Lockheed XH-51A (oz6690)

About this Plan

Lockheed XH-51A. Scale model helicopter.

Quote: "For the RCer who wants the ultimate, here's a scale 70in diameter rigid rotor helicopter for full house proportional. The author's text and engineering drawings will provide you with a sound basis for advanced experimentation.

HERE'S one for the fellows who are bored with things like multi-engine carrier landings and piggy-back sailplane launchings. It's an eight pound, four control, 70-inch diameter rigid rotor helicopter. It can be flown as a rectangular fuselage section experimental job and then finished up with a fuselage shell of balsa or fiberglass to be a scale model of the Lockheed XH-51A helicopter. Here's a model you can literally fly in your own backyard.

The model was made as small as possible to carry full quad proportional gear and still have light enough disk loading for safe vertical autorotational capability. One of the design objectives was to keep the machine work as simple as possible. Well, all I can say is you should have seen it before it was simplified. The model is about one order of magnitude more difficult than a multi-engine scale airplane, and should be attempted only by an experienced and clever machinist. Estimated time to build is about six months, spending most of your spare time on it. It took two such full months to design the thing. First came the preliminary specs and some aerodynamic calculations to determine size, hovering power, rotor rpms and autorotation capabilities. Then some preliminary designing and weight and balance estimates. Next came detail designing and working out the many technical problems, along with a little stress work. The CG was kept track of during the many changes. Finally came the work part, putting the design on Mylar so that other people could build it.

Design Features. Rotor. The rigid rotor and stabilizer bar were chosen not only to give stability in the air but also to minimize roll over on landing. A teetering or flapping rotor could have been made stable in the air by a gyro stabilizer bar, but they give no roll or pitch damping to the fuselage in the event of a sidewise or forward speed landing. The aircraft would bounce once and roll over, creaming the blades..."

This plan and article was published in the book 'The challenge of Radio Control Scale" published by RCM, 1967.

Update 02/08/2016: Replaced this plan with a better copy (CAD-redrawn, PDFvector format, full-size on 2 sheets) thanks to rchopper56.

Supplementary file notes

Previous scan version (unscaled, unstitched). Also, OCR text of article pages.

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