Pratt & Whitney Rzeszów S.A.
MAINTENANCE MANUAL
PZL-10W ENGINE
1992.08.28
77-22-00
Page 3
Export Control Classification: PL/UE 9E999
E .
The electronic limiter unit.
The electronic limiter unit is an arrangement (see 73-22-03, DESCRIPTION AND OPERATION), in which the
electronic systems create the electric control signal next delivered to the electrohydraulic servo valve to control
the fuel supply to the engine. The thermocouple voltage ( mean value from four thermocouples), which is
proportional to the gas temperature behind the compressor turbine is delivered among another signals to the
input of the electronic limiter unit. This signal is used for forming the output signal of the electronic limiter unit to
control the fuel supply to the engine. In this way the engine is protected against the limited running parameter
exceeding, including . the CTOT.
The electronic limiter unit is installed on the helicopter.
F .
The electrohydraulic servo valve.
The electrohydraulic servo valve is placed inside the fuel metering pump and is describedin73-22-01 Section,
DESCRIPTION AND OPERATION, subitem
1.C(13).
3.
Operation.
A .
The measurement system of the Compressor Turbine Outlet Temperature (CTOT).
The hot gas behind the compressor turbine flowing through the openings in the thermocouple plug cases (6) of
four thermocouple plugs located on the engine flows around and heats the thermocouple welds. Resulting and
averaged thermoelectric force from four thermocouple elements is transmitted from the thermocouple plug
terminals to the gas temperature indicator installed in the pilot cockpit. The thermocouple collector, the
thermocouple board and two electric leads connecting the thermocouple board to the gas temperature indicator
are the intermediate elements in the transmitting of this signal.
The conditions of proper system functioning are the worthiness of its composing elements and appropriate
insulation resistance, and so the electric matching the thermocouple circuit to the gas temperature indicator input
circuit (i.e. appropriate electric resistance of the thermocouple circuit measured between the terminals
disconnected from the gas temperature indicator). The gas temperature indicator is scaled in the temperature
units and indicates the gas temperature behind the compressor turbine (CTOT) during the starting and at all
engine ratings.
B .
The Compressor Turbine Outlet Temperature (CTOT) limitation system.
The thermoelectric force of four parallelly connected thermocouples, the same as the thermocouples used in the
CTOT measurement system is delivered to the electronic limiter unit. The elements transmitting this signal are as
follows: the thermocouple collector, the thermocouple board and two electric leads connecting the thermocouple
board to the electronic limiter unit.
