rudderrat
Finding a map shift "bias" as you described is true, but that "bias" may not always be the same throughout the datum area, hence applying that "bias" to all nav solutions is not safe or possible.
The answer is, I submit, to use the FMS with WGS-84 datum in the enroute structure, but cannot be used in terminal/approach structure. This is how to deal with different datums. Or use DME/DME RNAV, if the 'Bus is capable of it. Or, as I mentioned earlier, have the appropriate datum entered into the FMS. If you are not in WGS-84 airspace, you must use the ground-based navaids. All GPS positioning is based on WGS-84, so the plane will be calculating its position in reference to WGS-84 and assume lat/long positions are WGS-84. Where a different datum is used the plane will not be where it FMS believes it to be. Very unsafe.
Perhaps a petition to the Russian Directorate of Civil Aviation would help overcome their reluctance to survey Russia to WGS-84 datum.
GF
Last edited by galaxy flyer; 1st Jan 2010 at 15:00.