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FullWings
February 01, 2025, 21:58:00 GMT
permalink Post: 11819334

Quote:

Originally Posted by Chesty Morgan

Airline pilots do not, as a matter of course, avoid TCAS traffic unless given an RA, TCAS is notoriously inaccurate laterally, we will try to acquire traffic visually and may then react IF we can.

Also depending on the range selected on the TCAS or ND display you might get a load of garbled nonesense.

Yep, as you may be manoeuvring into a collision if you try and do it off the relative positions on the ND.

Also, with any kind of warning system, they lose effectiveness with the more that they go off. A full-blooded TCAS RA is, thankfully, pretty rare on an individual basis (I\x92ve had 3 over 30 years, two in the USA) and is trained and practiced regularly. The CA/STCA that ATC received might have been the 27th of the day in that airspace for all we know, given the traffic levels and the routings in and out of DCA and criss-crossing the area, plus they did have confirmation of visual acquisition which was now the sole means of separation.

Subjects ATC DCA Separation (ALL) TCAS (All) TCAS RA

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FullWings
February 03, 2025, 08:36:00 GMT
permalink Post: 11820320

Quote:

Originally Posted by dr dre

The helicopter pilots were a qualified instructor pilot with 7 years experience and a pilot under check who graduated in the top 20% of her class. The CRJ pilots were quite experienced for an regional crew. Nothing to suggest the controller did not maintain the standards required of an air traffic controller.

These were 5 aviation professionals who had gotten their roles through hard work and perseverance (like all aviation professionals) and fell victim to the circumstances they found themselves in that night.

The amazing thing is that there wasn\x92t an accident like this every month at DCA with the procedures and environment as they were. I suspect that there have been a lot of close calls and they\x92ll find a filing cabinet worth of reports but likely not much was done. If you continuously set up a dangerous scenario that in the end relies for safety on a procedure that is known to be unreliable (visual ID at night in a city environment), then statistics eventually intervene. This has likely been mitigated over the years by awareness, training, professionalism and sheer will to survive but when you are dealt the perfect bad hand and the last of the barriers to MAC fail, this is the result. Another factor pointed out recently is the \x93mission\x94 status of military flights: someone with more gold on their uniform and a bigger hat than you has said to go and do this task with that equipment, so you do it.

Speaking to some of my colleagues who have used NVGs operationally, they say they do reduce your field-of-view and flatten depth perception - one said he had mistaken a star for another aircraft for a while; it was only further away than he thought by a factor of ten trillion...

Subjects ATC CRJ Close Calls DCA Night Vision Goggles (NVG)

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FullWings
February 04, 2025, 10:43:00 GMT
permalink Post: 11821285

Quote:

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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FullWings
February 13, 2025, 10:16:00 GMT
permalink Post: 11827259

Quote:

Originally Posted by YRP

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).

I would say that TCAS is designed to issue guidance on a projected loss of separation, not necessarily an imminent collision (although it does that too). A highly simplistic explanation would be that it projects a nested set of egg-shaped volumes around the aircraft, which if it looks like they will be infringed can generate a TA or RA, depending on where the intruder is projected to make its closest approach. These volumes have nothing whatsoever to do with ATC separation standards.

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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FullWings
February 17, 2025, 20:56:00 GMT
permalink Post: 11830154

Quote:

Originally Posted by abax

Just some easily verifiable number crunching:

For a landing aircraft on Rwy33, and assuming:
(1) correct QNH dialed in
(2) perfect centerline following
(3) perfect 3deg PAPI following
baro altitude would be 278 ft exactly above the east bank. And 200 baro altitude would come appr. 1.175 ft from the east bank and over the water.

Very hard to believe that aircrafts were routinely allowed to cross simultaneously this crossing. Statistically, the accident would have happened long ago, or at, the least, have reports filed (even from passengers) and brown underwear.
And btw, even top VIP seems that are considered much more expendable than we originally thought.

Without going down the altitude rabbit hole again, no, aircraft were not allowed to simultaneously occupy almost the same space. They were either separated procedurally by ATC (radar) or maintained their own separation (visual). The DIY at night element failed in this case.

Think of it like a road with a traffic light (ATC) but you can merge on red if you can see it\x92s clear (helicopter). No rotary pilot I know would knowingly pass that close under/behind a jet transport as the wake could literally be the end of you at 200\x92AGL.

Subjects ATC QNH Radar Separation (ALL)

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FullWings
February 21, 2025, 23:22:00 GMT
permalink Post: 11833322

Quote:

Originally Posted by Easy Street

I can't see an obvious way of designing a route that crosses over the runway 33 approach that isn't forced to climb ever higher to separate from traffic in the runway 01/19 approach and departure lanes. You'd have to switch to routing below FW traffic at some point, but where?

I can think of one: you apply IFR separation standards (the minimum in the US is 1.5nm/500\x92?), at least for night operations. If two routes come closer to each other than that in either dimension, e.g. DCA RW33 approach and helicopter route 1, then traffic must be actively kept apart.

If two aircraft are converging on the same runway or look like they are going to occupy it simultaneously, then one of them has to give way. Why should it be any different for a small volume of sky?

Subjects DCA IFR Separation (ALL)

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FullWings
February 22, 2025, 07:49:00 GMT
permalink Post: 11833471

Quote:

Originally Posted by galaxy flyer

1.5 nm or 500\x92 is separation for IFR/VFR traffic, not IFR separation. So, an IFR aircraft in VMC might only have those separation distances with a VFR, not IFR aircraft.

Point taken but in reality, a low level (<200\x92) helicopter route is unlikely to have IFR traffic on it? Also, the conflict alerting systems now have real meaning to ATC rather than just being annoyances: something *must* be done to avoid a loss of separation. IFR/IFR minima (3nm/500\x92?) are higher for good reasons.

Subjects ATC IFR Separation (ALL) VFR

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FullWings
February 23, 2025, 17:37:00 GMT
permalink Post: 11834396

It\x92s anecdata, but I have noticed a trend over the years for US pilots to sometimes call visual with the airfield or other traffic when they may not be as a kind of reflex when asked. This is likely perceived as being on the ball, helping ATC, keeping the flow up but it falls smack under normalisation of deviance.

Last time I operated into LAX there was a cloud layer from 7,000\x92 down to ~2,500\x92, really thick and solid, bit of drizzle, no breaks until you suddenly came out of the bottom of it into a different airmass. A few people were calling visual from 10-15 miles out which raised eyebrows as it was highly unlikely to be the case. Yes, they were going to be visual at some point but not right then.

Would be interested in opinions from FAA-land as to whether this is isolated and/or very abnormal or they\x92ve noticed it as well...

Subjects ATC

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FullWings
March 31, 2025, 09:30:00 GMT
permalink Post: 11857820

Quote:

... then the airline has a Duty of Care to have a system which identifies such issues, assesses them and then, if necessary, to put additional mitigation in place - such as, say, banning the use of 33. AA may have looked at this and, if so, their Safety Case should explain why they concluded it was safe.

I refer to the case of Lufthansa identifying night visual separation as a safety issue and deciding not to allow it, then one of their aircraft having to divert from SFO because of this decision. AA banning DCA 33 might have had the same kind of result.

Anyway, after 72 pages it seems fairly clear that separating IFR from VFR at night by visual means inside the circuit pattern of a major airport is not a great plan. This could happen anywhere in the US and it would be an interesting exercise for the NTSB/FAA to see how many separation losses there were at other airports, as they have the software to do that. It is easy to fixate on this accident and the immediate environment when similar setups exist all over the place. It\x92s not just about helicopters and the military - civil and fixed wing on that kind of clearance could be just as risk-bearing.

Subjects DCA IFR Separation (ALL) VFR Visual Separation

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FullWings
October 18, 2025, 19:27:00 GMT
permalink Post: 11972195

Fitting and enabling ADSB has to have some positives, so I don\x92t think it\x92s a waste of time. The elephant in the room is mixing IFR and VFR at night on routes that have no (or totally inadequate) separation; this is inside controlled airspace - it should be controlled! The whole point of separating traffic by level, speed, direction and/or SID/airway/STAR is that if ATC goes down (or is distracted) or has to revert to procedural separation, aircraft are not immediately going to start hitting each other.

Subjects ADSB (All) ATC IFR Separation (ALL) VFR

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FullWings February 01, 2025, 21:58:00 GMT permalink Post: 11819334	Quote: Originally Posted by Chesty Morgan Airline pilots do not, as a matter of course, avoid TCAS traffic unless given an RA, TCAS is notoriously inaccurate laterally, we will try to acquire traffic visually and may then react IF we can. Also depending on the range selected on the TCAS or ND display you might get a load of garbled nonesense. Yep, as you may be manoeuvring into a collision if you try and do it off the relative positions on the ND. Also, with any kind of warning system, they lose effectiveness with the more that they go off. A full-blooded TCAS RA is, thankfully, pretty rare on an individual basis (I\x92ve had 3 over 30 years, two in the USA) and is trained and practiced regularly. The CA/STCA that ATC received might have been the 27th of the day in that airspace for all we know, given the traffic levels and the routings in and out of DCA and criss-crossing the area, plus they did have confirmation of visual acquisition which was now the sole means of separation. Subjects ATC DCA Separation (ALL) 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.
FullWings February 03, 2025, 08:36:00 GMT permalink Post: 11820320	Quote: Originally Posted by dr dre The helicopter pilots were a qualified instructor pilot with 7 years experience and a pilot under check who graduated in the top 20% of her class. The CRJ pilots were quite experienced for an regional crew. Nothing to suggest the controller did not maintain the standards required of an air traffic controller. These were 5 aviation professionals who had gotten their roles through hard work and perseverance (like all aviation professionals) and fell victim to the circumstances they found themselves in that night. The amazing thing is that there wasn\x92t an accident like this every month at DCA with the procedures and environment as they were. I suspect that there have been a lot of close calls and they\x92ll find a filing cabinet worth of reports but likely not much was done. If you continuously set up a dangerous scenario that in the end relies for safety on a procedure that is known to be unreliable (visual ID at night in a city environment), then statistics eventually intervene. This has likely been mitigated over the years by awareness, training, professionalism and sheer will to survive but when you are dealt the perfect bad hand and the last of the barriers to MAC fail, this is the result. Another factor pointed out recently is the \x93mission\x94 status of military flights: someone with more gold on their uniform and a bigger hat than you has said to go and do this task with that equipment, so you do it. Speaking to some of my colleagues who have used NVGs operationally, they say they do reduce your field-of-view and flatten depth perception - one said he had mistaken a star for another aircraft for a while; it was only further away than he thought by a factor of ten trillion... Subjects ATC CRJ Close Calls DCA Night Vision Goggles (NVG) Links are to this post in the relevant subject page so that this post can be seen in context. 7 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
FullWings February 04, 2025, 10:43:00 GMT permalink Post: 11821285	Quote: 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 Links are to this post in the relevant subject page so that this post can be seen in context. 4 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
FullWings February 13, 2025, 10:16:00 GMT permalink Post: 11827259	Quote: Originally Posted by YRP 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). I would say that TCAS is designed to issue guidance on a projected loss of separation, not necessarily an imminent collision (although it does that too). A highly simplistic explanation would be that it projects a nested set of egg-shaped volumes around the aircraft, which if it looks like they will be infringed can generate a TA or RA, depending on where the intruder is projected to make its closest approach. These volumes have nothing whatsoever to do with ATC separation standards. 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 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.
FullWings February 17, 2025, 20:56:00 GMT permalink Post: 11830154	Quote: Originally Posted by abax Just some easily verifiable number crunching: For a landing aircraft on Rwy33, and assuming: (1) correct QNH dialed in (2) perfect centerline following (3) perfect 3deg PAPI following baro altitude would be 278 ft exactly above the east bank. And 200 baro altitude would come appr. 1.175 ft from the east bank and over the water. Very hard to believe that aircrafts were routinely allowed to cross simultaneously this crossing. Statistically, the accident would have happened long ago, or at, the least, have reports filed (even from passengers) and brown underwear. And btw, even top VIP seems that are considered much more expendable than we originally thought. Without going down the altitude rabbit hole again, no, aircraft were not allowed to simultaneously occupy almost the same space. They were either separated procedurally by ATC (radar) or maintained their own separation (visual). The DIY at night element failed in this case. Think of it like a road with a traffic light (ATC) but you can merge on red if you can see it\x92s clear (helicopter). No rotary pilot I know would knowingly pass that close under/behind a jet transport as the wake could literally be the end of you at 200\x92AGL. Subjects ATC QNH Radar Separation (ALL) Links are to this post in the relevant subject page so that this post can be seen in context. 4 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
FullWings February 21, 2025, 23:22:00 GMT permalink Post: 11833322	Quote: Originally Posted by Easy Street I can't see an obvious way of designing a route that crosses over the runway 33 approach that isn't forced to climb ever higher to separate from traffic in the runway 01/19 approach and departure lanes. You'd have to switch to routing below FW traffic at some point, but where? I can think of one: you apply IFR separation standards (the minimum in the US is 1.5nm/500\x92?), at least for night operations. If two routes come closer to each other than that in either dimension, e.g. DCA RW33 approach and helicopter route 1, then traffic must be actively kept apart. If two aircraft are converging on the same runway or look like they are going to occupy it simultaneously, then one of them has to give way. Why should it be any different for a small volume of sky? Subjects DCA IFR Separation (ALL) Links are to this post in the relevant subject page so that this post can be seen in context. 4 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
FullWings February 22, 2025, 07:49:00 GMT permalink Post: 11833471	Quote: Originally Posted by galaxy flyer 1.5 nm or 500\x92 is separation for IFR/VFR traffic, not IFR separation. So, an IFR aircraft in VMC might only have those separation distances with a VFR, not IFR aircraft. Point taken but in reality, a low level (<200\x92) helicopter route is unlikely to have IFR traffic on it? Also, the conflict alerting systems now have real meaning to ATC rather than just being annoyances: something must be done to avoid a loss of separation. IFR/IFR minima (3nm/500\x92?) are higher for good reasons. Subjects ATC IFR Separation (ALL) VFR 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.
FullWings February 23, 2025, 17:37:00 GMT permalink Post: 11834396	It\x92s anecdata, but I have noticed a trend over the years for US pilots to sometimes call visual with the airfield or other traffic when they may not be as a kind of reflex when asked. This is likely perceived as being on the ball, helping ATC, keeping the flow up but it falls smack under normalisation of deviance. Last time I operated into LAX there was a cloud layer from 7,000\x92 down to ~2,500\x92, really thick and solid, bit of drizzle, no breaks until you suddenly came out of the bottom of it into a different airmass. A few people were calling visual from 10-15 miles out which raised eyebrows as it was highly unlikely to be the case. Yes, they were going to be visual at some point but not right then. Would be interested in opinions from FAA-land as to whether this is isolated and/or very abnormal or they\x92ve noticed it as well... Subjects ATC Links are to this post in the relevant subject page so that this post can be seen in context. 2 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
FullWings March 31, 2025, 09:30:00 GMT permalink Post: 11857820	Quote: ... then the airline has a Duty of Care to have a system which identifies such issues, assesses them and then, if necessary, to put additional mitigation in place - such as, say, banning the use of 33. AA may have looked at this and, if so, their Safety Case should explain why they concluded it was safe. I refer to the case of Lufthansa identifying night visual separation as a safety issue and deciding not to allow it, then one of their aircraft having to divert from SFO because of this decision. AA banning DCA 33 might have had the same kind of result. Anyway, after 72 pages it seems fairly clear that separating IFR from VFR at night by visual means inside the circuit pattern of a major airport is not a great plan. This could happen anywhere in the US and it would be an interesting exercise for the NTSB/FAA to see how many separation losses there were at other airports, as they have the software to do that. It is easy to fixate on this accident and the immediate environment when similar setups exist all over the place. It\x92s not just about helicopters and the military - civil and fixed wing on that kind of clearance could be just as risk-bearing. Subjects DCA IFR Separation (ALL) VFR Visual Separation Links are to this post in the relevant subject page so that this post can be seen in context. 9 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
FullWings October 18, 2025, 19:27:00 GMT permalink Post: 11972195	Fitting and enabling ADSB has to have some positives, so I don\x92t think it\x92s a waste of time. The elephant in the room is mixing IFR and VFR at night on routes that have no (or totally inadequate) separation; this is inside controlled airspace - it should be controlled! The whole point of separating traffic by level, speed, direction and/or SID/airway/STAR is that if ATC goes down (or is distracted) or has to revert to procedural separation, aircraft are not immediately going to start hitting each other. Subjects ADSB (All) ATC IFR Separation (ALL) VFR 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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