Chapter 2 - Section 3: Practical aircraft installation Flashcards
What are the two types of aircraft installations for HF radios?
Suppressed or wire types
Describe a notch antenna?
Suppressed in the vertical stabiliser, with an automatic tuner close to the notch
What does the guide tube of a stub mast provide?
Support for a 10 kV spark gap
Why is the cable from the output of an antenna tuner kept as short as possible?
It is unscreened, as a screened cable with this sort of voltage would cause insulation breakdown
How will a lightning strike be signified on an antenna cable?
Black discolouration inside the glass tube, where the gas has ionised and conducted at the preset voltage
Why is the feed-through mast containing the forward chuck so important?
If the wire were to come out in flight, the wire would go backwards and wrap itself around the fin or the elevators causing an uncontrollable jamming of flying controls
Why will the aerial wire be copper coated?
For low RF resistance around the outside of the wire due to skin effect
What is the purpose of the tension unit?
Contains a weak or shear pin so that under excessive stress, the cable will come out of the rear chuck and trail harmlessly over the wing edge
What is the maximum permitted bonding value and what value would be preferred?
0.05Ω
0.01Ω or less
What should the aspect ratio of the notch be?
No greater than 2:1
Where are notch antennas normally used?
High speed aircraft for frequencies from 2.5 MHz to 25 MHz
How does an overload protection unit work?
Two-stage protection against overload
At antenna load in excess of 190 lbs, shearing of a copper pin will allow a 3/16” extension of overall antenna length, resulting in a reduction in tension
Yellow warning band is also exposed
