NOTICE

SECTION 7 CESSNA
AIRPLANE AND SYSTEMS DESCRIPTION MODEL 208B G1000
PROPELLER TACHOMETER-GENERATOR
The propeller tachometer-generator produces an electric signal which
is used in conjunction with the propeller RPM indicator. The propeller
tachometer- generator drive and mount pad is located on the right side
of the reduction gearbox case and rotates clockwise with a drive ratio of
0.1273:1.
TORQUEMETER
The torquemeter is a hydro-mechanical torque measuring device
located inside the first stage reduction gear housing to provide an
accurate indication of engine power output. The difference between the
torquemeter pressure and the reduction gearbox internal pressure
accurately indicates the torque being produced. The two pressures are
internally routed to bosses located on the top of the reduction gearbox
front case and to a pressure transducer which is electrically connected
to the G1000 which indicates the correct torque. For standby indication,
the pressures are routed to bosses on the top of the reduction
gearcase front case and plumbed to the standby torque indicator.
STARTER-GENERATOR
The starter-generator is mounted on the top of the accessory case at
the rear of the engine. The starter-generator is a 28-volt, 200-amp
engine-driven unit that functions as a motor for engine starting and,
after engine start, as a generator for the airplane electrical system.
When operating as a starter, a speed sensing switch in the startergenerator
will automatically shut down the starter, thereby providing
overspeed protection and automatic shutoff. The starter-generator is air
cooled by an integral fan and by ram air ducted from the front of the
engine cowling.
INTERSTAGE TURBINE TEMPERATURE SENSING
SYSTEM
The interturbine temperature sensing system is designed to provide the
operator with an accurate indication of engine operating temperatures
taken between the compressor and power turbines. The system
consists of twin leads, two bus bars, and eight individual chromelalumel
thermocouple probes connected in parallel. Each probe
protrudes through a threaded boss on the power turbine stator housing
into an area adjacent to the leading edge of the power turbine vanes.
The probe is secured to the boss by means of a floating, threaded
fitting which is part of the thermocouple probe assembly. Shielded
leads connect each bus bar assembly to a terminal block which
provides a connecting point for external leads to the ITT indicator in the
airplane cabin.
7-58
U.S.
208BPHBUS-00