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| uncle_maxwell
February 02, 2025, 19:00:00 GMT permalink Post: 11820010 |
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. 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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| Bratchewurst
February 02, 2025, 19:02:00 GMT permalink Post: 11820013 |
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. a Getting TCAS to give RAs on final is not the solution in my opinion. Nuisance go-arounds caused by RAs don't seem like a high price to pay to avoid this kind of catastrophic event. And perhaps nuisance go-arounds might cause some re-considerations of poor airspace design, such as this appears to be. Subjects
ADSB (All)
Blackhawk (H-60)
TCAS (All)
TCAS RA
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| fdr
February 02, 2025, 19:25:00 GMT permalink Post: 11820027 |
The current version of TCAS II is at least a decade old and, so far as I can tell from a cursory reading of the literature available online, does not incorporate ADS-B to the extent now possible. Given the massive improvements in processing technology since the current version of TCAS was finalized, it seems entirely possible that the issues cited here could be resolved with the proper engineering, as could many others (such as the 2024 Haneda crash). Retrofitting fleets (and requiring military aircraft to participate) would be a huge political problem, but there don't appear to be any showstoppers technically.
Nuisance go-arounds caused by RAs don't seem like a high price to pay to avoid this kind of catastrophic event. And perhaps nuisance go-arounds might cause some re-considerations of poor airspace design, such as this appears to be. Going from TCAS II Change 7.0 to 7.1/7.1a was a simple matter of handing over enough cash to buy a couple of Porsches, for the new computer to effect a simple software change. What is irritating is the change was not an enhancement of the system it had all the hallmarks of incorporating the standard for TCAS at the time. An iPad with Foreflight or Garmin pilot an ADSB-in input is frankly more value when operating in the weeds, While we are at it, it is remarkable that Garmin Pilot and Foreflight provide better obstacle alerting than the certified EGPWS system does. Subjects
ADSB (All)
ADSB In
TCAS (All)
TCAS RA
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| Day_VMC
February 02, 2025, 19:26:00 GMT permalink Post: 11820029 |
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. Fairly confident (and reported earlier) that the Blackhawk only has Mode S, so no ADS-B. Mode S may report less than ADS-B which means that position updates can be (but not always) significantly slower than ADS-B out. I also believe that for RA to work both aircraft would need to have both ADS-B In and ADS-B Out so that 2 way data communication can take place. Subjects
ADSB (All)
ADSB In
ADSB Out
Blackhawk (H-60)
TCAS (All)
TCAS RA
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| Easy Street
February 02, 2025, 20:31:00 GMT permalink Post: 11820089 |
Fairly confident (and reported earlier) that the Blackhawk only has Mode S, so no ADS-B. Mode S may report less than ADS-B which means that position updates can be (but not always) significantly slower than ADS-B out. I also believe that for RA to work both aircraft would need to have both ADS-B In and ADS-B Out so that 2 way data communication can take place.
Subjects
ADSB (All)
ADSB In
ADSB Out
Blackhawk (H-60)
TCAS (All)
TCAS RA
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| Sailvi767
February 04, 2025, 01:09:00 GMT permalink Post: 11821065 |
Testing has been done and the determination was that commanding a climb at low altitude in a fully configured aircraft at approach speed was a bigger threat.
Subjects
TCAS RA
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| Someone Somewhere
February 04, 2025, 07:49:00 GMT permalink Post: 11821166 |
Arguably all a low-energy state does is imply that TCAS needs to give RAs from further out. That of course further reduces throughput, unless you come up with additional ways to reduce false positives.
The end result of all of this, perhaps the better part of a century down the track, is probably going to be closer to positive train control and atlantic tracks: these are the blocks of airspace and time that are reserved for your aircraft, plus a buffer in each direction including time. Conflicting movements cannot be authorised (though unlike rail, you can have clearances that forbid you stopping, and therefore give a plane 'advance clearance' through a section of space that the plane(s) in front haven't yet transited, as long as the times each aircraft is allowed to be in that space are non-overlapping). At any time, an aircraft would expect to have forward clearances for 2-3 routes - normal path, plus pre-clearances for some combination of missed approach, engine failure drift-down, emergency descent, ETOPS divert, perhaps a even pre-authorised radio failure track. As you clear each section or a future clearance becomes unnecessary, you release it behind you but collect new clearances for alternate routes. That's a long way away given even CPDLC is in fairly limited use. I'm sure there's a few cases of stalls during go-around, terrain avoidance, or TCAS activation. There's never such a thing as 'no threat'. I do agree that it's pretty minimal, though, and the Airbus procedure of 'pull the stick full back and pray' simplifies/de-risks it even further. Last edited by Someone Somewhere; 4th February 2025 at 08:09 . Subjects
TCAS (All)
TCAS RA
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| ATC Watcher
February 04, 2025, 09:13:00 GMT permalink Post: 11821217 |
P
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) ) 1) TCAS II can still be improved : No end of the story by now , no version 8 in the pipeline . We spent millions and years on getting 7.1 accepted .. and even not everyone mandates it . 2) ADS-B gets already saturated , add TCAS type system and it will be .But developing a new Anti-collision system based on ADS-B is in the pipeline however it will; mean ASD-S be out mandated for every flying aircraft , including military . Here is your problem . Some military aircraft cannot be retrofitted , no space .. 3) interoperability .? No , 2 completely different systems , TCAS is analog 1970 technology , 4) TCAS RAs on approach? you mean below 1000 ft ? No , in our scenario here , with the Blackhawk climbing , the logical RA would be a descent RA for the CRJ ,, you want a Descent RA at 300 ft ? The only solution I personally see is airspace segregation based on equipment . Class A, B and C restricted to aircraft carrying ADS-B out and TCAS equipped , and both Working and on the MEL as no go item s ( not the case today ) Waiting for AOPA and ATA remarks Subjects
ADSB (All)
ADSB In
ADSB Out
Blackhawk (H-60)
CRJ
TCAS (All)
TCAS RA
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| 21600HRS
February 04, 2025, 09:36:00 GMT permalink Post: 11821226 |
4) TCAS RAs on approach? you mean below 1000 ft ? No , in our scenario here , with the Blackhawk climbing , the logical RA would be a descent RA for the CRJ ,, you want a Descent RA at 300 ft ?
I think there is no problem for RA below 1000ft, it would only be like \x94TRAFFIC AHEAD, PULL UP\x94 in Airbus World. Horizontal separation might be smaller and system takes into account whether the traffic is between you and touch down. This DCA case is problematic because you join the final below 500ft, that is not acceptable in any case with an airliner. TCAS 8 is getting closer and sooner after this horrific accident. Subjects
Blackhawk (H-60)
CRJ
DCA
Separation (ALL)
TCAS (All)
TCAS RA
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| Someone Somewhere
February 04, 2025, 10:52:00 GMT permalink Post: 11821295 |
Radar orders also need to be given and actions taken sooner than if the crews are doing it of their own initiative. So a radar CA needs to be visible say 15 second pre-collision so ATC can wait for the radio to be clear then order pilots to manoeuvre. Pilots can aim to cross visually at more like 5 seconds. I'm not saying that this is overall a good idea, but the fundamental reason you fit more planes in with visual separation is that you can put them closer together with (given good visibility) not too dissimilar safety. [Edit: too late... Fullwings got this.]
]4) TCAS RAs on approach? you mean below 1000 ft ? No , in our scenario here , with the Blackhawk climbing , the logical RA would be a descent RA for the CRJ ,, you want a Descent RA at 300 ft ?
TCAS 8 is getting closer and sooner after this horrific accident. Subjects
ATC
Blackhawk (H-60)
CRJ
DCA
Radar
Separation (ALL)
TCAS (All)
TCAS RA
Visual Separation
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| galaxy flyer
February 06, 2025, 01:54:00 GMT permalink Post: 11822687 |
Condolences to all impacted.
Questions: Why was PAT 25 search light in the stowed position and not motored to a more forward position? Why are PAT helicopters not M models with FD's so PAT 25 could have been coupled on route 4 while at 200' giving the PF more time to look for traffic? Was there pressure to use NVG along route 4 to meet the hourly requirements for currency? Why did PAT 25 not slow down or hold at Hains in order to pass behind the CRJ as per their clearance? Why was it ops normal after a near miss the previous day and then only one crew chief instead of two for PAT 25? Why was the controller task saturated? Why over the years, as the airport got busier, someone didn't suggest, for night operations, only one aircraft on route 4 or only one aircraft on the approach to 33 at a time and prohibit simultaneous operations? IMO while the CRJ was turning final to rwy 33 PAT 25 may have experienced the CRJ landing lights in the cockpit and may have chosen up and right rather than left and down. Note worthy, PAT 25 RAD ALT gauge scale changes dramatically at 200'. Maybe an upgrade to Dulles with a high speed train connection... Not the latest model? Guess what, combat units get the latest models. These missions are transport, not combat roles. Budgets and priorities rule. There are VH-60s in the battalion, they\x92re probably not scheduled for check rides or training flights. One RA does not rewrite the schedule, likely not even unusual in DCA. The previous crew may not have passed the event on. I\x92ve had numerous RAs, never a report. The NTSB has stopped asking for reports for events involving VFR traffic. While nice to have, there\x92s no place for a second crew chief to have a forward view. And the CC may or may not be \x93in the loop\x94. They\x92re crew chiefs, not pilots. We had them on C-5 and they mostly slept in flight as they too much to do on the ground. Subjects
ATC
CRJ
Close Calls
DCA
NTSB
Night Vision Goggles (NVG)
Pass Behind
Pass Behind (All)
Route 4
TCAS RA
VFR
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| Locked door
February 06, 2025, 03:31:00 GMT permalink Post: 11822714 |
How can you make that statement without realising how many red flags are in it? LD Subjects
DCA
NTSB
TCAS RA
VFR
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| missy
February 06, 2025, 11:55:00 GMT permalink Post: 11822926 |
Tower: "PAT25, traffic just south of the Woodrow Bridge, a CRJ, it's 1200 feet setting up for runway 33"
PAT25: "PAT25 has the traffic in sight, request visual separation" Tower: "Visual separation approved" 0:26 here: https://youtu.be/r90Xw3tQC0I?feature=shared Perhaps, and this is big perhaps, it's a pavlovian response to whenever PAT is advised of other traffic. I listened to the TCAS RA missed approach from the previous day, and once again the response from PAT is "request visual separation". It's highly likely that the pilot requests for visual separation is the only way that this Class B airspace can operate with the mix of IFR vs VFR, and aerodrome traffic vs transits. I fail to understand why PAT is using UHF, surely this is another slice of cheese. The use of RWY 33 for arrival makes it easier for the ATC and the aircrew with one less runway crossing after they have landed. To emphasis the point, the following PSA actually requests RWY 33. Subjects
ATC
CRJ
IFR
PAT25
Separation (ALL)
TCAS (All)
TCAS RA
Traffic in Sight
VFR
Visual Separation
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| galaxy flyer
February 06, 2025, 13:32:00 GMT permalink Post: 11822989 |
Again, not excusing things, not saying it can’t improve, but the size of the problem is huge. Ultimately, the solution is less aviation. I’ve flown all over the world, nowhere has the traffic the US has. ATL, for example has a mix of traffic unheard of in Europe. I’ve been in the bizjets, airliners, I’ve seen jet fighters parked there and a Piper Cherokee on the GA ramp. Same in LAX, DFW, LGA, BOS. We do not expect the restrictions on aviation acceptable elsewhere and we have plenty of it. Our GA safety record is pretty awful, but at glance it’s probably 75% of the world’s total GA flying. It’s also no accident to see FAA-registered GA planes in the EU. Guess why? Subjects
FAA
TCAS (All)
TCAS RA
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| moosepileit
February 07, 2025, 12:37:00 GMT permalink Post: 11823616 |
1.5NM is obviously not applied, look at the south flow arrivals TCAS RA the day prior. It, a PAT merged previously with a SWA 737 at TCAS TA altitudes with Collision Alert to ATC radar, before causing the later RA. Last edited by moosepileit; 7th February 2025 at 15:53 . Subjects
ATC
Radar
Separation (ALL)
TCAS (All)
TCAS RA
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| bill fly
February 12, 2025, 12:15:00 GMT permalink Post: 11826676 |
I am sorry you see a witch hunt in my post. It was supposed to be an idea for a future improvement, rather than a criticism of the very hard worked man who was on the job. On the flying end, there is quite a rigid procedure to follow if a TCAS RA goes off. From posts since I see, that there seems to be one for for STCA triggers too. It seems to me that the gravity of the situation is brought faster to a pilot's attention if the Conflict warning is announced on the RT. That is just one factor in this sad affair of course. Both TCAS and STCA are last ditch saviours but only if full attention can be paid to them. Subjects
ATC
DCA
TCAS (All)
TCAS RA
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| ATC Watcher
February 12, 2025, 16:42:00 GMT permalink Post: 11826805 |
Hi, ATC Watcher,
I am sorry you see a witch hunt in my post. It was supposed to be an idea for a future improvement, rather than a criticism of the very hard worked man who was on the job. On the flying end, there is quite a rigid procedure to follow if a TCAS RA goes off. From posts since I see, that there seems to be one for for STCA triggers too. It seems to me that the gravity of the situation is brought faster to a pilot's attention if the Conflict warning is announced on the RT. That is just one factor in this sad affair of course. Both TCAS and STCA are last ditch saviours but only if full attention can be paid to them. Now on the Conflict alert on the BRITE display . I have no first hand info on the SOPs in DCA on how a TWR controller uses the BRITE and if STCA are even displayed . `, but if they are, seen the charts and the routes , I guess STCA alerts are very common .especially when you delegate separation and you then play with a couple of hundred feet, vertical separation Too many unnecessary alerts equals normalization of deviance, . Look at the Haneda preliminary report , same .. Finally since you mention TCAS RAs , there is a major difference with STCA , it is not the same as a TCAS RA . With an RA , as a pilot you have to react and follow , it is mandatory , for a controller a STCA is just an alert , just like a TCAS TA , if in your judgement it will pass you will not do anything , and if you have already issued a correcting instruction ( heading, level , etc,,) or here delegate visual separation , the STCA just becomes a nuisance. . I sincerely hope the DC Controller will not be made the scapegoat of this accident . Not so sure it will not. Subjects
ATC
DCA
FAA
NTSB
Preliminary Report
Separation (ALL)
TCAS (All)
TCAS RA
Vertical Separation
Visual Separation
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| PJ2
February 12, 2025, 19:46:00 GMT permalink Post: 11826918 |
Hi Bill , understood, I was a bit too harsh maybe, but I get upset to continuously read what the controller should have done. Remember he was trained like this , to follow procedures that were basically unsafe in order to move the traffic . I can say unsafe because they were removed immediately after the accident , not waiting for the NTSB to recommend it . No everyone is stupid in the FAA , they knew this route was in conflict with 33 Visual arrivals. And did not pass any safety case, but the procedure was kept , most probably due political or military pressures , relying on controllers and pilots to mitigate the risks.
Now on the Conflict alert on the BRITE display . I have no first hand info on the SOPs in DCA on how a TWR controller uses the BRITE and if STCA are even displayed . `, but if they are, seen the charts and the routes , I guess STCA alerts are very common .especially when you delegate separation and you then play with a couple of hundred feet, vertical separation Too many unnecessary alerts equals normalization of deviance, . Look at the Haneda preliminary report , same .. Finally since you mention TCAS RAs , there is a major difference with STCA , it is not the same as a TCAS RA . With an RA , as a pilot you have to react and follow , it is mandatory , for a controller a STCA is just an alert , just like a TCAS TA , if in your judgement it will pass you will not do anything , and if you have already issued a correcting instruction ( heading, level , etc,,) or here delegate visual separation , the STCA just becomes a nuisance. . I sincerely hope the DC Controller will not be made the scapegoat of this accident . Not so sure it will not. Rarely does the "bad apple" theory of accident causation survive the scrutiny of a robust, honest investigation. Last edited by Senior Pilot; 12th February 2025 at 23:14 . Reason: Quote was unreadable Subjects
ATC
DCA
FAA
NTSB
Preliminary Report
Separation (ALL)
TCAS (All)
TCAS RA
Vertical Separation
Visual Separation
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| YRP
February 13, 2025, 01:33:00 GMT permalink Post: 11827083 |
On the flying end, there is quite a rigid procedure to follow if a TCAS RA goes off. From posts since I see, that there seems to be one for for STCA triggers too. It seems to me that the gravity of the situation is brought faster to a pilot's attention if the Conflict warning is announced on the RT.
That is just one factor in this sad affair of course. Both TCAS and STCA are last ditch saviours but only if full attention can be paid to them. TCAS RA says that a collision is imminent (within the accuracy of the system, ie it probably means the system can\x92t prove the planes won\x92t hit). Conflict alert is to notify the controller well in advance \x97 maybe a few minutes for en-route. It isn\x92t a loss of separation, it is so they can avoid a loss of separation (3 or 5 miles for radar). Subjects
ATC
Radar
Separation (ALL)
TCAS (All)
TCAS RA
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| FullWings
February 13, 2025, 10:16:00 GMT permalink Post: 11827259 |
I am not a US controller but as I understand it their conflict alert is not a last minute save in the way TCAS is.
TCAS RA says that a collision is imminent (within the accuracy of the system, ie it probably means the system can\x92t prove the planes won\x92t hit). Conflict alert is to notify the controller well in advance \x97 maybe a few minutes for en-route. It isn\x92t a loss of separation, it is so they can avoid a loss of separation (3 or 5 miles for radar). The problem with conflict alerting is that in mixed-use airspace you will get a lot of warnings; I hesitate to say false as they are defined by preset parameters that may or may not be relevant to the potential conflict. Talking to controllers in the UK, they often turn this feature (STCA) off as GA traffic happily avoiding each other by visual and/or electronic means can fill the screen with so many alerts it distracts from the main job, especially if you are not in communication with either aircraft. I would expect, given the traffic density around DCA, that CAs are so commonplace they have become unremarkable, indeed expected. Twice the controller was told that the traffic was in sight, so in their mind they are applying visual separation (no minima, just don\x92t collide). The takeaway has to be that IFR/VFR separation at night by visual means is inherently risky and so a questionable pursuit. Subjects
ATC
DCA
Radar
Separation (ALL)
TCAS (All)
TCAS RA
Traffic in Sight
Visual Separation
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