Pneumatic/ Air Conditioning/ Pressurization Flashcards Preview

ATR 42-500 > Pneumatic/ Air Conditioning/ Pressurization > Flashcards

Flashcards in Pneumatic/ Air Conditioning/ Pressurization Deck (24)
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0
Q

Bleed Air Users

A

Air Conditioning
De-icing
Pressurization
Ventilation

1
Q

Air Bleed System (Description)

A

Designed to

  • select the compressor stage from which air is bled, depending on the pressure and or temperature
  • regulate air pressure between the HP Stage and the LP stage by the HP Valve
2
Q

Bleed Valve (Function)

A

Electro pneumatic bleed valve acts as a shut off valve when:

  • Bleed Duct OVHT
  • Bleed Duct LEAK
  • Actuation of the associated ENG FIRE handle
  • Engine failure at TO (UP TRIM signal)
  • Prop Brake selected ON (for left bleed only)
  • spring loaded closed in the absence of pressure
3
Q

Cross-Feed Valve (Function)

A

A spring loaded, solenoid controlled valve connects the LH and RH air bleed systems

  • On the ground, it is always open, except with both engines running and PropBrake disengaged
  • In flight the cross-feed valve is normally closed

The valve is de-energized closed

4
Q

Leak Detection System (Description)

A

Continuous monitoring system of 2 single loop assemblies (LH &RH) to detect leakage near the hot air ducts:

  • Wing leading edge and wing to fuselage fairing
  • Upper and lower fuselage floor
  • Air conditioning pack area
5
Q

Leak Detection System (Trigger)

A

Temperature above 153*C triggers LEAK light to illuminate and after 1s delay closes the associated Pack, HP and BLEED valves and GND X FEED if LH is affected

The crew must consider the associated bleed system as inop for the rest of the flight

6
Q

Overheat Control System (Description)

A

Includes switches (duplicated for safety) installed near the the HP compressor exit and ensures the bleed valve and bleed air shut off valve close when temperature at or above 274*C is sensed

Associated Bleed system may be recovered after cooling

7
Q

ENG BLEED OVHT Light

A

Illuminates amber and the CCAS is activated when either of the respective bleed duct OVHT sw operates at 274*C

System may be recovered

8
Q

ENG BLEED LEAK Light

A

Illuminates amber and the CCAS is activated when either respective bleed leak detection system signals an alert when temperature rises above 153*C

System is considered inop

9
Q

Air Conditioning (Description)

A

Air is processed through 2 packs installed in the main landing gear fairings. LH Pack for cockpit and cabin, RH for cabin only, though if either is inop, the other can supply both compartments.

10
Q

Pack Valve (Function)

A

The pack valve is an electro-pneumatic valve, spring loaded closed, having 2 functions:

  • Pack shut off
  • Pressure control (NORM 22psi and HIGH FLOW 30psi)
11
Q

Air flow through the AC Packs

A

Bleed air is admitted through the AC Packs, where it is cooled,dried, and compressed. It is cooled by air-to-air heat exchangers where external air is blown by:

  • Ram air above 150kts
  • 2 ground turbofans at or below 150kts with the gear extended or with gear retracted for <10mins
12
Q

Air Conditioning Ground Turbofans (Special Ops)

A
  • In case of ENG OIL LOW PRESS, the turbo fan on the opposite side starts and runs as long as speed is 150kts or less, regardless of gear position.
  • Incorrect position of a turbofan shut-off valve leads to closure of the associated pack valve.
13
Q

Flight Deck Ventilation (Description)

A

The flight deck, FWD CARGO and electric and electronic equipment are ventilated by the flow of ambient air. The OVBD valve and the U/F valve work in conjunction to recirculate the air to the pressure vessel or duct it overboard.
OVBD Valve open = U/F Valve closed, and vice virsa.
OVBD Valve full open only if press diff is <1psi

14
Q

Cabin Temperature Control

A

In AUTO MODE, the electronic temp controller computes temp control valve position using:

  • Duct Temperature
  • Zone temp demand selector
  • Associated compartment temp
  • Aircraft skin temp

In MAN MODE, only the associated zone temp demand selector controls the temp control valve

15
Q

Air Conditioning Overheat Protection

A
  • When duct temp rises above 88*C, the limiter closes the temperature control valve progressively to reduce hot air flow.
  • An OVHT caution is provided to the pilot when the duct temp rises above 92*C, leaving the pack valve open.
  • The Pack Valve will auto close in case of overheat downstream of the pack compressor.
16
Q

Flight Deck Ventilation Isolation

A

The EXTRACT AIR FLOW Valve allows the isolation of the flight deck in case of smoke in the FWD CARGO Compartment.

17
Q

Pressurization System (Description)

A

Cabin pressure and rate of change is maintained by:
-An automatic digital controller
-A manual pneumatic controller
With 2 outflow valves, one electro-pneumatic and one pneumatic
In Auto mode the pneumatic is slaved to the other, in Manual mode, the electro-pneumatic is closed.

18
Q

Pressurization System (Limitations)

A
Max Positive Diff Press      6.35psi
Max Negative Diff Press   -0.50psi
Max Landing Diff Press      0.35psi
Max OVBD Valve full open 1.00psi
Max ALT for one BLEED off 20,000'
19
Q

Pressurization Ops in AUTO MODE

A

The Digital Controller uses:
-Landing Elevation set in the landing elev. selector
-Takeoff Elevation stored in the controller
-Cabin Pressure
-Aircraft Static Pressure from ADC1 with CA Barro setting or ADC2 with STD Barro setting
This information is used to calculate a theoretical altitude which the controller uses to drive the outflow valves in order to match the actual altitude to the calculated theoretical altitude.

20
Q

Pressurization Dump Mode

A

A DUMP function is available, in AUTO Mode only, to drive the electro-pneumatic valve full open. The DUMP switch is mechanically guarded.

21
Q

Pressurization Manual Mode

A

The electro-pneumatic valve is maintained closed, leaving the pneumatic valve to maintain cabin pressure. The control knob is used to select any cabin rate of change from -1500fpm to +2500fpm

22
Q

Pressurization Ditching Mode

A

2 electrical motors are used to drive the outflow valves to the closed position in either MAN or AUTO mode

23
Q

Pressurization AUTO Mode Descent Rate

A

The Descent Rate pb allows a fast descent option.

  • NORM (pb released) max cabin descent rate is -400fpm
  • FAST (pb selected) max cabin descent rate is -500fpm