stiffening ribs. The upper and lower halves are
bolted together along the horizontal centerline.
The casing is bolted to the front frame at the for-
ward end and to the mainframe at the aft end.
The compressor rotor assembly is made up of
an integrated front shaft-disc-spacer assembly,
a drive shaft, spacers, and eight stages of rotor
discs and blades.
Stall and surge protection is provided for the
compressor by the variable geometry system.
Variable inlet guide vanes operate in conjunc-
tion with bleed valves at the third, fourth, and
fifth compressor stages to provide a safe stall-
surge margin during acceleration, deceleration,
and steady-state operation.
Mainframe
The mainframe (Figure 7-4) section is the main
structural support of the engine. It consists of
a frame which houses the power takeoff hous-
ing and drive assembly and provides a mount
for the twelve fuel flow divider fuel nozzles,
the fuel manifolds, two eighth-stage air leak-
age check valves, and the gearbox assembly.
The eighth-stage stators and exit guide vanes
are mounted on twelve segments dovetailed
into a track cut into the front of the mainframe.
The No. 2 bearing is enclosed in a bearing sup-
port which bolts to the mainframe.
7-4
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
CARBON SEAL RUNNER
SPACER
NO. 2 BEARING INNER RACE
FORWARD HALF
COMPRESSOR DRIVE SHAFT
AIR DUCT
8TH-STAGE
AIR SEAL
ROTOR DISC
BLEED PORTS
FORWARD AIR
SEAL
NO. 1 BEARING
INNER RACE
DISC SHAFT
CARBON
SEAL
RUNNER
OIL SLINGER
BALANCE
WASHER
ROTOR BLADE
STATOR CASING
STATOR VANE
Figure 7-3. Compressor Section