Starter
produced by the GG. The PT overspeed
protection is provided by an electronic overspeed
The starter has an inlet assembly, a turbine
switch that is located in the FSEE via signals from
assembly, and reduction gearing. It also includes
the two PT speed pickups. The fuel used by the
LM2500 GTE is supplied by the fuel service
a cutout switch, an overrunning clutch, and a
splined output shaft. The turbine is a single-stage,
system. For more information on your ship's fuel
axial-flow type. The reduction gearing is a
system, refer to the Engineering Operational
compound planetary system with a rotating ring
Sequencing System (EOSS).
The fuel system of the LM2500 GTE has
gear. The overrunning clutch is a pawl and
several components. These components are the
ratchet type. This provides positive engagement
during starting and overrunning when driven by
fuel pump and filter, MFC, a pressurizing valve,
the GG. The cutout switch is normally closed. It
two fuel shutdown valves, a purge valve, the fuel
is actuated by a centrifugal governor which
manifold and shroud, and 30 fuel nozzles. Also
trips open the switch. This also illuminates a
included are the CIT sensor, the VSVs, the VSV
actuators, and the power lever angle (PLA) rotary
STARTER CUTOUT indicator light at the
propulsion consoles. The output shaft has a shear
actuator. We will discuss these components
section to prevent overtorque damage. The starter
individually and explain how they relate to the
operating air pressure is 35 to 41 psig for starting
system. Refer to figure 2-41, which shows the
and 21 1 psig for water washing. Air to the
LM2500 GTE fuel system flow path, to help you
starter is piped from the starter air regulating
follow our discussion.
valve. The starter exhausts directly into the
Fuel Pump and Filter
module enclosure.
The fuel pump has two pumping elements, a
Starter Air Valve
centrifugal boost element (1) and an HP gear
The starter valve is a normally closed pneu-
element (2). It provides mounting pads and flange
ports for the fuel filter and the MFC. This feature
matic regulator and shutoff valve. It has a
reduces the amount of external piping required.
bleed-on regulator, a solenoid switch, and a
pneumatic switch. It also incorporates a check
The pump also provides a drive shaft for the
MFC. This eliminates the need for a separate TGB
valve, an actuator, and a butterfly valve. Air from
drive pad.
the ship's start air system is supplied through an
To assure an adequate supply of fuel for GTE
inlet fitting on the enclosure base to the starter
operation, the fuel pump has a higher flow
valve at 0 to 75 psig. When 28-volt dc power is
capacity than the GTE uses. Within the MFC the
supplied to the solenoid from the FSEE, the valve
pump discharge is divided into metered flow and
opens. It regulates discharge air pressure (to the
bypass flow. This division maintains a preset
starter) at 35 to 41 psig at a flow rate of 0 to
pressure drop across the metering valve by use of
3.5 lb/sec.
a bypass valve. Bypass fuel is ported to the HP
Regulation is accomplished by the balance
element inlet screen (3) of the fuel pump. If an
between the pneumatic actuator and a torsion
abnormal condition occurs that causes pump
spring on the butterfly. When the 28-volt dc signal
outlet pressure to become too high, a relief valve
is removed, the butterfly is closed by the
(4) in the pump bypasses fuel back to the HP
pneumatic actuator and the torsion spring. Valve
element inlet screen (3).
position is displayed by a mechanical position
Fuel from the ship's supply enters the pump
indicator at the valve. The valve position switch
through the fuel inlet port and is boosted
provides a valve position signal to the propulsion
in pressure by the centrifugal boost element (1),
console.
discharging into a circumferential scroll, The flow
passes through the strainer element (3) which has
FUEL AND SPEED-GOVERNING
an integral bypass; it then passes into the HP
SYSTEM
positive displacement gear element (2). The
combination of pumping elements is designed to
The fuel and speed-governing system regulates
provide improved fuel pump features so normal
and distributes fuel to the combustion section of
operation can be sustained without external boost
pumps. The pump incorporates an HP relief valve
PT speed is not directly controlled, but is
(4). This valve cracks at or above 1,350 pounds
established by the gas stream energy level
2-34
