Cessna 208B - Propeller Governor

CESSNA SECTION 7
MODEL 2088 (675 SHP) AIRPLANE AND SYSTEMS DESCRIPTION
ENGINE ACCESSORIES (Continued)
INTERTURBINE 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
chromel-
alumel 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
asse3mbly to a terminal block which
provides a connecting point for external leads to the ITT indicator in the
airplane cabin.
PROPELLER GOVERNOR
The Dro~eller aovernor is located in the 12 o'clock Dosition on the front
case of'the
rehction gearbox. Under normal conditions, rhe governor
acts as a constant
weed unit. maintainina the ~ro~eller weed selected
by the pilot by
varyiig the propeller bladepitch to 'match ihe load to the
enaine toraue. The
~ro~eller aovernor also has a Dower turb~ne
go;ernor section bu It lnro the unit. Its functlon 1s to protect the englne
aaainst a ooss~ble oower turblne overs~eed n the event of a Dro~eller
- a~~~~
gGvernor failure. If kuch an overspeed should occur, a governing orifice
in the propeller governor is opened by flyweight action to bleed off
compressor discharge pressure through the governor and computing
section of the fuel control unit. When this occurs, compressor discharge
pressure, acting on the fuel control unit governor bellows, decreases
and moves the metering valve in a closing direction, thus reducing fuel
flow to the flow divider.
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U.S. 7-65