Power Plant Controls
The engine and propeller combination is controlled by two pairs of levers, these are:
- the power levers, and
- the condition levers.
Power and Condition levers located on the centre cockpit pedestal.
The power levers operate in quadrant slots on the left side of the centre pedestal located closest to the pilot. The power lever positions (marked from rear to front) are labeled, REVERSE, GRND IDLE, FLIGHT IDLE, AIR START and MAX.
Power lever positions
The power levers can be moved freely forward of FLIGHT IDLE. A hard stop is provided at the FLIGHT IDLE position to prevent inadvertent selection of reverse thrust in flight. Finger latches located on each power lever must be pulled up to allow movement of the power levers rearward of the FLIGHT IDLE position.
Finger latches provided to prevent reverse thrust being accidentally applied.
The power levers are physically connected to electronic potentiometers, the manual fuel metering valve located in the fuel control unit and the propeller pitch control unit. The electronic potentiometers vary the electric signal sent to the electronic fuel computers as the power levers are moved by the pilot. The computer will then vary the fuel flow to the engine electrically through the electric fuel flow metering valve.
In Normal mode operation fuel flow is varied electrically through the metering valve
If the electronic fuel computers are switched off the power levers will vary the fuel flow to the engines mechanically through the fuel flow metering valve. Fuel flow to the engines is actually determined by P3 air pressure which is measured from the compressor section of the engine.
During manual mode operations this P3 air pressure must be sensed inside the fuel control unit before a power change will actually occur. Due to this fact, manual mode operations will result in slower power changes, therefore pilots must be aware of large power changes so as not to over torque or over temp. the engines during manual mode operations.
The mechanical connection between the power levers and the propeller pitch control allows for Beta mode control during ground operations and Beta follow-up during flight operations. Beta follow-up reduces propeller drag during an engine failure and is achieved by placing the respective power lever in the MAX power position.
This Beta follow-up procedure drains some of the oil pressure from the propeller dome to the gear case to minimise propeller drag should the NTS system fail to function correctly during an engine failure.
The condition levers operate in quadrant slots on the right side of the centre pedestal. The condition lever positions (marked from rear to front) are labeled, EMER SHUTOFF, START AND TAXI, CRUISE, and TAKEOFF CLIMB AND LANDING.
The condition levers are physically connected to electronic potentiometers, the manual fuel shutoff valve located in the fuel control unit and the propeller feathering valve. The electronic potentiometers vary the electric signal sent to the electronic fuel computers as the condition levers are moved by the pilot. The computer will then send an electrical signal representing engine RPM to the propeller governor.
During manual mode operations the engine RPM will automatically be governed at 100% RPM during all phases of flight. Note: Condition lever position has no effect on engine RPM during Manual mode.
The mechanical connection between the condition lever to the manual fuel shutoff and the propeller feathering valve is effective only in the EMER SHUTOFF position.
In the EMER SHUTOFF position the condition lever will close the manual fuel shutoff valve followed by positioning the propeller feathering valve (against spring pressure) to the feather position. The engine will flameout and the propeller will feather.