RNP in MNPS Airspace

[172_driver]

The new Oxford ATPL literature keep mentioning RNP 20 as the requirement in MNPS Airspace. I always thought it was RNP 12.6. There is a vague explanation in the book: Whilst the route is not defined by radio aids, the sophistication of the LRNS and RNP (defined as RNP 20 but statistically defined as RNP 12.6) is sufficient to permit the longitudinal separation to be reduced to 10 minutes.

Anyone knows what they mean by RNP 20 and 12.6 :confused:

Thanks!

[K.Whyjelly]

Anyone knows what they mean by RNP 20 and 12.6 http://static.pprune.org/images/smilies/confused.gif


RNP - Required Navigation Performance.

From the FCOM's :


The aircraft navigation system, required by regulation to fly within a Required Navigation Performance (RNP) airspace, shall comply with RNAV functionality criteria and with navigation position accuracy and integrity criteria.
When referring to RNP-X, e.g RNP 20 or RNP12.6, the value of X is the navigation accuracy expressed in NM, which has to be met with a probability of 95 %.
An RNP value can be associated with an airspace, a route, a SID, a STAR, a RNAV approach or an RNAV missed approach procedure.
Depending on the RNP value, and on the airspace environment (ground radio navaid), different navigation equipment may be necessary.
An operational approval from the airline’s national authorities may be necessary.


This site may also be of interest:

http://www.pprune.org/tech-log/260324-rnp-mnps-airspace.html

[172_driver]

Thanks, I am aware of what RNP is. Just wondering what they mean by mentioning both RNP 12.6 and RNP 20 in the same sentence.

My believing was that RNP and MNPS are to different concepts. And, being MNPS approved, you have sufficient equipment to operate within 12,6 nm of either side of the airway/OTS centre line. In other words, RNP 12,6.

Therefore I am wondering, where comes the 20 nm figure from?