TAM A320 crash at Congonhas, Brazil
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Rob21,
I think the question came up before, and it seemed that no-one was quite sure, but probably the EPR reading is unreliable when the reverser doors are deployed.
Airbus noted in the appendix of the Taipei-Sungshan-Report something to the effect that to give accurate thrust figures, N1 would be required, which was not recorded.
Bernd
I think the question came up before, and it seemed that no-one was quite sure, but probably the EPR reading is unreliable when the reverser doors are deployed.
Airbus noted in the appendix of the Taipei-Sungshan-Report something to the effect that to give accurate thrust figures, N1 would be required, which was not recorded.
Bernd
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So, OK, there is a prioritisation with an explicit selection criterion. The selection criterion is that a causal factor is prioritised because of what's on a piece of paper.
It is a semantics discussion here. Honestly I think we will get nothing from it.
So let's change the focus: Would you recomend longer runways for the A320 in the PR-MBK accident report ?
We both agree that a longer runway would probably save the day...
Or would you address the TL above idle question only ?
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Airbus noted in the appendix of the Taipei-Sungshan-Report something to the effect that to give accurate thrust figures, N1 would be required, which was not recorded.
I searched a little bit and found something about EPR and ETR being key to find actual thrust. But it demands some calculation.
Why isn't it recorded in the FDR ? How do pilots know (if they know) what is the actual thrust they get from the engines ?
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Originally Posted by flyingnewbie10
How do pilots know (if they know) what is the actual thrust they get from the engines ?
Only analysts such as ourselves might require a physical thrust figure to gauge brake efficiency, etc.
Bernd
A significant argument for keeping this thread open is to enable others to gain an insight to the range of views, attitudes, beliefs (mis-beliefs), and biases expressed by the contributors.
Based on some responses from claimed pilots or professionals, any regulatory authority would have to be concerned about the apparent low levels of technical knowledge, not only for specific aircraft types but aviation safety in general. Also, the range attitudes, communication style, analysis, and ideas could be dismaying for the CRM community, where training to improve these issues is a cornerstone of safety.
Alternatively it is rewarding to find a high level of informed debate and expertise from which we can learn, and develop and improve our safety defences, either as individuals or organisations. I much prefer to say ‘I didn’t know that’; then privately seek the evidence on which to base my judgement and future belief (subject to my understanding of the situation).
For those who wish to close the discussion or leave the thread, their wishes might reflect a false belief or bias. Is their request an indication of ‘it couldn’t happen to me’, because ‘I’ have made my mind up – failing to consider all of the information, explore all options, including learning from other’s misfortune.
Often accident reports have similar shortcomings and may not fully consider the practical aspects of implementing safety defences. Formal reports are written for authorities or governments and may be restrained from meaningful speculation and debate. This thread sets a new standard in these areas; one which the formal-reporting processes should take note of. There may be more to be learnt about the state of safety in our industry and the need for practical safety defences from the content of this thread than will ever be published in a final report; but then I should not prejudge that, wait and see.
For the unconvinced lurkers, remember that many of the human factor contributions in this accident appear to originated from the central L Liveware (human) in the SHELL model, and may have involved poor knowledge, mis-belief, bias, and problematic communication.
Also, any external contribution to the accident from the surrounding SHEL elements will interface with the central Liveware. The recent themed discussions of ‘cause’, being either human (L) or aircraft (H), might benefit from balancing these views with other eternal elements such as software (procedures, rules, etc), other people (management and NFP) and the environment (organisations as well as the weather/runway). Finally, remember that all of the arms of the SHELL model are formed from an external element (the situation) and the central human, and an interface between them, which in many systems is the weakest point.
Can the ‘Why–Because’ group map their thoughts to SHELL?
Based on some responses from claimed pilots or professionals, any regulatory authority would have to be concerned about the apparent low levels of technical knowledge, not only for specific aircraft types but aviation safety in general. Also, the range attitudes, communication style, analysis, and ideas could be dismaying for the CRM community, where training to improve these issues is a cornerstone of safety.
Alternatively it is rewarding to find a high level of informed debate and expertise from which we can learn, and develop and improve our safety defences, either as individuals or organisations. I much prefer to say ‘I didn’t know that’; then privately seek the evidence on which to base my judgement and future belief (subject to my understanding of the situation).
For those who wish to close the discussion or leave the thread, their wishes might reflect a false belief or bias. Is their request an indication of ‘it couldn’t happen to me’, because ‘I’ have made my mind up – failing to consider all of the information, explore all options, including learning from other’s misfortune.
Often accident reports have similar shortcomings and may not fully consider the practical aspects of implementing safety defences. Formal reports are written for authorities or governments and may be restrained from meaningful speculation and debate. This thread sets a new standard in these areas; one which the formal-reporting processes should take note of. There may be more to be learnt about the state of safety in our industry and the need for practical safety defences from the content of this thread than will ever be published in a final report; but then I should not prejudge that, wait and see.
For the unconvinced lurkers, remember that many of the human factor contributions in this accident appear to originated from the central L Liveware (human) in the SHELL model, and may have involved poor knowledge, mis-belief, bias, and problematic communication.
Also, any external contribution to the accident from the surrounding SHEL elements will interface with the central Liveware. The recent themed discussions of ‘cause’, being either human (L) or aircraft (H), might benefit from balancing these views with other eternal elements such as software (procedures, rules, etc), other people (management and NFP) and the environment (organisations as well as the weather/runway). Finally, remember that all of the arms of the SHELL model are formed from an external element (the situation) and the central human, and an interface between them, which in many systems is the weakest point.
Can the ‘Why–Because’ group map their thoughts to SHELL?
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Thanks for #2221, Bernd, I guess we've mended some fences. 
Maybe I'm being unduly cynical, Bernd, but I'm not in the least surprised that there isn't much information. The regulators and the manufacturer will eventually have to explain, as best they can, why more decisive action was not taken following the clear warning contained in the (to my mind, admirable) Taiwanese report on Taipei. But that will not happen for years, during the relatives' lawsuits etc. - in the meantime it is not in their interests to discuss the matter. That's 'the way of the world,' I'm not complaining about it.
That's probably the difference between us. My own analytical technique (as befits someone of my advanced age!) tends very much to be based on Rudyard Kipling's poem:-
"I keep six honest serving-men
(They taught me all I knew);
Their names are What and Why and When
And How and Where and Who."
Obviously one has to keep an open mind and be prepared to modify one's views when (if?) additional information becomes available. But on present evidence my views are:-
1. Had the ground spoilers and brakes operated as intended the overwhelming probability is that the aeroplane would have landed normally.
2. However, for whatever reason, one TL was not retarded.
3. The consequences were that the ground spoilers did not deploy and the autobrakes did not operate.
4. The pilots did not realise (and were not warned) that the problem was the wrongly-positioned TL, and therefore reacted by thinking that they were facing a spoiler and/or brakes malfunction.
As far as I'm concerned those factors (especially the fact that the pilots did not recognise and immediately rectify the initial problem) made an incident/accident of some sort virtually certain.
Other factors, such as darkness, poor weather/visibility, the ungrooved, wet, minimum-length runway, etc., almost certainly contributed to the severity of the accident. But, IMO, on present evidence, either singly or in combination, they cannot be said in any sense to have CAUSED it.
About your WBA, I read it with interest when it first appeared on here. I think it might be better if it started at an earlier point - specifically at the commencement of the flare (which any pilot will tell you is the beginning, and the foundation, of any landing) rather than at touchdown. There are some clues in the CVR transcript, around that time, that maybe shed a little light on the circumstances (particularly the pilots' likely priorities/pre-occupations) during the flare and touchdown. Happy to expand on those if you wish?
Tony
Originally Posted by bsieker
I thought it might be a good idea, but the information on it, apart from what you quoted, is sketchy. And PBL tried quite hard to find something more substantial.
The regulators and the manufacturer will eventually have to explain, as best they can, why more decisive action was not taken following the clear warning contained in the (to my mind, admirable) Taiwanese report on Taipei. But that will not happen for years, during the relatives' lawsuits etc. - in the meantime it is not in their interests to discuss the matter. That's 'the way of the world,' I'm not complaining about it.
Originally Posted by bsieker
So my point was trying to show that one should not prioritise
"I keep six honest serving-men
(They taught me all I knew);
Their names are What and Why and When
And How and Where and Who."
Obviously one has to keep an open mind and be prepared to modify one's views when (if?) additional information becomes available. But on present evidence my views are:-
1. Had the ground spoilers and brakes operated as intended the overwhelming probability is that the aeroplane would have landed normally.
2. However, for whatever reason, one TL was not retarded.
3. The consequences were that the ground spoilers did not deploy and the autobrakes did not operate.
4. The pilots did not realise (and were not warned) that the problem was the wrongly-positioned TL, and therefore reacted by thinking that they were facing a spoiler and/or brakes malfunction.
As far as I'm concerned those factors (especially the fact that the pilots did not recognise and immediately rectify the initial problem) made an incident/accident of some sort virtually certain.
Other factors, such as darkness, poor weather/visibility, the ungrooved, wet, minimum-length runway, etc., almost certainly contributed to the severity of the accident. But, IMO, on present evidence, either singly or in combination, they cannot be said in any sense to have CAUSED it.
About your WBA, I read it with interest when it first appeared on here. I think it might be better if it started at an earlier point - specifically at the commencement of the flare (which any pilot will tell you is the beginning, and the foundation, of any landing) rather than at touchdown. There are some clues in the CVR transcript, around that time, that maybe shed a little light on the circumstances (particularly the pilots' likely priorities/pre-occupations) during the flare and touchdown. Happy to expand on those if you wish?
Tony
Last edited by RWA; 16th Sep 2007 at 06:11. Reason: mistype
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Some sane words from alf once again.
Yes, more or less.
The SHELL "model", like Hopkins's Accimaps, is an attempt to classify factors into broad groups. Unlike Accimaps, there is some model of "how things happen" behind it. For pure classification, all one has to do is classify the factors in the WB-Graph, and we will shortly have SW that will display classifications. We have been aware of the value of classification for some explanations ever since Ernesto de Stefano's WBA of the Ladbroke Grove rail accident in 2002, at that time the largest WBG that had been put together (somewhat over 90 factors). But unfortunately the layout engine we prefer did not until recently have a layout for classified graphs that we liked along with an interface we could use.
In so far as a given "model" forces a specific architecture for "how accidents happen" ("the X-bone's connected to the Y-bone"-type explanations), then WBA remains neutral, because the Counterfactual Test is a model-neutral test for causality. A study in 2003 by our collaborators at the rail institude in Braunschweig compared a WBA of a rail accident with a model-based analysis, and showed that about one third of the factors in the model-based analysis did not actually occur in the WBG. See Brinkmann/Lemke at
http://www.tu-braunschweig.de/ifev/v...bieleschweig2/
In other words, these factors were introduced by pure theory, rather than being necessary causal factors in the causal net.
I also performed a comparison in 2005 of Hopkins's analysis of the Glenbrook rail accident in NSW with a WBA, with the graphs reproduced more readably in
http://http://www.rvs.uni-bielefeld....ookFigures.pdf
I am somewhat wary of the "extra baggage" that using a specific model brings with it, in so far as it goes beyond a certain purposeful classification of factors, and I prefer to allow, even aid, but not force, such classifications on top of the pure causality as determined by the Counterfactual Test.
PBL
Originally Posted by alf5071h
Can the ‘Why–Because’ group map their thoughts to SHELL?
The SHELL "model", like Hopkins's Accimaps, is an attempt to classify factors into broad groups. Unlike Accimaps, there is some model of "how things happen" behind it. For pure classification, all one has to do is classify the factors in the WB-Graph, and we will shortly have SW that will display classifications. We have been aware of the value of classification for some explanations ever since Ernesto de Stefano's WBA of the Ladbroke Grove rail accident in 2002, at that time the largest WBG that had been put together (somewhat over 90 factors). But unfortunately the layout engine we prefer did not until recently have a layout for classified graphs that we liked along with an interface we could use.
In so far as a given "model" forces a specific architecture for "how accidents happen" ("the X-bone's connected to the Y-bone"-type explanations), then WBA remains neutral, because the Counterfactual Test is a model-neutral test for causality. A study in 2003 by our collaborators at the rail institude in Braunschweig compared a WBA of a rail accident with a model-based analysis, and showed that about one third of the factors in the model-based analysis did not actually occur in the WBG. See Brinkmann/Lemke at
http://www.tu-braunschweig.de/ifev/v...bieleschweig2/
In other words, these factors were introduced by pure theory, rather than being necessary causal factors in the causal net.
I also performed a comparison in 2005 of Hopkins's analysis of the Glenbrook rail accident in NSW with a WBA, with the graphs reproduced more readably in
http://http://www.rvs.uni-bielefeld....ookFigures.pdf
I am somewhat wary of the "extra baggage" that using a specific model brings with it, in so far as it goes beyond a certain purposeful classification of factors, and I prefer to allow, even aid, but not force, such classifications on top of the pure causality as determined by the Counterfactual Test.
PBL
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Perhaps some enjoy the theoretical treadmill, that I am not so sure this thread has not become some time ago. Yet at some point the scenery must surely become a bore.
Perhaps perpetuity is a purpose in itself, perhaps the scenery is reflective.
I shall now conclude and leave you to it. Oops, did I just use a dirty word? How naughty of me.
Perhaps perpetuity is a purpose in itself, perhaps the scenery is reflective.
I shall now conclude and leave you to it. Oops, did I just use a dirty word? How naughty of me.
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Tony,
you suggested prioritising causes based on the availability of countermeasures. Now I think you are introducing a more subtle variation, namely prioritising countermeasures based on (say) previous rates of occurence.
So, for example, you might argue (I think you do):
* the phenomenon (mismatched TL) has happened twice before, leading to accidents
* a potential fix has been identified
your conclusion: prioritise this cause.
But there is no guarantee that this selection criterion leads to a unique selection (which you want: as you said, there can be only one "primary" cause).
In fact, the runway length issue fits the same criteria:
* overruns have happened there before (as recently as a year ago)
* a potential fix has been identified (actually, many:
- Shorten the runway and add an ERSA, maybe EMAS
- Require 2 REV OP as at Santos Dumont
- establish precise SOPs for landing at CGH
- use the Rwy only when dry)
So you haven't yet arrived at criteria which would ensure a unique selection.
I think this is indisputable. The WBA is incomplete. Issues of training and establishment of SOPs, basic organisational issues at the airline for example, have not been addressed, because we don't know anything about those yet. Similarly there are issues about the use of the runway at CGH which arose in a legal-regulatory context earlier in the year (as reported by marciovp) whose history is not yet completely clear. I think it inevitable that these organisational and regulatory factors will appear at some point in the WBG. These are the kinds of things that ideally a thorough investigation should identify.
PBL
you suggested prioritising causes based on the availability of countermeasures. Now I think you are introducing a more subtle variation, namely prioritising countermeasures based on (say) previous rates of occurence.
So, for example, you might argue (I think you do):
* the phenomenon (mismatched TL) has happened twice before, leading to accidents
* a potential fix has been identified
your conclusion: prioritise this cause.
But there is no guarantee that this selection criterion leads to a unique selection (which you want: as you said, there can be only one "primary" cause).
In fact, the runway length issue fits the same criteria:
* overruns have happened there before (as recently as a year ago)
* a potential fix has been identified (actually, many:
- Shorten the runway and add an ERSA, maybe EMAS
- Require 2 REV OP as at Santos Dumont
- establish precise SOPs for landing at CGH
- use the Rwy only when dry)
So you haven't yet arrived at criteria which would ensure a unique selection.
Originally Posted by RWA
I think it might be better if [the WBA] started at an earlier point
PBL
Paxing All Over The World
non-pilot speaking
I-FORD
PBL said
So, until the software mod is confirmed as available and implemented by the carriers on all their machines ... training (HF) gets priority?
I-FORD
There have been other events of runway excursion involving A320 in a single reverse configuration.
Same airplane, different runways.
To me the airplane gets priority.
Same airplane, different runways.
To me the airplane gets priority.
And the H2F3 SB, which describes new features in the release, contains not one word about such a warning. I don't think we are anywhere near a final coherent story about the mod yet.
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Bernd,
Do you have a WBA on the Taipei incident/accident?
IMHO, it would be very interesting to see an "overlay" of both maps.
Once I saw an overlay (or comparison) of two distinct operational situations (non aviation) PERT/CPM maps. It helped developing a procedure to "bypass" (on the map) a problem area.
Do you have a WBA on the Taipei incident/accident?
IMHO, it would be very interesting to see an "overlay" of both maps.
Once I saw an overlay (or comparison) of two distinct operational situations (non aviation) PERT/CPM maps. It helped developing a procedure to "bypass" (on the map) a problem area.
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PBL, how do you define "primary cause"? For in this accident, there may be many different factors that cumulatively added up to disaster... take away even one of them, the accident doesn't happen.
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Originally Posted by PBL
you suggested prioritising causes based on the availability of countermeasures. Now I think you are introducing a more subtle variation, namely prioritising countermeasures based on (say) previous rates of occurence.
Trying once more - I am of the opinion that one TL being left out of the 'Idle' position caused the accident, because (besides resulting in substantial forward thrust which cancelled out the effect of reverse thrust on the No. 1 engine) it ALSO ensured that neither the ground spoilers nor the autobrakes deployed. Further (because of the lack of any warning system as to one TL not having been fully retarded) the pilots were left confused as to what had gone wrong - for the vital few seconds which sadly proved to be all the time they had left to live.......
Just to get it straight - what IS your opinion? It APPEARS to be that, because the runway was 'only' 6,500 feet long, the accident would have happened anyway?
Is that correct?
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Originally Posted by RobertS975
PBL, how do you define "primary cause"?
Originally Posted by RobertS975
For in this accident, there may be many different factors that cumulatively added up to disaster... take away even one of them, the accident doesn't happen.
PBL
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Originally Posted by flyingnewbie10
How do pilots know (if they know) what is the actual thrust they get from the engines ?
Never sat up front in an Airbus - in fact, never FLOWN in an Airbus, there aren't many in service in Australia - but as far as I know N1 remains the normal guide. The only difference is that the non-moving throttle lever positions will not of course match the auto power settings. I believe, from talking to pilots, that that problem is solved by having lights (known as 'donuts') on the N1 gauge, one showing the autothrust setting and the other the lever position.
I gather that normal procedure on an Airbus is to move the appropriate (lever position) 'donut' to match the auto one before disengaging autothrust; this avoids any risk of a 'thrust bump' because the lever position doesn't match the auto setting.
Pro pilots, if I'm wrong in any of that, please put me right?
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Originally Posted by RWA
But in your case I find it impossible to find anything to say, because nothing you say in reply to me seems to have any relevance to what I have posted.
This is really pretty simple. You are selecting a cause from amongst the many causal factors of this accident, and you are calling it "primary". I am trying to get you to give me the criterion under which you select that one cause, in such a way that I can reasonably apply that criterion to other accidents also.
So far, you haven't given me one that
* identifies a single factor (rather than, equally, two or three) from amongst the many in this accident
* is somehow justified by causality alone, rather than by (say) social considerations, or political considerations or some such.
So you propose, I reply. And it seems you are getting frustrated. I am not surprised. I have been working on this issue professionally for quite a while and know my way around it; if you haven't similarly, then you are on a learning curve. We may meet on it after a while. Or you may hit the jackpot and come up with a criterion which seems to work for all relevant cases, and which we can then distribute to ICAO, and Transport Canada, the ATSB, the AAIB, and all those other institutions who have given up on identifying one "primary cause" as being largely misleading, and almost certainly unhelpful for prophylaxis.
Originally Posted by RWA
Trying once more - I am of the opinion that one TL being left out of the 'Idle' position caused the accident, because ................
Just to get it straight - what IS your opinion?
Just to get it straight - what IS your opinion?
PBL
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Thanks for the considered discussion from all contributors.. I am getting a great deal of info from this thread, despite its occasional detours. As a novice PPL I am trying to learn as much as possible about human factors, technology interfaces, etc. This accident seems to be involving many of these things simultaneously. Back to lurking mode....
Last edited by averow; 16th Sep 2007 at 15:43.
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I suppose they don't need to know the actual thrust in kN. Just if more or less than currently set is needed. And they get accurate indications about the effects of thrust and thrust changes, in particular vertical speed and air speed and speed trend.
Only analysts such as ourselves might require a physical thrust figure to gauge brake efficiency, etc.
Only analysts such as ourselves might require a physical thrust figure to gauge brake efficiency, etc.
Rob21;
Interstingly, I think you answered your own question. EPR is a ratio, not a rate. Ergo, it varies with conditions beyond those strictly influencing power generation such as RPM, fuel flow etc. A given TLA therefore cannot at the same time be "equated" with EPR and power generated. One cannot easily reverse-engineer EPR and this is why the thread is having some difficulty with the concept of deriving "power" (in terms of force exerted) from EPR. "EPR settings" are always driven by operational circumstance and outside pressure/temperature conditions, (the aforementioned Density Altitude). One would need to know the conditions under which varying EPR readings were recorded before knowing what power was being developed. See my response to Flyingnewbie10 below.
Bernd, enjoying your posts and your approach throughout... Looking forward to the paper. In re
. Reversers may or may not influence EPR readings but probably not, at least in a direct (varying interference = varying readings = unreliable readings) way. That said, the initial EPR "bloom" could have resulted from this - I don't know.
In the last century, we flew the DC8 (40 series through 63 series) and the DC9 on EPR, (I think the CFM-56 installation on the 71/73 series was N1), and we also set reverse thrust on EPR. There may have been certification corrections for the setting of reverse using EPR but that would be an engineering matter not a pilot matter. The A330 (Trent installation) uses EPR but the CFM56 340 installation uses N1.
Flyingnewbie10, re,
Not sure what you found but the following link is useful:
http://www.grc.nasa.gov/WWW/K-12/airplane/epr.html .
You are correct in stating that deriving power produced from EPR demands a little calculation.
In response to your questions, EPR, like hundreds of other parameters are indeed recorded on DFDRs as would N1, N2, (N3), fuel flow, EGT, N1/N2/(N3) vibration levels etc. It would be part of a legal (certified/required) parameter set. Flight Data Analysis (FDA) QARs (Quick Access Recorders) generally record far more parameters (in the thousands), at rates (per second) which can exceed regulated data-capture rates for DFDRs. However, QARs are not crash-protected.
In reference to N1, it would have been nice to have had the parameter in the TAM traces so we could see what the N1 was doing during the EPR 1.3 "bloom" as reverse was selected. The fuel flow doesn't change so we could assume neither did the N1 and the "bloom" may mean less than first appears.
Regarding your question about pilots knowing what the actual thrust they are getting from their engines is, this is approaching the issue in reverse, if you will. Pilots do not think in terms of "needing nnnnnn pounds/Kn of thrust" and then determine the EPR to get said thrust. EPR settings for takeoff, climb, cruise, approach and reverse on landing were, before the introduction of FADEC, set by reading a chart, usually a quick-reference card on the flight deck. The altitude and temperature were cross-referenced and an EPR power setting was read for the combination of same. For any given conditions outside the engine, the power developed either stayed the same (roughly) and the EPR changed with altitude, or it sometimes varied, keeping the EPR the same but varying power, (as in the MCT - maximum continuous thrust) case. Power settings using EPR representing a ratio of internal pressures to outside pressures and that is why the setting can vary with the same power being developed.
Appropos the above point regarding thrust developed then, knowing what power the engine(s) is/are developing, is immaterial. Knowing Kn or pounds is not as important as knowing that a referenced and selected setting, be it N1 or EPR, is "sufficient" for the conditions encountered in any one regime of flight. Whether 95% N1 or 1.3EPR is developing 9000lbs of thrust or 95,000lbs, (423 kN) is less important than knowing that the setting is "by the book" and can be expected to deliver on it's design certification "promise"... . After all, do we need to know that the engine under the hood delivers 230hp? We only need to know that it has (or hasn't) sufficient power to do the job in all operational circumstances and that, in the case of aviation, both our training and experience support a high degree of confidence "in the numbers".
PJ2
I am not talking about engine performance (density altitude), I am just wondering if EPR shouldn't be a result of a given TLA...
Bernd, enjoying your posts and your approach throughout... Looking forward to the paper. In re
but probably the EPR reading is unreliable when the reverser doors are deployed.
In the last century
, we flew the DC8 (40 series through 63 series) and the DC9 on EPR, (I think the CFM-56 installation on the 71/73 series was N1), and we also set reverse thrust on EPR. There may have been certification corrections for the setting of reverse using EPR but that would be an engineering matter not a pilot matter. The A330 (Trent installation) uses EPR but the CFM56 340 installation uses N1.Flyingnewbie10, re,
I searched a little bit and found something about EPR and ETR being key to find actual thrust. But it demands some calculation.
Why isn't it recorded in the FDR ? How do pilots know (if they know) what is the actual thrust they get from the engines ?
Why isn't it recorded in the FDR ? How do pilots know (if they know) what is the actual thrust they get from the engines ?
http://www.grc.nasa.gov/WWW/K-12/airplane/epr.html .
You are correct in stating that deriving power produced from EPR demands a little calculation.
In response to your questions, EPR, like hundreds of other parameters are indeed recorded on DFDRs as would N1, N2, (N3), fuel flow, EGT, N1/N2/(N3) vibration levels etc. It would be part of a legal (certified/required) parameter set. Flight Data Analysis (FDA) QARs (Quick Access Recorders) generally record far more parameters (in the thousands), at rates (per second) which can exceed regulated data-capture rates for DFDRs. However, QARs are not crash-protected.
In reference to N1, it would have been nice to have had the parameter in the TAM traces so we could see what the N1 was doing during the EPR 1.3 "bloom" as reverse was selected. The fuel flow doesn't change so we could assume neither did the N1 and the "bloom" may mean less than first appears.
Regarding your question about pilots knowing what the actual thrust they are getting from their engines is, this is approaching the issue in reverse, if you will. Pilots do not think in terms of "needing nnnnnn pounds/Kn of thrust" and then determine the EPR to get said thrust. EPR settings for takeoff, climb, cruise, approach and reverse on landing were, before the introduction of FADEC, set by reading a chart, usually a quick-reference card on the flight deck. The altitude and temperature were cross-referenced and an EPR power setting was read for the combination of same. For any given conditions outside the engine, the power developed either stayed the same (roughly) and the EPR changed with altitude, or it sometimes varied, keeping the EPR the same but varying power, (as in the MCT - maximum continuous thrust) case. Power settings using EPR representing a ratio of internal pressures to outside pressures and that is why the setting can vary with the same power being developed.
Appropos the above point regarding thrust developed then, knowing what power the engine(s) is/are developing, is immaterial. Knowing Kn or pounds is not as important as knowing that a referenced and selected setting, be it N1 or EPR, is "sufficient" for the conditions encountered in any one regime of flight. Whether 95% N1 or 1.3EPR is developing 9000lbs of thrust or 95,000lbs, (423 kN) is less important than knowing that the setting is "by the book" and can be expected to deliver on it's design certification "promise"... . After all, do we need to know that the engine under the hood delivers 230hp? We only need to know that it has (or hasn't) sufficient power to do the job in all operational circumstances and that, in the case of aviation, both our training and experience support a high degree of confidence "in the numbers".
PJ2
