Leaving a level

[Victor Mike]

OK, this is probably a really stupid question, but when I'm told to report out of a level, how far is that? I have a vague feeling someone told me 300', but I can't find it written down - I've even looked in the MATS pt1 with no luck!
So I thought I'd check with the experts...

Regards

Victor Mike

[blondie118]

A level is taken to be free when the previous aircraft has dropped by 400 feet.

I always make sure that if a pilot reports vacating a level I check the radar to ensure that the descent has started and I'm sure it will continue to descend.

I'm always cautious about asking pilots to report vacating in case there should be a delay between their call and the descent starting. I always double check just in case.

[fourthreethree]

If I asked a pilot to report leaving a level, it would mean just that, ie you tell me when you start your descent, so that I don't have to monitor your mode-c in order to notice your descent has begun. This does not mean that I can take that level to be free to assign to another aircraft, as pointed out by blondie118, it just means that my attention is brought to the fact that your descent has begun. This might be a trigger to change frequency or turn direct or whatever.

If asked to report out of a level, by which I suppose you mean passing a level in climb/descent, basically the same applies. I would only expect you to tell me when your mode-c indicates passing that level. That would mean, for example, the traffic 1000' above/below you would be clear, and could turn again. Bear in mind the delay between the actual mode-c and the mode-c indicated on radar adds an extra safety buffer.

More contraversial is reporting reaching a level. A lot of pilots, looking for continuous descent or climb, report "reaching level xxx" when they are in fact some way off, even a couple of thousand feet. A level can only be considered as reached when mode-c indicates within 200' of that level. But again, I would, in a perfect world, expect a pilot to report reaching say FL350 when his altimeter shows FL350.

The question is really one for ATC, don't take this the wrong way but it is not really something for pilots to worry about. Not a stupid question however, as I am sure the next 15 replies will all have 15 different opinions!! As far as I am concerned if asked to report passing/leaving/reaching a level, just go by what your instruments tell you. Hope this was helpful.

[Goldfish Jack]

Just been looking in the ICAO Air Traffic Management Manual, 14th edition, now replacing the good old Doc 4444 it says in section 8.5.4.2: "DETERMINATION OF LEVEL OCCUPANCY".........

An aircraft is considered to be maintaining its assigned level as long as the SSR mode c-derived level info. indicates that it is within 300ft of the assigned level.

In the same para, it says an aircraft is considered to have commenced its manoeuvre and vacated the previously occupied level when the SSR mode indicated a change of more than 300ft.

It also refers in the same para the aircraft reaching a level when they are within 300ft of the assigned level.

Hopefully this puts a bit of light on it.

[Warped Factor]

VM,

I think you're getting some confusing replies here where folks are quoting various ATC separation rules and probably not giving you the answer you are looking for.

For UK airspace the UK AIP is the horses mouth for the answer to this sort of question and at ENR 1-1-3-1 Para 2.1 it says.....

Vacating (Leaving) Levels

When pilots are instructed to report leaving a level, they should advise ATC that they have left an assigned level only when the aircraft's altimeter indicates that the aircraft has actually departed from that level and is maintaining a positive rate of climb or descent in accordance with published procedures.

HTH,

WF.

[Victor Mike]

Thanks all, I hadn't realised what a can of worms I was opening... I think I was asking the 'out of' question so Goldfish Jack's reply of 300' makes sense, though it seems odd that you then need to be within 200' when getting to a level!
Regards
Victor Mike

(...and if you want a really obscure question, why does LHR clear A319/320 off the hold at 220k and 757 at 210k when both can fly both speeds comfortably clean!)

[fourthreethree]

VM

Actually no ambiguity in the answers, within 200' when getting to a level is the same as the 300' answer. Put it this way, FL258 is considered FL260, FL257 is not.

Warped Factor's answer is exactly what I was trying to say but much more adeptly put!!

[Spitoon]

Don't confuse level occupation derived from Mode C and that derived from pilot reports. If a pilot tells me he or she has left a level I can clear another to that level (subject to the other conditions and common sense!). If I don't ask for a pilot report I'll have to wait until the Mode C shows 300ft or more in the right direction.

Edit - Doh! The last bit should say 400ft or more in the right direction ass pointed out by Bright-ling. Just a typo, honest!

[Bright-Ling]

Spitoon, I agree, but surely you mean 400 feet or more!!

[Impi]

4 3 3 - "Actually no ambiguity in the answers, within 200' when getting to a level is the same as the 300' answer. Put it this way, FL258 is considered FL260, FL257 is not."

Actually, I think that there is a little ambiguity as far as Eurocontrol is concerned...correct me if I'm wrong, ICAO says 300' whereas Eurocontrol uses 200'.

[Vlad the Impaler]

I think four three three is getting a little confused as well. FL257 is considered as FL260. Three hundred feet is the maximum allowable discrepancy for maintaining a level which is why the mode C has to be out of four hundred feet and moving in the right direction to consider a level vacated useing mode C. Also if you are in a holding situation, your Mode C readout may well be garbled with others in the stack and be unuseable for separation purposes, therefore we rely solely on pilot reports. If you are asked to report vacated then when you do, make sure you have really left the level. Once you report vacated I can perfectly legally assign that level to the next plane in the stack. If you are still there it could mean paperwork for all of us at the least!!!!!!!!!


(edited for stupidity)

[fourthreethree]

Nope, no confusion. (Wrong, possibly, but no confusion.) It is possible that Maastricht's internal procedures differ from those laid down by ICAO on this matter, I will check this tonight during my night shift.

[Warped Factor]

VM,

(...and if you want a really obscure question, why does LHR clear A319/320 off the hold at 220k and 757 at 210k when both can fly both speeds comfortably clean!)

Only because over the years at LHR ATC the feedback we've had from the flightdeck has been that 757s prefer 210 rather than 220kts.

We're conditioned now, don't ask us to change :D

WF.

[FlightDetent]

(fourthreethree)
As for the "quite advance reaching call" there may also be other reason for it to happen. Most autopilots/EFIS have a level mode (e.g. ALT HOLD) and few climb/desc. modes. Also, there would be a transition mode prior to level off. A good CRM would be to announce the transition mode in place, check altitude selection and baro setting so to ensure the aeroplane is properly set for level-off. Especially during descents into headwind, this transition mode can pop up when there is still quite some time to go. If a pilot would notify ATC at the very same time (reachin'..), the call would seem, well, premature. I was specifically told not to do so.

Which raises a question. It is my understanding (English not my mothertongue) that when instructed to, say "climb FL290, report reaching.", I do crawl up, level off, reach for the mike and scream "FluffyCloud590, FL290". That it was not actually required to report some time/height before HAVING reached the assigned level. Is this right at all?

(Warped Factor)
Now, is it right to think (and report) leaving a FL when in steady descent/climb out of the flight level, i.e. -/+ 300ft away from say 35000 feet? Beacuse while wrestling within 300 ft, you're still maintaining a level, right?
Although you may not maintaing your rating if on a check ride :} . Also it seems to me that the paperwork would start piling up once one'd be off by more than 300. If in a lee wave, CAT or an engine out situation 300' would trigger "Unable to maintain" call from my side, if not earlier.

---

I thought that 200' is the quasi limit for transponder mode C crosscheck accuracy. Remember, the equipment replies with data pilot never gets to see! By virtue of appropriate training your baro is set so it correlates, but still you look only at the dial, not the aneroid/ADC. Where as the beeper sends out QNE all the time no matter what.

[Warped Factor]

FD,

Now, is it right to think (and report) leaving a FL when in steady descent/climb out of the flight level, i.e. -/+ 300ft away from say 35000 feet? Beacuse while wrestling within 300 ft, you're still maintaining a level, right?

The following applies to the UK only.

When the atco is looking at displayed Mode C on a radar display, you are considered to be at or maintaining a level if the Mode C indicates +/- 200ft from that level.

When the atco is looking at displayed Mode C on a radar display, you are considered to have left a level when the Mode C indicates a change of 400 feet or more from that level and is continuing in the anticipated direction.

Neither of the above require any pilot input, these are rules for ATC separation and level assesment.

When a pilot is asked to report leaving a level, there is no requirement for the pilot to wait for 200ft, 400ft or whatever, he/she only has to do what it says in the AIP, which is....

ENR 1-1-3-1 Para 2.1 Vacating (Leaving) Levels

"When pilots are instructed to report leaving a level, they should advise ATC that they have left an assigned level only when the aircraft's altimeter indicates that the aircraft has actually departed from that level and is maintaining a positive rate of climb or descent in accordance with published procedures."

If you are asked to report reaching a level, I'd recommend that you make the report only when you have actually leveled off at the correct level.

If we don't ask you to report reaching, by looking at the Mode C on the radar display ATC are allowed to consider you have reached an assigned level when three successive Mode C readouts indicate 200ft or less from that level.


Although you may not maintaing your rating if on a check ride . Also it seems to me that the paperwork would start piling up once one'd be off by more than 300. If in a lee wave, CAT or an engine out situation 300' would trigger "Unable to maintain" call from my side, if not earlier.

In conditions of severe turbulence, or if you were unable to maintain a level accurately for other reasons, we'd increase the vertical separation accordingly.

Hope that helps clarify UK procedures.

WF.

[fourthreethree]

As promised, I have checked in the Maastricht Ops manual (part 2) and this is what it says.

Aircraft maintaining a level
An aircraft will be considered to be maintaining its assigned level as long as the SSR Mode-C derived level information indicates that it is within plus or minus 300 feet of the assigned level. The controllers' Mode-C read out, therefore, must show a value of not more than two level increments above or below the assigned level.

Aircraft leaving a level
An aircraft will be considered to have left a level when the Mode-C derived level information indicates a change of more than 300 feet in the anticipated direction from the previously assigned level. The controllers' Mode-C readout, therefore, must show a value of at least four level increments above or below the previously assigned level.

Aircraft passing a level in climb or descent
An aircraft in climb or descent will be considered to have passed a level when the Mode-C derived level information indicates that it has passed this level in the required direction by more than 300 feet. The controllers' Mode-C readout, therefore, must show a value of at least four level increments above (aircraft climbing) or below (aircraft descending) this level.

Aircraft reaching a level
An aircraft will be considered to have reached the level to which it has been cleared when three consecutive renewals of Mode-C derived level information have indicated that it is within 300 feet of its assigned level. The controllers' Mode-C readout, therefore, must show a value of not more than two level increments above or below the assigned level for three consecutive renewals.



Hopefully, this clears this point up, although of course these are procedures laid down within Maastricht, and are relevant specifically to MADAP.
So, was I confused? Naaa, never, not me guv!:\ :\

[radar707]

I set off the SMF a while back, had one a/c at FL88 (90) and another at FL 82 (80), 600' according to the machine, head on passed right over each other, but SEPARATED!!!!!