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Transponder Bi-Annual Test & Inspection 91.413 Suppression Buss

This article addresses the need to turn off all units connected to the Suppression Buss, [TAS/DME] while performing a Transponder Bi-Annual Test & Inspection, FAR 91.413


The Transponder under test will FAIL the performance specs observed on the Test Set due to its operation being suppressed by any system operating within the 1030 MHz Frequency Range.

[Traffic Advisory System (TAS) or Distance Measuring Equipment (DME)]


The active suppression buss will distort the replies being interrogated by the Test Set and cause a “Failed” Indication.  Ensure that all units connected to the suppression buss are turned off during the test. Normal test results should then be observed.


The normal Suppression of the Transponders Replies does not effect the standard airborne operation of ATC Interrogations.

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  • 24-Jan-2023