Procedural Separation.Is this acceptable?

[jalbert1]

Is it acceptable under ICAO 4444 to use rates of climb/descent for separation in a non radar environment?
Departing an African airport recently traffic was cleared through our level with very little lateral separation but we were both given a rate of climb restriction ie.no stop levels were issued to the other aircraft as would normally be the case .
Certainly caused a degree of concern to us. Had visual/TCAS but were both IFR.
Any input appreciated.Thanks.

[SINGAPURCANAC]

Succeeding a/c may be cleared to climb to previous occupied level once the preceding a/c report leaving that level unless....(not important for that case)

So, you can see there were a mistake regardless rate of climb restriction.
I am not familiar with restriction within documents regarding rate of climb/descent in proc environment but there is always some other restriction higher in priority so you aren't able to apply this.
Doc 4444 intends to cover as much as possible situation so many of them aren't applicable within TMA limits.
Like speed instruction. It is not forbidden but it is impossible to make required proc separation within 25/30 Nm as usually TMA extends(my own TMA and other similar in my neighborhood )
Hope that it helps....
I could explain better but I had hard day today. Brandy season starts. First 50 liters..
Cheers:)

[wagga]

I've never worked procedural with real traffic but I've had some simulator years ago. For what I can remember, under no circumstances assigning a vertical speed can influence the separation in a non-radar environment.
Either the routes/tracks are separated or they are not. You may have to cross a certain point at a specified level but, not knowing your exact position, ATC cannot obtain that through a rate but only with a specific restriction (Cross ABC at FLxxx or above/below...).
Same applies if the lateral separation is obtained from/to a radioaid. It should result in a level restriction related to a radial/bearing and distance.
Looks like you've experienced a "let's keep our finger crossed" separation. Not really recommended by ICAO!
Somebody correct me if I'm wrong.

[Dont tell um pike]

It is possible to use vertical speed to separate procedurally in certain situations. It would be difficult to comment on this particular incident without having all the details.
:)
DTUP

[criss]

Yeah, you should provide more details (opposite, or same track same direction etc.).

[2 sheds]

Jalbert

It is perfectly acceptable. Doc 4444 states that "aircraft may be cleared to change cruising level at a specified time, place or rate" and the relevant phraseology is included. However, vertical separation plus the rate of climb/descent ("...or greater") condition would have to be established first and a limit placed on that condition ("...until passing FL...") before the second aircraft were to be allocated its level with ROC/ROD restriction ("...fpm or less").

Obviously cannot comment on the specific situation without further detail.

Regards

2 s

[jangler909]

I'm not sure if I understood the facts correctly, but assigning climb rates is a very useful method for separating two departures (for example) with similar routes. In procedural environment. Gives lots of time to other tasks, you don't have to pump them to new levels every 20 seconds.

Preceding aircraft is cleared to, say, FL240. Let's give him 1500ft+/min until passing FL110 (rate depending on the aircraft type). Succeeding aircraft is restricted to FL100 and given 1500ft-/min until FL100. We'll only wait the first plane to pass through 1000ft AGL before issuing takeoff clearance to the second, and there it is. No problem, done that many times. Naturally this method works all the way up to the cruise levels, but here it's not necessary since they enter radar controlled ACC airspace and some other separation can be issued.

[Farrell]

The answer is in your first post - Africa!

[M609]

Now, I have not really done much procedural control, but I do think jangler909 is spot on. I remember doing it in the proc sim at college many moons ago.

I use it in the radar environment to separate flights on SIDs, particularly slow piston aircraft that take forever to reach the 6000+ MSA (Watching PA28s climb out IFR is like watching paint dry)
It's a procedural seperation even it i see them on the scope, radar separation is no use on twisting and turning SIDs in that situation.


Still, comment about Africa still applies methinks...... ;)

[Tarq57]

Been a while since I last used procedural separation as a primary tool, and that was as an area controller when the radar went down (literally - the head was blown off) for about three weeks or so.
IIRC, climb rates were perfectly acceptable, vertical separation having been first established.
Practically one would not usually use it over any kind of large climb (or to a lesser degree, descent) as it was known that climb rates/performance could change considerably over several thousand feet (or several hundred for a normally aspirated piston.) But as a way of maintaining separation for, say, initial climbout until the routes were separated, nothing wrong with it.
Normal caveats apply, of course. Monitoring needed, forget about it in turbulence, and if the frequency is busy enough that one of the crews might be delayed in getting the "Unable to maintain climb.." call out, forget it.
I usually considered it a handy stop-gap measure.

[5miles]

Specifying rate of climb/descent or standard rate is a valid separation tool. I worked procedural sectors for about 4 years and only ever used it twice though. It could not be applied to foreign carriers though (IIRC).

[Jat Jet]

Perfectly OK, problem occurs if one of the aircraft fails to comply with the restrictions

[RustyNail]

Got my procedural ratings 19 years ago and still work a procedural sector now.

Rate of climb is a legit form of separation and I continue to use it today (when appropriate). :ok:

As mentioned above, you just need to establish initial vertical separation and then bob's your uncle.

Care should be taken to ensure that the rate of climb can be maintained to the required altitude where another form of separation can exist, as most A/C ROC significantly decreases with altitude, I would not assign this form of sep above about FL250.

[abc.fp]

Rate of climb/descend is perfectly legal under procedural.

But, in my 12 years of experience I have gotten into trouble many times using this. So much so that our sector has been temporarily banned from using this seperation due to a "recent reduction of sepration".

Problem is that there is no way to monitor this except through frequent position reports, which defeats the purpose a little. If its alot of talking you wanna do, then just step-climb/descend the guys right from the start.

What is the opinion of other procedural sectors on this?

[2 Dogs]

Perfectly OK, problem occurs if one of the aircraft fails to comply with the restrictions


Surely this applies to any requirements/restrictions given by ATC.
They are all done for a reason, usually separation, not for fun and we expect you, as professionals, to comply. If you can't, just let us know and we will find another solution.

[Spitoon]

But, in my 12 years of experience I have gotten into trouble many times using this. So much so that our sector has been temporarily banned from using this seperation due to a "recent reduction of sepration".

Problem is that there is no way to monitor this except through frequent position reports, which defeats the purpose a little. If its alot of talking you wanna do, then just step-climb/descend the guys right from the start.
If you set it up properly, the only way it can go wrong is if a pilot does not or cannot comply with the clearance and doesn't tell you.

[abc.fp]

Whatever the reason may be. Pilots not complying or equipment not functioning properly, the problem remains that ATC simply cannot monitor a potentially dangerous situation from developing.

I'd like to hear from other procedural sectors.

[Spitoon]

I've done plenty of procedural work in my time. If you issue clearances that are sound - i.e, clear and provide an appropriate separation, but the aircraft do not comply with the clearances then there is a possibility that an unsafe situation will develop. In a procedural environment, and without the pilot advising that he/she cannot comply with the clearance, the only way this is likely to be identified is if the controller picks it up from pilot reports - or if one pilot reports that there's another right in front of him or whatever! That's life doing procedural control.

If you are worried about this I guess you can issue sound clearances and ask for progress reports every minute from every aircraft that you're working - but as already pointed out, this does rather defeat the object of issuing sound clearances in the first place. Doing procedural control one will - or should - always be alert to cues that might suggest that separation is not being achieved, but I must re-iterate, if the clearances are sound then the only way it can fail is if the aircraft do not comply for some reason. And surely in normal operations we have to trust what the pilots tell us.......

[Jimmah]

I use this one pretty regularly between takeoffs. Normally ATR following a Dash so the preceding would be expected to outclimb the following. I get 2 rates of climb out of the first one, up to 10,000', and then above that. The 2nd flight gets restricted to those ROC's. For protection, we're required to have the 1st through at least 2000' before the 2nd takes off, and we're required to check vertical sep each 5000' or 5 min, whichever is more frequent. Works a charm.

Normally, by the time the 2nd leaves the first is already through 7-8000', so they get unrestricted climb for a bit. I may even get 20D between them eventually.

Anyhow, to answer the original question, yes it's acceptable, and perfectly safe when done right (and we always do it right don't we!).

[Pera]

Problem is that there is no way to monitor this

In a procedural enviroment, you can only issue the clearances, and update the situation from position reports. You can't monitor.

A step climb would be the only way to keep more control of the situation.

[Skyjuggler]

As already stated by many, Yes, it's perfectly acceptable. Provided it's been applied correctly: In my years as a procedural Approach controller I'd use it "usually" in the following situations.

Two departures, en-route on the same track, slap them both with a ROC restriction, then the number 2 can depart when the first is through a couple of thousand feet. Saves having to wait for the 10/20 miles whichever is applicable. The can then get further unrestricted climb with the neighbouring (radar equipped) sector.

The second scenario is when two acft are on diverging tracks, let's say by 30degrees (off VOR), you can apply ROC until the first has reached the required 10nm. Saves a bit of time...

This is of course a highly simplified explaination and all assosciated laws/logic needs to be taken into account...:ok:

[ATCO94]

With my previous pure proc exp of about 6 years( without radar in TMA ) in quite busy traffic vertical rate restricted climb & descent is a very useful tool which can be easily applied to three acft simultaniously ( or more if you are experienced enough).
This is an exellent tool to reduce your rt load( report level,etc.) & give attention to other conflicts & traffic.

[qwerty2]

I come to this thread late but I used the technique only once to climb a BUA 1-11 under a Dan Air Comet.
I started with 2000ft vertical as they left Edinburgh and let the climb rate do the rest up to FL250 IIRC.
That's going back to the 1970s.

A perfectly good procedure!

[2 sheds]

ATCO94...in quite busy traffic vertical rate restricted climb & descent is a very useful tool which can be easily applied to three acft simultaniously ( or more if you are experienced enough)

Explain....?

PS Just answered my own question - can now visualise the scenario, not to mention the performance in getting the pilots to understand the required ROCs!

[peatair]

The question is "Is it acceptable under ICAO 4444 to use rates of climb/descent for separation in a non radar environment?" The answer is a qualified yes. It all depends on the air traffic environment (e.g. route structure etc) and the circumstances (e.g. aircraft types involved; weather etc). The most common use is to specify rates of climb so that vertical sep. is maintained between two aircraft and this is normally done between two successive departures.

Procedural approach control was quite common in the UK back in the 1960s and I was fortunate to do my training at Edinburgh (1964-65) when there was no alternative! It really made you learn the basics of being a controller!