Aircraft Systems 2 Flashcards
What is a key property of hydraulic fluid?
It is incompressible
What is a WOW switch?
Weight on wheels switch.
What is the process at which hydraulic systems work?
Force multiplication
What are the key common components of a hydraulic system?
Reservoir - fluid is stored in sufficient quantities.
Filters - there are several stages of filtration to prevent debris from being passed between components.
Pump - generates pressure, either engine or electrically powered.
Accumulator - A cylinder containing a floating piston.
Valves - Pressure control (pressure/thermal relief), directional control (selector valves), non return and selector valves.
Actuators - convert hydraulic power into usable mechanical power. Single and double action.
The majority of engine or motor driven hydraulic pumps are what type?
Rotary swash plate pump.
What is the purpose of a hydraulic accumulator?
Can be used from damping, absorbing sudden shocks and changes in system pressure.
Can also be used as a stored vessel of emergency hydraulic pressure.
What is a PFCU?
Powered Flying Control Unit
Enables the large aerodynamic forces on larger control surfaces to be overcome at high speeds.
What hydraulic system malfunctions can occur?
High hydraulic fluid temperature
Low hydraulic pressure
Landing gear faults.
How long must a backup hydraulic system operate for?
Indefinite period.
What system can provide a rapid emergency power source in the event of an emergency?
RAT
Ram Air Turbine
What does an actuator convert?
Fluid pressure into mechanical energy.
If landing gear presents red lights what does this mean?
The gear are travelling or unlocked.
Where is air for cabin pressurisation supplied from?
Pressurised air is normally obtained from a late compressor stage, as bleed air.
What is complement density?
Complement Density
The rate of ventilating airflow is dependent upon volume of cabin space per occupant, this is the complement density (in m3/passenger)
What is the comfort zone?
Comfort Zone
The range of ambient temperatures and humidity in which a crew can operate comfortably without rapidly becoming fatigued.
Within the cabin conditioning heat exchanges how is hot air cooled?
Cold ram air is routed through the primary and secondary heat exchanges to cool the hot air from the engine compressor.
What are the advantages and disadvantages of a Gaseous O2 system for aircraft oxygen system?
Gaseous O2
Relatively simple system, and O2 is not lost by venting when not in use, it can be used immediately after filling.
However, the cylinders are bulky and heavy. They are not suitable as a primary O2 source when space and weight are at a premium.

What are the advantages and disadvantages of a Liquid O2 system for aircraft oxygen system?
Liquid O2 System
Reduced bulk and weight compared to cylinders and will not explode when damaged.
However oxygen is lost via venting and must be stabilised, it can also become contaminated.

What is a Molecular Sieve O2 Concentrator (MSOC)?
Molecular Sieve O2 Concentrator (MSOC)
A molecular sieve is synthetic porous metal that removes nitrogen from the air under pressure. The result is oxygen enriched gas, back purging and depressurisation removed nitrogen when fully saturated (this is pressure-swing adsorption).
This system effectively removes contaminants, however a separate gas supply is required for ejection seats and may not provide enough oxygen under rapid decompression.
What is rectification?
The conversion of AC to DC.
What primary electrical sources are present on an aircraft?
Batteries
AC Generators
DC Generators
What is an EPU?
Emergency Power Unit
Small self-contained gas turbine capable of developing full power within two seconds of initiation. EPUs use mono-fuel such as hydrazine.
What is the difference between a Primary and Secondary cell?
Primary Cell - Cannot be recharged
Secondary - Always regenerating
What is a Transformer/Rectifier Unit?
TRU
Converts AC input of one voltage into DC outputs of other voltages.









