POWER PLANT Flashcards
WHAT IS THE ENGINE MODEL NUMBER AND WHAT ARE THE DIFFERENT SECTIONS OF THE TURBINE/COMPRESSOR?
CF 34-3B1 Hot & High
➢ N1 – Single stage fan rotor connected to a 4 stage low pressure turbine.
➢ N2 – 14 Stage Axial Flow Compressor Rotor connected to a 2 stage high pressure turbine.
WHAT IS THE RATED THRUST OF THE CF 34-3B1 H&H ENGINE?
Rated at 8,729 pounds of thrust.
Equipped with an APR system that increases thrust to 9,220 pounds of thrust (aprox 2%).
WHAT SYSTEM IN THE COMPRESSOR SECTION OF THE ENGINE WILL HELP PREVENT COMPRESSOR STALLS?
Equipped with a Variable Geometry System that uses fuel from the FCU to hydraulically change the position of the guide vanes and the first 5 stages of the stator vanes. This improves efficiency by:
➢ Optimizing the angle of attack at the compressor blades.
➢ Protecting compressor from stalls and surges.
WHAT DRIVES THE ACCESSORY GEAR BOX AND WHAT IS CONNECTED TO IT?
Accessory Gear Box is driven by the N2 Compressor, and consists of: ➢ Engine Oil Pump ➢ Alternator that powers the N1 control amplifier ➢ Engine Driven HYD Pump Page | ! 8 ➢ Engine Driven Fuel Pump ➢ Associated AC IDG ➢ Air Turbine Starter
WHAT IS THE FCU AND WHAT DOES IT DO?
FUEL CONTROL UNIT (FCU) ➢ A hydro mechanical metering device that supplies fuel in response to mechanical commands from the thrust levers.
➢ N2 Speed Control – At low power settings, the FCU adjusts fuel scheduling to match N2 power settings.
➢ N1 Speed Control – At higher power settings, T/O, CLMB and Cruise, the N1 Amplifier controls the engine RPM by trimming the FCU output to achieve matched N1 RPMs.
▪ With engine speed switches selected ON, switchover from N2 to N1 speed governing happens above 79% N1.
➢ L/H & R/H ENG SPEED Switches
▪ ON – Enables N1 Speed control system and APR system.
▪ OFF - N1 Speed control system and APR system inhibited
• NOTE: If the ENG SPEED switches are moved to OFF when high power is set, a rapid increase in engine rpm will occur and ITT maximum limits could be exceeded.
WHAT IS THE N2 SPEED CONTROL FUNCTION OF THE FCU?
➢ N2 Speed Control – At low power settings, the FCU adjusts fuel scheduling to match N2 power settings.
WHAT IS THE N1 SPEED CONTROL FUNCTION OF THE FCU?
➢ N1 Speed Control – At higher power settings, T/O, CLMB and Cruise, the N1 Amplifier controls the engine RPM by trimming the FCU output to achieve matched N1 RPMs.
▪ With engine speed switches selected ON, switchover from N2 to N1 speed governing happens above 79% N1.
WHAT IS ARE THE ENGINE SPEED SWITCHES?
➢ L/H & R/H ENG SPEED Switches
▪ ON – Enables N1 Speed control system and APR system.
▪ OFF - N1 Speed control system and APR system inhibited
• NOTE: If the ENG SPEED switches are moved to OFF when high power is set, a rapid increase in engine rpm will occur and ITT maximum limits could be exceeded.
GIVE A BRIEF DESCRIPTION OF THE THRUST REVERSER SYSTEM AND WHAT ARMS IT.
Thrust reversers are armed when the THRUST REVERSER switches are selected to ARM and the 14th Stage Bleed Air SOVs are open.
▪ Reverse thrust is initiated by redirecting bypass airflow through cascade vanes.
▪ 14th Stage bleed air pneumatically activates a power drive unit that mechanically moves the engine translating cowls rearward. As the cowls move rearward, blocker doors redirect airflow forward.
WHAT ARE SOME OF THE SAFETY FEATURES OF THE THRUST REVERSER SYSTEM?
Thrust reversers have the following safety features:
▪ Reverses are locked out inflight.
▪ Should the first safety feature fail, an automatic thrust lever retard system retards the affected thrust lever to idle during an inadvertent thrust reverser deployment. When retarded the thrust lever is locked in idle.
▪ A thrust reverser emergency stow system is installed. By selecting the EMER STOW switchlight when UNLK is illuminated directs 14th stage air to the PDU to stow the reverser.
▪ On landing or during a RTO, Thrust reversers have priority of 14th stage air over the anti-ice system.
WHEN IS THE APR SYSTEM ARMED?
The APR system is armed during takeoff when:
▪ WOW
▪ The APR switches are selected to ARM.
▪ ENGINE SPEED switches are selected to ON
▪ Engines are controlled by the N1 Amplifier (N1 RPM is above 79%).
▪ Both DCUs are operating
HOW DOES THE APR WORK AND WHEN DOES IT BECOME ACTIVE?
During the takeoff roll and for 5 minutes after activation, the APR system monitors N1 RPM of both engines. If a significant loss of N1 is detected on either engine (67.6% or less), APR automatically commands both engines to increase N1 speed. Only the normally operating engine can respond and increases RPM by 2% or about 500 pounds of thrust.
