GTX 33 Installation Manual
190-00906-00
Page B-14
Rev. F
63.
8.5.1
Pressure altitude provided to the
ADS-B transmit system needs to be in
accordance with existing require-
ments for ATC
transponders.
An encoding altimeter or other
altitude source provides
pressure altitude to the
transponder.
64.
8.5.2
The digitizer code selected needs to
correspond to within plus or minus
38.1 m (125 ft), on a 95% probability
basis, with the
pressure-altitude information
(referenced to the standard pressure
setting of 1013.25 hectopascals),
used on board the aircraft to adhere
to the assigned flight
profile. (ICAO Annex 10, Vol IV,
3.1.1.7.12.2.4. See also
EUROCAE ED-26).
The performance of the encoders and
of the sensors needs to be indepen-
dent from the pressure setting
selected.
The Mode C altitude data
reported by the GTX
transponder is the same as the
altitude used by the flight crew
to adhere to the assigned flight
profile.
Per the requirements of 14 CFR
91.411(a) and Part 43 Appendix
E sub-paragraph (c), installers
are required to verify
transponder altitude reporting
correspondence, both at initial
installation, as well as
subsequently every 24
calendar months.
Therefore, an installation that
meets the requirements for ATC
transponders also meets this
requirement.
65.
8.5.3
The transponder should indicate cor-
rectly the altitude resolution (quanti-
sation) used, i.e. 25ft (from an
appropriate source, default
resolution) or 100ft (Gillham’s coded
source, permissible alternative reso-
lution).
The conversion of Gillham’s coded
data to another format before input-
ting to the transponder is not permit-
ted unless failure detection can be
provided and the resolution (quantisa-
tion) is set in the
transmitted data to indicate 100ft.
Per Section 4.4 of this manual,
GTX 33 reports altitude in 25-
foot increments when altitude is
provided serially, and 100-foot
increments when altitude is
provided from parallel wire gray
code inputs. Altitude resolution
is Supported in BDS (6,5)
Aircraft Operational Status.
Conversion of Gillham (gray)
coded altitude data to serial
data is not authorized.
Table B-1. Version 1 ADS-B Field Approval Compliance Matrix
Item #
AMC
Section #
AMC Item
Compliance Summary
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