position complete electrical circuits for other
temperature, In turbojet aircraft, this also causes
systems. The pilot must raise the detent release
an increase in engine speed. The only electrical
handle of each condition lever to move the levers
circuits required are those to show temperature
to different positions. A detent holds the lever at
and speed.
F E A T H , GRD STOP, or RUN. When the
The engine temperature control system on
turboprop engines lets the operator control
condition lever is in the AIRSTART position, the
turbine inlet temperature and torque through the
propeller unfeathers and the engine starting cycle
begins. The lever is held in the AIR START
use of power and condition levers. These levers
position until the engine speed reaches 100 percent
connect to each engine coordinator through
RPM. Then, you release the lever, which springs
pushrods, sectors, cables, and pulleys. When the
back to RUN and remains there for normal
engine is operating in the flight range, engine
operation. When set to RUN, the condition lever
speed is constant. Engine power is controlled by
positions the mechanical linkage to open the fuel
increasing or decreasing fuel flow, which results
shutoff valve. A mechanical stop in the pedestal
in a corresponding change in turbine inlet
prevents both condition levers from being set to
temperature. The main components of the engine
FEATH at the same time. When set to FEATH,
temperature control system are--
the condition lever electrically and mechanically
closes the corresponding fuel shutoff valve and
Power levers,
feathers the propeller. At GRD STOP, the
condition lever electrically closes the fuel shutoff
Condition levers,
valve to shut down the engine.
Engine coordinators,
ENGINE COORDINATORS
Temperature datum controls,
The coordinators are mechanical devices that
coordinate the power and condition levers,
Turbine inlet thermocouples, and
propeller, fuel control, and electronic fuel
trimming circuit. One engine coordinator mounts
Temperature datum switches.
on each fuel control. The main components of
a coordinator are a variable potentiometer, a
Figure 5-7 shows the block diagram of an engine
discriminating device, and a cam-operated switch.
temperature control system. You should refer to
A scale calibrated from 0 to 90 degrees attaches
it while you study this section.
to the outside case, and a pointer secures to the
main coordinator shaft. Pushrods, connected
POWER LEVERS
from the coordinator to a cable sector, transmit
power and condition lever movement to the
The power levers (one for each engine) can
coordinator. Power lever movement through the
move separately or together to control engine
coordinator changes resistance of the variable
power. The range of power lever settings is from
potentiometer and changes the temperature datum
REVERSE (reverse thrust) to MAX POWER
control temperature reference signal. The
(takeoff). Power lever switches within the cockpit
cam-operated switch changes the temperature
pedestal supply electrical power to other systems.
datum control from temperature limiting to
A detent at the FLT IDLE position prevents
temperature controlling with power lever above
inadvertent movement of the power levers below
66-degree coordinator and engine speed above 94
FLT IDLE while airborne. To move the power
percent RPM. Power lever movement transmits
levers to the taxi range, you must raise the levers
to the coordinator, propeller, and fuel control
from the detent. During a catapult-assisted
through a series of rods and levers. With the
takeoff, a retractable catapult grip helps the pilot
condition lever in FEATH, the discriminating
maintain the power levers at MAX POWER.
device mechanically positions propeller linkage
toward feather and closes the fuel shutoff valve,
CONDITION LEVERS
regardless of the power lever setting.
The condition levers are located next to the
power levers on the cockpit pedestal. They have
The temperature datum control consists of
four positions--FEATH, GRD STOP, RUN, and
electronic units that automatically compensate for
AIRSTART. Switches at each condition lever
