Bleed Air System

Question 1

What is Bleed Air used for?

Answer 1

– Environmental Control System (ECS);
– Engine start;
– Engine anti-ice and wing anti-ice;
– Water pressurization

Question 2

How is Engine Bleed Air temp regulated?

Answer 2

bleed air temperature is regulated by the precooler and the Fan
Air Modulating Valve (FAMV) which modulates fan air to cool the hot bleed air

Question 3

Sources of Engine Bleed Air

Answer 3

• 5th stage LP

- 9th stage HP

Question 4

Primary use of APU Bleed

Answer 4

• Engine starting on the ground

- air con on the ground

Question 5

Systems monitored by the Overheat Detection System (ODS)

Answer 5

• engine bleed
• air conditioning ducts
• APU bleed
• air distribution and anti-ice supply ducting

Question 6

When does the AMS give priority to APU Bleed

Answer 6

• APU and X-Bleed in AUTO
• APU and X-Bleed operating normally
• GS below 50 knts and 30s after touchdown
• REF ECS OFF or REF A/I not ALL

Question 7

How is Pack Air Distributed?

Answer 7

• Pack 1 airflow ——> Flight Deck
• Pack 2 airflow ——> Cabin
• with single pack operation the effected zone will receive airflow via the mixer and operating pack

Question 8

Purpose of Recirculation Fans

Answer 8

• draw air from the recirculation bays and impel the air back into the flight deck and cabin
  distribution system
• total air flow is 52% Fresh Air and 48% Recirc Air

Question 9

When are Recirculation Fans Commanded Off?

Answer 9

• Both Packs Off
• cabin warm-up with APU as bleed source
• cargo bay fire signal
• DUMP button pressed
• smoke detected in recirculation bay

Question 10

How are the electronic bays ventilated?

Answer 10

FWD E-Bay:

• 3 fans
• air drawn from cockpit
• air expelled toward underfloor recirculation bay

CTR E-Bay:

• 3 fans
• air drawn from rear cabin
• air expelled toward underfloor recirculation bay

AFT E-Bay:

• 1 fan (on ground)
• air flowing from cabin (in flight)
• air expelled toward orifice in fuselage

Question 11

When are emergency ram air ventilation valves commanded open?

Answer 11

Pack 1 Ram Air Valve:

• Both Pack Off or Failed
• airplane altitude less than 25,000’

Pack 2 Ram Air Check Valve:
- ram air pressure greater than cabin pressure

Question 12

Components of Cabin Pressure Controller System

Answer 12

– Cabin pressure controller (CPC).
– One cabin outflow valve (OFV).
– One negative pressure relief valve (NPRV).
– One positive pressure relief valve (Safety valve).
– Static Pressure Port.

Question 13

Functions of Cabin Pressure Controller

Answer 13

• 2 independent channels (alternated each flight)
• commands outflow valve, modulating airflow to maintain pressurization
• each channel can be controlled manually as a back up

Question 14

What information is needed from automatic operation of CPCS

Answer 14

• Landing Field Elevation (from FMS or manual input)
• Cruise Altitude (or ambient conditions if not avail) from FMS
• Gross Weight (or default values if not avail) from FMS

Question 15

What nominal differential pressure is provided by CPCS

Answer 15

• up to 8.6 psi with FMS cruise alt below FL370

- up to 8.8 psi with FMS cruise alt above FL370

Question 16

What happens when DUMP Button is pressed

Answer 16

• used in the event of emergency evacuation, smoke
  evacuation or for fast cabin depressurization.
• ECS Packs and Recirc Fans Off
• Controls the OUTFLOW VALVE to maintain the cabin altitude rate
  of climb at 2000 ft/min up to 12400 ft
• commands OUTFLOW VAVLE closed when cabin alt reached 12400 ft

Question 17

CPCS Flight Modes

Answer 17

– GROUND
– TAXI
– TAKEOFF
– CLIMB
– CRUISE
– DESCENT
– GROUND
– ABORT

Question 18

When is CABIN ALTITUDE HI EICAS Warning displayed

Answer 18

Cabin alt above 9,700’

Question 19

What happens with the Dump Button is pressed

Answer 19

• commands packs off
• commands recirculation fans off
• opens outflow valves for cabin depressurization at 2000 ft/min up to 12,400’

Question 20

Cabin Altitude Hi EICAS message

Answer 20

Altitude reaches 9,700’