maintenance requirements for which you, the GSM, will
The voltages produced by the ignition
FUEL SHUTOFF VALVE. The fuel shutoff valve
exciter unit can be lethal.
performs the same function on all of the GTEs we have
discussed. This valve is the fuel's last stop before it
reaches the fuel nozzles.
The only engine that has a required maintenance
procedure on this valve is the Allison. This check is
You should also take special care when you
usually performed in conjunction with safety checks.
are handling the PD 680 type-II solvent you will
normally use to clean the igniters. The safety
There are really only two types of failures that
precautions you should use for handling this
will normally occur with the Allison's fuel shutoff
solvent are contained on the PMS card, in the
valve. The first failure is when the valve fails to
manufacturer's technical manual, and in
open and the engine does not start. This problem is
fairly simple to solve. The first thing you should
check is the fuel manifold pressure gauge. Do this
The igniters used on the Garrett and Allison GTEs
while attempting a start. If fuel pressure does not
are similar in design. They both have a fixed flange.
register on the gauge, you should have a GSE check
Unlike the igniters installed on the LM2500 GTE, you
the electrical signal to the valve. If a GSE verifies
will not have to take a depth measurement on the Allison
that the valve is receiving the proper electrical
and Garrett igniters before you install them.
signal, then you must replace the valve. The second
type of failure is when the valve fails to close or it
Exciters. As a rule, the Allison and Garrett ignition
leaks by. Valve leak by is not a rare occurrence on
exciter units will not require much maintenance.
the Allison GTE. This problem will usually
Cables. You must, however, make certain the
manifest itself in a spectacular fashioneither by a
cables are inspected at the appropriate intervals. On the
post shutdown fire or an exhaust boot fire. The only
Allison, you must inspect the cables during every GTGI.
remedy to this problem is to replace the valve.
On the Garrett, you must inspect the cables after each
shutdown and before each start-up.
for the fuel nozzles is also determined by hours of engine
The turbine section of your GTE will have very few
operation. Dirty fuel nozzles will not only rob the engine
shipboard serviceable components. As with most of the
of its power, the resulting poor spray pattern can damage
major engine components, the repairs will normally be
the combustion liners in the form of hot spots. To
accomplished by a SIMA.
maintain your GTE at peak operating efficiency, you
Most of the shipboard maintenance on the turbine
must keep the fuel nozzles clean.
section will be electrical. The GSEs will service the
FUEL MANIFOLD DRAIN VALVES. On the
thermocouples and the vibration pickup. You, the
Allison GTE and the Garrett GTE, your responsibilities
GSM, will service the rear scavenge oil pump and the
for maintaining the fuel manifold valves will be
air/oil vent system. Your maintenance of the rear
scavenge oil pump will be limited to the removal and
replacement of the pump and the inspection of the
Allison. The fuel manifold drain valves on the
pump cover oil seal.
Allison GTE must be checked for proper mechanical
and electrical operation approximately every quarter. As
a GSM, you will be testing the mechanical functions of
the Allison's valves to make certain they open and the
residual fuel can drain. The GSEs will be checking the
In each of the GTEs we have discussed, a generator
electrical signal sent to the valve. Both mechanical and
set will have an accessory gearbox. On the Garrett and
electrical checks will also be accomplished periodically
Sunstrand, however, the gearboxes serve a double role.
during safety checks.
They not only provide drive and mounting capabilities
for the accessories, they also serve as the reduction gear
Garrett. Even though a manifold drain valve is
and the turbine's oil reservoir.
installed on the Garrett GTE, there are no specific