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F5F Skyrocket

Grumman was long known for its small Navy fighters and two-engined amphibians. Early in 1939, however, the company broke a precedent by designing the XF5F-1 for the US Navy. In 1938, Grumman presented a proposal to the Navy for a twin engine carrier based fighter. Designated the G-34 proposal, the design was unlike any aircraft that had ever been considered before by the USN. These aircraft provided a base of data which was applied to Grumman's new G-51 proposal, which was to eventually became the F7F Tigercat.

This WW2 fighter was developed in response to a US Navy request for a light twin engine carrier fighter. Its unusual design resulted in a very short fuselage the started behind the leading edge of the wing. Grumman's concept called for a light weight (under 10,000 lbs maximum take off weight) aircraft powered by two 1,200 hp Wright R-1820 engines. Being a low wing monoplane, the fuselage began aft of the wings leading edge. At the rear of the markedly short fuselage, the tail assembly was not unlike that of a B-25 Mitchell, however, with an pronounced dihedral to the horizontal stabilizer. The propellers were geared to rotate in opposite directions to cancel the effects of engine torque. The tail wheel was fully retractable. The proposed armament was two 23mm Madsen cannons.

The Navy placed an order for one prototype, designated the XF5F-1, on June 30, 1938. The prototype took to the air for the first time on April Fools day, 1940. The XF5F-1 demonstrated good flight performance, attaining a maximum speed of 383 mph at 20,000 feet. Its rate of climb easily exceeded that of its sibling, the F4F Wildcat.

It does have a unique look, but it was not the failure commonly believed. In the summer of 1941, XF5F-1 was tested in competition against F2A, F4F, XF4U, XFL-1, P-39, P-40, and British Hurricane and Spitfire. After familiarization flights in each aircraft, pilots flew a specified series of maneuvers, then submitted pilot reports on each. LtCdr John Crommelin had this to say about F5F: "I remember testing against XF4U in a climb to 10,000'... I pulled away from the Corsair so fast I thought he was having engine trouble. F5F was a carrier pilot's dream ... opposite- rotating props eliminated all torque, and you had no engine in front to look around to see the LSO (Landing Signal Officer). Analysis of all data favored F5F, and Spitfire came in a distant second."

The F5F-1's test pilot, "Connie" Converse, in 1980 recalled "the flying qualities for the XF5F-1 were good overall. The counter-rotating props were a nice feature, virtually eliminating the torque effect on takeoff ... single-engine performance was good, rudder forces tended to be high in single engine configuration. Spin recovery was positive but elevator forces required for recovery were unusually high. All acrobatics were easily performed, and of course forward visibility was excellent."

The Navy was concerned that the F5F was overweight, but this was more a problem of their expectations than reality. The Navy was used to comparitively small, light biplanes. The newer, high performance monoplanes were all overweight by that standard. The F4U Corsair weighed more than the F5F, even though it had a single engine compared to the Skyrocket's two.

Despite continued modifications, Grumman failed to gain any production orders from the Navy. Although the fighter never entered production, its prototype demontrated outstanding flight characteristics. Availability of spare parts at the time and other particulars cancelled F5F, and the Navy chose F4F instead for production.

XP-50

The XP-50, Grumman Model G-41, was based on the Navy XF5F-1 carrier plane modified for a tricycle landing gear. The aircraft was runner-up for the Air Corps Circular Proposal 39-775 competition won by the Lockheed P-49. The XP-50 crashed into the Long Island Sound on 14 May 1941 during a test flight after the right engine's turbo-supercharger exploded. Further development of the aircraft was halted and design continued on the XP-65, an improved version of the XP-50. Meanwhile, the XF5F-1 continued in R&D service until the end of 1944.

This twin-motored land plane coincided with an Air Corps development for twin-engined fighters and was of particular interest to the Army because of its air-cooled engines. Circular Proposal 39-775 was issued in March 1939. Grumman submitted Model 41, an XF5F-1 except for its armament, landing gear and lengthened nose.

An evaluation board, meeting at Wright Field on August 4, 1939, recommended the purchase of 66 Lockheed P-38's and the Grumman 41 which became the XP-50. Negotiations were begun with Grumman in October 1939. During these discussions original specifications were somewhat modified and cost differences ironed out. Wright Field issued an AFP on November 9th. A contract was drawn up and, after certain minor changes, approved by ASW on January 17, 1940.

Engineering on the XP-50 began as early as November 1939. At any rate, progress was such that first drawings were released on March 7, 1940. A mock-up was started early in 1940 and was inspected by a Board of officers who visited the contractor's plant on April 22nd. The inspecting board voiced general approval but suggested that the radio antennae and the 20mm cannon chargers be replaced. Change Order No. 1 incorporated these changes. The C.O. also provided for two additional wing guns, more ammunition, armor plate, fluorescent lighting, etc. It was approved by ASW on June 29, 1940.

About this time, a 1/15 scale model of the XP-50 was wind-tunnel tested at Wright Field. Results indicated an inherent stability and good flying control. High speed was estimated at 420 mph. at 15,000 ft. and landing speed was approximately 97 mph.

No particular pressure was put on the XP-50 project, but progress was reasonably good. The plane was 38% complete in August. During the next three months the figure rose to 91%. Contract delivery was set for December 17, but the contractor could not keep the date. Delivery was estimated for mid-February 1941, but progress was further tied up by damage to the right landing gear. The plane was finally ready for flight-testing on February 19.

About this time, however, a ground run disclosed that when the XP-50's wheels were down engine exhaust gases were directed into the oleo struts of the landing gear. An Engineering Inspection, conducted late in February, showed, too, that the recoil mechanisms on the 20mm guns were too weak. A need for simplifying the engine arrangement was also voiced.

During March 1941, the XP-50 was flown intermittently due to sloppy field conditions at the Grumman plant. The contractor insisted on keeping the plane until a high speed run and a continuous flight of two hours had been conducted. During one test the ship was partly damaged by skidding on ice during a landing. This minor accident on top of troubles discovered in the fuel system held up delivery for several weeks. The fuel warning system and certain hydraulic pumps had to be replaced, but finally by the middle of May the plane was again in flying order.

All these months of struggle were proven in vain on May 14. During a test flight the turbo-supercharger on the right engine exploded and completely disintegrated. Not only did the engine fail, but the explosion destroyed the plane's hydraulic system. This prevented the test pilot from extending the nose wheel or retracting the main gear. The flier was forced to jump and the plane crashed into Long Island Sound.

In shallow water near where the XP-50 sank, searchers found the turbine wheel from the turbo on the right engine. This confirmed the cause of the accident. The Coast Guard dragged the region for several days without success, and salvage operations were eventually abandoned.



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