NAT OPS
 

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

As for Question No.1

-Look closely and you will find that they are saying the same thing, its just a matter of wording (jep. is kinda vague in a sense of just using the word "differ" without specifying details just like the ICAO did)....
but what they are trying to say basically is when you need to deviate from your altitude below or at FL410 the deviation should be 500 ft as long as your new altitude will be below or at FL410 but as soon as you need to be higher than FL410 then it should be 1000 ft (i.e FL390--->FL385 or FL395 BUT FL410 would be either FL405 or FL420...


As for Question No.2

No, FL 420 is not used for routing because RVSM LIMITS are from FL 280 and 410 inclusive, so above FL410 the vertical separation reverts to the non-RVSM 2000 ft., consequently, FL420 is out of the question for routing in any flight direction.(your next available FL for normal routing would be FL430 & FL450), so FL420 is merely a contingency for the FL410 for the facts stated above (Above FL410, you descend 500 or climb 1000), so think of it as a boundary limit for MNPS routes just like FL285 is used as contingency for FL290 (which is the actual minimum FL used in MNPS airspace)....so basically FL285 and FL420 form the brackets or the absolute limits that hold the MNPS airspace that you cannot go below or above even in abnormal situations.

Hi Heggo, Thanks for the response

Ok, no issues about Q.2. It was to confirm that FL420 is not used and climbing 1000 feet at FL 410 gives the best margin.

However the only issue which I still cannot figure out is the Jeppesen's wording.

Lets focus on Jeppesen's wording regarding climbing, if at FL410. I am deleting the "descend" and "below 410" part since that's not an issue.

According to Jeppesen:

If we climb to FL420 then it differs by the one normally used (i.e. FL 410 in this case) by 1000 feet and not 500 feet.

So according to Jeppesen it should be FL 415, which differs by 500 feet from the one normally used (i.e FL 410 in this case).

I still cant see how you look at it. Am I interpreting "the one normally used" wrongly?

Regards

It's badly worded, the level you select can never be FL410. The 'at or' in "at or below FL410" isn't required.


This is what NAT doc 007 says

You have every right to be confused by the poor wording....jeppessen really messed up big time there....

if you look again you will find "at or below" FL410....so the "climb or descend" 500 ft option was meant for the FLs below 410 but once you are at FL 410 then your only options are either descend 500 ft or climb 1000 ft....
To eliminate confusion just ask yourself what will your NEW altitude be after you initiate climb or descend?....if its going to be below 410 then use 500ft. and if above 410 then use 1000 ft.

Bear in mind that this procedure is aimed mainly at putting you on a FL that is separated from other aircraft on the same route, so, you will use the 500 ft when below FL410 (RVSM) because the normal separation is 1000 ft.
but once you consider going higher than FL410 (outside RVSM) then you use 1000 ft. because the normal separation is 2000 ft.
that's the whole trick there.....and also note that jeppessen are merely a provider for NAV publications and database, and they are prone to mistakes just like every one else, so if in doubt about anything, revert to the original publication that jeppessen used to copy the procedures (AIPs, AIRACS,ANNEX, etc.) because these publications always supersede Jeppessen.....

Ok I think I found the answer,

See: Amendment No 2 to ICAO Doc 4444 15th Edition 2007.

15.2.2.3

b) having initiated the turn:

2) if able to maintain the assigned flight level, once the aircraft has deviated 19 km (10 NM) from the assigned track centreline, climb or descend to select a flight level which differs from those normally used by 150 m (500 ft), if at or below FL 410, or by 300 m (1 000 ft) if above FL 410;

It makes sense though considering that above FL 410 one is allowed to climb or descend 1000 feet. If at FL 430 one descends 1000 feet he will be at 420. So its better that the guy at 410 just climbs 500 feet. I dont know if this was the logic for the amendment but that's the way it is. The wordings have no ambiguity.

However getting access to ICAO docs is a nightmare. It took me almost 2 hours to find the relevant docs :ugh:

if you use this logic it will confuse you because it applies also to below FL410 where the guy at FL400 descends 500 ft at the same time the guy at FL 390 climbs 500 ft.....but this it's the fact.....both traffic can be at FL420 at the same time since each if them will be off track by 10NM' so they should be laterally separated

There is still something confusing!

The PANS ATM Amendment 2 says:

"This edition incorporates all amendments approved by the Council prior to 2 June 2007"

Whereas The NAT OPS Manual (Doc 007) 2012 edition still says the same i.e. if at 410 climb 1000 feet.

Anyone has a clue on that?

PANS do not carry the same legal force as the Standards and Recommended Procedures (SARPS). Is it something to do with this or what?

Which document is the standard?

:confused:

Haroon,

Please apply some common "horse sense" here. The intent is to split the vertical separation in half, whether that is 500' or 1,000', matters not. Second, contingency procedures are drawn up to accommodate ONE emergency, so the probability of two planes above F410 both having contingencies and one descending and on climbing to place both at F420 is extrememly remote.

I am not a Horse so I cant apply that sense.

The question is about different statements in two different documents by the same authority.

Common sense?

Realistically, it is not even the 1,000th time two different documents have differed. Perfection isn't in the nature of aviation, I suppose.

"It depends" is aviation's most accurate answer,

these documents are quite reliable (not that mistakes are not possible), there must be some reason or legality behind.

Ok just posting to finalize the issue

NAT OPS DOC 007 is for guidance only as mentioned in its Foreword:

This means, ICAO Doc 4444 ATM/501, Air Traffic Management (PANS-ATM), Section 15.2, is the regulatory material for the Special Procedures For In-flight Contingencies In Oceanic Airspace and not Doc 007.