Cessna 208B - Propeller Tachometer-Generator; Torquemeter

SECTION 7 CESSNA
AIRPLANE AND SYSTEMS DESCRIPTION MODEL 208B (675 SHP)
ENGINE ACCESSORIES (Continued)
PROPELLER TACHOMETER-GENERATOR
The propeller tachometer-generator produces an electric current 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:l.
TORQUEMETER
The torauemeter is a hvdro-mechanical toraue measuring device
located
ins~de the f~rst stage reduction gear nous ng to pr6v1de an
accurate
~nd~cat~on of enalne Dower outout The d fference between the
torquemeter pressure
and the reduchon gearbox internal pressure
accurately indicates the torque being produced. On some Cargo
Versions, the two pressures are internally routed to bosses located on
the
too of the reduction aearbox front case and to a oressure
transducer wh ch
1s electncaiy connected to the torque ind~caior which
ndicates the correct torque pressure. On other Cargo Versions and the
Passenger Version, the two pressures are internally routed to bosses
located on the
to^ of tne reduct~on aearbox front case and are then
plumbed to the torque indicator
whkh indicates the correct torque
pressure.
( 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,
afler engine start, as a generator for the airplane electrical system.
When
o~eratina as a starter. a weed sensina switch in the starter-
generator will automatically shut down the starter, thereby provyding
0verSDeed Drotection and automatic shutoff. The staner-aenerator is air
cooled by an integral fan and by ram air ducted from the front of the
engine cowling.
(Continued Next Page)
1 7-64 U.S.
Revision
23