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who may be in the prop-wash area behind the propeller.
Stones, small pieces of metal, and sticks can
become dangerous projectiles if kicked into the propeller
during takeoff and landing. Just as with any
airframe or wing component of a powered parachute,
if the propeller becomes damaged, nicked or dinged,
the aircraft’s performance can be greatly affected.
Some pilots elect to use tape or rock deflector guards
to protect the leading edge from rock/debris damage.
Regardless, taking proper care of the PPC propeller is
as critical as proper engine and wing care.
Axle and Wheel Assembly
The rear and front wheels of the powered parachute
are an assembly and consist of a tire, a rim, and an
inner and outer set of wheel bearings. The wheel is
secured on a spindle and held in place by a nut and
a cotter pin. Each spindle is typically mounted on a
suspension system which provides elasticity and at
the same time is very strong. [Figure 3-18] The suspension
system varies by manufacturer from one cart
to another; refer to the POH for exact configuration
and components. Some powered parachute tires are
heavily treaded while others are smooth; pilot preference
and the terrain type are determining factors in
choice of tire profiles. [Figure 3-19] Tire sealant or
thorn guards can be used to minimize flat tires.
Figure 3-17. Airfoil sections of a propeller blade.
Figure 3-18. Suspension system.
Figure 3-19. Some powered parachute tires are heavily
treaded while others are smooth.
3-10
4-1
the difference being that an aircraft engine is optimized
for reliability with dual ignition often installed
for each cylinder. Two-stroke engines are popular because
they have fewer components than four-stroke
engines which makes them less expensive to manufacture,
and lighter, thus increasing their power-toweight
ratio.
Two-stroke engines require that oil be mixed into the
fuel to lubricate the engine, instead of being held in a
sump and having a separate recirculating system like
a four-stroke engine. Details on two-stroke oil mixing
are covered later under the “Lubrication” section.
One stroke as the piston moves up is intake and compression,
the second stroke as the piston moves down
is power and exhaust. The two-stroke engine performs
the same functions as a four-stroke engine in
half the strokes.
A wide range of valve systems are found on two
cycle engines, for the purpose of opening and closing
ports in the cylinder to let fuel in and exhaust out
at the proper time, similar to the intake and exhaust
valves on a four-stroke engine. One-way pressure
valves, called spring, reed, or poppet valves, open
when the pressure drops within the crankcase, pulling
the fuel from the carburetor into the crankcase.
[Figure 4-1]
Mechanical rotary valves are driven off the engine,
rotate to provide an opening at the precise time, and
can be on the intake and exhaust ports. [Figure 4-2]
Piston porting does not use any valves. The fuel inlet
port is opened and closed by the piston position as
it moves up and down in the cylinder. This is called
a “piston ported inlet” and will be used in the Two-
Stroke Process description that follows. [Figure 4-3]
Two-Stroke Process
The two-stroke process begins with the fuel entering
the engine and concludes as it exits as exhaust.
[Figure 4-3]
This chapter covers the engines found on most powered
parachutes and includes the exhaust, ignition,
fuel, lubrication, cooling, propeller, gearbox, induction,
charging, and fuel systems. Reciprocating engine
operating theory is covered, for both two-stroke
and four-stroke engines.
The powered parachute engine and propeller, often
referred to as a powerplant, work in combination to
produce thrust. The powerplant propels the powered
parachute and charges the electrical system that supports
PPC operation.
The engine is one of the key components of a powered
parachute and should be maintained according to both
the engine and airframe manufacturer recommendations.
Preflight information, along with maintenance
schedules and procedures, can be found in the Pilot’s
Operating Handbook (POH) and/or maintenance references
from the manufacturers.
Engine inspections and maintenance must be performed
and documented in a logbook. You should
review this logbook before flying an unfamiliar powered
parachute.
Reciprocating Engines
Most powered parachutes are designed with reciprocating
engines. Two common means of classifying
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Powered Parachute Flying Handbook动力伞飞行手册(27)
