hinged to the rear of the tailpipe. The secondary
Usually a set of 10 inserts of various curvatures
nozzle is secured by a stationary supporting shroud,
is provided with each aircraft. The different size
on which the pivot points for the flap-operated
inserts allow a total change of 10 square inches in
mechanisms are located. The flaps are slotted to
nozzle area in 1-inch increments. Thus, through
permit thermal expansion and are mounted onto the
experience, a mechanic can run the engine at
tailpipe. The flaps are controlled by four synchronized
maximum speed with one combination of inserts.
Check the temperature, and substitute another
combination to make up a temperature deficiency or
remedy an excess temperature situation.
NOTE: All advanced-technology engines
now used by the Navy have state-of-
the-art electronic parts that eliminate
The accessory section of the turbojet engine has
the need for physically changing the
various functions. The primary function is to provide
space for the mounting of accessories necessary for
the operation and control of the engine. It also
includes accessories concerned with the aircraft, such
The variable-area nozzle at the exhaust exit is
automatic. A very important use of this type of nozzle
secondary purpose includes acting as an oil reservoir,
is to increase the exit area during afterburning.
oil sump, and providing for and housing of accessory
The segment-type nozzle area opens and closes
drive gears and reduction gears.
by individual overlapping sliding segments. See
The arrangement and driving of accessories have
always been major problems on gas turbine engines.
Some engines use the inner- and outer-flap
Driven accessories are mounted on common pads
variable nozzle assembly, shown in figure 1-45. The
either ahead of or next to the compressor section.
assembly has an internal primary nozzle with
Figure 1-46 shows the accessory arrangement of
sectional flaps and an external secondary nozzle with
an axial-flow engine.
sectional flaps. The flaps of the primary nozzle are