Hughes XF-11
By Timothy Hogue
The Airplane That Nearly Killed The Aviator
The Hughes XF-11 aircraft was a prototype reconnaissance plane developed by Howard Hughes and his team in the early 1940s. It was a massive airplane with a wingspan of 104 feet and a length of over 65 feet. The XF-11 was designed to fly at high altitudes, reaching speeds of up to 450 miles per hour, and equipped with a sophisticated camera system capable of capturing high-resolution images.
The XF-11 utilized a tricycle landing gear, twin-engine, twin-boom all-metal mono-plane with a pressurized central crew nacelleand a much larger wingspan and higher aspect ratio than the P-38 or the D-2. The aircraft was of conventional aluminum alloyconstruction with flush riveted skin. The wings were equipped with single-slotted Fowler flaps; roll control was provided by mid-chord spoilers at high speeds and by ailerons near the wingtips at low speeds. To provide added fuel capacity and range, connection points were mounted under the wings for 700-US-gallon (2,600 L; 580 imp gal) auxiliary drop tanks, and design drawings also indicated provisions for mounting 600-US-gallon (2,300 L; 500 imp gal) auxiliary tip tanks. However, there is no evidence that auxiliary fuel tanks were ever fitted to the prototypes during flight tests.
The XF-11 was powered by a pair of Pratt & Whitney R-4360-31 28-cylinder radial engines rated at 3,000 horsepower (2,200 kW) of takeoff power at sea level and 2,500 horsepower (1,900 kW) at 33,000 feet (10,000 m). Contra-rotating propellers were originally a contract design requirement for both the XF-11 and XF-12, and Hughes Aircraft and Republic Aircraft were given a choice between competing designs from Hamilton Standard and Aeroproducts.The first XF-11 prototype was equipped with a pair of dual four-bladed, variable-pitch, contra-rotating Hamilton Standard propellers; these were very cool in their design and added to the overall design character of the airplane but proved to be troublesome in testing, having a tendency to suddenly and inexplicably reverse pitch. The second prototype was equipped with conventional four-bladed, variable-pitch Curtiss Electric propellers identical to those fitted to the P-61 Black Widow
Howard Hughes was known for his passion for aviation and his desire to push the boundaries of what was possible. He invested millions of dollars into the development of the XF-11, which he envisioned as a revolutionary aircraft that would change the course of aviation history. However, the project was not without its challenges.
One of the most significant setbacks in the development of the XF-11 occurred in July 1946 when the prototype crashed during a test flight. Hughes himself was piloting the plane at the time of the accident and was lucky to survive. The crash resulted in the destruction of the aircraft and significant injuries to Hughes.
An hour and fifteen minutes into the flight, after the 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, causing a major failure, disrupting that engine's thrust and causing the aircraft to yaw hard to the right and begin descending steeply. Hughes was approximately 2 miles (3.2 km) from the factory airfield at an altitude of about 5,000 ft (1,500 m) at the time of the failure, but he decided to fly away and troubleshoot the problem rather than returning to land, later saying he believed that some unseen part of the right-hand wing or landing gear had broken open and was causing severe aerodynamic drag.
Hughes lowered and raised the landing gear again, made various adjustments to the flight control surfaces, and made several power adjustments to both engines, ultimately leaving the right-hand engine at full power and reducing power to the left-hand engine. The aircraft continued to descend and Hughes considered bailing out, but realized he was too low to do so safely. He initiated a forced landing on 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 in Beverly Hills. The third house and the aircraft were both destroyed by impact and fire; Hughes was severely injured and 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,"but Hughes successfully brought suit against Hamilton Standard for the malfunctioning contra-rotating blades in the right propeller. The crash was dramatized in the 2004 biographical film The Aviator.
Hughes lowered and raised the landing gear again, made various adjustments to the flight control surfaces, and made several power adjustments to both engines, ultimately leaving the right-hand engine at full power and reducing power to the left-hand engine. The aircraft continued to descend and Hughes considered bailing out, but realized he was too low to do so safely. He initiated a forced landing on 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 in Beverly Hills. The third house and the aircraft were both destroyed by impact and fire; Hughes was severely injured and 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,"but Hughes successfully brought suit against Hamilton Standard for the malfunctioning contra-rotating blades in the right propeller. The crash was dramatized in the 2004 biographical film The Aviator.
Despite the crash, Hughes was determined to salvage the project. He worked with his team to rebuild the XF-11, making modifications to improve its safety and performance. The revamped aircraft made its first successful flight in August 1947 and went on to complete a series of test flights.
However, the XF-11 never entered into full production. It was deemed too expensive and impractical for military use, and advances in reconnaissance technology made the aircraft obsolete. Nevertheless, the XF-11 remains a fascinating piece of aviation history, representing the vision and determination of Howard Hughes and his team.
However, the XF-11 never entered into full production. It was deemed too expensive and impractical for military use, and advances in reconnaissance technology made the aircraft obsolete. Nevertheless, the XF-11 remains a fascinating piece of aviation history, representing the vision and determination of Howard Hughes and his team.
The XF-11's legacy is also a testament to the importance of innovation and persistence. Despite setbacks and challenges, Hughes and his team were able to overcome obstacles and continue to push the boundaries of aviation technology. Their dedication and passion for their work have inspired countless others to pursue their dreams and never give up in the face of adversity.
In conclusion, the Hughes XF-11 aircraft is a remarkable example of human ingenuity and perseverance. It may not have achieved the widespread success that its creators had hoped for, but it remains an important part of aviation history and a symbol of the power of innovation and determination.
In conclusion, the Hughes XF-11 aircraft is a remarkable example of human ingenuity and perseverance. It may not have achieved the widespread success that its creators had hoped for, but it remains an important part of aviation history and a symbol of the power of innovation and determination.
Timothy Hogue,
Contributor, MetronGarage-Elevated Garage Journal
Contributor, MetronGarage-Elevated Garage Journal
