Planetary Gear Shafts. The forward and aft ends
of the planetary gear shafts are supported by ball
bearings. Within the bearing carrier housing, there is a
and 7-25, automatically provides proper engine
circular bearing carrier. The circular bearing carrier is
fitted and bolted in the aft face of the drive housing,
acceleration and maintains a nearly constant operating
which holds the six planetary gears' ball bearings in
speed under all operating conditions. Fuel is supplied to
position inside the ring gear.
the GTE at 5 to 40 psig with a minimum flow capacity
of 200 pounds per hour.
Intermediate Accessory Drive Assembly. The
intermediate accessory drive gear is mounted on the gear
The Sunstrand's fuel system consists of the
support shaft in the forward, upper end of the reduction
following main components:
drive housing. The gear shaft is supported by a
Inlet fuel filter
double-row ball bearing.
The accessory drive is the upper portion of the
reduction drive assembly. The output shaft transmits
Start, main, and maximum fuel solenoid valves
power through the intermediate gear to the fuel pump
drive and starter gears, which convert the reduction
Start fuel nozzle
output speed to 6,000 rpm. This is the speed required to
drive the APU's accessories.
Fuel Pump and Starter Gears. The fuel pump
gear operates at 4,200 rpm. When the starter is
Acceleration control assembly
disengaged, the starter gear is free to rotate with the
intermediate gear. When the starter is engaged, the
Let's take a brief look at each of these areas.
starter gear drives the accessory drive gear train to
INLET FUEL FILTER. The inlet fuel filter
supply starting torque to the GTE.
assembly is threaded into the fuel pump inlet port and
These gears are mounted on shafts supported by ball
contains a fitting for the connection of an external fuel
bearings within the accessory drive portion of the
supply line. The filter assembly contains a 25-micron,
reduction drive housing. The gears and bearings are
lubricated by an air-oil mist from the reduction drive
FUEL PUMP. The fuel pump is a positive-
assembly. To prevent leakage of the air-oil mist, seals
displacement, gear-type pump. The pump is mounted on
are mounted in the reduction drive housing at the ends
the left forward pad of the accessory drive portion of the
of the output shaft, fuel pump drive, and starter gears.
reduction drive assembly. A 25-micron, cleanable filter
The fuel pump and engine acceleration control, which
element is installed in the pump housing. The fuel pump
is mounted in tandem with the fuel pump, is mounted on
the left forward pad of the reduction drive assembly. The
splined shaft fits into an eight-point square drive in the
starter assembly is mounted on the right forward pad.
shaft portion of the accessory drive gear. The other end
of the fuel pump driveshaft is spline-coupled to the
A drain port in the pump housing drains fuel that might
leak past the pump drive seal or past the drop regulating
In the next sections, we will look at the following
valve pin. At 4,200 rpm, the pump is capable of
operating systems of the Sunstrand T-62:
delivering 400 pounds per hour of fuel against a
discharge pressure of 400 psig.
Lubricating oil system
START, MAIN, AND MAXIMUM FUELSOLE-
NOID VALVES. The start, main, and maximum fuel
solenoid valves are hermetically sealed. They are
installed on the fuel valve mounting bracket. They are
operated by an electrical input of 14 to 28 volts dc.
In the following paragraphs, we will provide a brief
Stainless-steel tubing connects each valve with the
description of each of these systems. For additional
information, we recommend you consult the appropriate
valves are controlled by the ESU.