"USE OF SL30 VOR FUNCTION FOR NAVIGATION"USE OF SL30 VOR FUNCTION FOR NAVIGATION PROHIBITED."

"USE OF SL30 VOR FUNCTION FOR NAVIGATION PROHIBITED."

b. Insert a copy of this Directive into the Limitations Section of the approved Aeroplane Flight Manual.

3. Apollo SL30 VHF NAVCOM units, having P/N 430-6040-300 or 430-6040-301 may not be installed on any aeroplane, unless the requirements of this Directive are accomplished.

Note 2: FAA Emergency AD 2001-14-51 refers.

Compliance: For Requirement 1 - Before further flight after the effective date of this Directive.

For Requirement 2 - Before further flight following the determination that Software Version Number 1.00 is installed.

For Requirement 3 - As of the effective date of this Directive. This Airworthiness Directive becomes effective on 5 July 2001.

Background: The United States Federal Aviation Administration (FAA) has received a report from the equipment manufacturer indicating that, during installation of an Apollo SL30 NAVCOM unit on an aeroplane, 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 information has been attributed to an error in DSP Software Version Number 1.00. If the radio receives a signal from a VHF omnirange (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 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.