Brady Pneumatics

Question 1

What 9 other systems does the pneumatic system provide air for?

Answer 1

Air conditioning
Pressurization
Engine starting
Engine & wing anti-ice
Water tank
Hydraulic reservoirs
Auxiliary fuel tanks
Aspirated TAT probe
Inert gas system

Question 2

Where can the pneumatic system get its air from?

Answer 2

Engines, APU or a Ground Source

Question 3

What is the ONLY system that takes engine bleed air BEFORE it goes to the pre-cooler?

Answer 3

ENGINE anti-ice. Wing & other anti-ice systems take their bleed air AFTER the pre-cooler.

Question 4

Where does bleed air normally come from? What about the MAX?

Answer 4

The engine 5th stage, and the 9th stage can be added if needed at low power. (4th & 10th stage in the MAX)

Question 5

Where does the pre-cooler get cool air to cool the hot bleed air from?

Answer 5

The FAN stage of the engine. You can see a little rectangle sticking out into the air stream just aft of the fan blades.

Question 6

What will cause a BLEED TRIP OFF?

Answer 6

>= 220 psi (measured before the bleed valve) or
>= 254 deg C (measured after the pre-cooler)

Question 7

A bleed pressure >= 220 psi or a temp of >= 254 deg C will cause a BLEED TRIP OFF. Where is this data measured?

Answer 7

The bleed pressure is measured before the bleed valve (which is also before the pre-cooler).
The bleed temperature is measured after the pre-cooler.

Question 8

Which side of the pneumatic system does the APU bleed air blow into?

Answer 8

The left side

Question 9

Where does the mix manifold get air & what does it do with it?

Answer 9

Air comes in from the left & right packs AND from the left & right RECIRC fans via 4 pipes. The air mixes in a MANIFOLD area before being pushed out 2 pipes, one for the forward cabin & one for the aft cabin.

Question 10

Which pack does the flight deck air come from?

Answer 10

The LEFT pack

Question 11

What would cause a DUAL BLEED light?

Answer 11

Engine bleed air is MUCH more powerful than APU bleed air. So if an engine AND APU bleed valves were both open, the engine bleed air could backpressure the APU causing damage.

Question 12

What does a WING-BODY OVERHEAT light mean?

Answer 12

Indicates a leak in the corresponding left or right bleed air duct.

Question 13

Which is worse, a left or right WING-BODY OVERHEAT?

Answer 13

A WING-BODY OVERHEAT light indicates a leak in the corresponding left or right bleed air duct. This is particularly serious if the leak is in the left-hand side as this includes the ducting to the APU.

Question 14

When are you most likely to get a BLEED TRIP OFF light?

Answer 14

Most common on full thrust, bleeds off, takeoffs. The reason is excessive leakage past the closed high stage valve butterfly which leads to pressure build up.

Question 15

If you get a BLEED TRIP OFF light during a full thrust, bleeds off, takeoff, what is the easiest fix?

Answer 15

The simple in-flight fix is to reduce duct pressure by selecting CLB-2 and/or using engine and/or wing anti-ice.

Question 16

If the isolation valve switch is in AUTO, when will the isolation valve open?

Answer 16

With the isolation valve switch in AUTO, the isolation valve will ONLY open when an engine bleed air or pack switch is selected OFF.

Question 17

Where does the external air for air start plug in at?

Answer 17

The hatch is on the lower right hand fuselage near the wing leading edge.

Question 18

When doing an air start, which engine do you have to start first? Why?

Answer 18

The start air plugs in on the lower right hand fuselage near the wing leading edge. This is very close to the inlet for engine #2 which is why if you are using external air, you must start engine #1 first to allow the ground crew to be able to safely disconnect the air.

Question 19

Where does the PCA (cool or hot air) plug in?

Answer 19

The exact center bottom of the fuselage, which is very close to the mix manifold. The PCA feeds directly into the mix manifold.

Question 20

What is a “sidewall riser”?

Answer 20

It’s the tube where air goes from the mix manifold, up the side of the fuselage to the top of the fuselage for distribution in the cabin.

Question 21

How can you tell where the “sidewall risers” are?

Answer 21

There won’t be windows on that part of the fuselage.

Question 22

How is the pneumatic system in the MAX different from the NG?

Answer 22

The NG was an “all or nothing” as far as bleed air. The MAX is digital & only siphons off just the amount of bleed air needed, thereby preserving performance and fuel economy.