Experimenter

JAN 2013

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

Issue link: http://experimenter.epubxp.com/i/101874

Contents of this Issue

Navigation

Page 39 of 55

Un d e r t h e C o w l full throttle (full rpm), it will be disappointing at lower rpm; cruise performance will suffer. are acceptable on their LSA; that satisfies the FAA. But don't believe that there is any "certification" involved. Buying Used Balance A lot of good deals exist on used props, but there is no way a nonexpert can look at a pretty prop and tell if he's getting a cherry or a lemon. Before you buy a used propeller from other than a reputable prop shop, have the manufacturer check it out. It's better to be disappointed on the ground than to lose a blade in flight. Prop balance is critical to safe and pleasant flight. The prop is in "static" balance when it balances evenly around its hub. "Dynamic" balance, where the entire rotating system (engine, propeller, and spinner) is balanced, is often overlooked. "Aerodynamic" balance, where each blade pulls equally at any given rpm and angle of attack, is controlled in manufacture. A lot of metal props migrate to experimentals from certificated aircraft. Sometimes, they are great deals; sometimes, they are cut down because of tip damage. Some seem to be great deals but might not be. Other times, these are lovely to look at, but they contain hidden flaws (like nonairworthy repairs). Know what you're buying, and if you have any doubts, take the prop to a reputable shop before you buy it. Light-sport aircraft are another area of misunderstanding. As these machines age and get re-propped for better performance, the older props are showing up on the market. Likewise, many prop manufacturers will claim they're selling "LSA-certificated" props. There's no such thing as "LSAcertificated." ASTM compliant propellers are becoming available for LSA but currently are very limited in choices. For now, the airframe manufacturer specifies which prop(s) Above all, remember that your prop is one of the most critical elements in a safe flight and probably the most important component forward of the firewall (with the exception of the motor mount). If you think something is not right, check it out; use both your brain and your instinct. A prop failure in flight can easily be fatal. Tim Kern is a private pilot and has written for more than 40 different aviation magazines. He was a key builder on two aircraft projects and has earned the title of Certified Aviation Manager from the NBAA. Thanks to Sensenich Propeller for technical assistance in this piece. Tom Aberle's Phantom biplane runs this radical Paul Lippsdesigned prop at Reno. Takeof is long, but its top speed is dominant in the class. 40 Vol.2 N o.1 / January 2013 Photography by Tim Kern

Articles in this issue

Archives of this issue

view archives of Experimenter - JAN 2013