Environmental/Bleed air

Question 1

What are the primary functions of the bleed air system?

Answer 1

transfer bleed air from the low- and high-pressure ports to individual system requiring bleed air
control bleed air pressure
supply and control temperature of bleed air supplied to the air conditioning system
supply bleed air for engine starting
supply bleed air for the wing and cowl anti-ice systems
supply and control temperature and pressure of bleed air to the air preparation system (APS)

Note, The APS is also known as FITS in the fuel chapter. The first two answers are from the
list in the FCOM2, but don’t really answer the question.

Question 2

What is both the normal and maximum positive relief differential pressure? (AFM Limitations &
FCOM2)

Answer 2

Normal: 10.30psi at FL510
Maximum: 10.73psi

Question 3

What is the maximum negative relief differential pressure? (AFM Limitations)

Answer 3

-0.5psi

Question 4

What is the maximum differential pressure during taxi and takeoff? (AFM Limitations)

Answer 4

0.1psi

Question 5

What is the maximum differential pressure upon landing? (AFM Limitations)

Answer 5

1.0psi

Question 6

What is the maximum altitude AUX PRESS May be used? (AFM Limitations)

Answer 6

41,000ft
Note: this information is in the DUAL AC PACK FAIL checklist

Question 7

How is the landing elevation set during QFE operations? (AFM Limitations & FCOM2)

Answer 7

Must be manually set to 0
Via the CTP by MIN/LDG, LDG ELEV, MAN
On any MFW, MISC page, AVIONICS tab
Note: there is a checklist for operating in QFE. QFE is not a memory operation.

Question 8

Where is the cabin pressure and landing elevation information depicted?

Answer 8

Below the fuel quantities on the EICAS, or
On the BLEED synoptic page

Question 9

Which stages in the high-pressure compressor (HPC) are bleed air extracted?

Answer 9

4th stage LP bleed
7th stage MP bleed
10th stage HP bleed

Question 10

When is the high-pressure valve (HPV) prevented from opening?

Answer 10

When N2 is less than 55%
Note: the pressure bleed source changes when LP doesn’t provide enough pressure.

Question 11

During ground operation, what is the priority of bleed sources for engine starting?

Answer 11

(1) APU bleed air
(2) External high-pressure ground connection
(3) Crossbleed

Question 12

How are bleed air leaks monitored?

Answer 12

Dual loop sensing elements (loop A and B) are routed along the HP ducts and monitored by the IASCs

Question 13

What occurs automatically when a bleed air leak is detected?

Answer 13

IASCs automatically close the bleed air valve that supplies the affected duct

Question 14

How is a bleed leak depicted on the synoptic page?

Answer 14

Amber flow lines
The corresponding valves are closed

Question 15

What happens to the PACK airflow schedule when the heating/cooling demand is high?

Answer 15

PACK FLOW HI schedule is automatically selected by the IASCs to drive maximum airflow

Question 16

What are the two functions of the air conditioning packs?

Answer 16

Decrease the air temperature and
Decrease the water contained in the hot bleed air

Question 17

When do the IASCs automatically close the flow control valves?

Answer 17

When a pack fails and
either the DITCHING PBA is selected on, or
a pack system fault is detected

Question 18

Which valves close when selecting the TRIM AIR PBA switch to OFF?

Answer 18

Both hot air shutoff valves (HASOV)
All four trim air valves

Question 19

What are the two functions of the RAM AIR system?

Answer 19

Cool the packs and APS heat exchangers
Alternate source of fresh air at altitudes less than 15,000ft

Question 20

What malfunction will require the use of AUX PRESS?

Answer 20

Failure of both packs
Note: a CAS message will take the crew to a checklist.

Question 21

What are the typical cabin altitudes for FL510? FL450?

Answer 21

FL510: Not more than 5,673ft
FL450: Not more than 4,500ft

Note: this is more for pointing how low the cabin is compared to other aircraft. There are
several factors governing cabin altitude. These numbers are for illustration purposes only and
not an actual accounting of the cabin altitude

Question 22

Describe the two modes of operation with the cabin pressure control system (CPCS) in AUTO:

Answer 22

Primary mode (predictive): FMS has an active flight plan with altitude; autopilot is on, VNAV
selected on
Secondary mode (reactive): uses airplane altimeter and vertical speed (ADC)

Question 23

During a loss of pressurization, what cabin altitudes trigger the CABIN ALT caution/warning CAS
messages for airports below 7,230ft?

Answer 23

CABIN ALT (caution): 8200ft
CABIN ALT (warning): 9000ft

Question 24

How does the cabin altitude warning system react to airports above 7,230ft?

Answer 24

CABIN ALT caution and warning thresholds are increased progressively during TO and LDG
sequences up to 14,500ft
A Cyan CABIN ALT HI message is posted.

Note: The Caution will remain 1,000ft above the field elevation until it reaches the maximum value of 14,500ft. The Warning will remain 1,800ft above the field elevation until it reaches a maximum value of 14,500ft

Question 25

What is required to display the LDG ELEV in magenta on the EICAS or BLEED synoptic?

Answer 25

Active flight plan with a destination programmed in the FMS

Question 26

How is landing elevation manually programmed?

Answer 26

From the CTP: TUNE/MENU, MIN/LDG, LDG ELEV to MAN
From an MFW: MISC page, AVIONICS tab

Question 27

When would a pilot need to manually set the field elevation?

Answer 27

QFE operations
Airport not in the data base
Airport not WGS84

Note: Selecting both GNSS to OFF will force the system to navigate DME/DME. Historically
this will allow proper navigation in non-WGS84 areas like India

Question 28

What occurs when the guarded EMER DEPRESS PBA is selected ON?

Answer 28

The outflow valves open to depressurize the cabin at a rate of 2,500ft/min
Cabin altitude will climb to 14,500ft for high altitude airports; 13,800ft for lower altitude airports

Question 29

What does selecting the DITCHING PBA to ON provide?

Answer 29

Packs off
Outflow valves (OFVs) open
Once cabin is completely depressurized, both OFVs close

Note: the ditching function does not modulate cabin rate at 2,500ft/min, this PBA drives
outflow valves full open immediately.

Question 30

What is the purpose of the safety valves?

Answer 30

Ensures overpressure and negative pressure relief; when max ∆P is reached, the safety valves
open to outside pressure, independent from the IASCs

Note: A cyan SAFETY VALVE OPEN CAS will appear when opened