Retractable Gear Systems

The first evidence of a retractable landing gear design was in Europe circa 1911, but a working example didnt show up on aircraft until after WWI. As airplanes got heavier and faster, meanwhile, airport infrastructure-which mainly consisted of an open field and a windsock- couldnt keep up. As a result, some of the fastest airplanes in the 1920s and 1930s were seaplanes, even with the aerodynamic drag their floats imposed. By the time WWII erupted, the latest airplanes were equipped with retractable landing gear, even if in a conventional, taildragging configuration. Still, many long-range, multi-engine airliners of the day were seaplanes.

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Sunday, March 17, 2019 at 12:00 AM ET

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Key Takeaways:

Retractable landing gear, first seen in early 20th-century designs, became common by WWII to significantly reduce aerodynamic drag and improve aircraft performance, evolving from manual to more complex hydraulic and electric systems.
Modern retractable gear systems employ diverse mechanisms (electric, hydraulic, hybrid, manual) and incorporate critical safety features such as ground lockout switches, alternate extension methods, and warning indicators to prevent malfunctions.
Ensuring the reliability of retractable landing gear requires diligent maintenance, while pilots must rigorously use pre-landing checklists to prevent gear-up landings, and be prepared for emergency procedures like landing all-gear-up on a paved runway if extension fails.

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The first evidence of a retractable landing gear design was in Europe circa 1911, but a working example didn’t show up on aircraft until after WWI. As airplanes got heavier and faster, meanwhile, airport infrastructure—which mainly consisted of an open field and a windsock— couldn’t keep up. As a result, some of the fastest airplanes in the 1920s and 1930s were seaplanes, even with the aerodynamic drag their floats imposed. By the time WWII erupted, the latest airplanes were equipped with retractable landing gear, even if in a conventional, taildragging configuration. Still, many long-range, multi-engine airliners of the day were seaplanes.

Boeing and Lockheed, among others, introduced retractable gear in the 1930s, although many manufacturers didn’t fully enclose the main gear. In an eloquent statement of what the engineers thought about the reliability of retractable landing gear, they sometimes designed the system so the wheels would still roll, and protect the fuselage and engine nacelles, when landed gear-up. Thankfully, the technology has improved since then, if not the pilots.