The Ryan YO-51 Wowed with STOL Performance

The design was developed as a liaison and observation platform for the U.S. Army Air Corps.

Tuesday, February 06, 2024 at 09:06 PM ET

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One of three Ryan YO-51 Dragonfly prototypes demonstrates its leading-edge slats and massive, full-span Fowler flaps during a spirited takeoff. [Photo: USAAF]

Key Takeaways:

In the late 1930s, the U.S. Army Air Corps sought a specialized STOL liaison and observation aircraft, leading to a competition involving prototypes from Bellanca, Stinson, and Ryan.
Ryan's YO-51 "Dragonfly" featured a unique design with an open cockpit, parasol wing, and advanced aerodynamic elements such as full-span leading-edge devices and Fowler flaps, powered by a common Pratt & Whitney R-985 radial engine.
The YO-51 demonstrated extraordinary STOL performance, reportedly taking off in under 100 feet and achieving a stall speed of just 30 mph, consistently impressing test flight observers.
Despite its groundbreaking capabilities, the Ryan YO-51 ultimately lost the contract to the Stinson L-1 Vigilant, and all three YO-51 prototypes were subsequently scrapped.

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In the late 1930s, the U.S. Army Air Corps (USAAC) determined it needed a specialized aircraft as a liaison and observation platform with exceptional short takeoff and landing (STOL) capability. This was perhaps inspired by the Fieseler Storch performing many of the same duties for the Luftwaffe. The Storch excelled in its role, using a 240-horsepower inverted V-8 to pull a kite-like wing through the air and providing takeoff and landing distances of less than 200 feet.

The USAAC sent bids for such an aircraft to multiple manufacturers. The ensuing competition ultimately came down to three, each building three prototypes in 1939 for the contract. Bellanca responded with the YO-50, a high-wing taildragger with an enclosed tandem cabin powered by a 420-horsepower Ranger inverted V-12. Stinson responded with their L-1 Vigilant, an aircraft of similar design but with a more traditional 295-horsepower Lycoming radial engine.