The Hughes XF-11 (redesignated XR-11 in 1948) was a prototype military reconnaissance aircraft designed and flown by Howard Hughes and built by Hughes Aircraft for the United States Army Air Forces (USAAF). Although 100 F-11s were ordered in 1943, various factors would delay the program beyond the end of World War II, and only two prototypes and a static test mockup were completed. During the first XF-11 flight in 1946, piloted by Hughes himself, the aircraft crashed in Beverly Hills, California.The second prototype was completed and successfully flown in 1947. The program was extremely controversial from the beginning, leading the U.S. Senate to investigate the XF-11 and the Hughes H-4 Hercules flying boat in 1947–1948.
Design and development
The F-11 was intended to meet the same USAAF operational objective as the Republic XF-12 Rainbow: a fast, long-range, high-altitude photographic reconnaissance aircraft. A highly modified version of the earlier private-venture Hughes D-2, in configuration the aircraft resembled the Lockheed P-38 Lightning, but was much larger and heavier. The D-2's early gestation is historically obscure; aircraft historian René Francillon asserts that the project was probably initiated by Howard Hughes for a global circumnavigation speed record attempt, but the outbreak of World War II closed much of the world's airspace and made it difficult to buy aircraft parts without government approval, so Hughes decided to sell the aircraft to the U.S. military instead.After it became clear that the D-2 could not meet military requirements as a fighter or bomber, Hughes would persuade USAAF leaders to issue a contract to redesign it for photographic reconnaissance.

On the urgent recommendation of Colonel Elliott Roosevelt, who led a team surveying several reconnaissance aircraft proposals in September 1943, General Henry "Hap" Arnold, chief of the U.S. Army Air Forces, ordered 100 F-11s for delivery beginning in 1944. In this, Arnold overrode the strenuous objections of the USAAF Materiel Command, which held that Hughes did not have the industrial capacity or proven track record to deliver on his promises, and recommended that Arnold should instead approve a reconnaissance version of the Lockheed XP-58.Arnold made the decision "much against my better judgment and the advice of my staff" after consultations with the White House.

A preliminary contract issued on 11 October 1943 was immediately contested by Hughes, who sought $3,919,000 in compensation for the development of the D-2, and objected to Materiel Command's requirements for all-metal construction (the D-2 was built largely of wooden Duramold), self-sealing fuel tanks, and various other major design changes that threatened to undermine his argument that the F-11 was directly derived from the D-2.

Hughes at one point demanded partial reimbursement for his personal Boeing 307 Stratoliner, arguing that the purchase allowed study of the Boeing's pressurization system. Additionally, the War Production Board (WPB) wanted Hughes to build a new assembly plant near Hughes Tool Company headquarters in Houston, where labor costs were lower than in southern California. The WPB eventually allowed the company to use its existing Culver City, California, assembly plant and the USAAF made some small design concessions, but Hughes failed to secure reimbursement for the D-2 and Stratoliner, and ultimately agreed to most of the design changes, notably including the elimination of Duramold. The protracted negotiations consumed the better part of ten months, and the final contract was awarded on 1 August 1944.

The XF-11 emerged as a tricycle landing gear, twin-engine, twin-boom all-metal monoplane with a pressurized central crew nacelle, with a much larger span and much higher aspect ratio than the P-38 or the D-2. The XF-11 used Pratt & Whitney R-4360-31 28-cylinder radial engines. Each engine drove a pair of contra-rotating four-bladed, controllable-pitch propellers. (Due to persistent problems with the contra-rotating propulsion system, which led to the 1946 crash, the second prototype had regular single four-bladed propellers.)

The program was plagued by managerial and logistical delays. 21 engineers, including chief engineer Ed West, resigned in a May 1944 dispute over their offices being moved from Brea, California, to the Culver City plant.The prototype's wings–subcontracted to Fleetwings–were delivered six months behind schedule in April 1945.With the end of the European war in May 1945, the order for 100 F-11s was reduced to just three, a static test model and the two prototypes, and the USAAF de-prioritized the project. The engines were delivered seven months behind schedule in September 1945, and the first prototype was conditionally accepted by the USAAF on 5 April 1946, although its electrical and hydraulic systems were incomplete.

From 1946-1948, the Senate subcommittee to investigate the Defense Program, popularly known as the Truman Committee and then the Brewster Committee, investigated the F-11 and H-4 programs, leading to the famous Hughes-Roosevelt hearings in August 1947.The F-11 program cost the federal government $14,155,235, and Hughes absorbed at least a quarter of this amount in sunk costs from the D-2.
Operational history
The first prototype
The first prototype, tail number 44-70155, piloted by Hughes, crashed on 7 July 1946 while on its maiden flight from the Hughes Aircraft factory airfield at Culver City.

Hughes did not follow the agreed testing program and communications protocol, and remained airborne almost twice as long as planned. He may have been distracted by landing gear retraction problems, requesting that another aircraft be flown alongside to observe the operation of the gear. An hour into the flight (after onboard recording cameras had run out of film), a leak caused the right-hand propeller controls to lose their effectiveness and the rear propeller subsequently reversed its pitch, disrupting that engine's thrust, which caused the aircraft to yaw hard to the right. Rather than feathering the propeller, Hughes performed improvised troubleshooting (including raising and lowering the gear again) during which he flew away from his factory runway. Constantly losing altitude, he finally attempted to reach the golf course of the Los Angeles Country Club, but about 300 yards (270 m) short of the course, the aircraft suddenly lost altitude and clipped three houses. The third house was destroyed by fire, and Hughes was nearly killed.

USAAF investigators concluded that, "It appeared that loss of hydraulic fluid caused failure of the pitch change mechanism of right rear propeller. Mr. Hughes maintained full power of right engine and reduced that of left engine instead of trying to fly with right propeller windmilling without power. It was Wright Field's understanding that the crash was attributed to pilot error," yet Hughes successfully brought suit against Hamilton Standard for the malfunctioning counter-rotating blades in the right propeller. The crash was dramatized in the 2004 biographical film The Aviator.












The second prototype
The second prototype, 44-70156, was fitted with conventional propellers and flown by Hughes on 5 April 1947, after he had recuperated from his injuries. Initially, the USAAF had insisted that Hughes not be allowed to fly the aircraft, but after a personal appeal to Generals Ira Eaker and Carl Spaatz, he was allowed to do so against posting of $5 million in security.The USAAF also required that the aircraft be trucked from Culver City to Muroc Dry Lake for the flight, fearing the repercussions of another crash in a populated area.

This test flight was uneventful, and the aircraft proved stable and controllable at high speed. It lacked low-speed stability, however, as the ailerons were ineffective at low altitudes. When the USAAF evaluated it against the Republic XF-12, testing revealed the XF-11 was harder to fly and maintain, and it was projected to be twice as expensive to build. An F-12 production order was issued, but the USAAF ultimately canceled it in favor of the RB-50 Superfortress and Northrop F-15 Reporter, both of which had similar long-range photo-reconnaissance capability and were available at a much lower cost.

The United States Air Force (USAF) was created as a separate service in September 1947, and the XF-11 was redesignated as the XR-11 in July 1948. The surviving XR-11 prototype arrived at Eglin Field, Florida, in December 1948 from Wright Field, Ohio, to undergo operational suitability testing. The airframe was transferred to Sheppard Air Force Base, Texas, on 26 July 1949 for use as a ground maintenance trainer by the 3750th Technical Training Wing, and was dropped from the USAF inventory in November 1949.And eventually scrapped.
















Specifications (XF-11)
General characteristics
Crew: 2, pilot and navigator/photographer
Length: 65 ft 3 in (19.9 m)
Wingspan: 101 ft 5 in (30.9 m)
Wing area: 983 sq ft (91.3 m2)
Aspect ratio: 10.46
Airfoil: NACA 66(215)-216
Empty weight: 37,100 lb (16,828 kg)
Gross weight: 47,500 lb (21,546 kg) (4,000 mi (3,500 nmi; 6,400 km) range)
Max takeoff weight: 58,315 lb (26,451 kg) (5,000 mi (4,300 nmi; 8,000 km) range)
Powerplant: 2 × Pratt & Whitney R-4360-31 Wasp Major 28-cyl. air-cooled radial piston engines, 3,000 hp (2,200 kW) each
Propellers: 8-bladed Hamilton Standard Hydromatic contra-rotating propellers
Performance
Maximum speed: 450 mph (720 km/h, 390 kn) at 33,000 ft (10,000 m); 295 mph (256 kn; 475 km/h) at sea level
Service ceiling: 42,000 ft (13,000 m)
Rate of climb: 1,000 ft/min (5.1 m/s)
Time to altitude: 33,000 ft (10,000 m) in 17.4 minutes
Wing loading: 59.3 lb/sq ft (290 kg/m2) (5,000 mi (4,300 nmi; 8,000 km) range)
(Text from Wikki)