4. Control engine
and propeller speed outside
are the corresponding degrees as read from the
the limits of
operation of the propeller
engine coordinator.
governor. This
includes reverse thrust, low-
speed ground
idle, flight idle, and high-
Max reverse -- 0
speed ground
idle.
Ground idle -- 9
5. Provide a measure of engine protecion dur-
Start
--15
ing overspeed conditions by reducing fuel
flow and turbine inlet temperature.
Flight idle -- 34
6. Provide a starting fuel flow schedule
Air start
--48
that, with the temperature datum valve,
avoids overtemperature and compressor
surge.
Takeoff
-- 90 (max power)
7. Compensate for changes in air density due
The two ranges of operation of the power lever
quadrant are alpha and beta ranges. The beta
to variations in compressor inlet air
range is the portion of the quadrant from max
temperature and pressure.
reverse (0, to flight idle (34). With the power
lever set at ground idle, the propeller is at a
8. Provide a means of cutting off fuel flow
electrically and manually.
5-degree negative blade angle to compensate for
power section thrust. Movement of the power
lever toward flight idle increases fuel flow and
The fuel control senses compressor in-
let pressure, compressor inlet temperature,
blade angle. Movement from ground idle towards
max reverse increases fuel flow, but causes the
and engine speed. Using these three factors
propeller to schedule reverse blade angle. In the
and the setting of the power lever, the fuel
control meters the proper amount of fuel.
flight range (alpha), the power lever schedules fuel
Pressure and temperature compensating systems
flow only.
are designed to maintain constant turbine inlet
temperature as the compressor inlet conditions
vary.
Fuel Control
The fuel control includes a cutoff valve
for stopping fuel flow to the engine. This
A turboprop fuel control is similar to a
valve operates both electrically and manually.
turbojet fuel control. The difference is the
Electrical control is made possible by moving
turboprop fuel control operates in conjunction
with a propeller governor. The fuel control
the fuel and ignition switch to the OFF position.
This signals the cutoff valve motor to close
mounts on the engine accessory drive housing. It
the valve. Actuation of the emergency shutdown
is mechanically linked to the coordinator. The fuel
control closes the valve mechanically through a
control is designed to perform the following
cable and control rod system from the flight
functions:
station.
1. Provide a means of varying fuel flow
to permit a selection of power that is
Coordinator
coordinated with propeller blade angle and
engine speed.
Mounted on the rear face of the fuel control
is the engine coordinator. The function of
2. Regulate the rate of fuel metering during
the engine coordinator is to coordinate the
acceleration to prevent excessive turbine in-
propeller, temp control, and fuel control. A
let temperature.
connect the coordinator with the fuel control and
3. Control the rate of decrease of fuel meter-
the propeller control. Refer to the system
ing during deceleration to prevent flame-
schematic in figure 8-7.
out.
8-8
