TCAS philosophies
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Originally posted by joernstu
The Piper involved in the Aeromexico 498 collision (31.08.1986) was not equipped with a mode-C capable transponder.
The Piper involved in the Aeromexico 498 collision (31.08.1986) was not equipped with a mode-C capable transponder.
Originally posted by PBL
That statement is hard to reconcile with your statement that it is "irresponsible" for me to publish them on this forum.
That statement is hard to reconcile with your statement that it is "irresponsible" for me to publish them on this forum.
No doubt airspace changes such as TCA's(or should I say class B airspace) and mode-C veils have reduced midair collision potential. Is this what a confounding factor is? While we have seen several fatal midairs over the years(outside the U.S.) such as...
30 July 1971; All Nippon Airways 727-200 vs jet fighter; northern Honshu, Japan, CA-155 dead.
5 March 1973; Iberia DC9-32 vs Convair 880; Nantes, France-68 dead
1979 Aug 11 - Tupolev Tu-134 vs.Tupolev Tu-134 Near Dniprodzerzhynsk, USSR -178 dead
12 November 1996; Saudia 747-100 vs Il-76; near New Delhi, India-349 dead
29 September 2006; Gol Linhas Aereas 737-800 vs ERJ-135; near Peixoto de Azevedo, Brazil-154 dead
Sep 13 1997 - Luftwaffe TU-154 vs USAF C141 over Namibia, Africa-33 dead
...where properly working TCAS in both aircraft(or TCAS in one and working transponder inthe other) would likely have prevented them, there has never been a midair collision event caused when TCAS was installed and properly used. And actually, only one fatal accident when improperly using TCAS. Improper use of many different types of equipment has caused many deaths in aviation. No engineering data on my part just real world knowledge.
Page 103 of the midair accident report states in part:
The TU-154 AOM contains general recommendations regarding the use of TCAS. The AOM reference draws attention to the fact that manouvering opposite to TCAS can lead to a collision.
The TU-154 AOM stated that manouvering opposite to the RA is PROHIBITED.
The actions taken by the Tu-154 captain that night were not rational , they were, to use non-engineering terminology... F
ing Insane.As for the JAL incident, In the end it was an attempt to visually avoid conflicting traffic against the command of the TCAS RA. The causes leading up to the RA are irrelevant and could very well be due to different errors in each situation. Our discussion is about how to react to an RA.
I still eagerly await any engineering facts on the ability to successfully manouver visually around TCAS conflicting traffic while climbing or descending toward that traffic.
Last edited by punkalouver; 10th Dec 2007 at 00:09.
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pukalover, thanks for mixing all posts in this threat as (assumingly) a reply to my remarks. This makes your post unreadable. Also your ambigous use of bold types doesn't aid the readability.
Perhaps you should ask the engineers in you company for these. The notion of avoiding traffic by visual reference was introduced by you, as far as I am aware.
I still eagerly await any engineering facts on the ability to
successfully manouver visually around TCAS conflicting traffic while climbing or descending toward that traffic.
successfully manouver visually around TCAS conflicting traffic while climbing or descending toward that traffic.
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Originally Posted by joernstu
The notion of avoiding traffic by visual reference was introduced by you, as far as I am aware.
It was introduced by PBL, in post #20:
Originally Posted by PBL
[...]
They were faced with an "intruder" at 10 o'clock which they saw, and an unknown conflict at 2 o'clock which they didn't see, and for which they had an advisory to descend (that is, he was at or above their altitude).
[...] Or avoid him, descend towards an aircraft that you do see, and hope to avoid him using visual means?
They were faced with an "intruder" at 10 o'clock which they saw, and an unknown conflict at 2 o'clock which they didn't see, and for which they had an advisory to descend (that is, he was at or above their altitude).
[...] Or avoid him, descend towards an aircraft that you do see, and hope to avoid him using visual means?
However, this has nothing to do with "engineering facts", it is part of the argument why the Tupolev crew's actions were rational. A refutation has to offer more than "always follow the RA, because Eurocontrol says so in their marketing brochures, and I believe them, and it is also SOP."
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Page 103 of the midair accident report states in part:
The TU-154 AOM contains general recommendations regarding the use of TCAS. The AOM reference draws attention to the fact that manouvering opposite to TCAS can lead to a collision.
The TU-154 AOM stated that manouvering opposite to the RA is PROHIBITED.
The TU-154 AOM contains general recommendations regarding the use of TCAS. The AOM reference draws attention to the fact that manouvering opposite to TCAS can lead to a collision.
The TU-154 AOM stated that manouvering opposite to the RA is PROHIBITED.
it is prohibited to initiate a manoeuvre contrary to the advisory issued by the system.
The actions taken by the Tu-154 captain that night were not rational , they were, to use non-engineering terminology... Fing Insane.
ing Insane.
And a pilot making a decision based on these contradicting orders is in your opinon not only "not rational" but "[...] insane".
The causes leading up to the RA are irrelevant and could very well be due to different errors in each situation.
Our discussion is about how to react to an RA.
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Originally posted by joernstu
In a prior post, you said that you go along with the findings of BFU accident investigators and now you say, that accident investigator's findings are irrelevant.........No. Our discussion is on "TCAS philosophies".
In a prior post, you said that you go along with the findings of BFU accident investigators and now you say, that accident investigator's findings are irrelevant.........No. Our discussion is on "TCAS philosophies".
1) FOLLOW THE RA
2) The actions of the TU-154 crew was not rational and neither was the JAL captains. They were extemely dangerous decisions.
3) your statement "I cannot decide, what kind of action would induce the lowest risk - following an RA, not following an RA or flying without TCAS at all as the basis for my risk evaluation would be episodes. I think the same goes for you as your information basis is still only episodes." is irresponsible.
My opinions only. I agree with what the Japanese report says. I never said their findings were irrelevant. I am giving you an example of how visual manouvering against the RA around traffic is not necessarily a safe thing to do(whether it is due to a conflict from ATC error, pilot error or in uncontrolled airspace).
Originally posted by joernstu
Perhaps a legal loophole, but the TU154M first got the ATC order, than the TCAS RA and initiated the descend before the RA. In so far, the crew's action was not in contradiction with this part of the AOM. So you have a AOM / FOM which in one section states, that ATC has priority over TCAS and that TCAS is only a last-line barrier - and than that you are prohibited from acting contrary to the RA. And a pilot making a decision based on these contradicting orders is in your opinon not only "not rational" but "[...] insane".
Perhaps a legal loophole, but the TU154M first got the ATC order, than the TCAS RA and initiated the descend before the RA. In so far, the crew's action was not in contradiction with this part of the AOM. So you have a AOM / FOM which in one section states, that ATC has priority over TCAS and that TCAS is only a last-line barrier - and than that you are prohibited from acting contrary to the RA. And a pilot making a decision based on these contradicting orders is in your opinon not only "not rational" but "[...] insane".
The TU-154 AOM stated that manouvering opposite to the RA is PROHIBITED.
If you get or have much real world flying experience outside the office, you will find that or already know there are actions that are illegal yet safe to perform and actions that are legal but unsafe to perform(eg. engineering facts that say it is within limitations to land on a contaminated short or crosswind affected runway but you know better). Also actual contradictions of rules and regulations. We can't easily change these rules and procedures. That is when judgement comes into play and knowledge through experience, reading etc allow you to hopefully make a rational decision. As for the insanity statement, I'm sure it crossed the minds of the crews properly following their RA.
Finally concerning visual manouvering against the RA around conflicting traffic...
Originally posted by bsieker
However, this has nothing to do with "engineering facts", it is part of the argument why the Tupolev crew's actions were rational. A refutation has to offer more than "always follow the RA, because Eurocontrol says so in their marketing brochures, and I believe them, and it is also SOP.
However, this has nothing to do with "engineering facts", it is part of the argument why the Tupolev crew's actions were rational. A refutation has to offer more than "always follow the RA, because Eurocontrol says so in their marketing brochures, and I believe them, and it is also SOP.
I am starting to wonder if the so called rational decision to descend and visually manouver around conflicting TCAS RA traffic which is quite possibly attempting to manouver around you is based on an assumption. An assumption that this is a safer action, rather than being based on any study or engineering facts that this really is a safer action. I have no data to prove or disprove this. Only two unsuccesful examples.
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3) your statement "I cannot decide, what kind of action would induce the lowest risk - following an RA, not following an RA or flying without TCAS at all as the basis for my risk evaluation would be episodes. I think the same goes for you as your information basis is still only episodes." is irresponsible.
I am not willing to make any risk assessment without the appropriate data to found the results. If this is irresponsible for you - I can do nothing about it. But I hope that I will never rely on your risk evaluation.
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Well, that is fine. However, if you knew you had to go on one of two flights, both will get in similar situation as the TU-154(in terms of known and visually acquired RA traffic and ATC reported but unseen visually or on TCAS traffic) at night or day and you knew that one captain would follow the RA and the other would attempt to visually manouver against the RA.....who would you prefer to fly with.
I think that you will find that most pilots will follow their SOP's and Eurocontrol newsletters on how to react to an RA even if there is other traffic out the. This probably happens quite frequently when a conflict arises and there are lots of airplanes out there on the TCAS display some of which have no altitude displayed(usually light aircraft). They have made their risk evaluation.
I think that you will find that most pilots will follow their SOP's and Eurocontrol newsletters on how to react to an RA even if there is other traffic out the. This probably happens quite frequently when a conflict arises and there are lots of airplanes out there on the TCAS display some of which have no altitude displayed(usually light aircraft). They have made their risk evaluation.
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The one, where the Boeing's TCAS would have generated a reversal?
The one, which would be flying only under guidance of appropriate staffed ATC?
The one with a defect radio?
If the Ueberlingen case is boiled down to the last seconds before the collision, tweaking any of the variables only a little would have prevented it.
The one, which would be flying only under guidance of appropriate staffed ATC?
The one with a defect radio?
If the Ueberlingen case is boiled down to the last seconds before the collision, tweaking any of the variables only a little would have prevented it.
Last edited by joernstu; 7th Dec 2007 at 16:03. Reason: typo corrected
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punkalouver,
I'm starting to wonder if you have a serious problem understanding written words.
We have repeatedly stated, and you have repeatedly misquoted us or simply ignored that:
1) When one choice is "rational" that does neither mean that it is
- the only rational choice
nor
- the best choice
nor
- the safest option
2) Rationality has nothing to do with what hindsight tells you about the danger.
3) It can be argued just as soundly that the DHL crew's action were extremely dangerous. Had they not followed the RA, no collision would have occured.
4) More generally, without TCAS, Ueberlingen would not have been an accident, but merely a later-than-usual separation by ATC. A non-event.
ad 1)
Yet you say we had claimed it was safer to do as they did, instead of following the RA. You also repeatedly ignore that fact, that they received the ATC order, and started manoeuvering according to it, before they received the RA. Meaning they never initiated a manoeuvre opposite the RA.
The interaction between ATC and TCAS is one of the key points of discussion, and this accident, more clearly than anything, shows that the premise of TCAS specifications, that it is only active when ATC is out of the picture, does not hold. It is very serious and must be addressed. Simply ignoring it will not make it go away.
ad 4)
This, too, is a serious matter when discussing what TCAS can do, what it cannot do, what its shortcomings are, and that and how they should be made known. Simply ignoring them will not make them go away.
Repeating your mantra of "Follow the RA" will not make any of the problems go away, either.
Despite what you think and what EC bulletins tell you with pretty pictures, they are not always simply caused by reckless crews acting against RAs.
And in case it got lost again: We do not advise not to follow an RA, even if you seem to think so.
Bernd
I'm starting to wonder if you have a serious problem understanding written words.
We have repeatedly stated, and you have repeatedly misquoted us or simply ignored that:
1) When one choice is "rational" that does neither mean that it is
- the only rational choice
nor
- the best choice
nor
- the safest option
2) Rationality has nothing to do with what hindsight tells you about the danger.
3) It can be argued just as soundly that the DHL crew's action were extremely dangerous. Had they not followed the RA, no collision would have occured.
4) More generally, without TCAS, Ueberlingen would not have been an accident, but merely a later-than-usual separation by ATC. A non-event.
ad 1)
Yet you say we had claimed it was safer to do as they did, instead of following the RA. You also repeatedly ignore that fact, that they received the ATC order, and started manoeuvering according to it, before they received the RA. Meaning they never initiated a manoeuvre opposite the RA.
The interaction between ATC and TCAS is one of the key points of discussion, and this accident, more clearly than anything, shows that the premise of TCAS specifications, that it is only active when ATC is out of the picture, does not hold. It is very serious and must be addressed. Simply ignoring it will not make it go away.
ad 4)
This, too, is a serious matter when discussing what TCAS can do, what it cannot do, what its shortcomings are, and that and how they should be made known. Simply ignoring them will not make them go away.
Repeating your mantra of "Follow the RA" will not make any of the problems go away, either.
Despite what you think and what EC bulletins tell you with pretty pictures, they are not always simply caused by reckless crews acting against RAs.
And in case it got lost again: We do not advise not to follow an RA, even if you seem to think so.
Bernd
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Folks,
I had hoped that my explanation of and plea for professional behavior this morning might have changed the substance of the discussion.
Those of us who want to have a technical discussion here have a problem, or rather a series of them. Let me enumerate a few.
First, I told our abusive young friend this morning that if he was a member of a professional society his behavior would contravene the norms of that society. He claimed he wasn't doing that - and then did exactly that again a number of hours later.
First conclusion: he has no clue what to do when a professional clearly states he has a problem with certain exchanges, and why.
Second, our friend doesn't discuss. He contradicts, mimics, repeats himself, but doesn't enter anything any of us would regard as a serious attempt to sort out the issues.
Second conclusion: he doesn't know what a technical discussion is or how to engage in one.
Third, our friend cites data, but doesn't know what a confounding factor is.
Third conclusion: he has never taken an elementary course in data analysis.
Fourth, in response to a request to solve a decision problem,
he repeats "follow the RA!"
Fourth conclusion: he has no idea what a decision problem is, or what a solution to a decision problem looks like.
Fifth, TCAS is a procedural system, based on information and algorithms. The decision problem presented to the human operator by the TCAS information subsystem is an essential part of the TCAS system. Enumerating solutions to that decision problem is part of the technical analysis of TCAS. "Decision problem" here is a technical term with a well-defined meaning. Our friend claims that the possible solution to the decision problem which my analysis has brought to light is "irresponsible".
Fifth conclusion: our friend has little understanding of the analysis of algorithms, and little grasp of the appropiate concepts for analysing them. He is using a perjorative term to describe a technical fact. This is comparable with someone, say, calling the number 5 "perverse".
Sixth, he doesn't argue his case; he simply repeats it.
Sixth conclusion: if we continue to answer as we have been, this discussion will go nowhere.
It is this sixth conclusion to which I wish to draw particular attention.
PBL
I had hoped that my explanation of and plea for professional behavior this morning might have changed the substance of the discussion.
Those of us who want to have a technical discussion here have a problem, or rather a series of them. Let me enumerate a few.
First, I told our abusive young friend this morning that if he was a member of a professional society his behavior would contravene the norms of that society. He claimed he wasn't doing that - and then did exactly that again a number of hours later.
First conclusion: he has no clue what to do when a professional clearly states he has a problem with certain exchanges, and why.
Second, our friend doesn't discuss. He contradicts, mimics, repeats himself, but doesn't enter anything any of us would regard as a serious attempt to sort out the issues.
Second conclusion: he doesn't know what a technical discussion is or how to engage in one.
Third, our friend cites data, but doesn't know what a confounding factor is.
Third conclusion: he has never taken an elementary course in data analysis.
Fourth, in response to a request to solve a decision problem,
he repeats "follow the RA!"
Fourth conclusion: he has no idea what a decision problem is, or what a solution to a decision problem looks like.
Fifth, TCAS is a procedural system, based on information and algorithms. The decision problem presented to the human operator by the TCAS information subsystem is an essential part of the TCAS system. Enumerating solutions to that decision problem is part of the technical analysis of TCAS. "Decision problem" here is a technical term with a well-defined meaning. Our friend claims that the possible solution to the decision problem which my analysis has brought to light is "irresponsible".
Fifth conclusion: our friend has little understanding of the analysis of algorithms, and little grasp of the appropiate concepts for analysing them. He is using a perjorative term to describe a technical fact. This is comparable with someone, say, calling the number 5 "perverse".
Sixth, he doesn't argue his case; he simply repeats it.
Sixth conclusion: if we continue to answer as we have been, this discussion will go nowhere.
It is this sixth conclusion to which I wish to draw particular attention.
PBL
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It looks like the moderator has spoken just before I posted this. It is important not to let emotion cloud posts or analysis.
Regarding rational....
I think we'll have to just agree to disagree on how we interpret this. No need for further discussion on it. Perhaps something to do with mother tongue language.
Sort of similar to the car that runs a red light at a busy intersection and smashes into traffic going through the green light. If only the cars going through the green light had not done so, there would have been no collision. They were behaving extremely dangerously. Traffic lights are dangerous.
The TU-154 AOM stated that manouvering opposite to the RA is PROHIBITED.
That means initiating or while following ATC instruction. Are you sure it is me who has a serious problem understanding words?
Good. But please be more specific(I know it is just placement of words) butthis is important. Do you advise pilots(excepting stall warnings, GPWS, etc) to ALWAYS FOLLOW THE RA? Please reply.
Finally PBL...
For much of his posts now he just accuses me of being abusive. Once again Mr. Moderator, please let me know if this is so in your opinion and I will apologize. (edited later-the moderator has spoken)
PBL is correct on some things. I have never taken a data analysis course and don't plan to. I don't know what a confounding factor is. I know almost nothing about algorithms but do know how to spell it( and I think they can be used to solve a Rubik's Cube). I'm not even sure what perjorative means. Most pilots that I fly with don't know much about algorithms either. I'll ask around to see if many have taken a data analysis course.
But I do have something that much more important to a pilot than any of these things. I have common sense. One of the most important things a pilot can have. I hope this is not still tedious to you.
I also know, well, I suspect that there is no technical data or engineering facts on the relative safety manouvering visually around TCAS RA traffic at night. Just blind assumptions and we will never see any engineering facts unless it is somehow hastily created. I was accused of not answering a question. How the tables have turned.
So seeing as I agree that this dicussion isn't really going anywhere, why don't we end it. Perhaps a lock on the thread after bsieker lets us know if he would be willing to say "GPWS and stall warnings exluded, we recommend that pilots always follow the RA"
Regarding rational....
Originally posted by bsieker
I'm starting to wonder if you have a serious problem understanding written words.
I'm starting to wonder if you have a serious problem understanding written words.
Originally posted by bsieker
It can be argued just as soundly that the DHL crew's action were extremely dangerous. Had they not followed the RA, no collision would have occured.
It can be argued just as soundly that the DHL crew's action were extremely dangerous. Had they not followed the RA, no collision would have occured.
Originally posted by bsieker
You also repeatedly ignore that fact, that they received the ATC order, and started manoeuvering according to it, before they received the RA. Meaning they never initiated a manoeuvre opposite the RA.
You also repeatedly ignore that fact, that they received the ATC order, and started manoeuvering according to it, before they received the RA. Meaning they never initiated a manoeuvre opposite the RA.
That means initiating or while following ATC instruction. Are you sure it is me who has a serious problem understanding words?
Originally posted by bsieker
And in case it got lost again: We do not advise not to follow an RA, even if you seem to think so.
And in case it got lost again: We do not advise not to follow an RA, even if you seem to think so.
Finally PBL...
For much of his posts now he just accuses me of being abusive. Once again Mr. Moderator, please let me know if this is so in your opinion and I will apologize. (edited later-the moderator has spoken)
PBL is correct on some things. I have never taken a data analysis course and don't plan to. I don't know what a confounding factor is. I know almost nothing about algorithms but do know how to spell it( and I think they can be used to solve a Rubik's Cube). I'm not even sure what perjorative means. Most pilots that I fly with don't know much about algorithms either. I'll ask around to see if many have taken a data analysis course.
But I do have something that much more important to a pilot than any of these things. I have common sense. One of the most important things a pilot can have. I hope this is not still tedious to you.
I also know, well, I suspect that there is no technical data or engineering facts on the relative safety manouvering visually around TCAS RA traffic at night. Just blind assumptions and we will never see any engineering facts unless it is somehow hastily created. I was accused of not answering a question. How the tables have turned.
So seeing as I agree that this dicussion isn't really going anywhere, why don't we end it. Perhaps a lock on the thread after bsieker lets us know if he would be willing to say "GPWS and stall warnings exluded, we recommend that pilots always follow the RA"
Last edited by punkalouver; 10th Dec 2007 at 00:25.
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Having decided the thread was moribund, and at the risk of starting another BS Fest, let me nevertheless point people to a worrying incident of which I was not aware, published by TwoOneFour on another thread:
http://www.pprune.org/forums/showpos...75&postcount=3
PBL
http://www.pprune.org/forums/showpos...75&postcount=3
PBL
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I have read of previous cases of an aircraft's TCAS giving itself an RA. Same thing, the RA traffic was colocated with the aircraft receiving the RA. Perhaps the equipment in the back, as the person posting suggests, was causing some sort of malfunction. There have been many reports over the years of electronic equipment causing interference with electronic equipment in aircraft especially claims by pilots that a cellphone left on interfered with nav equipment. Worrying indeed, however I would think the pilots still use their nav equipment for navigation and low instrument approaches as they were designed to be used.
The reality is that if the equipment is written up, it will either be released as ground checked serviceable, or perhaps replaced and checked as serviceable and put back in an aircraft.
Sorry if you have found this thread becoming tedious, I hope you have not instructed your two coworkers not to post here. I still would like to know if bsieker recommends pilots always follow an RA. I have given up on expecting any engineering facts on visual avoidance of aircraft but if you care to actually conduct an analysis, I am happy to give you some starting information.
This is from a Canadian accident report which references actual research on the subject.
http://www.tsb.gc.ca/en/reports/air/...8/a95h0008.asp
1.9.9 Pilot Avoidance Techniques
Assuming that a pilot will be capable of visually detecting another aircraft in flight and determining that the closing geometry represents a mid-air threat, then the final stage in the see-and-avoid sequence is to initiate an effective avoidance response. The aim of that response will be to increase the miss distance between the aircraft. The effectiveness of that response is dependent on a number of factors; in general, either pilot can alter the geometry of a collision by changing some combination of aircraft speed, altitude, and heading. Because each of these actions will affect the geometry differently, it is essential that the pilot choose an appropriate combination of actions that will merge to achieve a corresponding effect.<7>
The optimum avoidance response will differ depending on the time to impact. There is research evidence<8> to indicate that, outside 10 seconds to the point of closest approach, the pilot should use compatible manoeuvres combining speed, altitude, and heading change. However, once the aircraft are inside the range of approximately 10 seconds to impact, the pilot should employ an altitude change only. This conclusion is based on an argument that, when two aircraft are confined in close quarters, the essential action is to minimize the relative cross-sectional areas of each aircraft. Under these circumstances, it has been generally found that any application of bank will increase the relative cross- sectional area and thereby increase the probability of impact.<9>
As an example, a Piper Navajo aircraft similar to the one involved in this occurrence will have a vertical cross-section of approximately 13 feet when in level flight. At bank angles in the range of 45 to 60 degrees, the vertical cross-section will be in the range of 28 to 34 feet. The final value of the vertical cross-section will be dependent on the aircraft's wing span and on the applied bank angle.
An Australian study on midair collisions referenced this as well.
http://www.atsb.gov.au/publications/..._see_avoid.pdf
3.2 Evasive manoeuvre may increase collision risk
James Harris in his paper "Avoid, the unanalysed partner of see" focuses attention on the ‘avoid’ side of seeing and avoiding (Harris 1983). He stresses that an incorrect evasive manoeuvre may cause rather than prevent a collision. For example, in a head-on encounter, a bank may increase
the risk of a collision. Figure 17 illustrates this. In the top diagram, two (stylised) high-wing aircraft are approaching head-on with wings parallel. There is a limited number of ways in which the aircraft can collide if they maintain a wings-level attitude, and the area in which the
two aircraft can contact or the ‘collision cross-section’ is relatively small. However, if the pilots bank shortly before impact, as in the lower diagram, so that the aircraft approach each other with wings perpendicular, then there is a much larger collision cross section and consequently, a higher probability of a collision. This is not to suggest that banks are always inappropriate
evasive manoeuvres, but that in some cases, evasive action can be unsuccessful or even counterproductive. At least one foreign airline accident has been attributed to an unnecessary evasive manoeuvre (Civil Aeronautics Board 1966).
Yet the parts of James Harris study that I have seen do not even discuss the possibility of an evasive manouver by an aircraft being incorrect due to misjudged trajectories as would appear to have happened in the JAL and DHL cases. Perhaps you have considered this. If so please let us know.
If you need any more assistance, please don't hesitate to ask. I am happy to have been able to provide some information on this subject to those who are reading this thread.
The reality is that if the equipment is written up, it will either be released as ground checked serviceable, or perhaps replaced and checked as serviceable and put back in an aircraft.
Sorry if you have found this thread becoming tedious, I hope you have not instructed your two coworkers not to post here. I still would like to know if bsieker recommends pilots always follow an RA. I have given up on expecting any engineering facts on visual avoidance of aircraft but if you care to actually conduct an analysis, I am happy to give you some starting information.
This is from a Canadian accident report which references actual research on the subject.
http://www.tsb.gc.ca/en/reports/air/...8/a95h0008.asp
1.9.9 Pilot Avoidance Techniques
Assuming that a pilot will be capable of visually detecting another aircraft in flight and determining that the closing geometry represents a mid-air threat, then the final stage in the see-and-avoid sequence is to initiate an effective avoidance response. The aim of that response will be to increase the miss distance between the aircraft. The effectiveness of that response is dependent on a number of factors; in general, either pilot can alter the geometry of a collision by changing some combination of aircraft speed, altitude, and heading. Because each of these actions will affect the geometry differently, it is essential that the pilot choose an appropriate combination of actions that will merge to achieve a corresponding effect.<7>
The optimum avoidance response will differ depending on the time to impact. There is research evidence<8> to indicate that, outside 10 seconds to the point of closest approach, the pilot should use compatible manoeuvres combining speed, altitude, and heading change. However, once the aircraft are inside the range of approximately 10 seconds to impact, the pilot should employ an altitude change only. This conclusion is based on an argument that, when two aircraft are confined in close quarters, the essential action is to minimize the relative cross-sectional areas of each aircraft. Under these circumstances, it has been generally found that any application of bank will increase the relative cross- sectional area and thereby increase the probability of impact.<9>
As an example, a Piper Navajo aircraft similar to the one involved in this occurrence will have a vertical cross-section of approximately 13 feet when in level flight. At bank angles in the range of 45 to 60 degrees, the vertical cross-section will be in the range of 28 to 34 feet. The final value of the vertical cross-section will be dependent on the aircraft's wing span and on the applied bank angle.
An Australian study on midair collisions referenced this as well.
http://www.atsb.gov.au/publications/..._see_avoid.pdf
3.2 Evasive manoeuvre may increase collision risk
James Harris in his paper "Avoid, the unanalysed partner of see" focuses attention on the ‘avoid’ side of seeing and avoiding (Harris 1983). He stresses that an incorrect evasive manoeuvre may cause rather than prevent a collision. For example, in a head-on encounter, a bank may increase
the risk of a collision. Figure 17 illustrates this. In the top diagram, two (stylised) high-wing aircraft are approaching head-on with wings parallel. There is a limited number of ways in which the aircraft can collide if they maintain a wings-level attitude, and the area in which the
two aircraft can contact or the ‘collision cross-section’ is relatively small. However, if the pilots bank shortly before impact, as in the lower diagram, so that the aircraft approach each other with wings perpendicular, then there is a much larger collision cross section and consequently, a higher probability of a collision. This is not to suggest that banks are always inappropriate
evasive manoeuvres, but that in some cases, evasive action can be unsuccessful or even counterproductive. At least one foreign airline accident has been attributed to an unnecessary evasive manoeuvre (Civil Aeronautics Board 1966).
Yet the parts of James Harris study that I have seen do not even discuss the possibility of an evasive manouver by an aircraft being incorrect due to misjudged trajectories as would appear to have happened in the JAL and DHL cases. Perhaps you have considered this. If so please let us know.
If you need any more assistance, please don't hesitate to ask. I am happy to have been able to provide some information on this subject to those who are reading this thread.
Last edited by punkalouver; 9th Dec 2007 at 15:50.
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Upon closer examination, I have discovered some very interesting information about the supposed rational decision made that night over Germany by the TU-154 captain to descend in accordance with ATC instruction but contrary to the TCAS RA.
According to PBL, Bseiker and Bernd this was a rational decision by the TU-154 captain because ATC had advised mistakenly of traffic at 2 o'clock while the crew saw lights and TCAS traffic at 10 O'clock. Better to descend visually around the known and seen traffic at 10 o'clock than risking a collision with the reported yet unseen traffic at 2 O'clock(which in fact did not exist) according to these three posters from the University at Bielfeld.
This was the statement made by PBL in post # 20...
Please read my analysis of the decision problem presented to the Bakshirian crew at Überlingen. They were faced with an "intruder" at 10 o'clock which they saw, and an unknown conflict at 2 o'clock which they didn't see, and for which they had an advisory to descend (that is, he was at or above their altitude).
What would you do? Climb towards another conflicting aircraft that you don't see but ATC does? Or avoid him, descend towards an aircraft that you do see, and hope to avoid him using visual means?
Please give some good reasons for your answer that will also be good reasons for any other pilot in this situation.
In fact, the decision to ignore the RA was made at least 10 seconds before they were even given this mistaken traffic location by ATC. When this erronous information was given to the Tupolev crew they were already descending at 2,000 feet per minute. So when the decision was made to ignore the RA, in the Tupolev crew's mind there was only one other aircraft out there. See this link(pg 3) as well as final report.
http://www.casa.gov.au/fsa/2004/aug/22-29.pdf
Interestingly, the Tupolev crew in the very last seconds realized the TCAS was correct and did finally follow his RA with control column fully back and thrust levers fully forward. Much too late.
So then the logic comes out that TCAS was at fault because if it wasn't installed the accident would not have happened instead of the logical thought process of...If the equipment was used as designed and regulations followed, this accident would not have happened.
Of course these posters are not responding to several pertinant questions I have asked. This really makes me wonder about the accuracy of all posts and studies done by this group.
According to PBL, Bseiker and Bernd this was a rational decision by the TU-154 captain because ATC had advised mistakenly of traffic at 2 o'clock while the crew saw lights and TCAS traffic at 10 O'clock. Better to descend visually around the known and seen traffic at 10 o'clock than risking a collision with the reported yet unseen traffic at 2 O'clock(which in fact did not exist) according to these three posters from the University at Bielfeld.
This was the statement made by PBL in post # 20...
Please read my analysis of the decision problem presented to the Bakshirian crew at Überlingen. They were faced with an "intruder" at 10 o'clock which they saw, and an unknown conflict at 2 o'clock which they didn't see, and for which they had an advisory to descend (that is, he was at or above their altitude).
What would you do? Climb towards another conflicting aircraft that you don't see but ATC does? Or avoid him, descend towards an aircraft that you do see, and hope to avoid him using visual means?
Please give some good reasons for your answer that will also be good reasons for any other pilot in this situation.
In fact, the decision to ignore the RA was made at least 10 seconds before they were even given this mistaken traffic location by ATC. When this erronous information was given to the Tupolev crew they were already descending at 2,000 feet per minute. So when the decision was made to ignore the RA, in the Tupolev crew's mind there was only one other aircraft out there. See this link(pg 3) as well as final report.
http://www.casa.gov.au/fsa/2004/aug/22-29.pdf
Interestingly, the Tupolev crew in the very last seconds realized the TCAS was correct and did finally follow his RA with control column fully back and thrust levers fully forward. Much too late.
So then the logic comes out that TCAS was at fault because if it wasn't installed the accident would not have happened instead of the logical thought process of...If the equipment was used as designed and regulations followed, this accident would not have happened.
Of course these posters are not responding to several pertinant questions I have asked. This really makes me wonder about the accuracy of all posts and studies done by this group.
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As an update to the idea that it would at all be rational to ignore an RA at night with a high speed intruder, I have provided a link to the limitations of the see and avoid principle study published by the Austalian accident investigation board. I have quoted a reference to it by the NTSB
http://www.atsb.gov.au/publications/..._and_Avoid.pdf
You may notice that this detailed report has a section on page 22 titled Evasive manoeuvre may increase collision risk that references a crash that I posted about in post #48 of this thread which was later dismissed as a confused post.
I would say that for someone posing as an accident analyst promoting the idea that going against the RA and attempt to visually manouver around conflicting high speed traffic as a rational decision is dangerous. There is no study to back this up theory and as far as I can tell, is based on nothing except perhaps an unwillingness to admit that the original statement was in error.
There has never been a midair collision between two TCAS equipped and operating aircraft where the RA instructions were followed. Yet coordinated RA's occur frequently.
http://www.atsb.gov.au/publications/..._and_Avoid.pdf
The report also indicated that there was considerable data available that was against the reliance on see-and-avoid. Although see-and-avoid was often effective at low closing speeds, it usually failed to avert collisions at higher speeds. It was estimated that see-and-avoid prevents 97 percent of possible collisions at closing speeds of between 101 and 199 knots but only 47 percent when the closing speed is greater than 400 knots. In addition, the human visual system is better at detecting moving targets than stationary targets, yet in most cases, an aircraft on a collision course appears as a stationary target in the pilot's visual field.
An approaching aircraft, in many cases, presents a very small visual angle until a short time before impact. In addition, complex backgrounds such as ground features or clouds hamper the identification of aircraft via a visual effect known as 'contour interaction'. This occurs when background contours interact with the form of the aircraft, producing a less distinct image. The report continued by indicating that even when an approaching aircraft has been sighted, there is no guarantee that evasive action will be successful, as it takes a significant amount of time to recognize and respond to a collision threat.
An approaching aircraft, in many cases, presents a very small visual angle until a short time before impact. In addition, complex backgrounds such as ground features or clouds hamper the identification of aircraft via a visual effect known as 'contour interaction'. This occurs when background contours interact with the form of the aircraft, producing a less distinct image. The report continued by indicating that even when an approaching aircraft has been sighted, there is no guarantee that evasive action will be successful, as it takes a significant amount of time to recognize and respond to a collision threat.
I would say that for someone posing as an accident analyst promoting the idea that going against the RA and attempt to visually manouver around conflicting high speed traffic as a rational decision is dangerous. There is no study to back this up theory and as far as I can tell, is based on nothing except perhaps an unwillingness to admit that the original statement was in error.
There has never been a midair collision between two TCAS equipped and operating aircraft where the RA instructions were followed. Yet coordinated RA's occur frequently.
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IEEE Spectrum Blog series on Midair Collisions and TCAS, by PBL
The IEEE runs a series of blogs associated with Spectrum. Prof. Peter Ladkin (PBL) is a guest blogger on the Risk Factor blog written by Robert Charette.
TCAS has been in the news again recently. In August, David Kaminski-Morrow of Flight International reported on a recommendation by Eurocontrol to implement change proposals CP112E and CP115 ASAP. These changes were approved in Spring 2008 in DO-185B, the RTCA document which defines the TCAS standard.
Aimee Turner of Flight International reported recently that the European Commission, in answer to a question tabled by a Euro-MP, has expressed its intent to mandate the new standard through EASA quickly.
PBL has been asked by Bob Charette to comment on an article from the Wall Street Journal, by Andy Pasztor, about an increase in perceived traffic conflicts in the U.S. and Europe, saying that "safety experts" agree that traffic growth is a major factor.
The first two installments appeared yesterday:
Part I and Part II.
The first part discusses some issues, and gives links to the Flight International articles on flightglobal.com. The second part is a short history of the U.S. air safety measures prompted by midair collisions involving commercial transport aircraft, which ended with Congress mandating TCAS installation in the commercial fleet.
Bernd
TCAS has been in the news again recently. In August, David Kaminski-Morrow of Flight International reported on a recommendation by Eurocontrol to implement change proposals CP112E and CP115 ASAP. These changes were approved in Spring 2008 in DO-185B, the RTCA document which defines the TCAS standard.
Aimee Turner of Flight International reported recently that the European Commission, in answer to a question tabled by a Euro-MP, has expressed its intent to mandate the new standard through EASA quickly.
PBL has been asked by Bob Charette to comment on an article from the Wall Street Journal, by Andy Pasztor, about an increase in perceived traffic conflicts in the U.S. and Europe, saying that "safety experts" agree that traffic growth is a major factor.
The first two installments appeared yesterday:
Part I and Part II.
The first part discusses some issues, and gives links to the Flight International articles on flightglobal.com. The second part is a short history of the U.S. air safety measures prompted by midair collisions involving commercial transport aircraft, which ended with Congress mandating TCAS installation in the commercial fleet.
Bernd
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"TCAS sometimes causes problems. A reported airprox (an event in which two aircraft come too close to each other) over Trasadingen in Switzerland in 2000 was triggered through excessive pilot reactions to TCAS advisories (it is an advisory system: any responsive actions are still human), and the report has just come out about an incident on 16 November 2006 over South Korea, in which the pilot's maneuver in response to an advisory was violent enough to injure 20 people on board his aircraft, four of them seriously. (Anecdotes and reports abound of “excessive” reactions.)"
That is not TCAS causing problems, that is pilots causing problems by not following proper procedures just like in the midair over Germany. In that midair and in the excessive manouvering incidents, TCAS worked as advertised.
That is not TCAS causing problems, that is pilots causing problems by not following proper procedures just like in the midair over Germany. In that midair and in the excessive manouvering incidents, TCAS worked as advertised.
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punkalouver,
1/ Yes, TCAS was a causal factor, because, by the simple counterfactual test, had TCAS not been installed and working, there would have been no incident.
2/ Yes, there is a problem with TCAS.
So, it worked "as advertised". More precisely, it was found that it worked as specified. (Advertising is quite a different matter ...)
And that tells us that the problem is not so much an implementation problem. For all we know the implementation is adequate with respect to the specification. But, as we've been saying for years, there are problems with the specifications, as they do not (always) serve the intended purpose.
See Ueberlingen, where no reversal RA was given, although both aircraft were still closing. A modification to the specification addressing this specific problem is finally being mandated (CP112E, which, in an earlier form without the "E" (extended) has been on the table since before Ueberlingen).
This is old news. And this is a problem with only the technical part of TCAS. The wider implications of the entire socio-technical system TCAS/Flight Crews/ATC have been discussed at length in this and other threads.
'nuf said.
Bernd
1/ Yes, TCAS was a causal factor, because, by the simple counterfactual test, had TCAS not been installed and working, there would have been no incident.
2/ Yes, there is a problem with TCAS.
So, it worked "as advertised". More precisely, it was found that it worked as specified. (Advertising is quite a different matter ...)
And that tells us that the problem is not so much an implementation problem. For all we know the implementation is adequate with respect to the specification. But, as we've been saying for years, there are problems with the specifications, as they do not (always) serve the intended purpose.
See Ueberlingen, where no reversal RA was given, although both aircraft were still closing. A modification to the specification addressing this specific problem is finally being mandated (CP112E, which, in an earlier form without the "E" (extended) has been on the table since before Ueberlingen).
This is old news. And this is a problem with only the technical part of TCAS. The wider implications of the entire socio-technical system TCAS/Flight Crews/ATC have been discussed at length in this and other threads.
'nuf said.
Bernd