Q400 Propeller
Dash8 - Q400 - Propeller
1. General
The propeller control system consists of the following components:
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•
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Propeller Electronic Control (PEC) Unit
Propeller Pitch Control Unit (PCU)
High Pressure PCU Oil Pump and Propeller O/S Governor Units (referred to as overspeed governor) Propeller Feathering Pump
Propeller System Sensors
The function of the propeller system is to modulate the propeller blade pitch to control the propeller speed in flight constant speed modes and in reverse, and to provide smooth thrust transients in response to PLA movement. This system also limits the minimum blade angle obtainable in flight. In addition, the system provides the ability to feather the propeller on demand, minimize cabin noise in synchrophase mode and automatically feather the propeller in the event of an engine failure, when the autofeather system is selected.
2. Propeller Electronic Control (PEC) Unit
The Propeller Electronic Control (PEC) (Figure 12.22-4) is a dual channel microprocessor-based controller which uses inputs from the aeroplane, propeller control system sensors, and the engine control system to control propeller pitch and speed. The PECs for both propeller systems are mounted in their respective engine nacelles.
Each unit performs a number of safety functions including Autofeather and Automatic Underspeed Propeller Control (AUPC) which causes the propeller to operate on the overspeed governor in the event if a drive coarse failure. It also provides an UPTRIM command to the
FADEC of the working engine. All of these functions are isolated from the basic control functions of the PEC.
3. Propeller Pitch Control Unit (PCU)
The propeller Pitch Control Unit (PCU) is a hydromechanical device that interfaces with the propeller. Commanded electrically by the PEC, the PCU meters high pressure engine oil to a two stage servo valve mounted on the PCU. The PCU controls the flow of high pressure oil into the fine or coarse pitch chambers of the propeller pitch
1. General
The propeller control system consists of the following components:
•
•
•
•
•
Propeller Electronic Control (PEC) Unit
Propeller Pitch Control Unit (PCU)
High Pressure PCU Oil Pump and Propeller O/S Governor Units (referred to as overspeed governor) Propeller Feathering Pump
Propeller System Sensors
The function of the propeller system is to modulate the propeller blade pitch to control the propeller speed in flight constant speed modes and in reverse, and to provide smooth thrust transients in response to PLA movement. This system also limits the minimum blade angle obtainable in flight. In addition, the system provides the ability to feather the propeller on demand, minimize cabin noise in synchrophase mode and automatically feather the propeller in the event of an engine failure, when the autofeather system is selected.
2. Propeller Electronic Control (PEC) Unit
The Propeller Electronic Control (PEC) (Figure 12.22-4) is a dual channel microprocessor-based controller which uses inputs from the aeroplane, propeller control system sensors, and the engine control system to control propeller pitch and speed. The PECs for both propeller systems are mounted in their respective engine nacelles.
Each unit performs a number of safety functions including Autofeather and Automatic Underspeed Propeller Control (AUPC) which causes the propeller to operate on the overspeed governor in the event if a drive coarse failure. It also provides an UPTRIM command to the
FADEC of the working engine. All of these functions are isolated from the basic control functions of the PEC.
3. Propeller Pitch Control Unit (PCU)
The propeller Pitch Control Unit (PCU) is a hydromechanical device that interfaces with the propeller. Commanded electrically by the PEC, the PCU meters high pressure engine oil to a two stage servo valve mounted on the PCU. The PCU controls the flow of high pressure oil into the fine or coarse pitch chambers of the propeller pitch