Chapter 4 — Powerplants
The fuel system is designed to provide an uninterrupted
flow of clean fuel from the fuel tank to the engine.
See Chapter 3 for more information on fuel tanks. The fuel must be available to the engine under all conditions
of engine power, altitude, attitude, and during all
approved flight maneuvers. [Figure 4-12]
Powered parachutes have fuel pump systems. The
main pump system is engine-driven and sometimes an
electrically-driven auxiliary pump is provided for use
in engine starting and in the event the engine pump
fails. The auxiliary pump, also known as a boost
pump, provides added reliability to the fuel system.
The electrically-driven auxiliary pump is controlled
by a switch in the cockpit.
A diaphragm pump is the primary pump in the fuel
system for two-stroke engines. Air pulses in the
crankcase actuate a diaphragm and provide fuel under
pressure to the carburetor. Four-stroke engines have a
mechanical pump driven directly off the engine.
Fuel Plunger Primer
The fuel plunger primer is used to draw fuel from the
tanks to supply it directly into the cylinders prior to
starting the engine. This is particularly helpful during
cold weather when engines are hard to start because
there is not enough heat available to vaporize the fuel
in the carburetor. For some powered parachutes, it is
the only way to deliver fuel to the engine when first
starting. After the engine starts and is running, the
fuel pump pushes fuel to the carburetors and begins normal fuel delivery. To avoid overpriming, read the
priming instructions in your POH for your powered
A choke or fuel enrichening system is an alternate
method to provide additional fuel to the engine for
initial cold starting. Actuating the choke control allows
more fuel to flow into the carburetor.
Fuel Bulb Primer
The fuel bulb primer is manually actuated by squeezing
the bulb to draw fuel from the tanks. This charges
the fuel lines and carburetor float bowls before starting
the engine the first time on a given day. After the
engine starts, the fuel pump is able to deliver the fuel
to the fuel bowls.