Pneumatics Flashcards
What are the three sources of HP air?
Engines, APU, and an HP ground cart.
Which (6) systems use the pneumatic system?
Water pressurization, hydraulic pressurization, engine start, air conditioning packs, air conditioning compartment ventilation, and wing anti-ice.
How is the pneumatic system controlled and operated?
It is electrically controlled and pneumatically operated.
How many BMCs are there, and what do they monitor?
There are two BMCs, one for each engine.
What happens if one BMC fails, and how do they interact?
The other BMC automatically takes over its functions, as they continuously exchange data with each other.
How is the air prepared before being supplied to the pneumatic system?
It is pressure and temperature regulated.
From which stages of the High-Pressure Compressor (HPC) is HP air tapped?
HP air is tapped from two HPC stages:
1- The Intermediate Pressure (IP) stage
2- The High Pressure (HP) stage
What valves control the bleed air supply from the HPC stages?
The Intermediate Pressure Check Valve (IPC) and the High-Pressure Valve (HPV) control the bleed air supply.
When is the HP stage used for bleed air, and when does the IP stage kick in?
The HP stage is used only when the engine is at low power. Once IP pressure is sufficient, the HPV closes, and the IPC opens, allowing air from the IP stage instead.
What valve regulates engine bleed air pressure before it enters the pneumatic system and what are its functions?
The Pressure Regulating Valve (PRV):
1- Regulates the system pressure
2- Acts as a shut-off valve
What monitors system pressure and shuts down engine bleed if overpressure occurs?
The BMC monitors system pressure & will shut down engine bleed if an over-pressure is detected.
What protects the aircraft pneumatic system from overpressure downstream of the PRV?
The Over Pressure Valve (OPV) is installed downstream of the PRV to protect the pneumatic system if overpressure is detected.
What is the purpose of the Precooler in the bleed air system?
The Precooler is an air-to-air heat exchanger that cools hot bleed air before it enters the pneumatic system.
How is the Precooler cooled?
Fan discharge air is used to cool the precooler. The Fan Air Valve (FAV) modulates the amount of fan air that flows across the precooler to maintain bleed air temperature within limits.
What happens if the bleed air temperature exceeds safe limits?
The Bleed Monitoring Computer (BMC) monitors system temperature and will shut down engine bleed if an over-temperature is detected.
When is APU bleed air mainly used?
APU bleed air is primarily used on the ground for:
1- Air conditioning
2-Engine start
It can also be used in flight but only below a certain altitude:
1- During climb up to 23,000 ft
2- During descent from 21,000 ft
To which part of the pneumatic system is APU bleed air connected?
APU bleed air is connected to the left-hand side of the Cross-Bleed Valve.
What happens to the Cross-Bleed Valve when APU bleed air is turned on?
The Cross-Bleed Valve opens automatically when APU bleed is on, allowing pneumatics to supply both sides of the aircraft.
Where is the Ground Cart Supply connected in the pneumatic system?
The Ground Cart Supply is connected to the left-hand side of the Cross-Bleed Valve
How can pneumatic air be supplied to the right-hand side of the system when using ground air?
By manually opening the Cross-Bleed Valve using the cockpit pushbutton, pneumatic air can be supplied to the right-hand side.
Where are the HP ground air connections located?
There are two physical HP ground connections located at the bottom left of the belly fairing.
What prevents backflow at the HP ground air connections?
Each HP ground connection is fitted with a non-return valve to prevent backflow.
Where are Leak Detection Elements installed in the pneumatic system?
Leak Detection Elements are installed along the pneumatic supply ducts and are monitored by the Bleed Monitoring Computers (BMCs).
How are the Leak Detection Loops designed?
The loops consist of multiple sensing elements connected in series.
There are two loops (A & B) routed in parallel along the pneumatic ducts.
How do the BMCs detect a pneumatic leak while avoiding false warnings?
The BMCs use AND logic, meaning both Loop A and Loop B must detect a leak before triggering a warning, reducing spurious alerts.
Where is the Dual Loop Detection System installed?
The Dual Loop Detection System is installed along:
1- The APU supply duct
2- The wings
3- The fuselage
4- The air conditioning compartments
Where is the Single Loop Detection System installed?
The Single Loop Detection System is installed in each engine pylon and is monitored by its respective BMC.
What does the white “GND” indication on the pneumatic system display mean?
The white “GND” indication appears only when the aircraft is on the ground and serves as informational only. It indicates that:
1- Ground pressure connects to the left-hand side of the pneumatic system.
2- It does NOT mean that bleed air is connected or that the ground air door is open.
