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- - RNP (https://www.pprune.org/tech-log/496474-rnp.html)

DutchOne

26th September 2012 06:01

RNP

FCOM PRO-SPO-51

Quote:

WITHOUT GPS PRIMARY FUNCTION
RNP accuracy criteria are met, provided radio navaid coverage supports it for: ‐ RNP-1 en route and in the terminal area, provided a required accuracy of 1 nm (See note below) is checked or manually entered in the MCDU.

‐ RNP-0.3 in approach, provided a required accuracy of 0.3 nm (See note below) is checked or, manually entered in the MCDU.

Note: It is possible to enter the radial equivalent to the specified Crosstrack (XTK) accuracy, that is the RNP multiplied by 1.2, the EPE being an estimated radial position error.

Can anyone explain me how i do the note above?

Microburst2002

26th September 2012 10:29

:confused:

Seems like EPE can be "radial EPE" that is: a circle around estimated position within which the actual position is thought to be,

Or it can be a "cross track EPE", that is: a linear distance to the track.

In the latter case the along xtrk EPE is not considered. Only the xtrack accuracy matters in that case.

JABBARA

27th September 2012 14:19

What I understand,

Normally the accuracy check is done as comparing the the NAVAID DME with calculated distance (i.e the distance on ND to that NAVAID).
E.g if the difference is less than 1 NM, RNP 1 is assured.

Note states that an alternative method can also be used: That is comparing NAVAID radial (i.e VOR Radial) with calculated Bearing (i.e the bearing on ND to that NAVAID). However this time, the bearing and NAVAID radial difference can be acceptable as long as this difference is within 1.2 times of the required RNP. For example if RNP 1 is required, the radial and bearing difference may be 1 x 1.2 = 1.2 degree.

If you ask me "is this practical ?".
Of course not at all, but this is Airbus.

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