Separation (ALL) Page: 14 of 23

DIBO
February 11, 2025, 13:27:00 GMT
permalink Post: 11826087

Quote:

Originally Posted by SLFstu

Everything above 200 feet was their airspace.

as indicated by several others (but without formal proof ufn) the Route4 / RWY33 APP combination was never designed to give any vertical separation nor protection. So "their airspace" (=CRJ's) was the normal approach sector/path for a RWY 33 approach, without any relation to the 200ft max (recommended?) on the Heli route

Quote:

Originally Posted by SLFstu

Otherwise according to your graphic even at 200 feet max elevation, being that distance from the east bank any helicopter not maintaining visual separation could collide if an AC was still positioning itself from being low on the glideslope .

my underline could well be the correct conclusion, hence the "no vertical protection" of the route design

Subjects Separation (ALL) Vertical Separation Visual Separation

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airplanecrazy
February 11, 2025, 19:28:00 GMT
permalink Post: 11826281

Quote:

Originally Posted by SLFstu

I’m not sure your quoting FAA helicopter routes as having no defined centreline or width would strictly apply in DC versus what they wrote about the North Shore of Long Island route in NYC where they are required to be 1 mile off the shoreline. As shown on the published helo chart (DIBO’s post #863, and your little chart insert) and in writing (BuzzBox’s post #998) Route 4 directs traffic to track “via the east bank of the Potomac” from the Wilson Bridge to Anacostia River. If the impact point was 1000 feet or so (give or take some trig) from the east bank of a 3000 feet wide river at that point wouldn’t this mean that PAT25 was not only too high but off track too? Otherwise according to your graphic even at 200 feet max elevation, being that distance from the east bank any helicopter not maintaining visual separation could collide if an AC was still positioning itself from being low on the glideslope.

My understanding is that the FAA depicted width of a helicopter route is governed by the following doc: https://www.faa.gov/air_traffic/flig...2-complete.pdf . It specifies that on a fully printed chart the route should be 0.1 inches wide regardless of chart scale. The chart I pulled from was 1:125,000 scale (full chart size is 51x33 inch poster), which would mean the routes "appear" to be 125,000 * 0.1 / 12 = 1,042 ft wide. In the same FAA chart package https://aeronav.faa.gov/visual/12-26...-Wash_Heli.pdf , the third page is a "Washington Inset" with a scale of 1:62,500. In that inset the routes "appear" to be 62,500 * 0.1 /12 = 521 ft wide. Also, if you look at the centerlines of the routes depicted on those two pages (which I "drew in" below), they do not exactly match. For example, look at how the full chart shows the route going east of Hains Point while the inset shows it very close to Hains Point.

DCA Helicopter Routes

Given these chart differences, I wonder how far a helicopter can stray from the various depictions of a route before it is considered a pilot deviation? Perhaps the NTSB will give us some insight with their accident report.

Last edited by airplanecrazy; 14th February 2025 at 23:53 . Reason: Emphasize the route "appear"

Subjects DCA FAA NTSB PAT25 Route 4 Separation (ALL) Visual Separation

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ATC Watcher
February 12, 2025, 16:42:00 GMT
permalink Post: 11826805

Quote:

Originally Posted by bill fly

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.

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.

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

Quote:

Originally Posted by ATC Watcher

Concur. Scapegoating stochastically guarantees a repeat incident/accident of the same kind under "rhyming" circumstances.

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

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YRP
February 13, 2025, 01:33:00 GMT
permalink Post: 11827083

Quote:

Originally Posted by bill fly

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.

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).

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

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

Quote:

Originally Posted by YRP

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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Downwind_Left
February 13, 2025, 22:16:00 GMT
permalink Post: 11827672

I just can\x92t help compare the general situation to London, where it\x92s again very busy airspace, and the helicopter routes generally follow the river. You have Heathrow at western end and London City at the eastern end.

ATC do a fantastic job of managing the flow, basically by issuing helicopter traffic clearance limits based on the VRPs - usually based on Thames bridges. The Eastbound clearance limit is usually the Isle of Dogs\x85. Before London City Tower take over to manage traffic closer to the airport. At the Western end the heli routes go nowhere near the LHR approaches due or traffic density.

ATC will not in my experience clear any helicopter traffic to visually proceed behind airline traffic based on the helicopters visual perception. Day or night. They do a great job of keeping both airline and rotary traffic advised about each other, and prioritise air ambulance and police helicopters as required. But, they keep control over the overall traffic flow and it works.

I just fail to see why the FAA couldn\x92t employ a similar system, where helicopter traffic is issued a clearance limit - pending a gap in traffic - either a natural one or an ATC created gap. Before being cleared to continue.

I have also been in the situation having started engines at London City and police helicopter then was tasked to something going on off the departure end of the runway. All departures and arrivals suspend. Indefinite delays. It\x92s part of the bigger picture. CAVOK day but no possibility of visual separation. So the London system gives priority to helicopters where appropriate. But seems infinitely safer for both airline and helicopter traffic.

Subjects ATC FAA Separation (ALL) Visual Separation

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Lonewolf_50
February 14, 2025, 21:10:00 GMT
permalink Post: 11828211

Quote:

Originally Posted by gevans35

Are they suggesting that 100' vertical separation would have been okay?

No, hence the tower telling the Blackhawk to pass behind.

Quote:

Originally Posted by EXDAC

Landing flap, 9 deg pitch up, and full up elevator! That is what I heard NTSB report at today's briefing.
No one in the assembled press made any comment and so likely no one understood that was not normal or what it most likely indicated.

Seems to me like a reaction to seeing the Blackhawk right before impact and a reflex/reaction with intent to avoid.

The subtext for me is that the Blackhawk crew never saw them...but there's more for the NTSB to sort out, as the lady was VERY CLEAR about.

Subjects Blackhawk (H-60) NTSB Pass Behind Pass Behind (All) Separation (ALL) Vertical Separation

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deltafox44
February 14, 2025, 22:44:00 GMT
permalink Post: 11828270

Quote:

Originally Posted by Lonewolf_50

No, hence the tower telling the Blackhawk to pass behind.
Seems to me like a reaction to seeing the Blackhawk right before impact and a reflex/reaction with intent to avoid.

The subtext for me is that the Blackhawk crew never saw them...but there's more for the NTSB to sort out, as the lady was VERY CLEAR about.

NTSB did not say (and nobody asked

) if there had been any discussion in the black hawk cockpit about the CRJ (where it was, whether the PF did see it or not) when PM requested visual separation

Last edited by deltafox44; 14th February 2025 at 23:19 .

Subjects Blackhawk (H-60) CRJ NTSB Pass Behind Pass Behind (All) Separation (ALL) Visual Separation

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Stagformation
February 14, 2025, 23:34:00 GMT
permalink Post: 11828293

Quote:

Originally Posted by deltafox44

NTSB did not say (and nobody asked

) if there had been any discussion in the black hawk cockpit about the CRJ (where it was, whether the PF did see it or not) when PM requested visual separation

NTSB didn\x92t mention much in the way of cross cockpit intercom chatter. Must be a lot more that could have been said about the SA on both aircraft, eg altimeter checks, visual lookout, intentions, perceptions, checklists\x85etc.

Subjects Blackhawk (H-60) CRJ NTSB Separation (ALL) Situational Awareness Visual Separation

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Commando Cody
February 15, 2025, 05:36:00 GMT
permalink Post: 11828365

Quote:

Originally Posted by Lead Balloon

It appears from the NTSB's most recent press conference that the instruction "pass behind the CRJ" was not heard in the helo's CVR and, therefore by inference, not heard by the crew. Am I correct in assuming that there is no requirement to readback an instruction like that in the USA? ATC appeared not to expect one.

The Aeronautical Information Manual lists a number of instructions that should be read back, but there are none that must be read back (unless the controller specifically requests). "Pass behind..." is not even one of the "should" be read back instructions, so ATC wouldn't be bothered by not getting a read back. Frankly, if there was a requirement to fully read back all things like "Pass behind..." the frequency would be constantly full. In any case, whether PAT25 heard the "Pass behind" or not, it had already said that it was providing its own visual separation, so not hearing an instruction to pass behind does not take away the requirement to maintain separation.

Last edited by Commando Cody; 15th February 2025 at 07:45 . Reason: precision

Subjects ATC CRJ PAT25 Pass Behind Pass Behind (All) Separation (ALL) Visual Separation

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Easy Street
February 15, 2025, 10:24:00 GMT
permalink Post: 11828489

Quote:

Originally Posted by ATC Watcher

absolutely . the altimeter talk is just a distraction or at best contributing factor, Not the cause .. which brings us back to the safety assessment of the procedure , which the NTSB did not mention at all,, but I am sure , or at least I hope they will go into in their final report.

+1 to everything you and Wide Mouth Frog said.

I sincerely hope the NTSB can avoid being distracted by the distractions of altimetry and the missing ATC words on the Blackhawk CVR.

Upthread, Luca Lion calculated the 3 degree PAPI approach path as crossing the eastern riverbank at 270ft. If that's correct, then the CRJ's 313ft radar height 2 seconds before collision puts it at least 43ft above the approach path, so the Blackhawk's radio height deviation of 78ft would have contributed only about 35ft to the erosion of any intended "procedural separation" (*) between the aircraft. Or, to put it another way, the same outcome would have resulted if the Blackhawk had been at 235ft radio and the CRJ on the glide. Height keeping of plus or minus 35ft can only be achieved by instrument flying, which is obviously not compatible with visual separation (or indeed VFR) so cannot be reasonably cited as part of a safety case for the procedure. And of course a landing aircraft could easily be below the glide. Altimetry and height keeping are not the cause of this accident.

Missing the word "circling" wouldn't have influenced the helo crew getting visual with the CRJ at the time of the trasnmission. At best, it would have given them an extra nudge that "runway 33" (which was audible) meant the CRJ would be taking an easterly flight path. Missing "pass behind" with only a few seconds to collision was irrelevant if, as seems likely, the helo crew did not see the CRJ at that point.

(*) The quotes around "procedural separation" are intended to convey a tone of disgust and sarcasm.

Last edited by Easy Street; 15th February 2025 at 10:47 .

Subjects ATC Blackhawk (H-60) CRJ Final Report NTSB Pass Behind Pass Behind (All) Radar Separation (ALL) VFR Visual Separation

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Winterapfel
February 15, 2025, 10:55:00 GMT
permalink Post: 11828510

Quote:

Originally Posted by Easy Street

Following "5*why", keep asking...
Why did the did miss part of the message
Why was the incomplete read back missed
Why does missing a few words lead to this disaster within seconds.

Does this lead an answer like: helicopter in a very busy airspace, busy controllers (insufficient time to be fully focused on full read backs) being by default too close to (and even needing to cross) the glideslope.

Subjects ATC Blackhawk (H-60) CRJ NTSB Pass Behind Pass Behind (All) Radar Separation (ALL) VFR Visual Separation

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Easy Street
February 15, 2025, 12:41:00 GMT
permalink Post: 11828596

Quote:

Originally Posted by Winterapfel

I hadn't intended to go all the way along the causal chain in my post. But since you ask, I think your answer only goes one step further. There are more steps to take.

Helicopters in busy airspace are not a problem if a safe system exists for separating them from airline traffic.

There is no evidence yet of the controller having made a mistake. He was undoubtedly busy, but that was not his fault. What could be done about it? The answers to that question take us another step along the causal chain:

The FAA could have provided more controllers. We know the helicopter controller position was unoccupied, and it's likely that closer monitoring and earlier intervention could have changed the outcome (notwithstanding point 3).
Controller workload could have been reduced by implementing effective procedural separation . If the DCA ATC rulebook allowed this segment of Route 4 to be in simultaneous use with Runway 33 landings, then procedural separation did not exist , however much anyone thought it did. At least 1.5nm or 500ft between flight paths would be needed to meet the least restrictive FAA separation standards, and this would have forced constraints to be applied to Route 4 or Runway 33 utilisation.
Regulations allowed the helo pilots to assume responsibility for separation. This is what happened, with the consequences which flow from the inherent difficulty of identifying and separating visually at night (especially while wearing NVG).

The authorities (by which I mean FAA and DoD) have questions to answer on all three points. Why was the helicopter controller position vacant? Did the ATC rulebook or staffing requirements rely on a false assumption that procedural separation existed? How did any such assumption remain in place after previous near misses? Is visual separation between helicopters and airline traffic a reasonable thing for regulations to permit, at night and using NVG? Ultimately it seems to have routinely been used as a release valve for the pressure building in the system due to the failure to address points 1 and 2.

Hopefully the investigation will be bold enough to ask these questions, which expand the potential scope of responsibility well beyond the individual controller and pilots.

Last edited by Easy Street; 15th February 2025 at 13:36 .

Subjects ATC Close Calls DCA FAA Night Vision Goggles (NVG) Route 4 Separation (ALL) Visual Separation

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MPN11
February 15, 2025, 18:34:00 GMT
permalink Post: 11828759

Whilst these are valid observations, it is also micro-managing a procedure whose altitude separation was always totally flawed. I cannot personally attribute any blame to ATC or either pilot when the scenario was so badly devised ... and that means not only the infamous Route 4 but the concept of visual separation in the dark.

It was doomed to fail, eventually, but sadly someone [other than those directly impacted] never saw it coming. THEY are the culprits.

MPN11, former Mil ATCO

Subjects ATC ATCO Route 4 Separation (ALL) Visual Separation

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island_airphoto
February 15, 2025, 20:36:00 GMT
permalink Post: 11828824

Quote:

Originally Posted by MPN11

Pretty much it, everyone had to be lucky every time, gravity only had to be lucky once. The altimeter issues are a red herring at best, the helicopter crew were not trying to go directly under the airplane.

Subjects ATC ATCO Route 4 Separation (ALL) Visual Separation

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HaroldC
February 16, 2025, 04:57:00 GMT
permalink Post: 11828979

Quote:

Originally Posted by ATC Watcher

I agree that the DC controllers should not be scapegoated. At the same time, the concept of professionalism must be addressed. The concept that professionals in a field must alone (without management, without lawyers, without the public) maintain the best practices of the given professional discipline.

In the US, physicians who work for "Health Maintenance Organizations" are asked to practice medicine, at times, in a "basically unsafe" manner...to keep patients moving. On occasion, such practices will bite a patient (and sometimes the physician). As a whole, HMO physicians do not enjoy the best reputation.

From my perspective, there is practically no difference between the plight of an American air traffic controller and an American HMO physician. Both are expected to "squeeze one more in." Both fields are staffed by above-average capable individuals who thrive on challenges. Both are managed in such a manner that they cannot say "no" and also keep their job. In this regard, at least physicians have job portability.

But the take home point is that one cannot admit to knowing a practice is fundamentally unsafe, yet do it anyway. The public, rightfully, should not accept this. I have no solution except more staff and/or more airports (and not some next-gen whizzbang computer system).

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Easy Street
February 16, 2025, 09:42:00 GMT
permalink Post: 11829100

Quote:

Originally Posted by HaroldC

But the take home point is that one cannot admit to knowing a practice is fundamentally unsafe, yet do it anyway.

It's an interesting comparison, but I am not sure it's fair to say that a controller would know that visual separation at night is unsafe or appreciate the counterintuitive point that NVG make it less safe. Of course, they *should* know, but since they don't need to have night flying (or any flying) experience of their own, they are reliant on being educated on that point. That would be a matter for the regulator (specifically, pilots and human factors specialists within the regulator) to ensure. The same goes for the more robust option of prohibiting night visual separation entirely.

Spoiler

Returning to your doctor analogy: if front line medics prescribed a drug which years later turned out to be harmful to patients, despite following all professional best practice and having no reason at the time to suspect that the drug had been wrongly certified, it would be grossly unfair to hold the medics responsible. Instead we would turn to the drug regulator and those who carried out the trials.

Spoiler

Last edited by Easy Street; 16th February 2025 at 10:32 .

Subjects ATC Night Vision Goggles (NVG) Separation (ALL) Visual Separation

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Easy Street
February 16, 2025, 18:30:00 GMT
permalink Post: 11829380

Quote:

Originally Posted by Not_apilots_starfish

Not quite sure why you all are being relaxed about the air space.

200 feet is the maximum and they had to get permission for this route. They\x92re flying past a busy airport. On one hand you\x92re all saying this accident was bound to happen, on the other hand this in and of itself indicates pilots don\x92t fly through these zones without concerns & vigilance. It makes no sense they would play roulette with the height - most pilots would be adhering to rules & a little on edge knowing a VIP or any number of emergency protocols could happen in the capital of America.

It just doesn\x92t add up - the complacency over elevation. Between two pilots it should have been rectified. May they rest in peace & this isn\x92t a slur against their name but in support of it not being their fault and something amiss.

The point is that PAT25 could have been tightly hugging the eastern bank at precisely 200 feet, and yet everyone would still have died if the CRJ had been slightly below its proper approach path (as it might easily have been). Yes, you can say that *this* accident wouldn't have happened if the helo had been at 200 feet, but that gets us precisely nowhere in preventing recurrence.

Systems that rely on human perfection are 100% guaranteed to fail. The only question is how often. The system in place at DCA required helo pilots to assume responsibility for visual (*not vertical*) avoidance of collisions in order to fulfil their ordered missions. Given what we know about human visual performance at night, that would eventually end badly, and sure enough it did. There is a strong element of the pilots having been set up to fail, which is why no-one here is going hard on them.

Altimetry and height keeping would be important matters for investigators if the collision had occurred due to a breakdown in vertical separation, which as a minimum would involve 500 feet (and more often 1000 feet) of planned spacing to account for instrument and height keeping errors. FAA instrument rating standards require pilots to be able to maintain altitude plus or minus 100 feet. This helicopter was being flown VFR at very low height, which means that looking outside takes primacy over monitoring instruments. I'm sure helo pilots could fly along at 175ft plus or minus 25ft if they really tried, but you can be certain they wouldn't be looking out for traffic (as is required when holding responsibility for visual separation).

However, as there was no vertical separation built into this procedure, all of this is at best a distraction. The more important questions are why procedural barriers were not in place to stop the route being used during landings on runway 33, and whether visual separation at night is an adequate barrier to collision when airliners and their human cargo are involved.

Last edited by Easy Street; 16th February 2025 at 18:57 .

Subjects CRJ DCA FAA PAT25 Separation (ALL) VFR Vertical Separation Visual Separation

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island_airphoto
February 16, 2025, 18:49:00 GMT
permalink Post: 11829389

Quote:

Originally Posted by Easy Street

The point is that PAT25 could have been tightly hugging the eastern bank at precisely 200 feet, and yet everyone would still have died if the CRJ had been slightly below its proper approach path (as it might easily have been). Yes, you can say that *this* accident wouldn't have happened if the helo had been at 200 feet, but that gets us precisely nowhere in preventing recurrence. Systems that rely on human perfection are 100% guaranteed to fail. The only question is how often.

Altimetry and height keeping would be important matters for investigators if the collision had occurred due to a breakdown in vertical separation, which as a minimum would involve 500 feet (and more often 1000 feet) of planned spacing to account for instrument and height keeping errors. FAA instrument rating standards require pilots to be able to maintain altitude plus or minus 100 feet. This helicopter was being flown VFR at very low height, which means that looking outside takes primacy over monitoring instruments. I'm sure helo pilots could fly along at 175ft plus or minus 25ft if they really tried, but you can be certain they wouldn't be looking out for traffic (as required when taking visual separation).

However, as there was no vertical separation built into this procedure, all of this is at best a distraction. The more important questions are why procedural barriers were not in place to stop the route being used during landings on runway 33, and whether visual separation at night is an adequate barrier to collision when airliners and their human cargo are involved.

N123, join the downwind, your traffic is a 737 on final 2 miles out, turn base behind him, you are #2. I can do that at night unless there are other 737s lined up and then I have to figure out which one.
N123, do you see the closest plane lined up, pass right below and behind him and never mind all the other planes right behind. Ah......NO.
There is night visual and there is night nutty visual. The first example leaves a lot of room for error and time for ATC to see if it is going wrong.

Subjects ATC CRJ FAA PAT25 Pass Behind Pass Behind (All) Separation (ALL) VFR Vertical Separation Visual Separation

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