GENERAL
This chapter contains an overview of jet powered
airplane operations. It is not meant to replace any
portion of a formal jet airplane qualification course.
Rather, the information contained in this chapter is
meant to be a useful preparation for and a supplement
to formal and structured jet airplane qualification
training. The intent of this chapter is to provide
information on the major differences a pilot will
encounter when transitioning to jet powered airplanes.
In order to achieve this in a logical manner, the major
differences between jet powered airplanes and piston
powered airplanes have been approached by
addressing two distinct areas: differences in
technology, or how the airplane itself differs; and
differences in pilot technique, or how the pilot deals
with the technological differences through the
application of different techniques. If any of the
information in this chapter conflicts with information
contained in the FAA-approved Airplane Flight
Manual for a particular airplane, the Airplane Flight
Manual takes precedence.
JET ENGINE BASICS
A jet engine is a gas turbine engine. A jet engine
develops thrust by accelerating a relatively small mass
of air to very high velocity, as opposed to a propeller,
which develops thrust by accelerating a much larger
mass of air to a much slower velocity.
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As stated in Chapter 14, both piston and gas turbine
engines are internal combustion engines and have a
similar basic cycle of operation; that is, induction,
compression, combustion, expansion, and exhaust. Air
is taken in and compressed, and fuel is injected and
burned. The hot gases then expand and supply a
surplus of power over that required for compression,
and are finally exhausted. In both piston and jet
engines, the efficiency of the cycle is improved by
increasing the volume of air taken in and the
compression ratio.
Part of the expansion of the burned gases takes place in
the turbine section of the jet engine providing the
necessary power to drive the compressor, while the
remainder of the expansion takes place in the nozzle of
the tail pipe in order to accelerate the gas to a high
velocity jet thereby producing thrust. [Figure 15-1]
In theory, the jet engine is simpler and more directly
converts thermal energy (the burning and expansion of
gases) into mechanical energy (thrust). The piston or
reciprocating engine, with all of its moving parts, must
convert the thermal energy into mechanical energy and
then finally into thrust by rotating a propeller.
One of the advantages of the jet engine over the piston
engine is the jet engine's capability of producing much
greater amounts of thrust horsepower at the high
altitudes and high speeds. In fact, turbojet engine
efficiency increases with altitude and speed.
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