Can I suggest to modify the IOrules which are located in " /install/flightgear/fgdata/Nasal/IOrules " by adding READ ALLOW $FG_SCENERY/* ?
The reason is that the standard route-manager and its function flightplan() can read the Level-D 767 procedure files if they are added to the Airports scenery data (ref. http://wiki.flightgear.org/Nasal_Flightplan)
But, if we use the FMS DB functions to read these data, it returns an error parsexml() : reading '/xxxxx/Airports/L/F/R/LFRK.procedures.xml' denied (unauthorized access) because "parsexml()" is not allowed to access $FG_SCENERY/*