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FAA EMERGENCY AD 2001-14-51

January 1, 2001

Summary:  The FAA has received a report from the UPS Aviation Technologies, Inc.  during installation of a certain UPS Model Apollo SL30 VHF NAV/COMM radio on a General Aviation aircraft, the installer noted that the radio was providing incorrect radial bearing information.  Subsequent testing by the equipment manufacturer revealed that the bearing information was off by 14 degrees.  This incorrect bearing has been attributed to an error in Digital Signal Processor (DSP) Software Version Number 1.00, as installed on Apollo SL30 VHF NAV/COMM radios having part number 430-6040-300 or 430-6040-301.  If the radio received a signal from a VOR ground station that deviates from the standard 30-Hertz signal, the error in the software causes the radio to incorrectly decode the bearing of the station.  Because the occurrence of the error is dependent on the signal coming from a given station and not on the radio itself, the pilot may not necessarily know if the bearing information is incorrect.  This condition, if not corrected, could lead the pilot to use incorrect bearing information, which could result in inaccurate navigation information.  The FAA has reviewed and approved UPS Service Bulletin SB2001-003, dated June 29, 2001.  That service bulletin describes procedures for determining what version of software the Apollo SL30 VHF NAV/COMM radio is using.  If the the radio is using Software Version Number 1.00, the service bulletin says to install a placard to inform the pilot that use of the radio's VOR function for navigation is prohibited.  The placard must be installed so that it is within view of the pilot during operation of the aircraft.

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