Pneumatics

Question 1

What does the pneumatic system provide HP air to?

Answer 1

• air conditioning
• pressurisation
• de-icing

Question 2

Where is bleed air taken from?

Answer 2

Low pressure and high pressure stages of the compressor

Question 3

What is air from the HP stage used for?

Answer 3

De-icing of the engines and air frame

Question 4

When is low pressure air available?

Answer 4

Anytime the engine is running

It flows through a one way check valve

Question 5

How is the high pressure air controlled?

Answer 5

High pressure valve - electrically controlled, pneumatically operated butterfly valve

Requires electrical power to remain open and will close or remain closed in the event of loss of electrical power

Powered by the associated DC bus

Question 6

What is the high pressure air temperature limit?

Answer 6

Sensor will allow high pressure valve to open provided the temperature is less than 270 degrees

If the va,Ve is open and the temp is exceeded the valve will automatically close

It will automatically reopen after a cooling period

Question 7

When will the high pressure valve close?

Answer 7

Anytime the low pressure exceeds 22 psi

Question 8

What is the bleed air valve?

Answer 8

Bleed air will flow to the air conditioning pack through a bleed air valve (regardless of HP or LP)

Electrically controlled and phneumatically operated

If electrical power is lost a solenoid will lock the bleed air valve closed

Powered by the DC ess bus

Automatically close if bleed air pressure is not available

Question 9

When will the bleed air valve automatically close?

Answer 9

• if the temperature exceeds 274 degrees (HP valve will also close)
• if a bleed leak is detected
• if fire handle has been pulled
• if the associated engine fails
• if uptrim signal has been generated by the ATPCS
• left will close if the prop brake has been selected ON
• for 30 secs during engine starts to ensure normal starting

Question 10

What is the purpose of the crossfeed valve?

Answer 10

One engine can supply both packs when the engine is on the ground only

Solenoid controlled shut off valve, spring loaded closed, requires electrical power to open

Automatically close in the event of loss of electrical power

Question 11

When will the crossfeed valve close?

Answer 11

When the engines are operating and the prop brake is disengaged

Question 12

How is the bleed air duct cooled?

Answer 12

By ram air in flight by a NACA air inlet located on the top of the engine nacelle

Air exhausted through a vent on the landing gear fairing

Question 13

Where does the leak detection system monitor?

Answer 13

• wing leading edge
• wing to fuselage sidewall
• upper/lower fuselage floor
• air conditioning pack area

Question 14

When will you get a leak alert?

Answer 14

Above 124 degrees

Question 15

What happens if a loop overheat is sensed?

Answer 15

• pack valve, high pressure valve and bleed air valve are latched in the closed position
• FAULT light on the pb
• affected bleed air system is inoperative for the rest of the flight
• if leak detected in the left system, the ground crossfeed valve will close automatically

Question 16

When does the FAULT light on the bleed pb?

Answer 16

• If the position of the bleed air valve disagrees with the commanded position
• in the event of an overheat or leak

Question 17

When can the bleed system be recovered?

Answer 17

When it is an overheat, NOT a leak