Experimenter

FEB 2015

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.

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26 Vol.4 No.2 / Februar y 2015 HINTS FOR HOMEBUILDERS Removing Damaged Fuel Drains Dick Koehler demonstrates a simple method to remove damaged fuel drain valves. Carburetor Heat Operation Dick Koehler describes how traditional carburetor heat valve systems work, including maintenance and repairs. Knife Trimming Composites EAA Technical Counselor Mike Busch demonstrates how to trim a layup while in the green state not fully cured. Removal of Stainless Steel Pulled Rivet Brian Carpenter from Rainbow Aviation Services demonstrates a technique to remove a stainless steel pulled rivet HINTS FOR HOMEBUILDERS VIDEOS HERE ARE SOME OF THE LATEST HINTS FOR HOMEBUILDERS ADDED TO THE MORE THAN 450 HINTS CURRENTLY AVAILABLE HERE: FUEL DRAIN VALVES ARE essential to your fuel system to remove debris and water from the low point(s) in your fuel system. There are many dif erent types of drain valves you can install, but most of the dif erent brands have equivalent types made by the Curtis Superior Valve Company. Perhaps the most common is the Curtis CCA-1550 valve, which is used in most gascolators and the wing tanks on many Piper aircraft. The valve is made from brass and has a 1/8-inch new pipe thread (NPT), which is a tapered thread designed to jam for a tight, leakless seal. The valve is opened by pushing up and gently rotating the crossbar. It can be locked open with a quarter turn. The internal seal looks like an O-ring but actually has a P shape. In the past, mechanics would substitute a small O-ring (AN6227B-1), but that is not good maintenance. If the valve is leaking, it is most likely due to a bit of debris stuck in the seal. A piece of grass, metal fi ling, or even a human hair can allow the valve to seep fuel. One approach that some- times works is to open the valve wide open and drain a lot of fuel, such as a pint or more, and hope the debris will be fl ushed out. A variation on this step is to open the valve and put a blast of air from your compressor inside the valve, momentarily reversing the direction of fl ow and hopefully dislodging the debris. Be sure to remove your fuel cap to allow the pressure surge to escape easily. Fuel tanks can be burst with a relatively low pressure increase of only a few pounds per square inch (psi). If the debris is in the drain in a gascolator, disassemble the gascolator and get to the valve from the inside. If all attempts to clear a leaking valve fail, today you only have one option—replace the valve. An FAA ruling a Fuel Drains Keeping your fuel lines clean BY RICHARD KOEHLER Photography courtesy of Richard Koehler

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