ATR 72 – Pneumatics - SmartCockpit - Airline training guides, Aviation, Operations, Safety

The pneumatic system supplies pressurized air to air conditioning, pressurization, and ice protection system. Compressed air is bled from the engine compressors at the:

LP or HP stages.

LP stage.

HP stage.

Correct! Wrong!

Air is usually bled from the low compressor stage (LP). At low engine speed if pressure from LP is not sufficient, air source is automatically switched to the high compressor stage HP (this may occur on ground and during descent at flight idle).

The crossfeed valve (X VALVE), on the crossfeed duct, enables to connect LH and RH air bleed systems. The crossfeed valve is pneumatically controlled.

True.

False.

Correct! Wrong!

The crossfeed valve is electrically controlled and pneumatically actuated.

Wing and Engine Deicing - Air is bled from the LP. Bleed air is transferred via electrically controlled pressure regulating valve.

True.

False.

Correct! Wrong!

Air is bled from the HP!

When considering the ATR 72 pneumatic system, there is a difference in philosophy between LEAK and OVHT. In the case of OVHT, the associated bleed system will be recovered after a cooling time. In the case of LEAK, the flight crew must consider the associated bleed system as inoperative for the rest of the flight.

False.

True.

Correct! Wrong!

The bleed air shutoff valve automatically closes in the following cases:

Bleed duct OVHT, or bleed duct LEAK, or actuation of associated ENG FIRE handle, or engine failure at takeoff (UPTRIM signal), or PROPELLER BRAKE selected ON (only for left bleed valve).

Bleed duct signal lost, Bleed duct OVHT, or bleed duct LEAK, or actuation of associated ENG FIRE handle, or engine failure at takeoff (UPTRIM signal), or PROPELLER BRAKE selected ON (only for left bleed valve).

Bleed duct OVHT, or actuation of associated ENG FIRE handle, or engine failure at takeoff (UPTRIM signal), or PROPELLER BRAKE selected ON.

Correct! Wrong!

The bleed air leak detection system provides a continuous monitoring of bleed duct leak to protect the structure and components near the hot bleed air ducts. The system is installed in the following areas:

Wing leading edge and wing to fuselage fairing, the upper/lower fuselage floor and the air conditioning pack area.

Wing to fuselage fairing and the air conditioning pack area.

Wing leading edge and wing to fuselage fairing and the upper/lower fuselage floor

Correct! Wrong!

The wing leading edge ventilation is on the top engine nacelle fairing, between the fuselage and the engine nacelle. The purpose of this ventilation system is to:

Maintain low temperature inside the wing leading edge zones.

Maintain an airflow circulation and to avoid any moisture accumulation (with a risk of dynamic icing).

Avoid any moisture accumulation and then a risk of dynamic icing.

Correct! Wrong!

Ventilation is provided in flight using dynamic air pressure through a ram air intake scoop. No cockpit monitoring or control is provided.

Bleed air from HP compressors is transferred via a pneumatically operated electrically controlled HP butterfly valve. When the HP valve is not energized the valve remains closed, air is directly bled from the LP stage through LP bleed check valves.

False.

True.

Correct! Wrong!

ATR 72 – Pneumatics