Module 1-2

Question 1

What is a PSEU and what is it function?

Answer 1

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

Question 2

Describe the proper installation of a switch

Answer 2

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

Question 3

What does SPST stand for?

Answer 3

Single pole single throw

Question 4

What does SPDT stand for?

Answer 4

Single pole double throw

Question 5

What does DPST stand for?

Answer 5

Double pole single throw

Question 6

What does DPDT stand for?

Answer 6

Double pole double throw

Question 7

What does normally open mean?

Answer 7

It is a break before make connection

Question 8

What does normally closed mean?

Answer 8

Its a make before break connection

Question 9

What does common mean?

Answer 9

A point to which both normally open / closed terminals connect to

Question 10

Whats the difference between a selenoid and a relay?

Answer 10

A relay has movable contacts and a stationary core, A selenoid has a movable core with stationary contacts

Question 11

What is a contactor?

Answer 11

Another name for a selenoid

Question 12

How does a prox sensor work?

Answer 12

Prox sensors are inductance coils that operate in conjunction with steel targets. The inductance changes with the proximity of the steel targets

Question 13

Derating factor: What is the CCR of a 24VDC switch drawing 6 amps?

Answer 13

Derating factor for 24VDC motor = 3

6amps x 3 = 18 amps

Question 14

What is rush-in current?

Answer 14

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

Question 15

Advantages of a rocker switch compared to a lever switch?

Answer 15

Its more flush with the panel, making accidental toggles or presses more difficult. It also makes the panel more attractive.

Question 16

Describe a thermal switch

Answer 16

Actuated by an increase in temperature by bending a bi metallic strip within that bends and touches the contacts with an increase in temperature

Question 17

Difference between thermal circuit breaker and electromagnetic circuit breaker

Answer 17

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.

Question 18

What is a current limiter?

Answer 18

used in heavy current circuits. It is essentially a slow blow fuse. The metal link melts and opens the circuit

Question 19

Explain each of the following

• Push to reset breaker
• Push pull type breaker
• Toggle type breaker

Answer 19

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

Question 20

How many times can a pilot reset a breaker?

Answer 20

Only once

Question 21

What is a current transformer?

Answer 21

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

Question 22

What is a circuit breaker meant to protect?

Answer 22

The wire, NOT the circuit / components

Question 23

What does trip-free mean?

Answer 23

All breaker contacts will remain open as long as a short circuit exists regardless of the actuating position

Question 24

What are the requirements for spare fuses on an aircraft?

Answer 24

At least 1 or 50%, whichever is more

Must be accessible to pilot in flight

Question 25

What size circuit breaker is required to protect a 15 awg wire?

Answer 25

15A circuit breaker