E190 near collision Mildura May 16 - ASI bulletin 56
If I'm understanding the numbers correctly, that was one highly ambitious approach by XGA - even disregarding there were 3 other aircraft inbound. Even leaving its turboprop big brother in its wake.
Can't help but think there is a fair bit more to the story, leaving one to speculate. Busting for a leak? See if the old girl can still handle Vne? What's that funny smell? Burning?
Can't help but think there is a fair bit more to the story, leaving one to speculate. Busting for a leak? See if the old girl can still handle Vne? What's that funny smell? Burning?
You're understanding the numbers correctly, but the numbers cannot be relied upon as accurate. Key position data is derived from TCAS and, as the report itself states, that data is "indicative only".
I'm convinced andrewr has it right. The indicative numbers don't add up.
A relatively benign situation may have resulted in the two aircraft ending up much closer than they would otherwise have been, as a consequence of a natural response to the TA and an aircraft out the window when feeling the cold chill of exposure in Class G airspace. But I acknowledge this is merely Monday morning quarterbacking.
I'm convinced andrewr has it right. The indicative numbers don't add up.
A relatively benign situation may have resulted in the two aircraft ending up much closer than they would otherwise have been, as a consequence of a natural response to the TA and an aircraft out the window when feeling the cold chill of exposure in Class G airspace. But I acknowledge this is merely Monday morning quarterbacking.
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The TCAS data suggests he was doing 140-150 knots on descent from 10000', then accelerated to around 200 knots on 4.5 mile final. A search for GA-8 VNE suggests it is 185 kt.
The distances are short enough that an error of 1/2 mile one way at the beginning and 1/2 mile the other at the end brings the required speed down to a more plausible 120kt. But if you need a margin of error to make it fit, assuming accuracy in rest of the analysis doesn't make sense.
I found this interesting link about TCAS accuracy in turns:
http://www.tc.faa.gov/its/worldpac/techrpt/tctn099.pdf
I don't know how relevant it is to current systems. But the entire "near miss" occurred while the jet was turning. Before the turn, XGA was slightly behind and around 700 feet higher. When the jet straightens on upwind, XGA suddenly appears south of the airfield (where he said he was going to go when asked to go around)
During the turn, TCAS says he was doing 200 knots and almost ran into the back of the jet (0.1 mile separation). It makes a lot more sense if the TCAS data is unreliable in the turn.
The distances are short enough that an error of 1/2 mile one way at the beginning and 1/2 mile the other at the end brings the required speed down to a more plausible 120kt. But if you need a margin of error to make it fit, assuming accuracy in rest of the analysis doesn't make sense.
I found this interesting link about TCAS accuracy in turns:
http://www.tc.faa.gov/its/worldpac/techrpt/tctn099.pdf
I don't know how relevant it is to current systems. But the entire "near miss" occurred while the jet was turning. Before the turn, XGA was slightly behind and around 700 feet higher. When the jet straightens on upwind, XGA suddenly appears south of the airfield (where he said he was going to go when asked to go around)
During the turn, TCAS says he was doing 200 knots and almost ran into the back of the jet (0.1 mile separation). It makes a lot more sense if the TCAS data is unreliable in the turn.
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andrewr I think you need to to read up on how TCAS works. The only thing that is accurate about TCAS is the altitude. Both bearing and distance are best guess worked out by an algorithm using a few assumptions on the signal strength. Generally accurate enough to visually identify the target, however I have experienced seeing a TCAS target to the left of my flight path when in fact we had visual contact with the aircraft and it was to our right. Too many pilots put too much faith in the bearing and distance of a TCAS target. Also seen target jumping around as system tried to work out the correct bearing in relation to us.
Perhaps the ATSB needs to read up on how TCAS works, before using the phrase "traffic conflict" to describe what happened.
A TA is not a traffic conflict.
A situation in which one aircraft is obliged to give way to another is not a traffic conflict.
A TA is not a traffic conflict.
A situation in which one aircraft is obliged to give way to another is not a traffic conflict.
Rubbish LB, nobody was giving way to anybody until well after the TCAS TA. The fact they ended up so close is testament to the seriousness of the situation. This is RPT jet stuff here, not 150 vs PA28. Things should not get anywhere near this close.
First, Capn, you don't know how close they ended up. As the report says, the TCAS derived data is merely "indicative" - a word that means ... what, precisely?
Secondly, you don't know whether the aircraft would have ended up 'less close' if the jet had merely continued its approach and XGA had been left to give way once XGA was alerted to the jet's position on base. The actual response may have made things 'worse'.
You say that "things should not get anywhere near this close". What is the minimum distance you apply when engaging in amateur ATC?
Secondly, you don't know whether the aircraft would have ended up 'less close' if the jet had merely continued its approach and XGA had been left to give way once XGA was alerted to the jet's position on base. The actual response may have made things 'worse'.
You say that "things should not get anywhere near this close". What is the minimum distance you apply when engaging in amateur ATC?
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andrewr I think you need to to read up on how TCAS works. The only thing that is accurate about TCAS is the altitude. Both bearing and distance are best guess worked out by an algorithm using a few assumptions on the signal strength.
If you think incorrect TCAS data is more likely than a GA-8 doing 200 knots and overtaking a jet, it also seems likely that there was no near collision.
If you use more likely speeds for the GA-8, it was probably never closer than a mile to the jet, with the gap increasing.
I think I get in now Leadsie (do you mind if I call you that?).
From your language ("heavy metal" "Amateur ATC" and "I know what my response to an "instruction" from another aircraft would be.") it is clear that you have a chip on your shoulder when it comes to operating at the same time as RPT aircraft.
Look, I get that you may be a moderately experienced GA pilot who's brother is a professional pilot, yet we don't know when communicating on CTAFs who we are operating with. Whether that voice is a student on a first solo nav, a crusty old crop duster or a private pilot on their once a month flight, it can be hard to ascertain.
Tell me, what more 'complex' issues are 'trite'?
You may be awesome and have exceptional situational awareness, but that doesn't mean everyone does.
So don't take it to heart if you've experienced 'amateur ATC', I'm sure that wasn't the intention. You may of been communicating with a crew who were tired after multiple sectors operating into a high workload environment in a high performance aircraft.
Tell me, do you operate an aircraft that has TCAS?
Perhaps lighten your grip on that yoke, stop sweating and mumbling curse words over 'heavy metal drivers' and realize that we all just want the best and easiest outcome.
You keep wanting clarification on 'what could I have done to mitigate such an incident happening' yet I get the impression that you are dipping your toe here in the big pool not to learn, but rather to validate your own opinions.
As I have said before, when in a CTAF, ensure your transponder is on ALT, ensure you have the correct frequency selected (listen for the beep back) and make clear and concise radio calls stating your position and intentions.
If you're 'asked' to clarify something, or your altitude or position once again when you thought you'd just given it, don't take it to heart.
Smile and enjoy the view, you're lucky you get to fly as much as you do
From your language ("heavy metal" "Amateur ATC" and "I know what my response to an "instruction" from another aircraft would be.") it is clear that you have a chip on your shoulder when it comes to operating at the same time as RPT aircraft.
Look, I get that you may be a moderately experienced GA pilot who's brother is a professional pilot, yet we don't know when communicating on CTAFs who we are operating with. Whether that voice is a student on a first solo nav, a crusty old crop duster or a private pilot on their once a month flight, it can be hard to ascertain.
Hi U
Good points.
However, I think all those more complex issues are trite. That is, they are all well known.
Good points.
However, I think all those more complex issues are trite. That is, they are all well known.
You may be awesome and have exceptional situational awareness, but that doesn't mean everyone does.
So don't take it to heart if you've experienced 'amateur ATC', I'm sure that wasn't the intention. You may of been communicating with a crew who were tired after multiple sectors operating into a high workload environment in a high performance aircraft.
Tell me, do you operate an aircraft that has TCAS?
Perhaps lighten your grip on that yoke, stop sweating and mumbling curse words over 'heavy metal drivers' and realize that we all just want the best and easiest outcome.
You keep wanting clarification on 'what could I have done to mitigate such an incident happening' yet I get the impression that you are dipping your toe here in the big pool not to learn, but rather to validate your own opinions.
As I have said before, when in a CTAF, ensure your transponder is on ALT, ensure you have the correct frequency selected (listen for the beep back) and make clear and concise radio calls stating your position and intentions.
If you're 'asked' to clarify something, or your altitude or position once again when you thought you'd just given it, don't take it to heart.
Smile and enjoy the view, you're lucky you get to fly as much as you do
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From the report:
'The flight crew looked out the right window of the flight deck and identified the traffic to their right and high against the skyline. The traffic appeared to them to be stationary in the windscreen relative to their own aircraft and with a high closure rate (from TCAS data the aircraft were 1.25 NM apart at the time of the TA alert)'
So the report does mention a visual confirmation.
'The flight crew looked out the right window of the flight deck and identified the traffic to their right and high against the skyline. The traffic appeared to them to be stationary in the windscreen relative to their own aircraft and with a high closure rate (from TCAS data the aircraft were 1.25 NM apart at the time of the TA alert)'
So the report does mention a visual confirmation.
Last edited by Utradar; 30th Jan 2017 at 22:31.
You evidently have a written comprehension problem, compylot. I have stated, repeatedly in this thread, that I have never had or heard any insolent interactions on a CTAF with any other aircraft - RPT or otherwise. That includes at YMIA.
I suspect that wherever you and the Capn operate, the insolent conversations may be precipitated by arrogant RPT pilots who presume to engage in amateur ATC on the basis that they "know better". For that is what it is, pure and simple: amateur ATC. And as I've also said in this thread, my only advice is that ya better get it right.
In the case of the event that led to the discussion in this thread, the amateur ATC may have made things worse. I know you can't bring yourself to concede that, but that just shows you're incapable of being objective.
Utrader seems to have a comprehension problem, too. (Are you people really in charge of aircraft full of passengers?) Who suggested a "conspiracy"? Who said there was nothing in the report about the jet seeing XGA?
Please read what andrewr has posted. Twice.
I suspect that wherever you and the Capn operate, the insolent conversations may be precipitated by arrogant RPT pilots who presume to engage in amateur ATC on the basis that they "know better". For that is what it is, pure and simple: amateur ATC. And as I've also said in this thread, my only advice is that ya better get it right.
In the case of the event that led to the discussion in this thread, the amateur ATC may have made things worse. I know you can't bring yourself to concede that, but that just shows you're incapable of being objective.
Utrader seems to have a comprehension problem, too. (Are you people really in charge of aircraft full of passengers?) Who suggested a "conspiracy"? Who said there was nothing in the report about the jet seeing XGA?
Please read what andrewr has posted. Twice.
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Actually that is my point. The report relies heavily (exclusively?) on the TCAS data. As far as I can tell it is only the TCAS data that indicates that the "near collision" even happened - there is no visual confirmation mentioned in the report.
I was just pointing out the report shows the pilots of the jet did see the conflicting aircraft and TCAS assisted in providing altitude information. It was shown to pass 200' above ZPJ. Let's not downplay the seriousness of this.
arrogant RPT pilots who presume to engage in amateur ATC on the basis that they "know better"
There's difference in airmanship and professionalism between RPT pilots and 'casual' pilots. It's usually ends up being the casual pilots who make it difficult for the RPT guys due to lack of skill, awareness, experience etc. That's why the initiative of separation by radio usually comes from the RPT pilots.
In the case of the event that led to the discussion in this thread, the amateur ATC may have made things worse
"Arrogant", "Insolent", "Amateur", "Know Better". Appears to sum up LB nicely.
As Porter (I think it was) does: everybody clear off until RPT on the ground. That would solve LB's "suspected" problem that "May" or may not be a problem.
And is exactly why something needs to change operating to these aerodromes.
LB there was no 'amateur ATC'. Communication was made with XGA to alter course to avoid collision in the heat of moment. This is hardly 'amateur ATC'.
Do you entertain the possibility - just the possibility - that the outcome was worse than if each aircraft had continued its approach?
If you read back through this thread, I was initially convinced that collision avoidance action was necessary. I then read the report, twice, and read andrewr's input, thrice, and am no longer convinced.
I am happy to stand corrected, but only on words out of the mouth of the pilot of XGA.
I call that being objective.
I've flown more approaches in my aircraft than the pilot of ZPJ has flown in the type that ZPJ is. Who you you reckon is better able to judge where my aircraft is going to go, how long it will take to get there, how slow it can fly and how quickly it can climb, on approach? The pilot sitting in ZPJ or me sitting in my aircraft on approach?
Who do reckon spends more time 'close' to other aircraft and manoeuvring to avoid collisions?
I do understand the principle and benefits of mutually agreed separation arrangements. I enter them quite frequently. I'm merely pointing out that the person in seat 0A of a jet is not necessarily best qualified to 'take the lead' or - shall we say - 'be assertive' as to what those arrangements should be. The fact that a sentence starts with: "I have 81 pax down the back" does not turn whatever operational 'suggestion' the sentence ends with into an objective truth. Just imagine if ZPJ and XGA had collided on the go around, and the last conversation on ZPJ's CVR was XGA agreeing, at ZPJ's 'suggestion', to break off the approach and head towards the point at which the aircraft subsequently collided.
When I read proposals like Capn's "everybody clear off until RPT on the ground" and statements like "the mix of aircraft is too complex at airports like Mildura", I just laugh. Not through disrespect - and I mean that seriously - but rather at how people would cope at first world aviation nation traffic densities.
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Do you entertain the possibility - just the possibility - that the outcome was worse than if each aircraft had continued its approach
It's obvious the pilots of both aircraft didn't know each other were there until the pilots of ZPJ saw the Airvan during base turn. What would you have said LB? "AIRCRAFT ON FINAL LOOK OUT WE'RE ON A COLLISION COURSE!" or would you have said nothing and continued the approach?
I've flown more approaches in my aircraft than the pilot of ZPJ has flown in the type that ZPJ is. Who you you reckon is better able to judge where my aircraft is going to go, how long it will take to get there, how slow it can fly and how quickly it can climb, on approach? The pilot sitting in ZPJ or me sitting in my aircraft on approach?
What matters is the positive outcomes, hopefully a review within CASA of the limitations of see and avoid and alerted search at non-controlled AD's.
"I have 81 pax down the back" does not turn whatever operational 'suggestion' the sentence ends with into an objective truth
Remember hindsight is always 20/20.
Last edited by Utradar; 31st Jan 2017 at 08:50.
Precisely the arrogance that I was alluding to before. You really are a special, LB. You may be an ace in your bugsmasher; the fact is that not only do you not have a clue about operating a jet in a CTAF, it is painfully obvious you don't want to know.
You are so blinkered that you can't even see the sarcasm in my suggestion that everybody rack off when I'm about.
There are none so blind as though who will not see.
You are so blinkered that you can't even see the sarcasm in my suggestion that everybody rack off when I'm about.
There are none so blind as though who will not see.
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'The flight crew looked out the right window of the flight deck and identified the traffic to their right and high against the skyline. The traffic appeared to them to be stationary in the windscreen relative to their own aircraft and with a high closure rate (from TCAS data the aircraft were 1.25 NM apart at the time of the TA alert)'
So the report does mention a visual confirmation.
So the report does mention a visual confirmation.
The GA-8 was also 500-600 feet higher. 2 miles and 500 feet doesn't seem like something to worry about with visual separation.
It was shown to pass 200' above ZPJ
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Andrewr,
Without radar, it's a bit tricky to assess the exact distance between the two aircraft but i've heard the E190 QAR is very good but even if there's errors with the TCAS you're overlooking that a potential collision was imminent if the crew were not alerted by TCAS and the aircraft being stationary in the windshield.
"The GA-8 was also 500-600 feet higher. 2 miles and 500 feet doesn't seem like something to worry about with visual separation."
This is a little concerning Andrewr. The big picture here is that a jet's airspace was compromised by a light aircraft. This IS something to worry about.
Without radar, it's a bit tricky to assess the exact distance between the two aircraft but i've heard the E190 QAR is very good but even if there's errors with the TCAS you're overlooking that a potential collision was imminent if the crew were not alerted by TCAS and the aircraft being stationary in the windshield.
"The GA-8 was also 500-600 feet higher. 2 miles and 500 feet doesn't seem like something to worry about with visual separation."
This is a little concerning Andrewr. The big picture here is that a jet's airspace was compromised by a light aircraft. This IS something to worry about.
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Are you serious? They are on a collision course!
An object far away will appear stationary in the windscreen even if you're not on a collision course. The "stationary in the windscreen" idea is that it remains stationary up to the point of impact. You don't run into everything that appears stationary in the windscreen.
At the beginning the jet was on base leg about 2.5 - 3 miles out, and the tracks suggest it was about 90 seconds from the threshold (does that sound the right ballpark?)
The GA-8 was on a 4.5 mile final which I would expect to take 3-4 minutes, giving around 2 minutes separation at the threshold.
If the jet continued straight from base leg and crossed final at 90 degrees things could have been close, but they don't, they have to turn final which puts them well ahead of the GA-8 and you would expect separation to increase from there.
This is a little concerning Andrewr. The big picture here is that a jet's airspace was compromised by a light aircraft
I don't see any evidence that the jets airspace was actually compromised. It's all about the TCAS which has some very suspect numbers for the horizontal position. If the TCAS data didn't show the suspect 200' 1/8 mile data, would there have been any investigation?