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