Tag Archives: Pratt & Whitney R-4360-31

7 July 1946

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Hughes XF-11 44-70155 at Culver City, California, 7 July 1946. A Lockheed C-69 Constellation is in the background. (University of Nevada, Las Vegas Libraries)
Hughes XF-11 44-70155 at Culver City, California, 7 July 1946. The prototype Lockheed XC-69 Constellation, 43-10309, now registered NX67900, is in the background. Note the XF-11’s counter-rotating propellers. (University of Nevada, Las Vegas Libraries)

7 July 1946: At the Hughes Aircraft Company’s private airport in Culver City, California, the first of two prototype XF-11 photographic reconnaissance airplanes took of on its first flight. In the cockpit was Howard Robard Hughes, Jr.

Howard Hughes in teh cocpit of the first prototype XF-11, 44-70155, with all propellers turning, at Culver City, California. (University of Nevada, Las Vegas Libraries)
Howard Hughes in the cockpit of the first prototype XF-11, 44-70155, with all propellers turning, at Culver City, California. (University of Nevada, Las Vegas Libraries)

The Hughes XF-11 was designed to be flown by a pilot and a navigator/photographer. Its configuration was similar to the Lockheed P-38 Lightning and Northrop P-61 Black Widow, as well as the earlier Hughes D-2. The prototype was 65 feet, 5 inches (19.939 meters) long with a wingspan of 101 feet, 4 inches (30.886 meters) and height of 23 feet, 2 inches (7.061 meters). The empty weight was 37,100 pounds (16,828.3 kilograms) and maximum takeoff weight was 58,300 pounds (26,444.4 kilograms).

Howard Hughes in teh cockpit of the XF-11 prototype. (Houston Chronicle)

The XF-11 was powered by two air-cooled, supercharged 4,362.49-cubic-inch-displacement (71.49 liter) air-cooled, supercharged Pratt & Whitney R-4360-31 (Wasp Major TSB1-GD) four row, 28-cylinder radial engines. This engine had a compression ratio of 7:1. It had a normal power rating of 2,550 horsepower at 2,550 r.p.m. at 5,000 feet (1,524 meters), and 3,000 horsepower at 2,700 r.p.m. for takeoff. The R-4360-31 was 4 feet, 4.50 inches (1.334 meters) in diameter, 9 feet, 6.25 inches (2.902 meters) long and weighed 3,506 pounds (1,590 kilograms). The engines drove a pair of contra-rotating four-bladed propellers through a 0.381:1 gear reduction.

The planned maximum speed was 450 miles per hour (724 kilometers per hour), service ceiling 44,000 feet (13,411 meters) and planned range was 5,000 miles (8,047 kilometers).

The first prototype Hughes XF-11, 44-70155, taking off from the Hughes Aircraft Company's private airport, Culver City, California. 7 July 1946.(University of Nevada, Las Vegas Libraries)
The first prototype Hughes XF-11, 44-70155, taking off from the Hughes Aircraft Company’s private airport, Culver City, California. 7 July 1946. (University of Nevada, Las Vegas Libraries)

After about an hour of flight, a hydraulic fluid leak caused the rear propeller of the right engine to go into reverse pitch. Rather than shutting the engine down and feathering the propellers to reduce aerodynamic drag, Hughes maintained full power on the right engine but reduced power on the left, attempting to limit adverse yaw to the right side.

Unable to make it back to the Culver City airport, Hughes planned to land at the Los Angeles Country Club. At 7:20 p.m., the airplane crashed into three houses on North Whittier Drive, Beverly Hills, California. The fire destroyed the prototype and one of the houses and heavily damaged the others. Howard Hughes was seriously injured in the crash.

Burning wreckage of Hughes' prototype XF-11 in the yard at 808 N. Whittier Street, Beverly Hills, California. (Unattributed)
Burning wreckage of Hughes’ prototype XF-11 in the yard at 808 N. Whittier Drive, Beverly Hills, California. (Los Angeles Times)
Howard Hughes in an ambulance following the crash of the XF-11. (Los Angles Times)

The investigating board criticized Hughes for not following the flight test plan, staying airborne too long, and deviating from a number of standard test flight protocols. The cause of the actual crash was determined to be pilot error.

The second Hughes XF-11 landing at Culver City. (Los Angeles Times)

A second XF-11 was completed and flew in April 1947, again with Hughes in the cockpit. The project was cancelled however, in favor of the Northrop F-15 Reporter and Boeing RB-50 Superfortress, which were reconnaissance aircraft based on existing combat models already in production.

The second prototype Hughes XF-11, 44-70156, on a test flight near Anacapa Island, off the coast of Southern California, April 1946. (Hughes Aircraft Company)
The second prototype Hughes XF-11, 44-70156, on a test flight near Anacapa Island, off the coast of Southern California, 1947. This airplane does not have counter-rotating propellers. (U.S. Air Force)

© 2019, Bryan R. Swopes