members forum
You raise several issues that I will attempt to cover. First, “What
is so different about aircraft engines from all other engines?” The
answer is nothing. It is not the engine itself that causes problems
when alcohol is introduced into an existing general aviation
aircraft fuel system. The problems come from many components
of the fuel system.
Immediate problems come from incompatibility of “soft” items
such as seals, O-rings, and carburetor floats. This would include
the carburetor float needle that you asked about. Yes, the tips
of some needles will swell when alcohol is introduced into the
fuel. This can and has caused engine stoppages. (I have personal
experience in this regard.) We have seen many instances of fuel
lines swelling and decomposing after being exposed to alcohol in
the fuel. We have also seen some sealing compounds and tank
“slosh” compounds breaking down and contaminating fuel
systems after being exposed to alcohol. Fuel tank bladders have
also shown problems when alcohol is introduced.
Longer-term problems come from the potential for corrosion in
metal fuel tanks and lines, as well as moisture contamination
of fuel system components. Alcohol has an affinity for moisture
and will readily absorb any moisture that is in the fuel system.
Since all our aircraft have “open vent” fuel systems that by design
allow air (and its included moisture content) to freely enter the fuel
system, there is always a ready supply of moisture for the alcohol
to absorb. The alcohol/water mixture that results will ultimately
break free of the fuel and settle to the bottom of the tanks or gather
in low points in lines. It is this moisture that causes the corrosion
rather than the alcohol itself. Also, this “settling” of the alcohol/
water mixture may be great enough to cause an engine stoppage
if it is not removed from the system by normal sump drainage or
by the gascolator.
It is for all these reasons that the Federal Aviation Administration
has mandated that auto fuel supplemental type certificates (STCs)
prohibit the use of fuels containing alcohol. Yes, the aircraft fuel
systems could be modified to tolerate the alcohol, but the cost
of approving individual engines and airframes and the cost of
modification of the aircraft in the field would far outweigh any
cost advantage that might be gained by using auto fuel instead of
aviation fuel in the aircraft. This would defeat the purpose of the
auto fuel STC, which is to lower the cost of flying.
Homebuilt aircraft are a different story. Since each aircraft is an
“experiment,” there is nothing that would prohibit a builder from
making modifications to the aircraft’s fuel system so as to make it
“alcohol proof.” This would not eliminate the issue of the open vent
fuel system, but that could be dealt with by not allowing auto fuel
to stay in the system for long periods of time. The short-term issues
could be dealt with by using proper materials and components.
Using auto fuel containing alcohol would be perfectly legal in an
experimental aircraft. But for standard category aircraft, the STCs
will continue to prohibit alcohol content in the auto fuel.
Do not hesitate to contact us anytime you have a question or
comment.
Joe Norris, EAA 113615 Lifetime
EAA Homebuilders’ Community Manager
New Lifetime Members
Ara Ashburne (EAA 720754), Berrien Springs, Michigan
Cliff Belleau (EAA 311027), Anchorage, Alaska
Daniel Dezauche (EAA 825449), Grand Bay, Alabama
Susan Dezauche (EAA 878281), Grand Bay, Alabama
Dwight Drefs (EAA 714088), Highlands Ranch, Colorado
Pierre DuPont (EAA 122258), Menominee, Michigan
David Greene (EAA 878874), Frankston, Texas
Philip Hartmann (EAA 334148), Middletown, Connecticut
John Koenig (EAA 878065), Center Moriches, New York
Vasco Marao (EAA 40557), Alfornelos Amadora, Portugal
Daniel Ness (EAA 378209), Holmen, Wisconsin
Edmund Orsini (EAA 860313), Littleton, Colorado
Richard Parsons (EAA 449064), Big Pine Key, Florida
Ira Weissman (EAA 111241), Cherry Hill, New Jersey
Roger Whyte (EAA 809751), Wichita, Kansas
Correction to Reno Story Caption
I was glad to see Tim Kern’s recent Craft & Technique article
that provided useful air racer ”tips” to builders and perhaps
some insight into the activities and the benefits that
amateur aircraft builders active in pylon air racing bring to
the table. It is nice to get a bit of exposure for this unique
side of the amateur builders’ community.
I do have one correction to the article. The picture of
Race #12 on page 93 is mislabeled. The racer shown is
actually a highly modified Cassutt named Outrageous. Race
#12 is a Formula One racer with a rich history at Reno and
is presently owned by John Kokshoorn of Australia. John is
coincidently the 2008 International Formula One “Rookie
of the Year.” The person responsible for the extensive
modifications to what was originally a plans-built Cassutt,
and for consistently flying this airplane in the top of the
Gold Formula One races at Reno, is Scotty Crandlemire
(EAA/IAC 368777).
Although the Formula One Class of pylon air racers
evolved from the “Midget” or “Goodyear” racers dating
back to 1947 and involved such notable EAA icons as Steve
Wittman, we are often overlooked because of the diminutive
nature of our racers. The very “formula” creating this
affordable “tech” class that has “amateur-built,” and thus
EAA, written all over it often disadvantages the promotion
of the class and can be discouraging at times. We just don’t
make the “noise” that draws the sponsors and attention
