Lat/lon crossing intervals

[Tom Gorzenski]

Hello,

Learning more about the FMS in the PSX I have found that "lat/long crossing intervals" procedures as described on pages 388-391 of the "Aerowinx Operations Manual" ver. 10.1.7 do not produce the expected outcome for polar routes. For example when trying to generate latitude crossing intervals for EPWA-PHNL route, with "N55-5" entered in the first leg, 8 latitude crossing points were created starting from N55 and the last latitude crossing point generated was N90 (N9000.0W01413.2). There were no points of DECREASING crossing latitude all the way from N90 to PHNL. Is this the simulator issue or real FMS as well?

Kind regards,
Tom

[Hardy Heinlin]

Hello Tom,

I can't remember if the real FMC would continue after the direction change. PSX intentionally stops at such a point to avoid a mathematical infinity or singularity. E.g. when a leg course changes so that it leads along a certain latitude, that leg would get an infinite number of latitude crossings. Also, a single great circle that changes the north-south direction will cross some latitudes twice, thus the definition of the first crossing will not be clear; PSX uses the first one. In general, this feature requires a continuous direction: For longitudes just east or just west, for latitudes just north or just south.


Regards,

|-|ardy

[Tom Gorzenski]

Thank you for the explanation Hardy.

Kind regards,
Tom