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
Thanks!