Chapter 5
LYCOMING T55
5.1.
INTRODUCTION
This chapter covers the Lycoming T55 gas turbine engine.
Section I gives an operational description of the T55, covering the
engine's five sections. Section II covers in detail each of the
engine's sections and major systems.
Basically, all models of the T55 are of the same design. The
major difference between the T5 5L7C and L11 engines is that the
L11 has a twostage gas producer turbine and the L7C uses a single
stage gas producer turbine. However, the description and information
given in this chapter are applicable to all models of the T55 except
where noted. The Lycoming T55 engine is used to power the CH47
Chinook helicopter.
Section I. Operational Description of the T55 Gas Turbine Engine.
5.2.
GENERAL
This section describes in detail the inlet, compressor,
diffuser, combustion, and power turbine sections, and the differences
between models and specifications are compared.
Except for the discussion comparing models and specifications,
the section's coverage is limited to the T55L7C and 11A engines.
5.3.
DESCRIPTION
The T55 gas turbine engine is a directdrive, annular reverse
flow, freepower turboshaft engine developed for use in rotarywing
aircraft. An exploded view of the T55L11A engine is shown in
figure 5.1.
The engine consists of an air inlet, accessory drive,
compressor, diffuser, combustion, and power turbine sections. All
the sections, except the accessory drive, form an annular (circular)
flow path for air and hot gases. in addition, all the sections are
structurally interdependent. The T55 is a direct drive engine,
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