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uncle_maxwell
February 02, 2025, 16:12:00 GMT
permalink Post: 11819886

TCAS enhancement?

Instead of no RA below 500ft (or whatever the floor is), how about telling one conflict to climb and the other one to \x91not climb\x92? \x91Not climb\x92 could then be understood (and trained) to mean \x91descend a little, terrain/aircraft/wx permitting or fly level\x92. Lots of ifs and buts, spurious warnings, limitations for when 3 or more conflicts, TCAS vs. GPWS considerations etc. but perhaps worth a thought.

Subjects TCAS (All)

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uncle_maxwell
February 02, 2025, 16:54:00 GMT
permalink Post: 11819920

Quote:

Originally Posted by SAR Bloke

I know I'm fighting a losing battle but here goes.....

What you are doing wrong is making guesses based on incomplete/inaccurate data that is in the public domain.

Assuming the NTSB figure of 375ft is correct, you still need more info for it to mean anything. Was that the AGL, AMSL or SPS height/altitude?
How accurate are the 'various plots' that indicate the collision occurred mid-river? They may be right; they may not be.
Was the CRJ on final or was it still positioning to final? If it wasn't on final then the trigonometric calculations of what height it should be at might not be correct.
What official evidence is there that the Blackhawk made a 45 degree turn, or could that be a data error in the publicly available information?

In summary what I am saying is that, despite all of the internet sleuths plotting tracking data, none of it is official and it is all subject to various errors. Whilst interesting to form an understanding of the circumstances, it can't be assumed to be accurate to within a few feet (vertically or laterally).

That 1-2 feet error would be a theoretical accuracy. The readout in the cockpit would be subject to significant errors during turns/pitch changes etc; without knowing the exact installation on a Blackhawk, it might also unlock based on the surface conditions. More importantly, the ATC instructions would probably be based on an altimeter setting and not Rad Alt.

How would that have worked in this scenario? Who do you think should have been directed by TCAS to do what? Does the Blackhawk even have TCAS?

It could have instructed the CRJ to climb (meaning initiate go-around immediately) and the heli to \x91not climb\x92 (meaning descend if practicable). Or it could have instructed heli to climb and CRJ to not climb (meaning continue descent or level and look out). I am saying that tech is there in principle and the 500ft RA floor was decided on 20-30y ago, probably to limit complexity and risk of dangerous RAs, but that this limitation could be revisited in future, especially with lots more data and modelling capability to assess.

Subjects ATC Blackhawk (H-60) CRJ NTSB TCAS (All) TCAS RA

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uncle_maxwell
February 02, 2025, 18:05:00 GMT
permalink Post: 11819971

Quote:

Originally Posted by fdr

TCAS RA have inhibits at low altitude, or do you have some other system in mind?

I know it is inhibited. I am saying that the concept of TCAS can be enhanced such that RAs are possible below 500ft without instructing one of the conflicting parties to fly into terrain. It may be worth looking at for safety engineers.

Subjects TCAS (All) TCAS RA

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uncle_maxwell
February 02, 2025, 19:00:00 GMT
permalink Post: 11820010

Quote:

Originally Posted by SAR Bloke

Do you honestly think that you've just thought of that and the system designers haven't?

In relation to your earlier response to my previous comment, how can the system tell someone to 'remain level' when that aircraft doesn't have TCAS? I am not sure of the Blackhawk fit, but I would be pretty surprised if it has TCAS fitted.

One of the main reasons that TCAS alerts are inhibited at low altitude is to avoid distraction during the landing phase, in an area that has a high traffic density and a high probably of nuisance alerts. The system would constantly be giving RAs and people would be going around and deviating all over the place. Even if just TAs were left active then it would be going off all the time, and we would be having the same conversation about becoming blase to the warnings as we are about the repetitive conflict alerts that were being given to the LC.

Getting TCAS to give RAs on final is not the solution in my opinion.

Assumption would of course be that conflicting parties are TCAS equipped, and that the system can distinguish between airborne, taxiing and stationary on ground vehicles.

And inhibition floor could still be greater than zero - say 100-200ft?

Separately, is it correct to say that CRJ were on final, or were they perhaps still turning onto final?

Subjects Blackhawk (H-60) CRJ TCAS (All) TCAS RA

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uncle_maxwell
February 04, 2025, 06:07:00 GMT
permalink Post: 11821131

Quote:

Originally Posted by YRP

Most likely the assumption is that in any conflict below 500\x92, the airplanes involved are in very low energy states.

Instructing a climb could be useless or dangerous. Instructing no climb, same thing.

Engineering safety systems is not simple. You adjust one case, it can worsen another case.

Point taken, appreciate the complexity. On this one, however, heli wasn\x92t in a low energy state. And on aircraft (for analogy), GPWS doesn\x92t care either what energy state you may or may not have when it tells you to pull up due to terrain or windshear. On the bus i recall the procedure for windshear in climb/after t/o is full stick back, and energy/speed/aoa envelope is managed by the machine, giving you best chances given SNAFU.

All i am really saying is that:
(1) TCAS II can still be improved
(2) Other systems (like ADS-B) can, as can their adoption
(3) Interoperability between them can be enhanced
(4) Procedures can be improved (like mindset and division of tasks with TCAS TA on approach, especially in IMC and at night)

TCAS and ADSB took decades to implement and cost billions to fund but probably saved tens of thousands of lives by now.

And if certain vendors (Honeywell) have a monopoly that is up to regulators and policymakers to tackle (open standards, patent duration etc.)

Subjects ADSB (All) TCAS (All)

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uncle_maxwell February 02, 2025, 16:12:00 GMT permalink Post: 11819886	TCAS enhancement? Instead of no RA below 500ft (or whatever the floor is), how about telling one conflict to climb and the other one to \x91not climb\x92? \x91Not climb\x92 could then be understood (and trained) to mean \x91descend a little, terrain/aircraft/wx permitting or fly level\x92. Lots of ifs and buts, spurious warnings, limitations for when 3 or more conflicts, TCAS vs. GPWS considerations etc. but perhaps worth a thought. Subjects TCAS (All) Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
uncle_maxwell February 02, 2025, 16:54:00 GMT permalink Post: 11819920	Quote: Originally Posted by SAR Bloke I know I'm fighting a losing battle but here goes..... What you are doing wrong is making guesses based on incomplete/inaccurate data that is in the public domain. Assuming the NTSB figure of 375ft is correct, you still need more info for it to mean anything. Was that the AGL, AMSL or SPS height/altitude? How accurate are the 'various plots' that indicate the collision occurred mid-river? They may be right; they may not be. Was the CRJ on final or was it still positioning to final? If it wasn't on final then the trigonometric calculations of what height it should be at might not be correct. What official evidence is there that the Blackhawk made a 45 degree turn, or could that be a data error in the publicly available information? In summary what I am saying is that, despite all of the internet sleuths plotting tracking data, none of it is official and it is all subject to various errors. Whilst interesting to form an understanding of the circumstances, it can't be assumed to be accurate to within a few feet (vertically or laterally). That 1-2 feet error would be a theoretical accuracy. The readout in the cockpit would be subject to significant errors during turns/pitch changes etc; without knowing the exact installation on a Blackhawk, it might also unlock based on the surface conditions. More importantly, the ATC instructions would probably be based on an altimeter setting and not Rad Alt. How would that have worked in this scenario? Who do you think should have been directed by TCAS to do what? Does the Blackhawk even have TCAS? It could have instructed the CRJ to climb (meaning initiate go-around immediately) and the heli to \x91not climb\x92 (meaning descend if practicable). Or it could have instructed heli to climb and CRJ to not climb (meaning continue descent or level and look out). I am saying that tech is there in principle and the 500ft RA floor was decided on 20-30y ago, probably to limit complexity and risk of dangerous RAs, but that this limitation could be revisited in future, especially with lots more data and modelling capability to assess. Subjects ATC Blackhawk (H-60) CRJ NTSB TCAS (All) TCAS RA Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
uncle_maxwell February 02, 2025, 18:05:00 GMT permalink Post: 11819971	Quote: Originally Posted by fdr TCAS RA have inhibits at low altitude, or do you have some other system in mind? I know it is inhibited. I am saying that the concept of TCAS can be enhanced such that RAs are possible below 500ft without instructing one of the conflicting parties to fly into terrain. It may be worth looking at for safety engineers. Subjects TCAS (All) TCAS RA Links are to this post in the relevant subject page so that this post can be seen in context. 3 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
uncle_maxwell February 02, 2025, 19:00:00 GMT permalink Post: 11820010	Quote: Originally Posted by SAR Bloke Do you honestly think that you've just thought of that and the system designers haven't? In relation to your earlier response to my previous comment, how can the system tell someone to 'remain level' when that aircraft doesn't have TCAS? I am not sure of the Blackhawk fit, but I would be pretty surprised if it has TCAS fitted. One of the main reasons that TCAS alerts are inhibited at low altitude is to avoid distraction during the landing phase, in an area that has a high traffic density and a high probably of nuisance alerts. The system would constantly be giving RAs and people would be going around and deviating all over the place. Even if just TAs were left active then it would be going off all the time, and we would be having the same conversation about becoming blase to the warnings as we are about the repetitive conflict alerts that were being given to the LC. Getting TCAS to give RAs on final is not the solution in my opinion. Assumption would of course be that conflicting parties are TCAS equipped, and that the system can distinguish between airborne, taxiing and stationary on ground vehicles. And inhibition floor could still be greater than zero - say 100-200ft? Separately, is it correct to say that CRJ were on final, or were they perhaps still turning onto final? Subjects Blackhawk (H-60) CRJ TCAS (All) TCAS RA Links are to this post in the relevant subject page so that this post can be seen in context. 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
uncle_maxwell February 04, 2025, 06:07:00 GMT permalink Post: 11821131	Quote: Originally Posted by YRP Most likely the assumption is that in any conflict below 500\x92, the airplanes involved are in very low energy states. Instructing a climb could be useless or dangerous. Instructing no climb, same thing. Engineering safety systems is not simple. You adjust one case, it can worsen another case. Point taken, appreciate the complexity. On this one, however, heli wasn\x92t in a low energy state. And on aircraft (for analogy), GPWS doesn\x92t care either what energy state you may or may not have when it tells you to pull up due to terrain or windshear. On the bus i recall the procedure for windshear in climb/after t/o is full stick back, and energy/speed/aoa envelope is managed by the machine, giving you best chances given SNAFU. All i am really saying is that: (1) TCAS II can still be improved (2) Other systems (like ADS-B) can, as can their adoption (3) Interoperability between them can be enhanced (4) Procedures can be improved (like mindset and division of tasks with TCAS TA on approach, especially in IMC and at night) TCAS and ADSB took decades to implement and cost billions to fund but probably saved tens of thousands of lives by now. And if certain vendors (Honeywell) have a monopoly that is up to regulators and policymakers to tackle (open standards, patent duration etc.) Subjects ADSB (All) TCAS (All) Links are to this post in the relevant subject page so that this post can be seen in context. 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.

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