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This chapter covers the engines found on most pow- ered parachutes and includes the exhaust, ignition, fuel, lubrication, cooling, propeller, gearbox, induc- tion, charging, and fuel systems. Reciprocating en- gine 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 sup- ports 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 recommenda- tions. Preflight information, along with maintenance schedules and procedures, can be found in the  Pilot’s Operating Handbook  (POH) and/or maintenance ref- erences from the manufacturers. 

Engine inspections and maintenance must be per- formed and documented in a logbook. You should review this logbook before flying an unfamiliar pow - ered parachute. 

## Reciprocating Engines 

Most powered parachutes are designed with recipro- cating engines. Two common means of classifying reciprocating engines are: 

1. By the number of piston strokes needed to complete a cycle: two-stroke or four-stroke; and 

2. By the method of cooling: liquid or air-cooled. 

Refer to Chapter 5 of the Pilot’s Handbook of Aero- nautical Knowledge for a comprehensive review of how reciprocating four-stroke engines operate. 

## Two-Stroke Engines 

Two-stroke engines are commonly used in powered parachutes. Two-stroke aviation engines evolved from two-stroke snowmobile and watercraft engines, 

the difference being that an aircraft engine is opti- mized for reliability with dual ignition often installed for each cylinder. Two-stroke engines are popular be- cause they have fewer components than four-stroke engines which makes them less expensive to manu- facture, and lighter, thus increasing their power-to- weight 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  com- pression , the second stroke as the piston moves down is power and exhaust . The two-stroke engine per- forms 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 clos- ing 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, pull- ing 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 enter- ing the engine and concludes as it exits as exhaust. [Figure 4-3] 

