AD 2004-13-20
Unsafe Condition
The GPS navigation unit, under certain conditions, may provide erroneous cross-deviation information, causing the aircraft to deviate from its intended course briefly and placing an excessive workload on the flightcrew.
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Required Actions
Modify and test the software for the Apollo GX50/55/60/65 TSO-C129a GPS navigation unit by following the instructions in UPS Aviation Technologies Service Bulletin 561-4002-001. Reidentify the modified GPS navigation unit according to the service bulletin.
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Compliance Time
Within 6 months after the effective date of the AD.
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Affected Aircraft
Aircraft equipped with Garmin AT, Apollo GX50/55/60/65 TSO-C129a GPS navigation units with software versions 3.0 through 3.4 inclusive, as listed in UPS Aviation Technologies Service Bulletin 561-4002-001, dated April 19, 2002.
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Source: Official FAA Source ↗
Retrieved: Apr 4, 2026
Rights: U.S. Government Public Domain
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