Page 718 - PPL-engelsk 2025
P. 718
Aircraft general knowledge
A voltage regulator ensures that the voltage is constant. The voltage is fed via a
fuse to the main rail (”Primary Bus”) in the electrical system.
On this aircraft there is a wire down to the “Avionics Bus” - most often a switch
is placed between the 2 rails, so that you don’t have to turn off each individual
radio before stopping the engine.
The radios are sensitive and can be damaged if they are connected to voltage -
either during engine start-up or when stopping the engine/generator.
The ammeter may be placed differently in the circuit depending on the aircraft
type. Some ammeters show the total load of the generator.
Another type has a middle position and can show whether power is being used
from the battery or the generator.
You must familiarize yourself with the current system.
8.6.4.2 Master switch
The 2 red switches constitute the “main switch” (Master).
In the event of an electrical fire or other system fault, it is important to switch
both off.
The voltage is fed via the master switch to a main rail. From there through fuses
to the individual items of use.
On some aircraft, the main switch may be divided into 2, and by disconnecting
the generator switch (ALT) and reconnecting it, you can reset the system and
perhaps get the generator going again.
8.6.4.3 Fuses
There are 2 types of fuses, fuses that blow (metal melts) when overloaded and
circuit breakers that can be reset.
Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 718
