Both cleared to same level inthe hold?

[captainsmiffy]

Excuse my ignorance but would like to hear some input ref an experience in DXB last week. Was extremely busy arrivals pattern (worst I have seen in 3.5 yrs flying here) and we were cleared to the BUBIN hold, FL280. I was just taking this in mentally when an a/c ahead called that he was also cleared to the same hold at the same level. Yes, I thought, switched on fellow (and I was getting there, too - alarm bells were going off inside the cranium!) The - very busy - ATCO told him firmly that, yes, he was but that he would be dropped furhter before his arrival. Now that turn of events worried me since it was already very busy and the frequency was getting congested and the ATCO might forget or get distracted. I could envisage him turning outbound and me getting a rather too-close look at his paint scheme.

Is this common practice? It was certainly something that I had not heard of before, 2 a/c cleared to the same bit of sky at the same level even though the intention was to onward clear/descend one of them before it became an issue? I heard it used a few times that night and I was a little concerned to say the least. Maybe I just haven't taken it on board before but I have been flying for some 24 years or so and I couldn't help but be curious. Would love some feedback from those that 'push tin'.

[ron83]

Can't tell you about DXB, but speaking generally I would never do it intentionally.

[kontrolor]

its good that you are vigilant, but distance to "point where two or more planes are cleared to same level" also has to be counted in. Thus there are just two posibilities with your case,
a) ATCO error
b) intent to start descent of preceeding traffic before you come into scene

in both cases you should look out for our mistakes, as we are for yours. To eliminate them that is, not to put anybody on the shame list :)

[captainsmiffy]

Intention, believe me, is not to shame anyone! Am just curious as to whether or not this is a common practice (that I have clearly missed in 24 years of flying!). Don't think it was ATCO error, he knew that he had cleared us both to the same level and point and he stated that he intended to drop the preceeding a/c shortly. It just sits somewhat uncomfortably with me....we all speak of 'the holes in the swiss cheese lining up' - is this one that we don't need to line up?

[Number2]

It happens. There are agreements with adjacent units where aircraft are descending to the same level and cleared to the hold. Appropriate (separated) levels are assigned before reaching the hold. It's nothing new.

[Fox3snapshot]

when an a/c ahead called that he was also cleared to the same hold at the same level :rolleyes:

Before we panic Cap'n Smiff....how far was the preceding a/c ahead of you and how many miles were you to run on BUBIN?

[captainsmiffy]

Hey, nobody is panicking here - it took me over a week to write about it! Guess I was about 20 miles or so to run and he obviously had less! No idea. Am just interested to see if this is a standard tactic or a 'creative bit of controlling'. It was used a few times that night.

BTW, not adjacent units but the same unit.

[ATCO1969]

I fear the thread's title is a little misleading, it should read: "Both cleared to the hold at the same level".

As captainsmiffy illustrates, a/c were not in the hold yet (was it not DESDI btw, a common DESDI hold level, not BUBIN?), and until a/c have entered the hold, radar separation can be applied, what was done is perfectly legal, and possibly the only option (at the time) at the ATCO's disposal.

I agree that should both a/c have gone 7600 or should ATC have lost radio's, a loud bang may have resulted, but in this airspace, as in most these days, if one were to control without an element of experience/trust/faith/self belief, then air traffic would come to a grinding halt.

'69

[Oubi]

Normally you don't clear 2 a/c's to the same point at the same level. Radiocom failure being one of the reasons.

[chevvron]

Way back in the early '70s, two aircraft with similar callsigns from the same well known Irish airline were inadvertantly cleared to the same level in the BNN hold. They saw each other, chatted on company frequency, adjusted their position to be exactly 180 deg apart, then told London Control what they were doing!!

[captainsmiffy]

No, it was definitely BUBIN at 280 - not a standard level, agreed. (Got a pm from a local controller who pointed that out). Got moved on very quickly to the RASKO hold and then a DARAX arrival, followed by lots of vectors! The FMS programming was going thick and fast, I can tell you!

It was the thought of R/T failure that prompted this initial post....

[captainsmiffy]

Don't get me wrong, I think that the boys and gals on duty that night did a sterling job, given the amount of traffic and I think that, on both sides, the 'experience, trust, faith and self-belief' was there in spades. I do think that this airspace is now creaking under the weight of traffic currently coming in and out and i just get a little concerned when people start alluding to the fact that 'maybe both cleared to the same level to hold' was his only option. That says, surely, that we are already too busy?

Just an aside, flew back with another guy who insisted on taking min fuel to DXB - and even found ways of cutting this back - and he justified this by saying that his diversion fuel gave him his 20 mins extra if he committed to DXB and that if he dropped below xxxx kilos then he would simply declare a PAN/MAYDAY as required and get in first! Personally I thought that he was mad but he did it anyway (nice CRM). It actually worked out fine that night but, had it been the night that i was referring to earlier, then this sort of thinking is going to screw the system big time!
I did point out to him during the approach that things could get quite interesting if the last 10 guys that he had flown with all adopted the same approach to fuel planning as he did on the same night at the same time!

[middles]

SOP in the London TMA. The LAM arrivals are all cleared to FL150 level by Saber and if the world then went 'pop' they would all enter the Lam hold at FL150. The same applies to the other 3 arrival stacks. It is mitigated by the LAM etc stack controller descending them to a proceedurely safe level before the hold is entered. If things start to get a bit 'hairy' and and levels up to FL150 are either not being cleared quickly enough or LL APC are unable to take sufficient from the said stack the 'standing agreement' of FL150 must be ammended.

[BlueSkye]

Cleared to hold and actually in the holding pattern are two vastly different situations. Personally I refer the OP's described scenario as "anticipated separation". They're at the same level now, but when it matters they won't be.

As an aside, the chances of two aircraft, that one is trying to separate, having a radio failure at the same time is so remote that it isn't even worth considering.

[Nobodys Desk]

the chances of two aircraft, that one is trying to separate, having a radio failure at the same time is so remote that it isn't even worth considering.
Chance of total ATC radio fail isn't so remote though :uhoh:

[Defruiter]

"As an aside, the chances of two aircraft, that one is trying to separate, having a radio failure at the same time is so remote that it isn't even worth considering."

I have seen a radar replay of that very thing happening, so I would say it is worth considering!

[Spitoon]

As a simple principle, clearances should be fail safe wherever and for as long as possible. This was hammered into me from day one of training and has always seemed sensible. To clear two aircraft to the same holding fix at the same level just adds another opportunity for it all to go wrong.

Don't worry about the probability of multiple radio failures - it takes far less to distract the controller. And as Defruiter says, multiple radio failures do happen - I suspect I have watched the same radar recording and it wasn't fun imagining how the controller felt.

'Anticipated separation' and all the other examples of 'It'll be OK, I'll keep an eye on it' seem to have featured disproportionately in incidents that I have been involved in reviewing or investigating.

[kme]

Chance of total ATC radio fail isn't so remote though http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/worry.gif


Fully agree :ok:



"As an aside, the chances of two aircraft, that one is trying to separate, having a radio failure at the same time is so remote that it isn't even worth considering."



If we go to the numbers, a debateable issue that will end up with discussing the definition of the word failure and the quality of radio equipment at different places in the world.

In practice, which means two aircraft that it is impossible to reach, with enough clarity to deconflict, on the frequency during a short but critical time period - it is not even very rare (by my admittedly very subjective opinion/definition). Fact is that this happens and has led to accidents/incidents in the past, at least one quite famous by the way.

A lot of opinions, definitions & speculations you might say but the fact remains.

By the way I dont judge the controller at the time in any way. Anticipated clearences might not be one of the safest ways of operation in general but without the whole picture its valueless to speculate.

I must say I personally do find the statement of Bluesky slightly worrying.
But I also chose to not draw any parallells to attitude or imagination related skills from a forum entry and leave it at that - a slight feeling of worry.

[BlueSkye]

If you start to apply the "what if" principle to aviation we wouldn't be flying. What if the engine catches fire? What if the thing gets hijacked? What if the cargo catches fire? What if I clear him to a level and he busts the level? What if he strays onto the active runway? What if ad nauseam

Compare the above mentioned incidents to the amount of incidents because of multiple radio and/or radar failures.

[captainsmiffy]

Actually, Bluesky, i play the 'what if?' game every time I drag my weary butt into the sky! Every single time we brief what we will reject for and up to what speed and then we brief what we would do post-v1, despite getting checked every 6 months (and, often in between), with, say, an engine failure or engine fire. Every commercial pilot does/should. It is part of the reason why aviation is so inherently safe these days.....the other reason is that you guys are doing an equally conscientious and good job on your side of the screens. Which brings me back, full circle, to a debate on is this practice safe? I wasn't really even thinking of a radio failure, per se, which is undoubtedley a problem (as pointed out) - the big thing that night was the sheer level of traffic and that surely provides its own big-enough distraction? From conversation with local controllers we were already cleared to hold at a non-standard level and then moved to a point that i'd never even heard of to hold shortly thereafter. My concern is that, sooner or later, something will 'give' - I just hope, for everybodies sake, that this doesn't happen whilst 2 a/c are cleared inbound to the same hold at the same level.....happy new year!

[GoodJobBaas]

Not to be dismissive, but would it help if we told you that you were in the most screwed up airspace many of us have ever seen?

FL280 isn't too standard for the BUBIN hold, but the routing via DARAX arrival has been going on for months.

There are pages and pages on this forum about what is wrong with the UAE, I won't make this one of them - 2 planes at the same level isn't standard but without more facts about distance to run to the hold, no one can tell you exactly how wrong.

As a side note, I did see a guy have two at the same level in a pattern at FL260! He was very lucky as they both did direct entry and went round and round not getting within 5nm.

[Grabbers]

FWIW, as an OJTI I always instruct to assign a level/radar heading that will be safe against known traffic at that time. Clearing an ac into a hold level already assigned, even though it is anticipated that the ac occupying that piece of sky will have vacated by the time the ac in question arrives, is to my mind bad practice. Hold levels can be adjusted once separation has physically been achieved with little or no hit on expedition.

[jackieofalltrades]

I tried in the simulator once and had two aircraft in the hold at the same level (FL90 if I recall correctly). The STCA never went off and with both aircraft at opposite ends of the holding pattern and fixed speeds were never going to collide.

It's NOT something I would do in real life though. I don't like the idea of having two aricraft assigned the same level in the same piece of sky without another form of separation (ie headings).

[aterpster]

jackofalltrades:

I tried in the simulator once and had two aircraft in the hold at the same level (FL90 if I recall correctly). The STCA never went off and with both aircraft at opposite ends of the holding pattern and fixed speeds were never going to collide.

By "fixed speeds," do you mean both aircraft were operating at identical indicated airspeeds?

[Annex14]

Let´s talk business, not "computer gamers mentality"! May be I am a dinosauer compared to those that run that discussion, but as a retired CoO ATC I remember a few rules we were trained on
1. Never base control on assumptions
2. It´s either 1000 ft. vertical or 3 or more miles horizontal
3. Never assighn identical altitudes to aircraft on converging courses or to the same clearance limit.
4. Same altitude can only be assighned if there is either constant speed / constant distance or the tracks of the planes involved diverge.

Of course from my own experience I know that the one or the other rule may be in jeopardy for a moment in heavy workload situations, but to consider something like was mentioned here in this thread as standard control procedures is far away from "safe and orderly flow of traffic"
Jo

[jackieofalltrades]

By "fixed speeds," do you mean both aircraft were operating at identical indicated airspeeds?

Yes. Both aircraft had been assigned the same indicated airspeed. I apprciate there's a difference between handling characteristics of a simulator and real-world, but it was neat to see it could be done.

Let´s talk business, not "computer gamers mentality"!
And by simulator I mean the state of the art one at my NATS unit used for T.R.U.C.E. and for trainees new to the unit, not some Microsoft toy.

[On the beach]

The solution is very simple to the AUH/UAE/DXB problems, however, its implementation may not be quite so simple.

You move the Dubai and Abu Dhabi approach units and the UAE centre to a neutral site, maybe just south of Jebel Ali, straddling the border. This would then place all controllers involved in the same building and preferably in the same room so that each knows and can see the problems of the other. They can then, at least, start working as a single cohesive unit.

You would then undergo a recruitment campaign to bring in fresh management for both the approach and en-route sides. The task ahead of you requires personnel who can think "outside the box" and don't come with any previous baggage. Then you'd need to recruit enough experienced ATCOs to fully staff all the positions, with some contingency.

A complete redesign of the airspace would then need to be done to optimise the traffic flows to/from DXB and AUH and Jebel Ali World together with a redesign of the overflying airways. Let's face it you're going to have to do that anyway when you've got 6 runways up and running and Emirates have another 150 aircraft, plus the 100 new planes that Etihad start accepting this year.

And how long would all this take? Well, my guess is if you had started the process about 5 years ago you would just about now be approaching a satisfactory solution.

In the meantime, I think I'll be stopping off in Doha more frequently, once their new airport is up and running. Can't be bothered with the increasing hassle at DXB any more.

Anyway chaps, good luck & stay safe. Got to go, is that the sound of an "oink" I just heard flying past the window?

On the beach

[Annex14]

Just to clarify. My greatest respect to those that have taken the burden and do their best efforts to transform trainees into real controllers. And of course, this is unthinkable in nowadays environment of ATC without computer simulation.

My wording was directed to those that may think, just as on a computer game, one can freeze the life picture to look for solutions. ATC is an kind of art, just like flying, that needs professionals not gamers.
Jo

[Guy D'ageradar]

is that the sound of an "oink" I just heard flying past the window?

More like a supersonic pink elephant, I would say!

Dream on........

[novation]

Captainsmiffy, you sound like a sensible chap, Bluesky however?! Not sure about your atc training but in my experience "what if" scenarios are very much apart of what i do. Considering what could happen if something fails allows you to form alternate plans should you need them.

[captainsmiffy]

Thanks Novation; I try my best! Well said, sir,to Annex14, in post #25. Those are some sensible rules and should be intransigent.

[Gulfstreamaviator]

Is it just me, or has it been busier more the last week, than usual.

Glf

[radarman]

Clearing two aircraft into the hold at the same level is a sure invitation for Mr Murphy to put in an unwelcome appearance. It may be seen as acceptable by some of the more gung-ho guys, but as you get older you become much more wary of the insidious ways the wily Murphy can creep up on you.

I once got totally maxed out during a mass F-111 recovery into Lakenheath, but managed to squeeze a vital couple of aircraft into the top of the hold by using 500ft levels. Certainly not SOP, but done by using 'experience, trust, faith and self-belief'.

Perhaps this might be an unofficial solution to the OP's scenario. Better 500ft separation than a paint job.

[BlueSkye]

On the beach, you must be on something else. Something goooood.:E

GVaviator, yes it has been.

Novation, nothing wrong with my training or my pre-planning. I'm fully aware of the consequences of something going wrong. 20+ years of awareness to be exact. The difference seems that most people count on things going wrong. I count on things going right. I have two responsibilities: Give the correct clearance and make sure the read-back is correct. After that I trust the pilot. 100%. As much as I sometimes rue the fact, my influence on the operation of an aircraft ends there.

It's an exercise based on trust. Pilots trust their co-pilots. Pilots trust the engineers. ATCs trust the pilots. Pilots trust the ATCs. So if you hear me clear you into the hold at the same level as someone else, trust me to have you at a different level when you actually get to the holding fix. If all seven of my radios and your radios fail, then trust in TCAS.

Some of you guys make it sound as if having two planes at the same level going to the same point as being tantamount to mass murder. It happens everywhere, everyday.

I treat my responsibilities and limitations like I treat a firearm, I respect it but I'm sure as f..k not scared of it.

[captainsmiffy]

Remind me again.........where do you work?!!

[Guy D'ageradar]

Remind me again.........where do you work?!!

No need to tell us which side of the pond you come from though! :hmm:

Having been through a simultaneous failure of radios/radar/navaids/airfield lighting/control room lighting in this part of the world, I'm afraid I prefer to err a little more on the side of caution these days!

Keep em safe :ok: Orderly and expeditious are options.

[novation]

Blueskye- i myself have experienced both rt fails and radar fails and on neither of the ocassions have i felt it necessary to trust Tcas, the situation having failed safe due to good technique. I have a feeling you might be insane. Likening your responsibilities to your use of firearms confirms it. Thankfully where I'm from poor technique is frowned upon and guns are illegal.

[off watch]

In post #25, Annex14 said :
" 3. Never assighn identical altitudes to aircraft on converging courses"

I wonder how many cadets were failed on their APR exam by "Chopper *****" at Hurn for doing just that ? :ooh:

[BrATCO]

jackieofalltrades,
I tried in the simulator once and had two aircraft in the hold at the same level (FL90 if I recall correctly).
2 ACFT at the same level during a simulation, why not ?

As a trainer, I would ask the trainee what must be the minimum (same) speed to get a minimal separation between outbound and inbound leg.
I won't bother you with the calculations.

My results :
- 200 kts IAS at FL100 / 140kts IAS at FL200 to get a 5 NM separation.
- 235 kts IAS at FL100 / 185kts IAS at FL 200 to get a 6 NM separation.

The problem is that the protection areas around the hold would not be compatible anymore (at least in lower levels), so we would have to vector the rest of the traffic far-far-away. Not easy in an overcrowded sector.
And if my trainee doesn't aim at least 6 NM, then Murphy-me would implement a RNAV failure.
Furthermore if the outbound leg is upwind (drift towards the opposite traffic can be funny when already just above the minima :E).

Another solution would be to vector the new-coming close enough behind/before the other so we get a 6 Nm separation over the fix. Thus they are both in the same in/outbound leg, with only the wake-turbulence-separation.

Totally unsafe, I wouldn't do it for real.... as long as I've got another solution (never say never...).
But it must be fun in the simulator ! :ok:
Maybe as "fun" as changing a sequence...:}

captainsmiffy,
In your case, you were 25 NM to the fix, so there were 3 mins remaining. The cleared level was 280.
Counting 10 secs per clearance/readback/pilot's reaction, 1000' per minute assigned. The controller needs only one gap at FL120 or above so the FL280 is vacated in time.

But this means no failure at all (radio, radar,...) in the next 3 minutes : TCAS-RA in a hold can have surprising consequences. So this should not be considered SOP, anywhere.
It seems the situation was unusual, so I believe some of the solutions they found that evening were unusual too...

You wrote :
i play the 'what if?' game every time I drag my weary butt into the sky!

People who work in aviation (pilot, controller, fuel supplyer, snow plough company manager...) and don't play the "What if game" have probably forgotten that aviation is all about locking hunreds of human beings in an alluminium tin, throw the tin 8 miles high, 500 knots, thousands miles away.
People who don't play the "What if game" only believe this will land safely on a 50 m-wide concrete strip on the other side of the Earth.
People who do play the game do the necessary to let it happen tens of thousands times every day.

[BlueSkye]

Capainsmiffy, why don't you PM me and schedule a visit to the ACC center in Abu Dhabi (assuming you are based in the UAE). I'm sure a lot of your questions will be answered.

P.S. If you don't, I'll shoot you. :}

[ATCO1962]

Fox3,

How on earth did you manage to frighten so many people there that you managed to get a mention in post #33 above? Your rep is growing, lad!

[Guy D'ageradar]

Now that's what I call creative interpretation!

[captainsmiffy]

Blueskye,

I surrender...now put the firearm down! Would love to come and view the ACC in operation; will need to pick a time when my roster is a little quieter - will be top bid in march so might get some nice gaps - and would like to take you up on your offer. Can we get others in, too, from EK?

Cheers and a happy new year

Captainsmiffy

[GoodJobBaas]

If a guy in a long shirt asks, say you met picking up Chinese takeout. Whatever you do, don't mention the pprune in the room!!

[Vercingetorix]

Yep, certainly don't mention Pprune.

However, on a more upbeat note 'tis rumoured that:
1. The pot bellied Danish cartoon character will be going at the end of his contract (May '11).
2. He has been offered a job in his native Denmark although hard to see what he can offer there as his only Danish ATC qualifications are Twr & APP from the mid '70s.

Perhaps NATS might be in the bidding to advise the GCAA.

Cheers:ok:

[Stella Polaris]

However, on a more upbeat note 'tis rumoured that:
1. The pot bellied Danish cartoon character will be going at the end of his contract (May '11).
If the local anti-corruption force doesn't get him first:rolleyes:

2. He has been offered a job in his native Denmark although hard to see what he can offer there as his only Danish ATC qualifications are Twr & APP from the mid '70s.

That would probably be with Integra, a company that already has him on their payroll and has been rewarded with some lucrative contracts with the GCAA.

[BlueSkye]

Captainsmiffy, PM sent.

[Vercingetorix]

Stella Polaris

If the local anti-corruption force doesn't get him first

There was an investigation into some fraudulent financial dealings (read kick backs for getting inflated contracts signed) but the results will probably be shoved under the sofa cushions just like the envelopes of money from roster planning companies were in the recent past.

Hopefully the anti corruption force gets there first.:ok: