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DO-253D Change 1
© 2019 RTCA, Inc.
Clarification of Environmental Tests
The following paragraphs provide additional guidance for the environmental tests
described in RTCA/DO-160G.
Power Input Tests
When Normal Operating Conditions Tests, outlined in RTCA/DO-160G Sections 16.5.1
and 16.6.1 (excluding 18.104.22.168 "Engine starting under-voltage operation"), are being
performed, the equipment shall [LAAS-186] operate without interruption, such that the
accuracy requirement shall [LAAS-187] continue to be met.
When Abnormal Operating Conditions Tests, identified in RTCA/DO-160G Sections
16.5.2 and 16.6.2, are being performed, the equipment is not required to operate normally
during the specified minimum voltage period, but shall [LAAS-188] not provide misleading
information neither during nor after the test. If functionality is lost during the course of
these Abnormal Operating Conditions tests, the equipment shall [LAAS-428] recover
normal operation in accordance with the requirement in Section 22.214.171.124.5.
Icing tests have been specified primarily for the antenna(s) portion of the GPS/LAAS
equipment. They are required to be conducted only if the manufacturer wants to qualify
the antenna as part of the GPS/LAAS equipment. If an antenna is used that already has
been qualified in this area, this environmental test is not required.
RF Susceptibility Tests
The GPS/LAAS equipment shall [LAAS-189] be qualified at least to equipment Category
T of Section 20 of RTCA/DO-160G for conducted and radiated radio frequency
susceptibility. The high level radiated susceptibility does not apply between 1500 MHz
and 1640 MHz.
To limit test time during the frequency scans of Sections 19.3.2 and 20, the accuracy test
can be run on the aggregate data and repeated only at the frequencies of greatest
susceptibility. The frequencies of greatest susceptibility should be determined by at least
the following two methods. First, by inspection of the receiver design, the most susceptible
frequencies are identified. Second, the value of pseudorange error during the test will be
compared to the standard deviation (not RMS) of the error during the scan and the
frequencies with errors that deviate significantly from the aggregate are identified. The
identification of frequencies can be made over sub-regions of the full frequency range as
convenient given the set-up changes required when switching frequency bands; in this case,
the aggregate data will be evaluated over each sub-region. Full accuracy tests are run at
each of the specific frequencies identified by both methods for each type of test
(conduction, radiated, and induced susceptibility).
Alternatively, the C/No (or the σnoise) can be monitored to determine susceptibility as long
as frequency dwell time is sufficient to detect the effect.
In addition, the GPS equipment shall [LAAS-190] provide the required accuracy when
subjected to a radiated signal with continuous wave modulation at a frequency of 1.57542
GHz and an electric field strength of 20 mV/meter measured at the exterior case of the GPS
receiver. The radiated susceptibility test procedures of RTCA/DO-160G, Section 20,
should be followed when conducting this test. The test should be conducted with simulated
inputs including data broadcast and appropriate ranging sources. During this test, the
GPS/LAAS equipment should not experience loss of the data broadcast or loss of track
with any ranging source used for navigation. The duration of the test must be sufficient to
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