Level Abeam
 

Hello all,

After flying overseas for many years many in the US, I've come back to EU flying and have encountered the slightly tricky UK ATC clearance of being on a radar heading and then "descend to FL xx be level abeam XYZ wpt"

I'm sure many aircraft FMS systems can cope with this easily but on my simple machine, if I'm not going to the wpt then VNAV isn't very useful, so we're left with swagging it, which feels a bit wrong and depending on the geometry is prone to error.

Just curious how other people manage this? Also, I can see now useful it is for a controller but just to raise the point that it's a bit of a tricky clearance for some less advanced aircraft!

Cheers

TDK

Former Blue Suit ATCO at LATCC many moons ago...

Norrnally 'abeam beacons/waypoints' will be close enough to track to apply simple 1 in 3 to the abeam point and then a bit of TLAR. It cannot be that difficult to crack! Heavens, we even managed it BEFORE VNAV, you know.

I understand it can be tricky to plot a position abeam fix escpecially when you have nothing more than a basic analog instruments or no GNSS. If you think you are unable to conduct your descent as required by atc and may bust the level, you should just say "unable" - a word so rarely used by pilots yet so useful.
It is REALLY better to say "unable" than to make a good but failed effort.

It's easy

1) Input waypoint into GPS / FMS

2) Set VNAV to be level 5nm prior to waypoint (Your clearance will, 99.9% of the time want you level BY, not levelling at

3) Use computed TOD on FMS whilst still flying Heading

That's accurate enough from both an ATC and a flying point of view.

- as Chilli says, it's a doddle. I get the impression that even being level AT a beacon would be a challenge for some here without the pink string.:ugh:

Interesting point raised by Chilli that is missed (from an understanding perspective) by most (if not all) pilots.

If ATC ask you to be level, for example FL270 BY RESNO, what they really want is you to be level 5 miles before that point.

That's about 40 seconds before you get there.

What this does for the controller is give the assurance that you will actually be level at the point and remove the need for any coordination (because 9 times out of 10 the LEVEL BY requirement is on a sector boundary).

What happens too often is a VNAV descent that the computer on board initiates as late as possible before the waypoint. This give ATC the heebyjeebys because it looks like you've forgotten to descend or will be too high.

In short - go down early. Wont kill you, since you dont really care what level you cross the point at do you?

You could ask how many miles to the point and do the math, or request a rate of descend to be able to meet the restriction (not friendly to a busy controller, as he has to do the math), or even easier, ask for a time to be level before.

The last would give an answer like "be level before time xx" or "in xx minutes", then you should be able to calculate the rate of climb/descend yourself.

That's the really oldschool answers, if your flying without FMS and whatnot....

Fly in France.

From my experience they nearly always give a rate of descent to fly which will get us level at the waypoint eg FL220 at Anglo or FL190 at Ratuk.

Thanks for the posts, will have a fiddle about with it all next time. Seem to always manage ok...

Thought we might avoid the sadly inevitable "back in the day we did this with a compass, stopwatch and candlelight brigade, but the temptation is too great for some people"!!! :ugh:

No, if ATC really want you to be level 5 miles before a point, they'll ask for it, if they really want it and don't issue an instruction to that effect then the controller is being shoddy. We don't work in an environment where we say one thing but mean something else.

- tough titty. Learn to operate an aeroplane (with or without a candle).:)

Scary thread !

BOAC - I think your refernce to the "bible" has gone unnoticed :)

Bit harsh BOAC, a reasonable question I think about a clearance I haven't come across before. No need to impune my flying ability.

I remember a procedure being introduced for the interface between Manchester area sectors and Swanwick which involved parallel tracks with a/c on radar headings. The ops people came up with the splendid phraseology to be used......
"Climb FL190 to be level 10 miles before abeam Honiley".
I can't remember any of us ever saying that.

Plenty of rubbish FMSs out there that can't create abeam points. The UNS-1 comes to mind. You simply have to pick a vertical speed that looks about right and aim slightly on the conservative side in the more basic aircraft. If you are given a direct, keep the original routing in one of the FMS boxes to give you a reference for distance to the target point.

The three times table for profile awareness and dividing your groundspeed by two and adding a zero at the end (or multiplying by five) to get your required rate of descent to make good the profile, always stood me in good stead on my last type when it came to descent planning.

An aircraft is "abeam" a fix, point, or object when that fix, point, or object is approximately 90 degrees to the right or left of the aircraft track.

I do think FinallyFlying makes a valid point - Although "level by . . . ." means exactly that I can't think of a colleague who would mind, or complain, if you levelled 1 or 2 miles early!!

I know it's slightly non-standard (and therefore must be frowned upon!) but i have sometimes used "be level at or before . . . . "

It does appear sometimes that, as said before

An aircraft descends at 3000fpm or more which will make the restriction with about 100yds to spare, then, of course reduces its descent rate, as it needs to level off, and misses the restriction by about 600ft or more!!

No, vnav, if programmed correctly, will be level at the waypoint!

I do understand that it can give controllers the impression that the restriction won't be made.

What about If you were on a STAR .....which included a level restriction
 

So same scenario....you are put on a heading.....my understanding is the level restriction still applies abeam the waypoint even though you are no longer flying the lateral STAR clearance?

Thanks in advance.

RMC, not in the UK, the ATCO needs to re-state the requirement to be level abeam if necessary once he/she has taken you off the STAR by issuing a heading.

Now now Fat Controller, things may have changed since you last did operational ATC:p
Rgds
AyrTC

My understanding is its's not, but to be nice I might just continue in level change with thrust idle to kind of make the restriction.

RMC, you are correct, the level restriction does still apply when put on a heading. People are getting confused by being cleared to a point beyond one with a restriction where the level by clearance does need reiterating if still required, but not for the case of headings.

Level By means exactly that - level by, so you can descend at maximum rate from the moment the clearance has been read back, or stay high and descend at the last minute, and everything inbetween, the choice is yours. As long as you are level by the time you cross the point, that is all that matters. If you are having difficulty in complying then aiming for a safer 5nm before the point works, and asking for either a distance or time from London Area ATC doesn't cause too much extra hassle, the computer can work it out very quickly and simply.

...and both of those restrictions are often missed as a result. It doesn't work, but being told to be level by does. It baffles the receiving London sectors why the reluctance for France to use Level By restrictions.

OK guys ....can I read it back to you to make sure I have understood the subtlties of this.

What Fat Controller (and subsequently ZONOMA ) are saying is that if we were on the Willow 3D towards KUMIL (FL180 restriction) and are sent direct to GWC (FL130 restriction) then the FL180 restriction must be reiterated if it is still required (otherwise only FL130 at GWC).

ZONOMA is confirming that In my scenario of getting a 10 degrees off STAR heading some way before BILNI then I need to be FL180 abeam BILNI (even though the restriction was not restated).

Appreciate the replies guys because in the above case if VNAV is followed it will put you at FL 187 abeam BILNI (as it thinks you will be making a 90 degree turn because you still have miles to run)!

RMC, being an old git and having blagged my way onto many flight decks over the years, I know exactly what you mean in your last sentence.
If you are vectoring off any route where a level restriction has been applied, never a good idea to rely on compliance "abeam" the point !
If you still need the restriction, tell the pilot !

RMC:- Yes, that is the case. If we still need you level at/abeam Kumil then we should restate that part of the clearance.

The reason for that restriction is for when the sectors are split and it brings you into the sector underneath traffic that is descending to FL190 at Avant and it gives the guy who's working the LL/KK I/Bs from the south something to drop on top of. In reality, those two sectors are rarely split, except when there's a flood of outbounds and inbounds at the same time. These times don't often coincide with KK arrivals through Gibso as it's mostly transatlantic and the odd Ryanair, except when our cousins to the south of us are on strike....again.

If you get a chance, come and see us and it'll make a bit more sense than trying to explain it on a computer screen.

RMC, yes your last post covers it perfectly.

Think about it, I give you FL180 LVL KATHY/KUMIL, then put you on a heading, and then resume you back to KATHY/KUMIL, the restriction is always in force. However I do not expect compliance at a point if I subsequently route you beyond said point without reiterating the restriction.

The greyer hairs in my head have seen all too often what happens when you give vectors after a level by restriction, my experience always works with that in mind and isn't surprised to see you sail by the point 500' high. If it is crucial, I would have already done something else to make sure we are all safe.

OK thanks, Unfortunately I explained this to my FO on the day and ( as is always the case with the challenge everything brigade ) he comes back with " where is that written". I don't really mind that (as it also serves to protect against a huge amount of cross cockpit hot air)...but it would be great to be able to point this out as a reference if someone was willing and able to dig it out. Would like to take you up on the offer of a visit...any contact details? Thanks again.

Perhaps this could be of interest? London ATC TRUCE

RMC,

The below is a direct quote from the MATS Pt1, it's freely available online, and contains the rule quotes you need:

Chapter 4
7. Amendments to Clearances

7.1 When an amendment is made to a clearance the new clearance shall be read in full to the pilot and shall automatically cancel any previous clearance. Controllers must be aware, therefore, that if the original clearance included a restriction, e.g. “cross ABC FL150 or below” then the issue of a revised clearance automatically cancels the earlier restriction, unless it is reiterated with the revised clearance.

7.2 Similar care must be exercised when a controller issues a clearance, which amends the vertical profile of an aircraft on an SID. For example, “climb FL120” automatically cancels the vertical profile of the SID. If the profile contains a restriction that provides vertical separation from conflicting traffic on another SID, the restriction must be reiterated, e.g. “climb FL120 cross XYZ 5000 feet or above”, unless separation is ensured by other means.

7.3 Similarly, when controllers issue instructions which amend the SID route, they are to confirm the level profile to be followed, e.g. “fly heading 095, climb FL80” or “route direct EFG, stop climb at altitude 5000 feet”.

Regards
30W

30 W....I thought I had it .....but if I read your quote correctly it means that unless the original level is restated it no longer applies? This is the opposite to what Zonoma and I thought. TRUCE sounds like a decent plan. Most of my previous ATC detail knowledge came from pilot / controller beer nights?

The only time I've given this clearance is when handing parallel LHR arrivals over to Swanwick on headings. Let us know if it's a problem and we'll sort something else (ROD, Speed control etc). We hate paperwork as much as anybody

It is no problem.....had to make STAR levels on headings descending into Manch from the East.....just hoping someone can give me the ammunition I need to adequately defend it.

30W's documentation has muddied the waters, however you cannot write down every last detail for every minor difference and common sense must be used. It is impossible to reissue a level restriction every time JUST because an aircraft has been put on a heading, if we go down that route, then how far do you want to go? Reissue it again and again every time the heading is changed? Vectoring is a method employed by ATC to provide separation from other aircraft, it is not a change of routing.

Ironically, the UK AIP only mentions that issuing a level clearance cancels any previous level restrictions unless the previous restrictions are repeated.

Apologies if it has, it was not the intention.....

RMC asked for a source document on this issue and so I quoted the Pt1, and to make life easy, what it contained.

I fully agree with your sentiments Zonoma and for what's it's worth I always continue to ensure I make the initial abeam restriction or very close to even though it hasn't been restated. In 30 years of flying it's always stood me in good stead and avoided any confusion, incident or embarrassment for either party......

I'm sure someone can correct me if I'm wrong but the clarification and entries were introduced to the Pt1 some years ago now on the basis that this was a continuous point of confusion and mis-understanding.

The fact is however what's quoted is what the Pt1 says. If a LoS occurred in relation to it I'm sure the incident investigation would make reference to it and the ATCO would be found at fault if the RT instructions had not been compliance with the Pt1 criteria?

Everyone on both sides is working extremely hard, traffic levels growing, RT can be fast and continuous. Again I fully agree that the extra RT demanded by the Pt1, to ensure compliance with what an ATCO is sensibly expecting is unwelcome and crams the frequency even further. It's an ATS document, so if it doesn't work for ATCO's perhaps it's time to push for internal discussion/review of this specific content?

Brgds
30W

I understand what you are saying 30W, and the extract you posted was added after a review. It was decided to thin out the MATS Part 1 (also many other items have disappeared) and make it more generic and high level. By adding the specific content back in will only continue confusion, as every scenario just cannot be written down otherwise the Part 1 will be the size of the whole set of the Britannia Encyclopedia.

Are you insinuating that by being given a vector, it will technically amend the route so any level restrictions need reiterating? That is how I am understanding the issue here and I disagree. If I have given a level restriction using the example originally quoted to be FL180 level KUMIL, then I give a vector or two (3,4,5....) and then resume the aircraft own navigation back to KUMIL in plenty of time, why would the aircraft not achieve the restriction, or what have I done to cancel the restriction? How about on first call I say descend FL200, expect FL180 by KUMIL, then issue a vector?

The MATS Part 1 as far as ATCOs are concerned covers what is needed. If a new routing or new level is issued, any required restriction needs repeating. A vector does not constitute as either of these.

zonoma, you have to look at it from the flight crew's view too, if they are on a heading how do they know when they will get "own navigation"?
They cannot second-guess whether it will be to the original point where a restriction was expected or to somewhere beyond.
If that happens before the original restriction point but they are sent to the next elsewhere, that is a new clearance so cancels any expectation of "level abeam" unless the ATCO reissues that requirement.
As I have just finished my 30+ years in NATS, I leave the job rather dismayed at the almost complete disconnect these days between ATCOs and pilots, to my mind it would be a great idea for NATS to use 2 of the "additional attendance" days to send people on compulsory familiarisation flights.

as i understand it:

if flying to a waypoint with a level restiction and then being a radar vector, it becomes impossible to meet the initial Vertical clearance as you will be crossing 'Abeam' the point and not 'over' it, so a new ATC vertical clearance must be issued. eg fly hdg xxx cross abm xyz at fl210.

if 2 or more heading changes have been issued and the cross abm clearance was issued with the first heading clearance, then no need to reissue the vertical part of the clearance as it still applies. ie it is still possible to cross abm xyz.

if the heading change is a momentary one and a clearance direct to the original waypoint is reissued then the vertical part of the clearance should also be reissued.

If the pilot thinks that he will eventually be re-cleared back on track then it will be smart to maintain the ROD incase the original clearance is reissued (dct to xyz cross xyz at fl210).

If Unable to comply just say so.

So by flying a longer route, it becomes impossible to make a level restriction?

I'm getting very scared by some of the responses here.