Air & Pneumatics

Question 1

Which systems rely on bleed air for operation?

Answer 1

Air conditioning
Pressurization
Wing and thermal anti ice
Engine starting
Hydraulic reservoirs

Question 2

What causes PACK light to illuminate

Answer 2

Indicates pack trip off (temperature related)

or

Failure of both primary or standby pack control

Question 3

What causes WING BODY OVERHEAT light to illuminate?

Answer 3

Overheat with the bleed air system, typically associated with a duct leak.

Question 4

What causes a LEFT side WING BODY OVERHEAT to illuminate

Answer 4

Overheat in bleed air duct in either

• left engine strut
• left inboard wing leading edge
• left air conditioning bay
• keel beam
• APU bleed air duct.

(right side same except for keel beam & APU duct)

Question 5

What causes a BLEED TRIP OFF

Answer 5

Over temperature or overpressure (this closes bleed air valve).

Question 6

Which lights can be reset with the trip reset?

Answer 6

BLEED TRIP OFF, PACK or PACK TRIP OFF, or ZONE TEMP

Question 7

What causes DUAL BLEED light to come on?

Answer 7

No 1 engine bleed and APU bleed open

or

No 2 eng bleed, isolation valve and APU bleed open

Question 8

When must APU valve be closed?

Answer 8

1. ground air connected and ISOL valve open
2. ENG no.1 bleed open
3. ISOL valve and ENG no.2 both open

Question 9

Do not operate packs in HIGH for

Answer 9

Takeoff, Approach or Landing

Question 10

Recirculation Fan purpose

Answer 10

Reduces air cond system pack load and bleed air demand

Question 11

RECIRC Fan
AUTO in flight
On Ground

Answer 11

flight - right fan runs if both packs are running unless both are in high

on ground - right fan runs even if both packs are in high

Question 12

PACK SWITCH on AUTO or HIGH

Answer 12

AUTO -

• both packs on, both in low flow
• one pack on in flight with flaps up operating pack` will be in high flow
• one pack operating from APU (both engine bleed switches OFF) operating pack in HIGH flow

HIGH -

• pack regulates to high flow
• provides maximum flow rate on ground with APU on

Question 13

Isolation Valve switch in Auto

Answer 13

• open if any corner switch (pack or bleed) is in the off position.
• closed if all corner switches are ON which is normal.
• AC operated from transfer bus #1
• not affected by position of APU bleed switch

Question 14

Equipment Cooling

Answer 14

Supply duct supplies cool air to the flight deck displays and electronic equipment in the E&E bay.
Each duct has a normal and an alternate fan.

Exhaust duct discards warm air from flight deck displays, electronics and CB panels and the E&E bay.

Question 15

Lower FWD cargo compartment

Answer 15

This area is warmed in flight with air from the E&E compartment. Right recirc fan and fwd outflow valve ensure this warm air flow.

Question 16

Pressure relief valves

Answer 16

Two valves provide safety pressure relief by limiting diff pressure to 8.65.

A negative relief valve also prevents external atmosphere pressure from exceeding internal pressure.

Question 17

CPCS (Cabin pressure controller)

Answer 17

Auto - uses AC motor / altitude sensed from static ports

STBY - semi auto uses DC motor / altitude sensed from air data computer (ADC)

MAN AC and MAN DC modes manually operate outflow valves

Question 18

AUTO FAIL light illuminates

Answer 18

• loss of AC power
• excessive rate of cabin pressure +/- 1890 fpm
• high cabin altitude (above 13,875 ft)