Module 1-2 Flashcards
What is a PSEU and what is it function?
Proximity Switch electronic unit - Provides positioning sensing for various aircraft systems. Sensors provide input data and PSEU processes this data and then controls relays, lights and other components
Describe the proper installation of a switch
A switch should always be installed in panels so the lever will move up or forward to turn the circuit on. Switches that activate moving parts should always be oriented to correspond to part movement
What does SPST stand for?
Single pole single throw
What does SPDT stand for?
Single pole double throw
What does DPST stand for?
Double pole single throw
What does DPDT stand for?
Double pole double throw
What does normally open mean?
It is a break before make connection
What does normally closed mean?
Its a make before break connection
What does common mean?
A point to which both normally open / closed terminals connect to
Whats the difference between a selenoid and a relay?
A relay has movable contacts and a stationary core, A selenoid has a movable core with stationary contacts
What is a contactor?
Another name for a selenoid
How does a prox sensor work?
Prox sensors are inductance coils that operate in conjunction with steel targets. The inductance changes with the proximity of the steel targets
Derating factor: What is the CCR of a 24VDC switch drawing 6 amps?
Derating factor for 24VDC motor = 3
6amps x 3 = 18 amps
What is rush-in current?
When the circuit is initially turned on, there is excessive current across the switch contacts. As it becomes more reactive, the more voltage is dropped across the resistor and the total circuit current is higher
Advantages of a rocker switch compared to a lever switch?
Its more flush with the panel, making accidental toggles or presses more difficult. It also makes the panel more attractive.
Describe a thermal switch
Actuated by an increase in temperature by bending a bi metallic strip within that bends and touches the contacts with an increase in temperature
Difference between thermal circuit breaker and electromagnetic circuit breaker
Thermal circuit breaker opens the circuit when excess current heats an element in the switch and snaps the contacts open. An electromagnetic breaker will open the contacts when the magnetic field is strong enough to pull the contacts open.
What is a current limiter?
used in heavy current circuits. It is essentially a slow blow fuse. The metal link melts and opens the circuit
Explain each of the following
- Push to reset breaker
- Push pull type breaker
- Toggle type breaker
Push to reset breaker - Normally closed, pops out when overloaded
Push pull - Can be pushed to reset or pulled out to open the circuit
Toggle type - Uses a control switch as well as a breaker
How many times can a pilot reset a breaker?
Only once
What is a current transformer?
The current flowing through a conductor is measured using inductive pickups called current transformers. The signal is picked up by the PSEU and if an over-current condition exists, the computer opens the breaker
What is a circuit breaker meant to protect?
The wire, NOT the circuit / components
What does trip-free mean?
All breaker contacts will remain open as long as a short circuit exists regardless of the actuating position
What are the requirements for spare fuses on an aircraft?
At least 1 or 50%, whichever is more
Must be accessible to pilot in flight
What size circuit breaker is required to protect a 15 awg wire?
15A circuit breaker
