Eng Control System Flashcards
NATOPS Chap 2 Engine Control System The Eng control system….
“Includes all components necessary for the proper and complete control of the eng to maintain a constant Np/Nr”
NATOPS Chap 2 Engine Control System What are the major components?
HMU, EDECU, engine driven Alternator, ODV, and a series of fuel flow control valves
NATOPS Chap 2 Engine Control System What does the Eng control quad consist of?
2 PCLs, two fuel slectors, two T handles, and a rotor brake interlock
NATOPS Chap 2 Engine Control System What shuts off fuel with the PCL off?
The Power Available Spindle shuts off fuel at the shutoff valve w/i the hmu
NATOPS Chap 2 Engine Control System What do you lose with the PCL in lockout?
TGT Limiting, NP governing, and load sharing. You retain Np overspeed protection system
NATOPS Chap 2 Engine Control System With the rotor brake on, can you advance a PCL to fly?
No, there is a solenoid on the quadrant that activates a mechanical locking device to prevent the pcl from being advanced to fly. If the Rotor Brake is released, the solenoid energizes and unlocks the PCLs
NATOPS Chap 2 Engine Control System What connects the HMU and collective?
The load demand system.
NATOPS Chap 2 Engine Control System What is the Engine driven fuel boost pump designed to do?
- Provide reliable suction feed from the aircraft fuel tank to the engine, minimizing vulnerability and fire hazard in the event of damaged fuel lines 2. Provide discharge pressure to satisfy min inlet pressure requirement of the HMU or Hi Pressure fuel pump
NATOPS Chap 2 Engine Control System What doesn’t the fuel filter filter?
Water
NATOPS Chap 2 Engine Control System What does the HMU contain?
Hi-Px fuel pump, Ng governor, metering valve, LVDT, torque motor servo, variable geometry vane servo, vapor vent, and shutoff valve
NATOPS Chap 2 Engine Control System Fuel is tapped off to operate servos in the HMU for? (FSS)
- Fuel— Positioning a metering valve for proper fuel flow to eng 2. Servo— position a servo piston that actuates var. geometry vane servo and start bleed valve 3. Signals— amplifying signals (T2, P3, Ng) that influence fuel flow and variable geometry servo position
NATOPS Chap 2 Engine Control System Inputs to HMU (mechanical vs. Electronic)
2 mechanical: 1. LDS directly coordinates Ng speeds via collective position 2. Position of PCL manipulates the PAS at the HMU setting the desired power 1 Electronic: Signal from DECU actuates the torque motor servo in HMU to trim Ng speed for power turbine control and load sharing
NATOPS Chap 2 Engine Control System The HMU responds to the PCL for: (FSSFD*)
- Fuel shutoff 2. Setting eng start fuel flow w/ auto accel to ground idle 3. Setting permissable NG up to max 4. Fuel Priming 5. DECU Lockout *The HMU also responds to T2, P3, and Ng. These inputs aid the HMU in controlling variable stator vanes and anti-ice/start bleed valve position during engine start and normal operation, reducing the chance of compressor stall
NATOPS Chap 2 Engine Control System What does the HMU control to reduce the chance of compressor stall?
The HMU controls variable stator vanes and anti-ice/start bleed valves during eng start and normal ops.
NATOPS Chap 2 Engine Control System How does fuel flow in HMU
The fuel first enters the hi Px pump and is then routed to the metering valve
NATOPS Chap 2 Engine Control System What does the metering valve do?
Schedules engine fuel flow commensurate to current power demand and is trimmed to the required level by the torque motor servo via the EDECU
NATOPS Chap 2 Engine Control System How does the HMU respond to the EDECU
The HMU uses the LVDT to provide feedback and null the torque motor servo input which stabilizes the metering valve to prevent eng hunting
NATOPS Chap 2 Engine Control System When and how does the Ng overspeed valve trip?
If the Ng servo within the Ng governor reaches a position corresponding to an overspeed, a spring-loaded ball valve ports fuel pressure causing the minimum pressure valve to secure flow to the engine. The Ng overspeed valve is set to trip at 110+/- 2% Ng
NATOPS Chap 2 Engine Control System With the PCL in FLY the HMU..
Intentionally schedules higher-than-required power level for two reasons: 1. Fail-safe to high power 2. Power avail with OEI
NATOPS Chap 2 Engine Control System Why Fail safe to high power?
With a loss of torque motor servo from DECU, the fuel schedule returns to highest power level. This prevents engine damage and engine stall in the event of loss of all electrical power to torque motor
NATOPS Chap 2 Engine Control System OEI?
With the loss of one engine, the other Ng can increase power sufficiently up to its limit (contingency power) to carry the load at the LDS setting.