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G'day all,

Quick one - If an aircraft was tracking via lat/long => lat/long and I required him to report an estimate for crossing longitude how would you calculate that point?. Additionally could you calculate the (lat) as well??. Is this the same for crossing latitude?

Example: a/c tracking 50S080E thence 45S070E and I required an estimate for crossing 75E how would you do it??.

Specifically for B747-400 series FMC but all answers welcome.

Thanks in advance.

DBE...

In your example we'd have an estimate via the FMS for 80E and 70E - the estimate for 75E would be halfway between the two.

DBE
The longitude info can be generated by the FMC as intermediate waypoint(s) for specified increments by inputting (from memory :( ) /5 (for 5 degree increments) after a starting lat/long. The exact method should be in the FM.

A340 FMS can generate an ETA for any crossing lat or long. In DBE's example, select Lateral Revision at the appropriate waypoint, type "75E" in scratch pad and enter at 2R. Select "Insert" (6R) and it will be entered as a waypoint on the flight plan, complete with ETA and co-ordinates.

Fiendishly clever, these Airbusses :)

The 744 can also generate a crossing point. Just input E075 into 1L on the Legs page, and the point along track will be generated in its proper sequence. The point, with ETE if DATA is selected, will appear on the ND, and it becomes another waypoint on the route if Executed. Punch 2L (assuming the point appears on the second line of the Legs page), and the full coordinates will appear in the scratchpad.