TX56/56A and TX57/57A Installation Manual
5 April 2022
01776-00-01
Issue AD
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Trig Avionics
Page 13
3.11 Installation Approval
The conditions and tests required for the ETSO approval of the TX56 and
TX57 Nav/Coms are minimum performance standards. It is the responsibility
of those installing this Nav/Com on or within a specific type or class of aircraft
to determine that the aircraft operating conditions are within the ETSO
standards. The Nav/Com may be installed only if further evaluation by the
user/installer documents an acceptable installation that is approved by the
appropriate airworthiness authority.
3.12 Non-ETSO Functions
The TX56/TX57/TX56A/TX57A Nav/Coms contain the following non-ETSO
functions:
A simple two place intercom.
Audio routing and control for auxiliary audio input and stereo music
input.
The operation of each of these functions is described later in this manual.
3.13 Limitations
3.13.1
Installation
If the aircraft is intended to operate under IFR, it is recommended that it be
equipped with at least two VHF Com radios and two Nav receivers (such as
two TX56 Nav/Coms). A single TX56 as the sole VHF Com and Nav solution
does not meet the failure probability requirements of CS 23.1309 for an
aircraft flying IFR.
3.13.2
Nav Dual Watch
In Nav Dual Watch the Nav/Com displays the radial to/from the VOR station
in the secondary frequency window by periodically sampling the secondary
VOR signal. This is intended to identify a crossing radial and as an aid to
situational awareness. The update rate of this information is lower than the
primary navigation signal and it is therefore susceptible to lag and some
ambiguity. Whilst sufficient for en-route navigation, it is not suitable for
