Posts about: "Separation (ALL)" [Posts: 442 Page: 10 of 23]ΒΆ

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JohnDixson
February 03, 2025, 19:05:00 GMT
permalink Post: 11820804
From the FAA website:\x93When Radar Came to Town

On January 7, 1952, after five years of testing and modifications to a radar system used

by the Army and Navy in World War II, the Civil Aeronautics Administration

inaugurated radar departure control procedures at its Washington National Airport. Six

months later it began radar approach control procedures at the airport.\x94

How do we connect the dots from 1952 to the tragedy described in this thread? 72 years later we have devolved to visual separation.

Subjects FAA  Radar  Separation (ALL)  Visual Separation

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flash8
February 03, 2025, 20:05:00 GMT
permalink Post: 11820851
How do we connect the dots from 1952 to the tragedy described in this thread? 72 years later we have devolved to visual separation.
Go back nearly fifty years with the Cessna and visual lookout from the PSA.. that I believe (could be wrong) led to the advent of TCA's....

Subjects Separation (ALL)  Visual Separation

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ATC Watcher
February 03, 2025, 20:19:00 GMT
permalink Post: 11820865
Originally Posted by JohnDixson
From the FAA website:“When Radar Came to Town

On January 7, 1952, after five years of testing and modifications to a radar system used

by the Army and Navy in World War II, the Civil Aeronautics Administration

inaugurated radar departure control procedures at its Washington National Airport. Six

months later it began radar approach control procedures at the airport.”

How do we connect the dots from 1952 to the tragedy described in this thread? 72 years later we have devolved to visual separation.
indeed, Indeed . interesting to remember where it all comes from and having the first collision this century coming back in the same airport they introduced APP radar over 70 years ago while doing a visual approach a night following a PAPI .
But remember , here the APP radar controllers with the proper ratings and radar tools ( including Conflict alerts) are not in the TWR cab in DC, , they are located in Potomac TRACON , another town , in Warrenton , Virginia ,

.
​​​​​​​ Jumseater
A UK Tower/LC can’t give headings unless they are radar qualified and current, and have the appropriate equipment.
Correct , Same in EASA land. in addition in FAA web site DC TWR is classified as TWR only .
Last edited by ATC Watcher; 3rd February 2025 at 20:24 . Reason: adding comment to jumpseater post

Subjects FAA  Radar  Separation (ALL)  Visual Separation

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galaxy flyer
February 03, 2025, 20:22:00 GMT
permalink Post: 11820867
Originally Posted by flash8
Go back nearly fifty years with the Cessna and visual lookout from the PSA.. that I believe (could be wrong) led to the advent of TCA's....
NY TCA was first one about 1972. San Diego was later after the mid-air there. TCA (Class B) still uses visual separation.

Subjects Separation (ALL)  Visual Separation

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ATC Watcher
February 03, 2025, 21:07:00 GMT
permalink Post: 11820895
Originally Posted by MPN11
That is a question I posed way back. Does DCA Tower have a slaved radar display?
I do not know , what kind and how it is used. Some US controllers said in another forum they now have one , but what is it , where it is located and what the procedures are I do not know. Normally at large airports you have a radar picture repeater for situation awareness not for providing radar control unless you are in a TWR-APP combined facility of course , but DC is not.
and
Does a non-trained/qualified controller have the authority to use that data in extremis?
if you mean in emergency , to prevent a collision ? , yes absolutely because in legal terms you always have the duty of care That is what the judge will come back to in the end. Now that said, where was the display located ? remember the guy was working 2 positions at same time . If there was a radar repeater display somewhere , was it located at the position he was working from ? The NTSB investigation will tell us that
.
If you are a controller you know how we work , Problem identified , = Conflict with PT detected , solution found = delegate separation , delegation accepted = problem solved. Next ... The guy was quite busy with departing and arrival traffic in runway one . Now of course with hindsight ,, what he should, and could perhaps have done is very easy for us to say . Feel very sorry for the guy . I hope he is not made the scapegoat for this mess.

Subjects ATC  DCA  NTSB  Radar  Separation (ALL)

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Jetstream67
February 03, 2025, 22:06:00 GMT
permalink Post: 11820948
Originally Posted by GroundedDinosaur
The Helicopter wasn't landing at DCA, but, most likely would have the airports barometric setting in it's altimeter? If it was off by 0.2 inches, that would be about 200 ft?
I assume the altitude reading that the Altimeter in the aircraft displays in the cockpit is identical to the Transponded signal that ATC shows on it's screen? Is there a chance
that the Helicopter would have a different altimeter setting set? A new ATIS came out recently, or a pressure front was moving in?
I'm not sure this is the key point here. 100ft vertical separation at 150 Knots +/- equipment error in any safety plan is going to go wrong one day.
Although the route / approach crossed the main plan was surely to never let two aircraft on different courses /stages get even 10 times that close in passing . . which takes us back to the real issue

Subjects ATC  DCA  Separation (ALL)  Vertical Separation

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MikeSnow
February 03, 2025, 23:43:00 GMT
permalink Post: 11821022
Originally Posted by DIBO
If people (and even 'reliable Youtubers') would stick to the available facts, instead of complicating things
No crossing of 'Route 4' prior to ...
Still, if the helo crew misidentified the A319 as the CRJ, and they assumed the A319 will start turning right soon to circle for 33, turning right as well would have increased horizontal separation. And the extended centerline for 01, which the A319 was aligning with, does actually intersect with Route 4 a bit after the Wilson Bridge. And, looking at the radar replay, the A319 did actually turn right for a bit, to align to 01. At around the same time, the helo starts turning right.


I agree that these are just guesses, but the alternative seems to be that the helo just drifted to the right randomly, for no specific reason, which seems unlikely.

Subjects CRJ  Radar  Route 4  Separation (ALL)

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SAM 2M
February 04, 2025, 00:28:00 GMT
permalink Post: 11821044
Suggested policies for review in the investigation
Whilst the rules differ between different countries, I am sure the following will be evaluated during the investigation:

- Any policy that permits visual separation from traffic at NIGHT should be reviewed.

- Any policy that permits routes - especially with such minimal planned separation - that cross final approach tracks should be reviewed.

- Any policy that permits 'band-boxing' of UHF and VHF radio communication frequencies should be reviewed, especially as it does not enable the crew of the UHF and VHF aircraft to hear the transmissions of the other crew. This reduces flight crew situational awareness (SA).

Some other items not directly related to this incident, but that could lead to collisions are:

- Land and Hold Short (LAHSO) operations should be reviewed.

- Clearing aircraft to land with traffic ahead but yet to land, should be reviewed. (e.g. "XXXX123 number 4 cleared to land")

- Having Ramp areas uncontrolled by ATC.

- Encouraging crew to 'report visual' (and thus becoming completely responsible for their own separation from that moment) should be reviewed.

787 Capt / SE / TRI / TRE






Subjects ATC  Land and Hold Short  Separation (ALL)  Situational Awareness  Visual Separation

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patrickal
February 04, 2025, 00:36:00 GMT
permalink Post: 11821050
Originally Posted by MikeSnow
Still, if the helo crew misidentified the A319 as the CRJ, and they assumed the A319 will start turning right soon to circle for 33, turning right as well would have increased horizontal separation. And the extended centerline for 01, which the A319 was aligning with, does actually intersect with Route 4 a bit after the Wilson Bridge. And, looking at the radar replay, the A319 did actually turn right for a bit, to align to 01. At around the same time, the helo starts turning right.

https://www.youtube.com/shorts/bHBKptJWXtU

I agree that these are just guesses, but the alternative seems to be that the helo just drifted to the right randomly, for no specific reason, which seems unlikely.
Could they have been over-correcting for a quartering tail wind from their right which was at 15mph gusting to 25mph? That's not insignificant.

Subjects CRJ  Radar  Route 4  Separation (ALL)

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Equivocal
February 04, 2025, 00:44:00 GMT
permalink Post: 11821056
Suggested policies for review in the investigation
So, you mean make it like home?

There are many comments in this thread which say procedure X should not be allowed. The procedures that were applied by ATC immediately before the accident are \x91standard\x92 and used the world over. None are intrinsically unsafe but their application (as with all the other rules that need to be followed) needs to be appropriate. Visual separation at night is likely to be fine on a clear night with just two or three aircraft in the sky but, as others have pointed out, it\x92s not in any way appropriate in high traffic density environments. Just because there\x92s a rule that says you can do something doesn\x92t mean it\x92s necessarily a good idea.

Subjects ATC  Separation (ALL)  Visual Separation

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21600HRS
February 04, 2025, 08:47:00 GMT
permalink Post: 11821199
Originally Posted by galaxy flyer
Using visual separation, the system will generate CAs, they\x92re issued to alert the controller, not to provide guidance. Thats why the controllers ask, \x93do you have the traffic in sight?\x94
There is a problem in the system if you don\x92t react to CA. The visual avoidance should be aborted when the technically calculated separation is lost.

Subjects ATC  Separation (ALL)  Visual Separation

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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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FullWings
February 04, 2025, 10:43:00 GMT
permalink Post: 11821285
Originally Posted by 21600HRS
There is a problem in the system if you don\x92t react to CA. The visual avoidance should be aborted when the technically calculated separation is lost.
I think the issue is there are no visual separation standards, only IFR ones. Conflict Alerting (ATC) and TCAS (aircraft) have yet another set of parameters they use in different ways. The most common reason visual separation is requested by either party is to reduce separation below 1,000\x92/500\x92, 1.5, 2, 3, 5 miles or whatever is appropriate to the categories of airspace, aircraft and flights.

This means the automated tools (which don\x92t know the aircraft are using visual means to deconflict) will go off based on a predicted or actual loss of the separation criteria that they\x92ve been programmed with. If the helicopter in this instance had passed 1/4m behind and below the CRJ, a CA may still have been generated although the conflict had been resolved visually. The controller actually picks up on the apparent proximity and queries the heli that they are still visual, to which they reply in the affirmative - there is no minimum separation for visual avoidance, just sometimes it\x92s too dang close. Which is an Airprox.

Subjects ATC  CRJ  IFR  Separation (ALL)  TCAS (All)  Visual Separation

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Someone Somewhere
February 04, 2025, 10:52:00 GMT
permalink Post: 11821295
Originally Posted by 21600HRS
There is a problem in the system if you don’t react to CA. The visual avoidance should be aborted when the technically calculated separation is lost.
The issue here, I believe, is that there's different standards for visual separation vs radar separation. A separation that results in a CA from the radar may still be entirely legal and acceptable. It's like trying to work out if two cars at an intersection will crash into each other from their GPS trackers: the data just isn't good enough and you don't know if one car will actually stop at the stop sign at the last second.

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.]

Originally Posted by 21600HRS
]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 ”TRAFFIC AHEAD, PULL UP” 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.
One aircraft gets a PULL UP, the other gets a NO CLIMB. Ideally you would have each aircraft advertise how much altitude it can gain/lose in 5/10/15 seconds and make the decision based on that. It would also fix needing to turn to TA only after engine failure.

Subjects ATC  Blackhawk (H-60)  CRJ  DCA  Radar  Separation (ALL)  TCAS (All)  TCAS RA  Visual Separation

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spornrad
February 04, 2025, 10:54:00 GMT
permalink Post: 11821297
Originally Posted by DIBO
If people (and even 'reliable Youtubers') would stick to the available facts, instead of complicating things
No crossing of 'Route 4' prior to ...
One major fact: the wreckage is located in the middle of the river, west of route 4. SA question is, what lateral separation image had the helicopter crew in mind trying to stay behind the jet, possibly focussing on the second jet on approach to 01.

Subjects Route 4  Separation (ALL)  Situational Awareness

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Del Prado
February 04, 2025, 11:44:00 GMT
permalink Post: 11821332
Originally Posted by 21600HRS
There is a problem in the system if you don\x92t react to CA. The visual avoidance should be aborted when the technically calculated separation is lost.

CA will activate whenever certain separation minima are going to be lost (600\x92 and 2 miles for example).
Visual separation is a perfectly legal tool that allows separation to reduce below radar minima.
CA will (almost) always activate when applying visual separation. That doesn\x92t mean the aircraft are on a collision course or are definitely going to crash, it just means they will be in confliction and separated by less than the IFR radar minima.

Its activation in this scenario (and countless others in the days before) was totally normal. Anyone who thinks it should have been reacted to differently or that it was a last line of defence really doesn\x92t understand the role of Conflict Alert.

And it\x92s not the role of the radar centre to phone tower and warn them of a conflict alert between two aircraft they would expect to be visually separated - that\x92s a scenario that probably happens several times a day.






Subjects IFR  Radar  Separation (ALL)  Visual Separation

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galaxy flyer
February 04, 2025, 13:02:00 GMT
permalink Post: 11821410
Originally Posted by 21600HRS
There is a problem in the system if you don\x92t react to CA. The visual avoidance should be aborted when the technically calculated separation is lost.
Its VISUAL separation by the pilots, the controller did react, \x93PAT 25, do you have the traffic in sight?\x94

Subjects ATC  Separation (ALL)

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BrogulT
February 04, 2025, 19:05:00 GMT
permalink Post: 11821639
Originally Posted by DaveJ75
Well, I suspect our very senior pilot possesses more heavy / military rotary wing knowledge than you and Juan Browne do? And as for FLARM near a commercial airport... well, it would be 'interesting'...
No need for emergency maneuvers or quick-stop aerobatics here. If they had adopted and enforced reasonable separation rules, compliance could have been had by simply having the helicopter slow down (earlier), hold (earlier) or do a right-hand orbit around the river (earlier). Every reasonable chance to avoid this collision was *earlier*. IDK how many warning signs are needed to take some sort of action, but clearly various people simply ignored them or set up procedures that required ignoring them.

Now here we are having a public debate about whether the helicopter was at 200 or 300 feet. My question is at what point would you consider the CRJ to be impermissibly low at that point? At the point of impact they were less than 5000 feet from the aiming point and, I presume, the PAPI. That's less than 4000 feet from the numbers. It's a short runway, 3 degrees to the numbers is 208 feet, to the aiming point 260 feet. So how low can they be at this point without violating some FAR or other rule? Keep in mind it is a visual approach at this point.

Subjects CRJ  Separation (ALL)

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EGPFlyer
February 04, 2025, 19:20:00 GMT
permalink Post: 11821649
Originally Posted by BrogulT
No need for emergency maneuvers or quick-stop aerobatics here. If they had adopted and enforced reasonable separation rules, compliance could have been had by simply having the helicopter slow down (earlier), hold (earlier) or do a right-hand orbit around the river (earlier). Every reasonable chance to avoid this collision was *earlier*. IDK how many warning signs are needed to take some sort of action, but clearly various people simply ignored them or set up procedures that required ignoring them.

Now here we are having a public debate about whether the helicopter was at 200 or 300 feet. My question is at what point would you consider the CRJ to be impermissibly low at that point? At the point of impact they were less than 5000 feet from the aiming point and, I presume, the PAPI. That's less than 4000 feet from the numbers. It's a short runway, 3 degrees to the numbers is 208 feet, to the aiming point 260 feet. So how low can they be at this point without violating some FAR or other rule? Keep in mind it is a visual approach at this point.
Yes, it\x92s a moot point. I suspect the low altitude on the heli routes are to allow them passage when the main runway 01/19 is in use, rather than to provide any vertical separation if there\x92s an aircraft using 33. The helicopter chart has holding points along it that probably should have been used.

Subjects CRJ  Separation (ALL)  Vertical Separation

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BrogulT
February 04, 2025, 21:02:00 GMT
permalink Post: 11821702
Originally Posted by EGPFlyer
Yes, it\x92s a moot point. I suspect the low altitude on the heli routes are to allow them passage when the main runway 01/19 is in use, rather than to provide any vertical separation if there\x92s an aircraft using 33. The helicopter chart has holding points along it that probably should have been used.
If I understand the sequence of events, PAT25 requested visual separation before they got to the report/hold point near Hains Point. IDK what they refer to this point as, but if the controller had denied the request and instructed them to hold at Hains Point, what would everyone have done? Is that a normal procedure? We're told that we have knowledgable senior people here so I'd like to know if that's plausible or doesn't work for some reason.

Subjects ATC  PAT25  Separation (ALL)  Vertical Separation  Visual Separation

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