AGK Systems - Pneumatic Systems

Question 1

What are Pneumatic system uses?

Answer 1

Operating air driven gyroscope instruments.
Heating/cooling cockpit,cabin and cargo.
Pressurisation.
De/Anti - Ice.
Emergency backups.
Inflating cabin door seals.
Pressurising hydraulic resivoirs.
Gad turbine engine starting.
Reverse thrust.
Rain repelling nozzles.
Water tank pressurisation.
Toilet.
Sensing conditions around the aircraft.

Question 2

How many sources or compressed air do gas turbines have?

Answer 2

Three.
Bleed air from the main engines,
Compressed air from the APU,
Compressed air from GPU.

Question 3

How does the APU generate compressed air? (Not step by step but the system)

Answer 3

Dedicated land compressor,
Gas generator compressor bleed.

Question 4

What is bleed tapping?

Answer 4

Bleed air passes through high pressure shut off valve to limit it to 100psi.
Then through a pressure reducing shut off valve.
Pressure is now 40psi.
Pre-cooler which uses low pressure fan air to reduce temperature.

Question 5

At the compressor, during ground idle what should the pressure + temperature be? (Intermediate and high pressure)

Answer 5

Intermediate - 15psi at 16degrees
High pressure - 50psi at 180degrees

Question 6

At the compressor, during takeoff what should the pressure + temperature be? (Intermediate and high pressure)

Answer 6

Intermediate - 25psi at 65degrees
High pressure - 410psi at 540 degrees

Question 7

At the compressor, during cruise what should the pressure + temperature be? (Intermediate and high pressure)

Answer 7

Intermediate - 8.5psi at 15degrees
High pressure - 150psi at 400degrees

Question 8

Pneumatic system architecture.

Answer 8

Air is distributed in ducts.
Shut off valves control the supplies to differential systems.
Cross over valve allows air to supply services on other side.
The APU has its own SOV.
Non-return valves used extensively to ensure no back flow.

Question 9

How does the overheat detection system work?

Answer 9

Loops located in areas of airframe, called zones. 2 loops per zone. Often cover air conditioning packs and leading edge.

Question 10

Can you operate with one overheat detection loops inoperative?

Answer 10

Yes, for a limited amount of time.

Question 11

What are the principal bleed air malfunctions?

Answer 11

Over temperature.
Over pressure.
Low pressure.
Overheat/duct leak.