3_AIR CONDITIONING

Question 1

How does the ac system provide temp controlled air

Answer 1

it processes bleed air from the engines, apu or ground air source in air cond packs

Question 2

Describe the flow, in general of the system

Answer 2

conditioned air from the left pack, upstream of the mix manifold, goes to the flt deck

excess air from left pack, air from rt pack and air from recirc system is combined in the mix manifold

this then goes to the left and right sidewall risers and to the pax cabin

Question 3

What controls the flow of bleed air to the pack?

Answer 3

the pack valve

Question 4

Describe the normal bleed air sources for the packs

Answer 4

normally the left pack uses bleed air from Eng 1

right pack from eng 2

Question 5

Can a single pack provide adequate pressure

Answer 5

Yes - a single pack in HIGH FLOW is capable to sustain both Press and Temp up to 41k

Question 6

Can APU provide adequate bleed air?

Answer 6

yes - the APU can supply bleed air for

2 - packs on the ground

1 pack in flight

Question 7

Are there any pack operating concerns when it comes to bleed air?

Answer 7

Do not operate MORE THAN ONE PACK from ONE ENGINE

Question 8

if everything is operating normally, 2 engines, packs to auto and both eng bleed switches ON what is the pack flow rate

Answer 8

Normal flow

Question 9

Describe Pack Auto logic

Answer 9

• AIR - and flaps are UP (pack auto and eng bleed are ON)
  
  • if one pack fails - 1 engine fails - or 1 pack switch is turned OFF
    
    • the other automatically switches to HIGH FLOW
• GROUND or FLAPS ARE DOWN (pack auto both eng bleed ON)
  
  • if one pack fails - 1 engine fails - or 1 pack switch is turned OFF
    
    • the remaining pack will NOT automatically switch to HIGH FLOW
  • auto switch is inhibited to ensure adequate eng power or sgl eng operation

APU PACK LOGIC.

• if APU bleed ON (both eng bleeds OFF) w/ both packs in AUTO
  
  • auto switch to high flow occurs with a single pack failure
    
    • regardless of flaps or air/ground status
  • NOTE - in this configuration the flt crew can FORCE and APU HIGH AIR FLOW rate when either or BOTH packs are in HIGH (give max airflow) when APU is sole source

Question 10

Describe and state purpose of the RAM air system

Answer 10

• to provide cooling for the PACKS
• automatically controlled by the packs (through the ram air doors)

Question 11

When do the RAM air doors open and close

Answer 11

• FULL OPEN
  
  • on the ground
  • during slow flight with flaps not fully retracted

Normal Cruise

• door modulate between open and closed

Question 12

Describe purpose and operation of the deflector doors

Answer 12

• installed forward of the ram air inlet doors
• prevent slush ingestion prior to liftoff and after touchdown
• they extend electrically by the air/ground switch

Question 13

How is overheat protection provided for the PACK

Answer 13

there are temp sensors in the cooling cycle

an overheat causes PACK VALVE to CLOSE and PACK light illuminate

Question 14

How is pack temp output controlled?

Answer 14

• Electronic controllers command the temperature control valve (to open or closed)

Question 15

Describe what happens with a single or dual pack temp controller failure

Answer 15

• if a primary pack control fails ( SINGLE PACK CONTROLLER FAIL )
  
  • the affected pack is controlled by the standby controller (opposite controller)
  • causes PACK, MC and AIR COND lights during RECALL

​

• if BOTH controllers fail - FOR THE SAME PACK
  
  • PACK, MC and AIR COND lights illuminate immediately
  • the pack will continue to operate WITHOUT TEMP CONTROL unless excessive temps cause the pack to trip off

Question 16

How many ‘zones’ are in the aircraft - how are they controlled (temp) - and what is the temp range?

Answer 16

• 3 zones
• temps are controlled with individual temp selectors
• temp range: 65 - 85

Question 17

How is air temp determined with pack output

Answer 17

packs produce an air temp that satisfies the zone that requires the MOST cooling

zone temp is controlled by introducing trim air to the other zones

the AMOUNT of trim air is controlled by the individual trim air modulating valves

Question 18

Describe single pack ops -

with TRIM AIR ON -

with TRIM AIR OFF -

Answer 18

• ON: zone temps are controlled the same as 2 pack operation
• OFF: the pack attempts to produce an average temp of ALL 3 ZONES

Question 19

Describe the zone temp controllers and their areas of responsibilites

which controller controls what zones?

Describe the failure modes of the PRI FLT DECK TEMP CONTROLLER and what happens

Answer 19

• Left controller
  
  • controls AFT zone (primary)
  • Flight Deck (backup controller)
• Right controller
  
  • forward & flight deck (primary)
  • aft zone (backup)

FAILURE OF THE PRIMARY FLT DECK TEMP CONTROL (i.e. Right electronic controller)

• causes an AUTO switch to backup controller
• illuminates ZONE TEMP light (CONT CAB)
  
  • ON RECALL if its just the primary controller
• failure of BOTH controllers will illuminate those lights AUTOMATICALLY

Question 20

What happens to the trim air modulating valves when you have a failure of the FWD or AFT CABIN temp controller.

Answer 20

• causes the associated trim air modulating valve to close
• the TEMP SELECTORS operate normally
  
  • BUT - the temp selector settings of the 2 pax cabin zones will be averaged.
• ZONE TEMP light will illuminate ON RECALL which indicate failure of the associated zone control
  *

Question 21

Any failure affecting the supply of trim air will cause the temp control syst