the latter part of October 1942, but a minor fire occurred in the engine due to the lack of cooling air in the shrouds surrounding the exhaust manifold. The turbo-supercharger and long exhaust manifold were, therefore, removed and short exhaust stacks fitted, the first flight being effected on November 1, 1942.

Official interest in the P-60 had waned throughout the summer of 1942, but Curtiss-Wright's proposal to install the R-2800 in the XP-60C and the substantial performance improvement that this modification promised aroused such a renewal of interest in the fighter that, in November 1942, a letter contract was prepared to cover the construction of 500 R-2800-powered
P-60A-1-CU fighters.

95D XP-60E (Dan Shumaker Collection) APS No. 3532

However, it appeared unlikely that the contra-rotating airscrews and necessary engine gearing specified by the contract would be available for installation in the first production P-60A-1-CUs, and therefore the XP-60B was completed with an R-2800-10 engine driving a four-blade airscrew as the XP-60E (Model 95D).

The XP-60C was flown for the first time on January 27, 1943 with an R-2800-53 engine driving contra-rotating airscrews, and apart from somewhat high elevator and rudder forces, the aircraft's characteristics were generally satisfactory. Owing to the lighter airscrew installation of the XP-60E, it was found necessary to move the engine forward ten inches by comparison with that of the XP-60C, and owing to a fault experienced during initial ground running which necessitated an engine change, the first flight did not take place until May 26, 1943.

Prior to this event, however, the USAAF had decided to undertake comparative tests at Patterson Field with various fighter types in an attempt to eliminate the least desirable and concentrate production on the best types available at that time. During the latter part of April 1943, Curtiss-Wright were notified that the XP-60E would have to be delivered to Patterson Field to participate in these trials within four days. The XP-60E had not then flown, and the request was received only a few days after a piece of engine accessory cowl had been lost in flight from the XP-60C which had subsequently been dismantled. The XP-60C was, therefore, hurriedly reassembled without the intended modifications being made, and delivered to Patterson Field.

During the trials with the XP-60C at Patterson Field it proved impossible to obtain full power. Also the experimental wing finish had cracked off the leading edge of the wing, destroying the laminar-flow characteristics and resulting in a further loss in speed. In consequence, the XP-60C made a very poor showing and the P-60 Series was virtually eliminated from the production schedules, the contract being reduced from 500 to two aircraft! At this time, work was proceeding on twenty-six P-60A fighters on a pilot production line, and engineering and tooling for full-scale production were being prepared.

Following the return of the XP-60C to Curtiss-Wright, further flight testing was undertaken, but these tests terminated in a forced landing, and in January 1944 the XP-60E was flown to Eglin Field for official trials. The USAAF pilots found that the XP-60E did not compare favorably in level flight with later fighters but did possess a comparable climb rate. The aircraft was sensitive to slight changes in flight condition and had to be constantly retrimmed, stability in level flight was poor and climbing speeds were difficult to maintain.

In May 1944 Curtiss-Wright indicated their wish to abandon further work on the fighter, but the USAAF insisted on the completion of one of the two aircraft still under construction. Originally ordered as YP-60A-1-CUs when the production contract was cancelled, these had been redesignated YP-60E owing to the number of design modifications incorporated and the fact that they were directly descended from the XP-60E.

95 YP-60E (Ray Crupi Collection) APS No. 3675

The first YP-60E (Model 95) was eventually flown on July 13, 1944, and only one further test flight was made before the aircraft was transferred to Wright Field where it was eventually disposed of without further trials. The YP-60E differed from the XP-60E principally in having a 2,100 hp R-2800-18 engine and an all-round-vision bubble-type cockpit canopy."