AD 2005-01-19
Unsafe Condition
The GTX 33/33D/330/330D Mode S transponders may detect the S1 (suppression) interrogating pulse below the minimum trigger level (MTL) and, in some circumstances, not reply. This could lead to inaccurate replies and reduced vertical separation.
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Required Actions
Install GTX 33/33D/330/330D Software Upgrade to at least Version 3.06. No additional action is necessary for those airplanes that have transponders Software Upgrade 3.03 installed.
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Compliance Time
Within 12 months of the effective date (February 23, 2005).
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Affected Aircraft
GARMIN International Inc. GTX 33, GTX 33D, GTX 330, and GTX 330D Mode S transponders installed on airplanes.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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