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Pilot's Handbook of Aeronautical Knowledge
Aircraft Systems

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Depending on the engine manufacturer, all of these
arrangements can be designed to utilize spark or compression
ignition, and operate on either a two- or four-stroke cycle.

In a two-stroke engine, the conversion of chemical energy
into mechanical energy occurs over a two-stroke operating
cycle. The intake, compression, power, and exhaust processes
occur in only two strokes of the piston rather than the more
common four strokes. Because a two-stroke engine has a
power stroke each revolution of the crankshaft, it typically has
higher power-to-weight ratio than a comparable four-stroke
engine. Due to the inherent inefficiency and disproportionate
emissions of the earliest designs, use of the two-stroke engine
has been limited in aviation.

Recent advances in material and engine design have
reduced many of the negative characteristics associated
with two-stroke engines. Modern two-stroke engines often
use conventional oil sumps, oil pumps and full pressure fed
lubrication systems. The use of direct fuel injection and
pressurized air, characteristic of advanced compression
ignition engines, make two-stroke compression ignition
engines a viable alternative to the more common four-stroke
spark ignition designs. [Figure 6-3]

Two-stroke compression ignition.
Figure 6-3. Two-stroke compression ignition.

Spark ignition four-stroke engines remain the most common
design used in general aviation today. [Figure 6-4] The
main parts of a spark ignition reciprocating engine include
the cylinders, crankcase, and accessory housing. The intake/
exhaust valves, spark plugs, and pistons are located in the
cylinders. The crankshaft and connecting rods are located
in the crankcase. The magnetos are normally located on the
engine accessory housing.

components of a spark ignition
Figure 6-4. Main components of a spark ignition reciprocating

In a four-stroke engine the conversion of chemical energy
into mechanical energy occurs over a four stroke operating
cycle. The intake, compression, power, and exhaust processes
occur in four separate strokes of the piston.
1. The intake stroke begins as the piston starts its
downward travel. When this happens, the intake
valve opens and the fuel/air mixture is drawn into the
2. The compression stroke begins when the intake valve
closes and the piston starts moving back to the top of
the cylinder. This phase of the cycle is used to obtain
a much greater power output from the fuel/air mixture
once it is ignited.
3. The power stroke begins when the fuel/air mixture is
ignited. This causes a tremendous pressure increase
in the cylinder, and forces the piston downward away
from the cylinder head, creating the power that turns
the crankshaft.
4. The exhaust stroke is used to purge the cylinder of
burned gases. It begins when the exhaust valve opens
and the piston starts to move toward the cylinder head
once again.