RNAV/RNP maximum leg distance

[BA46RJ]

Hello,

I am wondering about the reason for the following navigation limitations prescribed for the Airbus A220:

"The individual flight plan leg or between aircraft position and the TO waypoint must not exceed: RNAV-1/RNP-1: 200 nm and RNAV-2/RNP-2: 400nm"

Does anybody have an idea why the length of flight plan leg should be limited to meet these required navigation accuracy values?

Thank you.

[safelife]

Because computation of a great circle track upon this odd-shaped planet isn’t exactly trivial.

[jimtx]

Can't remember the exact details but in the 90's while enroute over continental US in a Fokker 100, out of curiosity, we entered a direct to, I think, 0, 0 longitude and latitude. We didn't even get to execute. The FMS crashed but came back up without any nav capability. Finished the trip in hdg select

[FLX/MCT]

Collins' FMS on the 220 uses a rather simple spherical earth model instead of the commonly used WGS84 spheroid. The maximum leg distances depending on RNP were necessary to keep the deviation between the two reference systems within an acceptable limit.

[turbidus]

Collins' FMS on the 220 uses a rather simple spherical earth model instead of the commonly used WGS84 spheroid.

ummmm, where on Earth did you get that information?????

RNAV/RNP using simple radius????wow...

Check the defaults in your flightplan setup.....(like Jepp FlightStar.....)