The Platt-LePage XR-1, also known by the company designation PL-3,[1] was an early American transverse rotorshelicopter, built by the Platt-LePage Aircraft Company of Eddystone, Pennsylvania. The winner of a United States Army Air Corps design competition held in early 1940, the XR-1 was the first helicopter tested by the USAAF, flying in 1941. The flight testing of the XR-1 proved troublesome, and although continued testing showed that the design had promise, other, improved helicopters were becoming available before the XR-1 was ready for service. As a result, the development of the aircraft was terminated in 1945.
Design and development
Developed during 1939 from an earlier, unsuccessful design, the PL-1,[2] the Platt-LePage Model PL-3 was the winner of a 1940 design competition, held under the terms of the Dorsey-Logan Act, for the supply of a helicopter design to the United States Army Air Corps.[3] Platt-LePage's submission was judged by the Army to be superior to its competitors, which included a helicopter submitted by Vought-Sikorsky, and autogyros developed by Kellett and Pitcairn.[N 1]
[1] Following the selection of the Platt-LePage design in May 1940, a contract for the construction of a prototype and a static test airframe was issued in July of that year.[1] The contract specified delivery of the flying prototype in January 1941, however the aircraft was not completed until three months later than the contract schedule,[1] a delay that led to Sikorsky receiving Dorsey-Logan Act funding for development of its design, which became the XR-4.[4]
XR-1 early in testing
In its design, the XR-1 bore a strong resemblance to the Focke-Wulf Fw 61, a helicopter developed by Henrich Focke in Germany that, flown by Hanna Reitsch, had impressed Platt-LePage co-founder Wynn LePage during a tour of Europe.[5] The XR-1 was powered by a Pratt & Whitney R-985radial engine, mounted in a buried installation within the fuselage.[1] The aircraft had two, three-bladed rotors, mounted in a side-by-side arrangement on wing-like pylons.[1] The pylons were aerodynamically designed to produce some lift when in forwards flight, slightly unloading the rotors.[6] The construction of the XR-1 was conventional by the standards of the time, with the aircraft's frame consisting of a steel-tube framework, which was covered with fabric.[1] The XR-1 had tail surfaces similar to those of a conventional aircraft, and was equipped with a fixed, taildragger landing gear.[1] The aircraft's wheels freely castered for easier maneuvering on the ground.[6]
The cockpit of the XR-1 seated the aircraft's two crew members in a tandem arrangement, the pilot located ahead of the observer, and was extensively glazed to provide good visibility in the aircraft's intended observation and army co-operation role.[1] During the development of the aircraft, Major General Robert M. Danford proposed to the War Department that the XR-1 be evaluated against the Stinson YO-54 and the Kellett YG-1Bautogyro.[7]
Operational history
Following several months of ground testing, the XR-1 conducted its maiden flight on May 12, 1941, although the aircraft was restrained by a tether for its early flights.[8] On June 23 the aircraft conducted its first free flight, albeit remaining within a few feet of the ground.[8] As flight testing continued and the aircraft's performance envelope was expanded, the XR-1's quickly proved troublesome, the testing showing a variety of troubles with the design.[8] These included issues with the aircraft's controls, insufficient control authority being present, and in addition there were resonance issues with the airframe[9] that made the XR-1 prone to pilot-induced oscillations.[8] The aircraft was modified in an attempt to resolve these issues, and the Army modified Platt-LePage's contract to provide additional funding for improvements to the design, but despite this the XR-1's problems continued.[8] In addition, the company's test pilot, Lou Leavitt, lacked confidence in the design, refusing to fly the aircraft to its full potential.[6] The situation was only resolved when Colonel H. Franklin Gregory, director of rotor-wing projects for the Army Air Forces, flew the aircraft himself, reaching 100 mph (160 km/h) on his first flight in the aircraft.[6]
XR-1top view
With the worst of the aircraft's problems believed to have been resolved, the XR-1 was submitted for service testing by the Army Air Forces in 1943.[8] During the course of the Army's evaluations, the XR-1's empennage failed during structural testing, the surfaces being strengthened as a result and testing, following the repairs, resuming in 1944.[8] Despite the modifications to the design, however, the XR-1 still proved to be deficient in control authority.[8] In July 1943, the XR-1 program suffered a setback when the aircraft crashed, seriously injuring test pilot Jim Ray, who had replaced Leavitt following the latter's dismissal from the company.[6] The crash was caused by an inspector's error in leaving a suspect part on the aircraft, the rotor hub failing in flight as a result of the decision.[6] The aircraft was repairable, but it would be a year before the XR-1 was ready to fly again.[6]
Testing was, however, able to continue in the meantime, as Platt-LePage had re-negotiated the XR-1 contract to cover a second flight-test aircraft.[6] Built to a revised and improved version of the XR-1's design and designated XR-1A, the second aircraft had flown for the first time in May 1943.[8] The XR-1A featured a revised cockpit covering compared to that of the XR-1, with the area of glazing being increased for improved visibility, and the pilot and observer's positions being reversed, the pilot now seated in the rear cockpit.[8] During flight testing the XR-1A was found superior in flight performance to the XR-1;[8] however, the controls were still proving troublesome,[8] although the worst of the bugs did seem to have been worked out.[6]
Following a cross-country flight to Wright Field in Ohio from Platt-LePage's Pennsylvania plant, testing of the XR-1A continued until a mechanical failure in the rotor hub led to a crash landing[6] on 26 October 1944,[8] the company deciding to sell the wreckage for scrap.[6]
The XR-1, having been repaired in the meantime, was once again flying,[6] and a contract had been awarded to Platt-Lepage for the construction of seven pre-production aircraft, to be built to an improved version of the XR-1A design, and designated YR-1A.[10] Motivated by Congressional concerns about potential favouritism towards Sikorsky Aircraft, which had in the meantime been given a contract for development of an improved version of their VS-300 experimental helicopter, the contract called for delivery of the first YR-1A to the Army in January 1945.[10] However, due to continued financial and flight-testing problems, Platt-Lepage proved incapable of meeting this schedule.[10]
Although the XR-1's problems seemed to be approaching resolution by late 1944,[11] the protracted development of the aircraft meant that alternative, improved helicopters, such as Sikorsky's XR-4, less expensive and more maneuverable than Platt-LePage's aircraft, were becoming available.[8] In addition, even the XR-1A's improvements had failed to cure the aircraft of all of its control and vibration problems,[6] and the AAF's Air Materiel Command considered the company "inept" in its work, applying a "hit-or-miss method" to research and development.[6] As a result of this assessment, the Army's contracts with the company were universally cancelled in early April 1945.[8]
Following the cancellation of the Army's contract, the XR-1 was returned to the company, Platt-LePage believing that the design had potential as a civilian aircraft.[8] The planned civilian version, the PL-9, would have been an enlarged, twin-engined aircraft;[6] however Platt-LePage was by now in serious financial difficulty following the cancellation of its Army contract,[8] and in mid 1946 the XR-1's flight test program was concluded,[6] the aircraft being retired to the Smithsonian Institution.[8]
In the meantime, the company's former test pilot, Lou Leavitt, had purchased the wreckage of the XR-1A at a price of 4 cents per pound.[6] Leavitt was a pilot with Helicopter Air Transport,[6] which was providing helicopter services in anticipation of a postwar aviation boom, and the XR-1A was returned to flying condition.[10] The projected boom failed to materialise, however, and HAT quickly entered bankruptcy, selling the XR-1A to Frank Piasecki, another former Platt-LePage employee who had now started his own helicopter company.[6] Leavitt flew the helicopter to Piasecki, who never flew it due to airworthiness concerns, and used the airframe in the development of the PA-2B, a planned tiltrotor which failed to proceed beyond the mock-up stage.[6]
^Despite being rejected in favour of the XR-1, the Vought-Sikorsky design would be developed into the Sikorsky VS-300, while Kellett's autogyro would be purchased for evaluation by the Army as the Kellett XR-2; Pitcairn's proposed design was the Picairn PA-36.[2]
