New Boeing Patent Details Conceptual Auxiliary Landing Gear Designed to Protect Engines
In August of 2022, Boeing was awarded a patent for a novel auxiliary landing gear concept. First published in January of 2020, the patent involves the installation of emergency auxiliary landing gear, normally concealed from view, that would protect the engines in the event of a gear-up landing.
Patents rarely incorporate impressive visuals, and this one is no exception. As with most, it is simply intended to illustrate a general concept. Nevertheless, the technical illustrations do the job and give us an idea of how the concept is intended to work.
Recognizing that landing gear can and occasionally do fail to extend, Boeing’s concept involves an auxiliary wheel and shock absorber that are housed within each underwing engine nacelle. The assembly would normally be fully faired to minimize drag. From the outside, an observer would see only a small, smooth bump on the underside of each engine nacelle as in the diagrams above. To the vast majority of the traveling public, the feature would likely go entirely undetected.
FIG. 2C – In the event of a gear-up landing, the fairings would be the first part of the aircraft to make contact with the ground. Designed to be frangible, they would be torn away instantly, revealing small auxiliary landing gear that protrude just far enough below the engine nacelle to prevent it from contacting the ground. Boeing alternatively describes a fairing that would remain in place as a low-friction skid that would remain in place until worn down enough to expose the wheels inside. A cutaway view shows the auxiliary gear nested within the engine fairing.
FIG. 4 – As the tires would likely only have to perform their duty one time in an emergency capacity, Boeing appears to propose a solid, non-pneumatic variant. This would offer several benefits over a traditional pneumatic tire, including less weight, maintenance, and volume. A closer look at the theoretical wheels reveals a striking similarity to the tailwheel of the U-2, which is equipped with this type of tire
FIG. 5B – Here, a side cutaway offers a closer look at the shock absorber and longitudinal brace.
In the absence of a significant number of gear-up landings, this patent appears to be proactive rather than reactive in nature. Rather than serving as a remedy to an existing problem, the patent is likely nothing more than a means of reserving the intellectual property in the event future customers show an interest in it.
But regardless of their motivation, it’s a compelling concept. Thus far, the closest anyone has come to it is main gear designs that do not fully retract the wheels into the aircraft. The DC-3 and A-10, for example, leave a small portion of the main gear tires protruding out into the airstream when retracted. This produces drag but also prevents the airframe from incurring damage during a gear-up landing.
Boeing’s concept is unique in that it incorporates the rip-away fairing, thus minimizing drag when not in use. Kudos to Boeing and the inventors for thinking outside the box.
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