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Chapter 4 — Powerplants
Fuel Contamination
Clean fuel is imperative for the safe operation of a
PPC. Of the accidents attributed to powerplant failure
from fuel contamination, most have been traced to:
• Failure to remove contamination from the fuel
system during preflight.
• Servicing aircraft with improperly filtered fuel
from small tanks or drums.
• Storing aircraft with partially filled fuel tanks.
• Lack of proper maintenance.
Rust is common in metal fuel containers and is a common
fuel contaminant. Metal fuel tanks should be
filled after each flight, or at least after the last flight of
the day to prevent moisture condensation within the
tank. Another way to prevent fuel contamination is
to avoid refueling from cans and drums. Use a water
filtering funnel or a funnel with a chamois skin when
refueling from cans or drums. However, the use of a
chamois will not always ensure decontaminated fuel.
Worn-out chamois will not filter water; neither will a
new, clean chamois that is already water-wet or damp.
Most imitation chamois skins will not filter water.
Bad Gasoline
Letting fuel sit for weeks without using it will cause
it to go bad. Even if gas does not go bad, it will often
lose its octane with time. For those that premix gasoline
and two-stroke oil, there is another set of problems.
Fuel and oil are normally mixed at a 50:1 ratio.
If premixed gas sits in a plastic container for a while,
the gas will evaporate out leaving a richer oil mixture
in the container. In any case, fresh gas should be used
as much as possible.
Refueling Procedures
Never mix oil and fuel in an enclosed area. Not only
are the fumes irritating, but with the right fuel-air
mixture you can cause an explosion. Do all oil and
gas mixing outside. Refueling from fuel cans should
also be done outside. Never smoke while refueling.
Be careful refueling an aircraft that has just landed.
There is the danger of spilling fuel on a hot engine component,
particularly an exhaust system component.
Refueling should be done using only safety-approved
fuel containers. The fuel containers should be marked
with the type of fuel stored in them. Confusing premixed
fuel and fuel that has no oil in it can be disastrous.
There are advantages to both metal and plastic containers.
Metal cans won’t allow the sun’s ultraviolet
rays in to harm the fuel. It also won’t develop static
charges like a plastic container may. However, a metal
can will be more prone to sweating when going from
cool to warm temperatures on humid days. Metal cans
and metal gas tanks are best kept either empty, or full
of fuel to leave no room for moist air.
Plastic fuel containers are easy to handle, inexpensive,
available at discount stores, and do not scratch
the finish on airframes. Plastic cans also do not sweat,
so they don’t need to be stored topped off. However,
fuel does deteriorate a little faster in plastic. Also,
plastic containers can get charged with static electricity
while sliding around in the bed of a pickup truck,
especially if the truck has a plastic bed liner. Many
states now have laws prohibiting people from filling
plastic containers unless first placed on the ground.
Static electricity can also be formed by the friction of
air passing over the surfaces of a powered parachute
in flight and by the flow of fuel through the hose and
nozzle during refueling, if fueling at a pump. Nylon,
Dacron, and wool clothing are especially prone to
accumulate and discharge static electricity from the person to the funnel or nozzle. To guard against the
possibility of static electricity igniting fuel fumes, a
ground wire should be attached to the aircraft before
the fuel cap is removed from the tank. The refueling
nozzle should then be grounded to the aircraft before
refueling is begun, and should remain grounded
throughout the refueling process.
The passage of fuel through a chamois increases the
charge of static electricity and the danger of sparks.
The aircraft must be properly grounded and the nozzle,
chamois filter, and funnel bonded to the aircraft.
If a can is used, it should be connected to either the
grounding post or the funnel. Cell phones should not
be used while refueling as they could pose a fire risk.
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