7. Engines, APU Flashcards
A/T LIM Indication
- The FMC is not providing the A/T system with N1 Limit values,
- A/T is using a degraded N1 thrust limit from the related EEC
EGT Start Limit Redlines
- Shown for ground starts and some in-flight starts as determined by EEC,
- Displayed until the engine achieves Stabilized IDLE (approximately 59% N2)
EEC Abnormal Start Protections
- For ground starts only it has 4 Protections:
1-) Hot Start (rapid rise in EGT or approaching start limit),
2-) Compressor Stall,
3-) EGT Start Limit Exceedences,
4-) Wet Starts (15s) - For all EEC turns off ingnition and shuts off fuel to the engine,
- For Hot start and Compressor Stall, EGT white box flashes white,
- If EGT limit exceeded both box and dial turns initially. Turns to white when below limit,
- After engine shutdown it turns to red again
ENG FAIL Alert
Displayed:
- In amber and on the EGT indicator,
- Engine operating below sustainable IDLE (< 50% N2) and,
- Engine Start Lever in IDLE position
Alert remains until:
- Engine recovers or,
- Engine Start Lever moved to CUTOFF or,
- Engine Fire Switch pulled
Upper DU Engine Alerts
- Illuminates amber,
- All boxes blink for 10s,
- After 10s related alert remains on steady
Engine Alerts Blinking Inhibit
- During T/O from 80KT to 400FT or 30s after reaching 80KT, whichever occurs first,
- During landing below 200FT until 30s after touchdown,
- When blinking inhibited, alerts illuminate steady
Secondary Engine Indications Automatic Pop-up
- Inflight when an Engine Start Lever moved to CUTOFF,
- Inflight when an engine fails,
- When a secondary engine parameter exceeds normal operating range,
- Once displayed they cannot be cleared until the condition is no longer present
Low OIL PRESS Amber Band
- Not displayed below 65% N2,
- Variable depending on N2 above 65%
OIL QTY Windmilling Value
As low as zero is normal if windmilling N2 RPM < 8%
X-BLD
- Location is above N2 dial,
- Displayed when airspeed is less than required for windmilling start
ENGINE START Switch GRD
- Opens Start Valve (using Battery power),
- Closes Engine Bleed Valve (using Battery power),
- For ground starts, arms selected igniter to provide ignition when Engine Start Lever is moved to IDLE,
- For inflight starts, arms both igniters to provide ignition when Engine Start Lever is moved to IDLE,
- Releases to OFF at Start Valve Cutout
ENGINE START Switch OFF
Ignition is normally OFF but both igniters activated when Engine Start Lever is in IDLE and:
- An uncommanded rapid decrease in N2 occurs or,
- N2 is between 57% and 50% or,
- Inflight, N2 is between idle and 5%
ENGINE START Switch CONT and FLT
CONT:
- Provides ignition to selected igniters when engine is operating and Engine Start Lever is in IDLE,
- Inflight, provides ignition to both igniters when N2 is below idle and Engine Start Lever is in IDLE
FLT:
- Provides ignition to both igniters when Engine Start Lever is in IDLE
REVERSER Light
Illuminates when:
- Isolation Valve or Thrust Reverser Control Valve is not in commanded position,
- One or more Thrust Reverser sleeves are not in commanded state,
- Auto-restow circuit has been activated,
- A failure has been detected in Synchronizaiton Shaft Lock circuitry
During normal operation:
- Thrust Reverser commanded to stow and extinguishes 10s later when Isolation Valve closes,
- If illuminated more than 12s, MASTER CAUTION and ENG illuminates,
ENGINE CONTROL Lights
Illuminates for a Non-dispatchable fault and operates when:
- Engine is operating and,
- Airplane on ground and,
- Below 80KT prior to T/O or,
- Approximately 30s after touchdown
EEC Switches
ON:
- If only ON shown, indicates normal control mode is selected,
- When ON is not in view, the EEC has been MANUALLY selected to the Hard Alternate mode
ALTN:
- EEC has AUTOMATICALLY or MANUALLY switched to alternate control mode,
- If both ON and ALTN in view, EEC has automatically switched to alternate mode,
- EEC provides rated thrust or higher
Reverse Thrust Lever Lock
Blocked at Reverse Idle position until related Thrust Reverser is > 60% deployed
Engine Start Levers IDLE
- Energizes Ignition system through EEC,
- Electrically opens Spar Fuel Shutoff Valve in the wing leading edge outboard of the pylon,
- Electrically opens Engine-Mounted Fuel Shutoff Valve via the EEC
APU OVERSPEED Light
Illuminated when:
- APU RPM limit has been exceeded resulting in an automatic shutdown,
- Overspeed Shutdown Protection feature has failed a self-test during a normal APU shutdown,
- If illuminated when APU switch is placed to OFF, light extinguishes after 5 minutes,
- Light is disarmed when APU switch is OFF
APU FAULT Light
Illuminated when:
- A malfunction exists causing APU to initiate an automatic shutdown,
- If illuminated when APU switch is placed to OFF, light extinguishes after 5 minutes,
- Light is disarmed when APU switch is OFF
APU LOW OIL PRESSURE Light
Illuminated when:
- During start until APU oil pressure is normal,
- Oil pressure is low causing an automatic shutdown (after start cycle complete),
- If illuminated when APU switch is placed to OFF, light extinguishes after 5 minutes,
- Light is disarmed when APU switch is OFF
Engines General
- CFM56-7 axial flow,
- Dual rotor N1 and N2,
- N1 consists of: Fan, LP Compressor and LP Turbine,
- N2 consists of: HP Compressor and HP Turbine,
- N2 rotor drives Engine Gearboxes,
- Bleed air powered Starter Motor is connected to N2 rotor
EEC
- Electronic Engine Control,
- Dual channel EEC regulates each engine,
- With each engine start or attempt, the EEC alternates between control channels,
- Monitors A/T and Flight Crew inputs to automatically set engine thrust,
EEC and Engine Indications
- When EEC not powered N1, N2, Oil Quantity and Engine Vibration are displayed directly from engine sensors,
- During Battery Start only N1, N2 and Oil Quantity is shown,
- Positioning ENGINE START switch to GRD supplies power to the EEC and displays all engine parameters,
- EEC is not powered until 15% N2
EEC Modes
Normal:
- Uses sensed flight conditions and bleed air demand to calculate N1 thrust ratings,
- EEC compares commanded N1 and actual N1 adn adjusts fuel flow to achieve the commanded N1
Soft Alternate:
- If required signals are not available to operate in the normal mode, EEC automatically changes to Soft Alternate mode,
- Loss of either DEU results in Soft Alternate Mode,
- The ALTN and ON lights shown together,
- EEC uses the last valid flight conditions to define engine parameters,
- If ambient conditions change, thrust rating shortfalls or exceedances may occur
Hard Alternate:
- Soft Alternate changes to Hard Alternate by: retarding the thrust levers to IDLE (ON light remains) or,
- Manually selecting ALTN with the EEC switch (ON light extinguishes),
- Thrust is always equal or greater than normal mode for the same thrust lever position,
- EEC limiting is not provided and Maximum Rated Thrust may be reached before the forward stop
Full Rated T/O and Maximum Rated Thrust
In normal mode:
- Full Rated T/O Thrust is available before the forward stop,
- The Maximum Rated Thrust is available at the forward stop
EEC Structural Limit Protection
- EEC provides N1 and N2 redline overspeed protection in both normal and alternate modes,
- EEC does not provide EGT redline exceedance protection
Approach Idle Operation
General:
- N1 and N2 RPM is higher than Flight Idle,
- This improves engine acceleration time in the event of a go-around,
Engages when:
- EAI Switch ON for either engine or,
- < 19000FT MSL and left or right Main Landing Gear is down and locked or,
- < 19000FT MSL and left or right Flaps are 15 or greater or,
- If there is a fault preventing EEC to receive Flaps or Gear Signals, engages < 19000FT,
- Maintained until after touchdown when Ground Idle is selected
Engine Fuel System
- Fuel delivered under pressure from fuel pumps,
- Flows through Spar Fuel Shutoff Valve at the engine mounting wing station,
- Then passes through 1st stage Engine Fuel Pump where pressure increased,
- Then passes through 2 fuel/oil Heat Exchangers (IDG and Main Engine Oil),
- After that a Fuel Filter removes contaminants (bypasses it if it becomes saturated),
- Then 2nd stage Engine Fuel Pump adds more pressure before fuel reaches HMU,
- EEC meters fuel through HMU, After HMU fuel flows through Engine Fuel Shutoff Valve
Fuel Flow Measurement Location
After passing Engine Fuel Shutoff Valve
Engine Oil System
- System pressurized by the Engine Driven Oil Pump,
- From the pump it goes to engine bearings and gearbox,
- Sensors for oil temperature and pressure indicators and LOW OIL PRESSURE alert are downstream of pump prior the engine lubrication,
- Oil is returned to the tank by Engine Driven Scavenge Pumps,
- After the pump oil passes through Scavenge Filter (bypasses it if it becomes saturated),
- 2 Pressure sensors before and after Scavenge Pump used to illuminate OIL FILTER BYPASS
- Prior returning to the tank, the Oil passes through the Main Engine Oil Cooler
Fuel Flow and EGT During Engine Start
- Initial Fuel Flow indications lag actual Fuel Flow by approximately 2s,
- During engine start an EGT rise may occur before Fuel Flow indication
Engine Ignition System Power Source
- Left Igniters supplied by the associated AC Transfer Busses,
- Right Igniters supplied by the AC Standby Bus
Auto-Relight
- Provided for Flameout Protection,
- Whenever EEC detects an Engine Flameout, both igniters are activated,
- Flameout detected when: Uncommanded rapid decrease in N2 occurs or N2 is below idle RPM
Inflight Starting EGT Limit
- Can be shown depending on the start logic as determined by the EEC,
- If only the EGT limit is shown, this is the inflight start EGT limit,
- If both EGT Redline and EGT Start Limit are shown, EGT Start Limit is the start limit
Thrust Reverser Basic Operation
- Aft movement of the L & R translating sleeves causes Blocker Doors to deflect Fan Discharge Air forward,
- Air deflected through Fixed Cascade Vanes, producing reverse thrust
Thrust Reverser Deployment
- Can be deployed when RA senses less than 10FT or Air/Ground Safety Sensor in the ground mode,
- When selected:
1-) Electro-mechanical Lock releases,
2-) Isolation Valve opens,
3-) Thrust Reverser Control Valve moves to deploy position, allowing hydraulic pressure to unlock and deploy the Reverser System,
4-) An Interlock mechanism initially restricts movement of the Reverse Thrust Lever movement (Sleeves > 60% open),
5-) After Sleeves are deployed, Reverse Thrust Lever can be raised to Detent 2 or further to Maximum
REV Indication
Amber:
- When either Reverser Sleeve moves from the stowed position,
Green:
- Thrust Reverser reaches deployed position
Thrust Reverser Stowing
- Downward motion of Reverse Thrust Lever past Detent No. 1 (Reverse Idle) initiates the stow command,
- When Reverse Thrust Lever reaches full down position, Control Valve moves to the stow position,
- Allowing hydraulic pressure to stow and lock the Reverser Sleeves,
- After the Thrust Reverser stowed, the Isolation Valve closes,
- Then Electro-mechanical Lock engages
Thrust Reverser Stowing Caution
- A pause in movement of the Reverse Thrust Lever past Detent No. 1 toward the stow position,
- May cause MASTER CAUTION and ENG lights to illuminate,
- A pause of approximately 16s engages Electro-mechanical Lock and prevents Sleeves from further movement,
- Cycling the Thrust Reversers may clear the fault
Thrust Reverser Stowed Protections
- In stowed position an Electro-mechanical Lock and,
- Hydraulically operated Locking Actuator inhibit motion to each Reverser Sleeve until extension is selected,
- Also has an Auto-Restow circuit
Thrust Reverser Auto-Restow Circuit
- Compares actual and commanded position,
- In the event of incomplete stowage or uncommanded movement circuit opens the Isolation Valve,
- Commands the Control Valve to the stow position directing hydraulic pressure to stow the sleeves,
- Once activated, the Isolation Valve remains open and Control Valve held in stowed position until,
- Thrust Reverser is commanded to deploy or corrective maintenance action is taken
Airborne Vibration Monitoring System
- Primary function is the display of Low and High Pressure Rotor Synchronous vibration,
- Also used to balance the Low Pressure Rotor,
- Balancing reduces high vibration or audible noise and tactile vibration
APU
- Auxiliary Power Unit is a self-contained gas turbine engine installed within a fireproof compartment
APU Fuel Supply
- Comes from left side of the fuel manifold when AC Fuel Pumps are operating,
- If AC Fuel Pumps not operating, fuel is suction fed from No. 1 tank,
- During APU operation, fuel is automatically heated
APU Engine and Cooling Air
- Engine air enters via inlet door on the right side of the fuselage,
- APU exhaust gases discharge via Exhaust Muffler on the tail,
- APU cooling air enters via Cooling Air Inlet above the Exhaust Outlet,
- Cooling air circulates through the APU compartment, oil cooler and vents via Exhaust Outlet
Electrical Requirement For APU Operation
- Battery Switch must be ON,
- Power to start comes from AC Transfer Bus 1 or the Main Battery if AC power not available,
- Moving Battery Switch to OFF automatically shuts down APU due to power loss to the Electronic Control Unit
APU Start
- Moving APU switch to START initiates opening of the Air Inlet Door,
- When Inlet Door reaches fully open position, the start sequence begins,
- After reaching proper speed, ignition and fuel are provided,
- When APU is ready to accept a bleed air or electrical load the APU GEN OFF BUS light illuminates
APU Indications During Start
- EGT may fluctuate between 0-1100 degrees,
- LOW OIL PRESSURE light may cycle on and off several times
APU Start With Battery Only
When the AC Meters Selector is set to APU GEN:
- CPS FREQ indication will be blank,
- AC VOLTS indication will be 0,
- When APU GEN OFF BUS light illuminates actual values will be shown
Engine Start Cycle Duration
May take as long as 120s
Recommended Wait Time for APU Bleed Air
- After start, operate the APU for 2 full minutes before using it as a bleed air source,
- Before shutdown, operate APU for 1 full minute with no bleed air,
- When the APU switch moved to OFF, this time delay is met automatically
APU Shutdown
- Shutdown occurs automatically 60s after APU switch moved to OFF,
- When the APU speed decreases sufficiently during shutdown, the Fuel Valve and Inlet Door close,
- If the Fuel Valve does not close, the FAULT light illuminates after approximately 30s,
- Immediate shutdown can be done by pulling APU Fire Switch
ECU
- Electronic Control Unit of the APU,
- If detects a fault that may cause damage to the APU or the aircraft,
- It will automatically execute a protective shutdown,
- Automatically controls APU speed through the Electronic Fuel Control
APU Bleed and Electrical Load Shedding
If EGT raises above acceptable levels:
- During engine start, electrical load shedding occurs first,
- Other times, Inlet Guide Vanes move toward a closed position, reducing bleed air extraction first
APU Automatic Load Shedding
If the APU is the only source inflight:
- All Galley and Main Busses are automatically shed,
- If still not enough both IFE Busses are automatically shed
On the ground:
- APU attempts to carry a full electrical load,
- If overload sensed, APU sheds Galley and Main Busses until the load is within limits
Manual restoration of Galley and Main Bus power can be attempted via cycling CAB/UTIL switch
