November 30, 2021 |

Hughes XF-11 Gearboxes and Wind Tunnel Model

Hughes XF-11

The air was calm and the sun was starting to creep down towards the horizon as Howard Robard Hughes donned his signature hat and carefully stepped into the cockpit of his newly constructed reconnaissance aircraft, one of two Hughes XF-11 bearing serial number 44-70155. Designed by Hughes and his team to fly high-speed reconnaissance missions, it was to compete directly against the Republic XF-12 Rainbow, another clean-sheet design built for the same mission. Hughes kicked over the two Pratt and Whitney R-4360 28-cylinder engines and secured the canopy glass with a satisfying clunk. As he advanced the throttles and climbed out of his Culver City, California airport the aircraft’s performance was at the forefront as this was the first flight of the aircraft type. The contra-rotating propellers angrily swung through the air, using every last bit of the 3000hp rated take-off power provided by each R-4360.

The flight progressed normally for the first hour before an issue arose with the right rear contra-rotating propeller. The complex propellers utilized centrifugal force and hydraulic pressure to change the propeller blade’s Angle of Attack in flight, maximizing performance stability and efficiency. During the flight, a hydraulic line or fitting failed, which caused a steady leak. As the hydraulic fluid leaked out, the rear propeller went into reverse pitch, putting Mr. Hughes in a perilous asymmetrical yaw situation.

The report made by the Army cited Hughes’ Ignoring many of the common-place test-flight procedures as a primary cause of pilot error. Howard stayed aloft twice as planned, deviated from the test flight card, and strayed too far from the safety of his airport. In addition, when he realized the issue with the prop, he failed to feather the right engine, and instead cut power to the left to try to limit the Asymmetric yaw and cycled the landing gear to test the hydraulics. Unable to stay airborne, Hughes aimed for the Beverly Hills Golf Club but came up short. He clipped three houses, of which one completely burned in the ensuing blaze. Mr. Hughes sustained 3rd-degree burns to a majority of his body before being rescued by a young Marine bystander, whom he paid for the remainder of his life in gratitude.

At the Florida Air Museum, we have hundreds of artifacts, photos, and documents regarding the XF-11, including the original 1940’s wind tunnel model constructed of wood and brass, and a set of original 0.381:1 reduction gear-boxes that would’ve been found behind the infamous contra-rotating propellers. While in the Hughes display, also check out Hughes and Katherine Hepburn’s 1938 custom-made Abercrombie & Fitch leather flight suits. Interestingly enough, Abercrombie & Fitch also outfitted Charles Lindbergh on his historic solo Atlantic crossing of 1927!

Submitted by Glenn Gallagher

Latest News

Smithsonian Day

Free Admission for Smithsonian Museum Day!

Join us on Saturday, September 17th to celebrate Smithsonian Museum Day! Daily admission will be free for all ...
Read More
Florida Children's Museum

The Florida Air Museum is partnering with Explorations V!

We are excited to announce that the Florida Air Museum and Explorations V (soon to be renamed the ...
Read More
Father's Day 2022

Father’s Day Promotion

Join us on June 19th, 2022 as we celebrate Father’s Day! Dads will receive free admission with the ...
Read More
Scroll to Top