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.