OCTA Separation Minima in IMC

[muffman]

I'm wondering if anyone can provide me with references to indicate what the minimum separation standard is while OCTA in IMC. For example, the minimum vertical separation whilst more than one aeroplane is in a holding pattern. Also interested in horizontal separation.

People seem to have extremely varied ideas about what the minimum safe separation is, and I've never seen anything in the AIP or regs to suggest that anything is actually mandated.

With that in mind, I would also be interested to hear what other people's ideas about separation are when operating OCTA in IMC.

[helopat]

This is really an ATC question. I just file a plan, talk to centre and, generally, they provide information on traffic, etc.

Many a time OCTA I've become aware of (potentially) conflicting traffic and made up my mind early to be the master of my own fate (either asked the other aircraft to climb or descend or climbed/descended myself).

I think its less a question of separation standard and more about what distance/altitude/time between aircraft requires ATC to mention other traffic to you.

Certainly happy to discuss. Good question...fertile ground for discussion.

HP

[Dick Smith]

Fantastic thread! Now you are on to something- as it's basically up to the pilot - who could have all of 200 hrs- or less.

Of course with Class E there is a proper standard for IFR to IFR separation but we wouldn't want that because 1) It's not how we have done it in the past , and 2) It won't work in Australia because it won't. !!

[Spikey21]

There are numerous approaches where the procedure points you at other traffic.

Imagine a high performance a/c executing a missed approach off the Hamilton Island Rwy 32 VOR.

Ayers Rock NDB is another and OCTA where high performance equipment operates.

My biggest concern is situations such as this where a published procedure brings you into possible conflict.

What would you descend to in the holding pattern if there was an a/c ahead on the approach ?

[Dick Smith]

Spikey, that's exactly what happened at Orange when a REX RPT and an IFR Baron were performing instrument approaches from different directions in IMC at the same time.

Good radar coverage there but we don't use it or class E due to there being some pretty dumb people in decision making positions in our industry.

[Stationair8]

Bit like the "E" airspace over a certain regional airport that is served by both Virgin and Jetstar, yet no radar to keep the big shiny fast jets with fare paying pax on board away Jo Bloggs in his ultralight.

Funny how that got changed after a B737 and a Tobago went nose to nose! Even more fun when a certain large law firm placed an ad in the local paper asking for people off the flight to come forward so they could start a class action against the goverment agencies involved.

[Stationair8]

10nm and a 1000' feet always works well.

Likewise leave the minimum altitude in the holding pattern clear in case the aircraft on the approach overshoots and has go back to the holding pattern.

These rules do not apply if your are flying a Learjet and going to the Bathurst care races with VIP's on board, and like wise if you a VFR pilot stooging along in marginal VFR conditions don't make any calls entering/transitting the CTAF(R) to save landing fees and talking to those pesky IFR pilots who want to know your position and intentions.

[morno]

Spikey, that's exactly what happened at Orange when a REX RPT and an IFR Baron were performing instrument approaches from different directions in IMC at the same time.

I dunno Dick, that just sounds like plain stupidity on someone's behalf (be it the Baron or the SAAB). Why would anyone, with any common sense, commence an instrument approach in completely the opposite direction to someone who's already doing an approach?

Doesn't matter what the radar coverage would have been like, they were OCTA and I assume talking to each other, so it's stupidity on the pilot's behalf. Not stupidity on the behalf of someone in an office in Canberra.

morno

[Plazbot]

IFR to IFR (and MLJ) OCTA

10 minutes
15 miles
1000 feet

This can be reduced by using radar if it is available.

The rest is see and avoid.

[Spikey21]

IFR to IFR (and MLJ) OCTA

10 minutes
15 miles
1000 feet

Impossible in a CTAF or in an instrument app octa, great theory from the comfort of an airconditioned taxpayer funded office.

Reality is a different scenario and that is what Dick is referring to.

[Arm out the window]

Impossible in a CTAF or in an instrument app octa, great theory from the comfort of an airconditioned taxpayer funded office.

Why is it impossible?
One holds at missed approach finish alt + 1000 till the other gets in.

[ravan]

Good answer Arm out the Window.

Seems like common sense (which we all know is not that common:))

[ForkTailedDrKiller]

One holds at missed approach finish alt + 1000 till the other gets in

Now why would I want to hold until the Performance Category C or D aircraft that just flew the approach and "missed" gets in, when my A or B category aircraft has lower minima?

I reckon you get your shot at the approach in order of arrival and if you "miss" you go to the top of the stack until it is your turn to have another go!

Dr :8

[Gundog01]

FTDK

Stay away from anywhere i'm operating IMC OCTA. How is an a/c on MAP going to climb to the top when plonkers are above him??

Plazbot and arm out the window have it sussed.

[ForkTailedDrKiller]

How is an a/c on MAP going to climb to the top when plonkers are above him??


Carefully!

Dr :8

[Dick Smith]

Stationair, the incident between the Tobago and the B737 at Launy was a beatup to reverse the NAS2b.

The Tobago pilot had the 737 sited at all times and told the ATSB there was never any chance of a collision.

The 737 crew never sited the Tobago and the incident was only reported because class E introduced a mandatory transponder requirement for that airspace for the first time.

If there was a genuine safety concern we would not have a load of 737's and other jet airlines still flying in riskier class G terminal airspace every day at places like Proserpine and Ballina without even class E let alone a mandatory transponder requirement.

And when a lighty has a transponder and causes an RA to an airline aircraft at one of these class G locations does anyone call for the airspace to be reversed?

Of course not- if we have had this airspace in the past it must never be changed!

Cover up the faults in our existing airspace and beatup any incidents in any changed airspace so we always revert to what the "no change" fundamentalists want.

Fortunately new young pilots and controllers are coming along- they send me private messages of support all the time.

[Plazbot]

Spikey, the thread starter asked

I'm wondering if anyone can provide me with references to indicate what the minimum separation standard is while OCTA in IMC.

I gave the answer.



Dick Smith

Fortunately new young pilots and controllers are coming along

Don't be painting current and older ATCs as resistent to enhancements of the current arrangements. NAS had issues due to pathetic implementation. I for one am very much in favour of the E airspace model and separating when IMC exists and letting everybody work themselves out in VMC. The US model with the same staffing in similar areas and funding streams to match would be a great addition. The change management process is what needs fixing before the actual airspace.

[ForkTailedDrKiller]

Gundog, pull out you DAPs and take a look at NDB approaches. I don't have mine with me but in a quick look at a dozen or so on the web, I cannot find one that has a missed approach that returns you to the aid at the minimum holding alt or into the protected area of the holding pattern at the minimum holding alt. All of the missed approaches I have looked at send you off away from the aid on climb to a minimum safe alt. Most aircraft would be able to find an additional 1000' on their way back to the aid.

Rest assured that should should find yourself sharing the airspace over an approach with me, and you for some reason are unable to manage a climb that will keep you out of my way - this "plonker" will accommodate your big shiny jet, otherwise keep outta my way cause I once you are established in the missed approach, I will be headed down!

Dr :8

[Spikey21]

Rest assured that should should find yourself sharing the airspace over an approach with me, and you for some reason are unable to manage a climb that will keep you out of my way - this "plonker" will accommodate your big shiny jet, otherwise keep outta my way cause I once you are established in the missed approach, I will be headed down!FTDK, assume you are turning inbound from the outbound leg of the Hamilton Island Rwy 32 VOR holding pattern and you hear the Lear 45 advising that he is not visual and is now on the missed approach, you would now..... ??????

Take into account that he has commenced his missed app at 2.5 miles and at 800', where do you think he will get to 3000' ???

I agree with you Arm OTW, that is what should happen, it rarely does unfortunately.

I know of one case where two a/c from the same company nearly clobbered one another because one was holding at the published holding altitude.
Easier in a turbine a/c, a bit harder to get down from 4500 to MSL in an unpressurised piston though.

[Gundog01]

FTDK

Without even looking check out Bowen, for one.

Plus what do you expect the MAP aircraft to do fly 10-15nm away climb then track back overhead. 1000' is great if only 1 a/c is stacked above, what about a real stack???

Dont assume my "big shiny jet" is a) big, b) shiny, or c) a jet. your a/b class buggie would probably out climb me anyday.

Your recklessness in dealing with fellow aviators is not required OCTA, please.

[Gundog01]

Innisfail, not overhead but sure close.....you should be familiar with that area,

[ForkTailedDrKiller]

FTDK, assume you are turning inbound from the outbound leg of the Hamilton Island Rwy 32 VOR holding pattern and you hear the Lear 45 advising that he is not visual and is now on the missed approach, you would now..... ?????? Take into account that he has commenced his missed app at 2.5 miles and at 800', where do you think he will get to 3000' ???

If he is the professional pilot that he should be, he will adjust his climb so that he does not climb above 2000' until he is past the VOR. At that time, I will be outbound in the approach!!

Dr :8

[Gundog01]

Wagga....so they are out there..

[Gundog01]

west wylong.....another

[ForkTailedDrKiller]

Innisfail, not overhead but sure close.....

Hmmmm! Yeah, well YILF is a pretty archaic NDB Appr - and I'd be holding at IFLEB for the RNAV Appr anyway! :E

Dr :8

[Gundog01]

FTDK

If his fellow pilots are professional he shouldn't have to adjust his MAP climb gradient.

Go fly the Atherton GPSRNAV for CASA approved users only like you insinuated you would in a previous post because it was your god given right......PROFESSIONAL!!

[Spikey21]

If he is the professional pilot that he should be, he will adjust his climb so that he does not climb above 2000' until he is past the VOR. At that time, I will be outbound in the approach!!So you are going to fly a 1 minute leg and pass over the aid while a Lear goes 2.5 nm and climbs 2200', I somehow don't think so.

You are scaring me doc... Oh dear !!!

Arm OTW, you were saying...
Why is it impossible?
One holds at missed approach finish alt + 1000 till the other gets in.

[Capt Fathom]

And just be aware that someone out there in IMC could be heads down on Pprune! :=

[No Body]

I gave the answer.

Plazbot - have you got a reference for that?

Our company ops manual specifies very similar figures, but I am not familiar with a reference in the regs

[ForkTailedDrKiller]

Go fly the Atherton GPSRNAV for CASA approved users only like you insinuated you would in a previous post because it was your god given right......

GD, a bit off thread, but since you brought it up ........ I applied to CASA for approval to fly that approach, and was told that approval cannot be given for a fixed-wing aircraft to fly that approach because YATN is not a registered aerodrome. That is the only reason. Apparently it is OK if the aerodrome is registered, the Appr approved and then the aerodrome registration is allowed to lapse. Go figure!

Mig, a C150 can fly that missed approach profile and stay within the safe area - the Lear would not be in any danger flying a little less than its max rate climb!

I still find it hard to accept that the aircraft at the bottom of the holding stack gets to fly the approach/missed approach and arrive back at the bottom of the stack where it can stooge around until it feels like having another go!

And just be aware that someone out there in IMC could be heads down on PPRuNe! :=

Yeah, and also be aware that someone out there in IMC could be heads down on their weather radar! Its a real worry!

Dr :8

PS: Damn, its a pity Julia has stood me up yet again!

[Capt Fathom]

And just be aware that someone out there in IMC could be heads down on PPRuNe!
Yeah, and also be aware that someone out there in IMC could be heads down on their weather radar! Its a real worry!

Sorry Doc, you're not in the ball game with that comparison!

[43Inches]

Plazbot - No problem with the 1000ft and maybe 10 mins, but the 15nm would have to only apply to same direction traffic at reasonably the same speed. Opposite direction or converging traffic you would have to guarantee 1000ft at least by 15nm in a non-radar environment.

In the case of a missed approach unfortunately there is an infinite number of scenarios which could occur and even holding 1000ft above the missed approach alt may not be sufficient.

Large aircraft operators will follow a standard procedure including required speeds and power for a missed approach which will terminate at the missed approach altitude, they will not vary this and may be quite busy until the procedure is complete.

In the reversal procedures mentioned the missed approach may take the aircraft through the holding pattern, especially if the missed approach is commenced early due tracking etc.

On an RNAV the holding aircraft (assuming the same approach is flown by all aircraft) is about 15nm behind the MAPt and should be well clear. Simultaneous opposite direction approaches to the same runway is just poor airmanship. First in chooses the approach they would prefer, the other either procedes to fly that approach in turn or holds well clear until the first has landed/completed missed approach. Notify ATS of your intentions to hold so they can pass on the details to others inbound.

In any case good communication is essential so as all aircraft are aware of the relative position of each other, if you don't like the position of the other aircraft ask them nicely to relocate prior to it becoming an issue.

[peuce]

Hey guys, you are all getting confused....

The initial question was ... "what are the separation standards OCTA in IMC ?"

The answer is ... there are NO separation standards outside controlled airspace (Class G)

PLAZBOT was referring to the standard parameters used in assessing IFR/IFR traffic information ... from an ATC's point of view. It's up to the PIC as to what separation he/she arranges with other aircraft OCTA. That's a totally different and subjective topic

[amberale]

Peuce, I agree.

Back in the day the YBRK MAP was to A037 [I think] the base of CTA with the tower off duty was A035.
I remember having aircraft stacked to FL110 one night with fog.
Low QNH so extra sep for the transition layer.
Single pilot ops holding in IMC, 2000' Sep in those days.

One below A040 on the approach.
One at A060, A080, FL110.

Oh the joy.:}

ATC usually has separation points where you are clear of the holding stack.
If you ask "what distance outbound will I be procedurally clear of the holding pattern" the RAS provider may be able to help.
Give them some advance notice as I'm not sure that this data is held at the console these days and it will be quite a long distance.

AA

[KRviator]

And when a lighty has a transponder and causes an RA to an airline aircraft at one of these class G locations does anyone call for the airspace to be reversed?I was under the impression that TCAS cannot give an RA unless both aircraft are actually fitted with TCAS, to ensure the RA does not produce a further conflict.

Is this not the case?

[Gundog01]

peuce, what do you consider appropriate separation?

[peuce]

I don't ... I'm not an IFR pilot, so I'm not in a position to say.

My only point is that there is no ATC Separation Standard in Uncontrolled Airspace. It's a pilot responsibility.

[Dog One]

KRviator

You are correct, for RA solutions, both aircraft need to be fitted with TCAS. Aircraft with only Mode A, C or S will only give a TA. Aircraft with their transponder switched off will give no warning at all.

One of the problems within this industry is that the lives of passengers depend on the lowest common denominator, ie the VFR aircraft whose transponder is either switched off or U/s.

How many times do you hear on the CTAF frequency, XXX, is your transponder on? and voila!, they appear on your TCAS.

[muffman]

I'm glad I asked this question, it proves there is a lot of debate about it. I would have thought this is one area where at least some guidance in the AIP would be useful to avoid any of the more dangerous practices slipping through the cracks.

Sounds like the most widely accepted law of the land is 10 min, either 10/15nm horizontal and 1000ft vertical, and to leave the missed approach finishing alt + 1000 clear until the bloke before you gets in.

As for:
I still find it hard to accept that the aircraft at the bottom of the holding stack gets to fly the approach/missed approach and arrive back at the bottom of the stack where it can stooge around until it feels like having another go!

I can see the unfairness there.

What is the opinion on the higher aeroplane (i.e. the one at +1000ft) commencing the approach from that altitude, presuming the approach leads in the opposite direction to the holding pattern? If they are in contact on the CTAF and the lower aeroplane broadcasts he is outbound in the hold and the higher aeroplane then starts outbound on the approach. I realise descending an extra 1000ft may not always be achievable unpressurised, but some approaches (e.g. YBTH) there is no problem with losing the required altitude.

[waren9]

KRviator

You are correct, for RA solutions, both aircraft need to be fitted with TCAS. Aircraft with only Mode A, C or S will only give a TA. Aircraft with their transponder switched off will give no warning at all.


Dont think so.

I have had 3 RA's in my career. All of them have been "climb, climb" after the initial "traffic, traffic" TA's. One was off a C152 whilst I was decending into NZTG, another off an RNZAF CT4 going into NZPM and the last one was off an R22 at YBCG.

AFAIK, none of these had TCAS fitted.

No RA will be issued if Mode A only from threat aircraft.

If multiple aircraft are about, all with TCAS it is my understanding that they can all talk to each other so that an RA can be made by one or two aircraft without further upsetting a third or fourth aircraft that werent originally on the collision course.

Or summat like that:rolleyes:

[LeadSled]

I'm wondering if anyone can provide me with references to indicate what the minimum separation standard is while OCTA in IMC.Muffman,
At the risk of stating the obvious, OCTA means (now) Class G airspace, and the answer, quite simply is--NONE.
What guidelines various pilots might use, in arranging their operations in Class G is a matter for them. What is it that is so difficult about understanding "uncontrolled", is it the "un" or the "controlled".
The requirements for an aircraft to be given as "traffic" to other IFR aircraft are not "separation standards". Perhaps one of you from AsA might like to expand on the "known traffic" criteria, it's not "any IFR" aircraft within 5 minutes/15 m. etc.

Tootle pip!!

PS: Folks, please remember, being "RPT" in Class G CTAF does not give you any rights or priorities over any other "traffic", and does not exempt you from CAR 166.

[muffman]

Leadsled:

Your sarcasm is unhelpful and out of 40 odd replies, you're the only one who hasn't added anything useful.

In the same sense that there are rules to ensure separation from terrain OCTA, I am interested in the subject of separation from other aircraft OCTA. The known traffic criteria have already been listed elsewhere in the thread by a more helpful contibutor.

[Gundog01]

I can see the unfairness there.

Muffman

I dont think "fairness" should be player when talking about safe separation between aircraft in IMC. The first aircraft to arrive overhead should get the first opportunity to land. If that means 2-3 attempts because the weather is ****e so be it. Obviously is someone stacked above is short of gas then the lower aircraft should arrange separation in the hold and let the low-gas aircraft have a crack.

Leadsled

It was established early in the thread that there is no legislated or even advised minimum separation requirement. Perhaps informing fellow ppruners about what you use would add more to the thread.

[OZBUSDRIVER]

WRT the Wagga approach. Stateing first up that I am still hitting the books, I would hope the Lear calls missed, I have taken up the hold at 3000ft awaiting my turn, I would then in turn inform Mr lear driver my whereabouts in relation to the aid...whether I am inbound or outbound or passing the aid. As it is now my approach I would guess that it is now my airspace and the Lear has to keep clear of me. If the lear went missed I would also be taking stock if I should even attempt the approach and use my fuel to bug out to my ALT.

It sounds like common sense to me that any IFR on the SAME approach would be intently communicating their position where there is a conflict such as a missed heading back and climbing through the hold point. After all, it would be no surprise that everyone would be on the same page, so to speak.

EDIT-saying the same thing twice.


ANNNND a plug for ADS-B IN..Dick if everyone had IN in an IFR machine then YES a pilot would be able to maintain his own separation accurately to a distance and elevation with confidence. TCAS cannot do this!

[waren9]

Obviously is someone stacked above is short of gas then the lower aircraft should arrange separation in the hold and let the low-gas aircraft have a crack


Arriving at an aerodrome that is below landing minima low on gas? Holding until low on gas? I think to get to that point you have passed through a couple of other holes in the cheese to get to there. I would like to think we would all have the smarts to speak up before it gets to that stage.

Seriously guys, how often does any of this occur?

[Gundog01]

Waren

Low on gas dosen't necessarily mean below mins. Perhaps approaching divert fuel and would like a crack at getting in before needing to divert? I have been #3 in a hold for 35mins with people missing below, so this sort of thing can and does happen.

OZ

Do you realise that if you just waited and held at the hold alt +1000 until the lear has called visual (as is good practice) and landed that there would be no need to communicate your position and try to sort out separation. You would already be separated. Keep it simple stupid is my moto.

[OZBUSDRIVER]

GunDog..agree one hundred percent KISS. The conflict would only occur IF the Lear called missed and would be turning inbound to the aid and climbing to 3000ft...would you keep that in mind until after the Lear called on the ground before you actualy descended to the initial approach altitude, will have to ask instructor on that. My guess would have been my original view, once the Lear left 3000 on descent you could descend to that altitude and hold.

EDIT Do see your point tho, However, would that mean if the Lear climbs to 3000 to the aid, they can keep going until they land or bug out for the ALT?

[waren9]

In that case mate, youve just gone some way to contradict yourself.

Compare these 2 statements you posted:

I dont think "fairness" should be player when talking about safe separation between aircraft in IMC. The first aircraft to arrive overhead should get the first opportunity to land.

and:


Low on gas dosen't necessarily mean below mins. Perhaps approaching divert fuel and would like a crack at getting in before needing to divert?


Not sure where youre going with this. Low on gas? Declare it. If not, take your place in the queue. If that means diverting coz you didnt bring hold fuel then so be it.

[das Uber Soldat]

I dunno Dick, that just sounds like plain stupidity on someone's behalf (be it the Baron or the SAAB). Why would anyone, with any common sense, commence an instrument approach in completely the opposite direction to someone who's already doing an approach?

Happens all the time. I had an easterns dash 8 do it to me at port mac, at night. We ended up head to head despite my repeated calls as to our intentions and the fact we had commenced the approach before they probably even commended TOD. Those things look a bit scary going around directly over your head opposite direction at 200ft at night.

[Gundog01]

Waren

First aircraft gets first crack every time. However, they might have enough airmanship or good manners to allow an aircraft with enough fuel for 1 approach only and a divert if MAP to go first. Assuming the first aircraft was fat for gas.

"VXX, i'm approaching my divert fuel do you mind if i go next".

You can speak in pain language with your fellow aviators to sort out whats happening. It's not that difficult.

[43Inches]

muffman - the purpose of the 1000ft is just to provide breathing room for the lower aircraft. Once the lower aircraft has attained this altitude he can manuevre out of the hold and climb to a higher altitude, go to an alternate or retry the approach. If he decides not to try the approach again the higher aircraft can either commence the approach from 1000ft, which is generally achievable, or descend in the hold and pass the IAF at desired height. The only issue i see with the higher aircraft commencing the approach first comes back to the iniatial argument, if he then goes round where does he go?

ozbusdriver - giving the preceding aircraft room to manuevre in the event of missed approach is good airmanship. If you descend on top of them they will be forced into either climbing through your altitude with only minimal time to ascertain your position via radio or maintain a height below a lowest safe/MSA. The holding aircraft is only governed by a minimum altitude and can easily maintain a height above it with no effort.

If all else fails just slow down en-route so the other guy gets there well ahead then there's no holding and you may save some fuel, why the rush?

[waren9]

Yeah ok whatever. Cant be bothered any more.

What about airmanship and manners from the numpty who didnt bring hold in the first place fuel like everybody else did?


It's not that difficult

Im off for a beer

Laters

[OZBUSDRIVER]

Simple enough, another little gem to remember. Comes back to SA, just hope everyone else is as courteous.:ok:

[Spikey21]

FTDK said...
I still find it hard to accept that the aircraft at the bottom of the holding stack gets to fly the approach/missed approach and arrive back at the bottom of the stack where it can stooge around until it feels like having another go!He doesn't doc, the missed approach should take him clear of the hold and allow someone else to have a go, nowhere that I am aware of does it automatically position you back in the hold, just the opposite actually, it may (usually does) take you through the holding pattern on the missed approach though.

To re-enter the hold is your decision after you have carried out the missed approach, re-evaluated your fuel status, your options, then you may consider a return.

The point I was concerned with is that most procedures are designed as if there is only one a/c at the location because most missed approaches seem to fly you through where the next a/c would be holding especially if the pilot in charge had adopted the "I'm next so get outta my way i'm coming in" attitude and wasn't using common sense and staying above the (potential) missed approach.