NAT OPS

[Haroon]

Hi

Q.1. In-flight Contingencies in NAT Region

Current practice as mentioned in Jeppsen is:

Having initiated the turn: If able to maintain the assigned flight level, once the aircraft has deviated 10NM from the assigned track centreline, climb or descend to select a flight level which differs from those normally used by 500ft, if at or below FL410, or by 1000ft if above FL410.

However according to:

NORTH ATLANTIC OPERATIONS AND AIRSPACE MANUAL Edition 2012

Chapter 13 - In-flight Contingencies

Subsequent Action

13.3.3 An aircraft that is able to maintain its assigned flight level, after deviating 10 NM from its original cleared track centreline and therefore laterally clear of any potentially conflicting traffic above or below following the same track, should:

a) climb or descend 1000 ft if above FL410

b) climb or descend 500 ft when below FL410

c) climb 1000 ft or descend 500 ft if at FL410

I just want to know If I am right in my understanding that ICAO criteria is not a standard and just a recommendation, as indicated by the word "should", or else why is there a difference?


Q.2. Is FL 420 (which is in MNPSA) used while routing flights?

If FL 420 is not used, then ICAO criteria (mentioned above in Q.2.) provides a better vertical separation by climbing 1000 ft. Why only climb by 500 ft?

If FL 420 is used, then how does ICAO criteria allow to climb 1000 feet above (from FL 410) to FL 420?

Thanks