Pressurisation/Air Conditioning/Pneumatics Flashcards
What system are the #1 and #2 BLEED HOT caution lights associated with? What does the caution light mean?
Pneumatic system. It warns of an overheat condition in the respective bleed air supply duct downstream of the nacelle shut off.
What does HBOV stand for? What is its purpose?
Handling Bleed Valve. It Bleeds air from the low speed compressor to prevent compressor surge and stall at low power settings or during rapid power lever advancement.
What controls the HBOV?
The ECU
When you turn the bleed air switches on, what happens?
The solenoid of the HP shut-off valve is energised open and the nacelle shut-off valve is de-energised open.
In the event of an electrical failure to the bleed air system, what will occur?
The HP bleed valve will close, but the nacelle shut-off valve will remain open. LP bleed air will supply the system at its full rate irrespective of the flow controller position.
What does the CABIN DUCT HOT and FLT COMP DUCT HOT caution lights mean? What will occur?
Overheat in the respective supply duct. The control valves (cabin) or trim valves (flight compartment) are automatically driven to the maximum cooling position.
Describe the path of air through the air conditioning system.
From the bleed supply duct, assure is cooled through the primary heat exchange, then enters the compressor side of the ACM where Temp and pressure are increased. it then is cooled by the secondary heat exchangers, then goes through the divergent side of the ACM pressure reduces and it is further cooled. It then mixes with recycled air and hot bleed air in the mixing box to the desired temperature.
How are the avionics cooled? What and where is the indication of a failure?
A fan draws air through the avionics equipment to cool it. If the fan fails a light illuminates on the flight attendant control panel.
What causes and what will happen if the AIR COND PACK HOT caution light illuminates?
Overheat in the ACM. Bleed air systems automatically shut down to cut off hot air supply. The system will cool and system operation will be restored. If the issue occurs again the light will cycle.
If the pressurisation system is lost, how is the cabin ventilated?
The ram air ventilation system in the tail will supply air to the cabin and flight compartment.
When in the auto setting, what controls cabin pressurisation requiring minimal pilot input?
Cabin Pressurisation Controller
How does the rear cabin outflow valve work? How is the front Safety outflow valve different?
A spring holds it closed. to open it, a venturi which is supplied by 18PSI De-ice air creates suction that opposes the spring which opens the valve.
The safety outflow valve is similar in construction but uses suction generated by a slipstream. The suction is controlled by the man control knob in the flight compartment.
If the forward outflow valve is manually opened, what will happen to the rear valve?
It will automatically close in an attempt to maintain cabin pressure.
What is the position of the rear outflow valve while on the ground?
The rear (normal) outflow valve is held open to prevent the cabin from pressurising.
What cabin pressure is maintained during cruise?
The system is able to compare the normal cruise scheduled cabin pressure with the destination airport altitude. The system will maintain the higher of the two.
