Maintenance is preparing to disconnect an ignition lead from an exciter. Why is simply placing the engine start switch to OFF insufficient as the primary safety precaution?, The start switch does not remove the direct-current supply from the ignition-selector circuit., The ignition exciter can continue generating spark energy indefinitely from internally stored battery power., The ignition system can produce 15,000 to 20,000 volts direct current with an energy output of approximately 14.5 to 16 joules, so the exciters must be positively de-energized before maintenance., The Electronic Engine Control commands movement of a High Pressure Turbine Active Clearance Control valve. Which sequence correctly describes how the command is converted into valve movement and then monitored?, The Electronic Engine Control directly powers an electric actuator, while the Display Processing Computer provides position feedback., The Electronic Engine Control commands a servo in the Split Control Unit, servo fuel pressure moves the valve actuator, and dual Linear Variable Differential Transformers return valve-position feedback to the two Electronic Engine Control channels., The Electronic Engine Control commands the valve pneumatically through fan discharge pressure, while a Rotary Variable Differential Transformer reports position., Why does the High Pressure Turbine Active Clearance Control system improve both fuel economy and transient engine performance?, Cooling the High Pressure Turbine case reduces blade-tip clearance and also helps control Exhaust Gas Temperature rise during rapid acceleration., Heating the High Pressure Turbine case increases blade-tip clearance and prevents rotor rub during takeoff., Cooling the High Pressure Turbine blades directly increases compressor stall margin during deceleration., The Low Pressure Turbine Active Clearance Control valve is commanded open. Which airflow path and purpose correctly describe the resulting system operation?, High Pressure Compressor tenth-stage air is directed internally to cool the first-stage Low Pressure Turbine blades., Fan discharge air flows through the Low Pressure Turbine Active Clearance Control manifold to cool the Low Pressure Turbine case and minimise blade-tip clearance., Seventh-stage High Pressure Compressor air is discharged around the Low Pressure Turbine case to prevent turbine icing., The engine is at idle and begins accelerating. What should happen to the Variable Stator Vanes as N2 increases?, They move progressively toward a more open position., They remain fully closed until N2 exceeds 80 percent., They move progressively toward a more closed position to increase compressor pressure ratio., Why are two Variable Stator Vane actuators used on opposite sides of the High Pressure Compressor rather than a single actuator?, Each actuator independently controls different compressor stages., The two actuators operate together through bellcranks and actuation rings to move the Inlet Guide Vanes and the first four stages of stator vanes uniformly around the compressor case., One actuator provides normal control while the second remains mechanically disengaged as a backup., During a rapid engine deceleration, why does the Variable Bleed Valve system command the bleed doors toward a more open position?, To increase Low Pressure Compressor stall margin by diverting more discharge air into the secondary airflow., To increase High Pressure Compressor inlet pressure and maintain maximum engine thrust., To direct additional compressor air to the High Pressure Turbine for cooling., During steady-state operation, N1 rises above approximately 80 percent. What should the Variable Bleed Valve doors do?, Move to their fully open position to maximise compressor airflow., Close, because less Low Pressure Compressor discharge air needs to be bypassed at high engine speed., Remain at the last scheduled position until N2 also exceeds 80 percent., The Transient Bleed Valve is opened during an engine transient. What airflow is being redirected, and what is the primary purpose?, Seventh-stage High Pressure Compressor air is redirected to the booster inlet to prevent icing., High Pressure Compressor tenth-stage air is discharged into the turbine rear frame and exhaust gaspath to improve compressor stall margin., Fan discharge air is routed to the High Pressure Turbine case to reduce blade-tip clearance., Why does the Modulated Turbine Cooling system reduce cooling airflow at lower engine power settings rather than maintaining maximum cooling continuously?, Reduced cooling airflow increases turbine temperature deliberately to improve thrust response., Less cooling air is required at lower power, and reducing unnecessary compressor-discharge cooling flow improves fuel efficiency., Continuous maximum cooling would overcool the turbine case and cause compressor stall.

ATA 75

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