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What is the Automatic Pressurization Sequence on the Ground and for Takeoff?
- ♦ Engine 1 thrust lever to THRUST SET position or above
- ♦ Then the cabin descends toward a 0.2 psi equivalent altitude
- ♦ With air conditioning supply, cabin altitude descends at -450 fpm
- ♦ Without air conditioning, outflow valves are closed
- ♦ Leaving the ground, cabin altitude continues descending towards 0.2 psi below takeoff altitude
- ♦ Takeoff sequence ends when theoretical cabin altitude becomes greater than actual cabin altitude or 15 minutes have elapsed since beginning of sequence (whichever occurs first)
♦ Helps to avoid cabin bumps
What is the Pressurization schedule during Flight?
- Digital controller schedules a cabin altitude that is the greatest value between the theoretical cabin altitude and the selected landing altitude, minus 300 ft.
- Cabin altitude rate of change is limited to 650 fpm climbs and -450 fpm descents
- If airplane descent rate is greater than -2,000 fpm, rate may be increased up to -1,300 fpm
What does it mean if the cabin rate displays dashes?
It is either greater than 2,000 fpm or -2,000 fpm
What is the automatic depressurization sequence on the ground?
- Initiated when aircraft is on the ground and Thrust 1 lever is brought to IDLE position
- Cabin altitude is already at 300 ft. below landing elevation set on digital controller
- Airplane lands with a small differential pressure
- Then the cabin climbs at 650 fpm until the outflow valves are fully open
What items are on the Accessory Gear Box?
- Hydraulic pump
- Electrical generators (2)
- Air Turbine Starter (ATS)
- Permanent Magnet Alternator (PMA)
- Oil Pump
- Fuel Pump and Metering Unit (FPMU)
What kind of generators do we have?
- 4 independent engine driven
- 28 vDC/400 A
- Come online when engine speed stabilizes above 56.4% N2
What kind of starter-generator is on the APU?
- 28 vDC/400A
- 300 A above 30,000'
What kind of Batteries do we have?
- 2 NiCad
- 24 vDC/44 Ahr @ 1 hour rate
What kind of backup battery do we have? And what is it's purpose?
- 24 vDC, 5 amp-hour Lead-Acid
- Provides stabilized power for the GCU's protective function in case of a short circuit or near zero system voltage
What is the primary purpose of the Central CD Bus?
- To connect the APU generator or GPU to the load buses through Bus Tie Contactors
- Also provides bus interconnections in case of asymmetrical configurations, such as gen failures or engine shutdowns
- Normally tied to DC Bus 2 (all gens operating)
What is an electrical emergency?
Loss of all generators in flight.
What is the electrical emergency configuration?
Batteries 1 and 2 are powering the essential DC busses and sharing the load, and the central bus is powered.
What is an electrical emergency abnormal?
ELEC EMERG ABNORM Caution
- Improper transfer to the electrical emergency configuration occurs during normal operation
- All busses except backup bus 1 and 2 are powered
- Generators supplying DC buses and shed buses
- Batteries supply remaining buses (40 mins of battery power)
What is an electrical essential transfer fail?
ELEC ESS XFER FAIL Warning Message
- May be having an electrical emergency, but the EDL fails to properly configure
- DC bus 1 and/or 2 may remain energized because contactors fail to open
When starting the APU, when does the APU Gen join the network?
When it reaches 95% RPM + 7 seconds
Why can't battery 1 be used to start the APU?
Because it is segregated from the load busses during start in order to provide stable electrical power to the transient sensitive equipment.
How many batteries power the emergency lights? How long do they last?
4 batteries, last 15 minutes
What is the priority valve in Hydraulic System 1 for?
- Closes only during landing gear operation with only the electric motor driven pump supplying the system
- Isolates the landing gear system and gives priorty to the flight control services
How many hydraulic accumulators are there and what are their purposes?
- Each hydraulic system has 1 accumulator
- System 1 accumulator maintains 3,000 psi pressure for landing gear operation
- System 2 accumulator maintains 3,000 psi for parking brake operation
What is the difference between the Engine driven hydraulic pump and electric motor-driven pump?
- Electric motor-driven pump has a lower flow capacity
- When operated in Auto mode, turns on when the associated hydraulic pressure drops below 1,600 psi, or N2 below 56.4%
- Provides 2,900 psi (Engine driven pump provides 3,000)
When is the stick pusher inhibited?
- On the ground (except testing)
- Below 0.5 G
- While the quick disconnect button is pressed
- Below 200 ft. AGL (radio altimeter)
- 10 seconds following takeoff (if radio altimeter has failed)
- If any cutout button is pressed
- Above 200 KIAS
- If at least one channel is inoperative