Posts about: "Separation (ALL)" [Posts: 442 Page: 18 of 23]¶

Is there such a thing? I flew gliders, there have been mid-airs (some fatal) despite only flying in daylight & decent vis, and despite the development of Flarm.

ATCDumbo
I'm all ears, excellent point. This focus on ADSB-OUT, and ADSB-IN is really a furphy in terms of this investigation to determine the facts, the whole facts and nothing but the facts.

If 5342 had ADSB-IN then PAT25 not having or not displaying ADSB-OUT could be relevant depending on 5342's cockpit display, the training of the pilots and their scanning.
5342 didn't have ADSB-IN so move along, move along, nothing to see, these aren't the droids you're looking for.

**Caveat. If the TWR display were using ADS-B for their updates and to generate Collision Alerts then the absence of PAT25 ADSB-OUT could be relevant.
But would the TWR ATC even know (or care) whether PAT-25 was ADSB-OUT capable. TWR ATC involves looking out the windows and judging the relative positions of aircraft.

Note: ATC display systems are not referenced in the NTSB Aviation Investigation Preliminary Report. This seems to be a glaring omission. So perhaps the NTSB are either very dumb or deceitful or both.

To further illustrate the focus on ADSB. Figure 1 Google Earth image with preliminary ADS-B data for flight 5342 and radar data for PAT25.
The ADS-B plots are 1 seconds intervals, the radar data are 4 second interval (as stated during US Congress Q&A).
So the focus is on the whizz bang ADS-B kit rather than what the ATC saw on their display.

There is reference to ATC radios, and 5342 was on frequency 119.1 MHZ and PAT25 was on frequency 134.35 MHZ. The ATC could've had them on the same frequency (changed PAT25 to 119.1 MHZ) but this would be abnormal. ATC Voice Switch systems like Frequentis, SITTI and Rohde & Schwarz typically have a frequency coupling, whereby controller broadcasts on multiple frequencies (2 or more) and voice communications on one frequency are heard on the other. In this case, ATC would broadcast on 119.1 MHZ and 134.55 MHZ and 5342 would hear instructions for aircraft on 134.55 MHZ, and PAT25 would hear instructions for aircraft on 119.1 MHZ.

Yes, visual separation is typically used close to an aerodrome where the ATC is applying visual separation to reduce the standard from 3NM to something less, 2NM, 1NM, or even less, depending on the circumstance which includes weather (included visibility), day / night, workload to monitor the separation, plus other considerations such as equipment.

I just wonder how many of the January Route 4 Helicopter plots crossing RWY 33 Approach (post 1346) were the result of ATC issuing a control instruction to change the track to closer to the shoreline or further over water.

Use of Route 4 during RWY 33 Approaches or RWY 15 Departures is possible providing a clearance limit is imposed prior to assigning relevant traffic, positive control instruction(s) and in the case of 5342, advising them of the relative position of PAT25 and that PAT25 would be maintaining separation from them.

Example for Route 4 southbound would be a clearance limit of Hains Point. Helicopter would be released past this point when there is no conflict (nil traffic) or assigned separation to avoid (pass behind). If there is a in-line stream of arriving traffic then Route 4 may not be available.

Sydney KSA has something similar for one of their helicopter routes - BONDI 5 (yep, named after the beach), delays may occur when RWY 07 is in use for DEP, or RWY 25 is in use for ARR. Further, the route is not available when RWY 16 PRM approaches are being conducted. Sydney KSA helicopter routes are in text form - TRACK TO..., TRACK VIA..., EAST OF..., and the INBOUND routes to Sydney KSA have a clearance limit in the clearance. A map display is very useful however it should be based on route descriptions. Perhaps the committee of 17 knows the history of the helicopter routes in and around DCA.

Since we\x92re discussing the DCA accident, let\x92s be clear about U.S. terminology as specified by 7110.65.

There is tower-applied visual separation . That is not relevant to the DCA accident.

There is also pilot-applied visual separation . That is what PAT25 requested and the LC approved.

As for the perfectly-safe visual separation, the DCA accident might have been avoided had the LC applied all of the elements of pilot-applied visual separation; i.e.

I really value your contributions, as you bring an analytical and legalistic mind to bear, and help others understand some of the issues. However... from my (simplistic) viewpoint, the helo pilot explicitly requested visual separation. That's explicitly requesting the right? responsibilty? to keep themselves separated from other traffic. This they failed to do. Surely that is negligence.

There were other holes in the cheese, so the pilot was working in a compromised environment.

I'm just an SLF, so no domain expertise at all.

Let's say that the reasoning you have described is not only valid but also the dominant theme of an anticipated trial. Is it not difficult to contemplate a trial in which the central theory of liability is invoking a dread phrase, one with both the words "pilot" and "error", or at least the "negligence" version of that phrase. This would be a horrible case to see unfold. Of course the lawyers representing the families and other loved ones of the accident victims will press hard to make exactly such an unfolding happen - and their clients, the families and other loved ones, will be pressing just as hard as the families of the MAX accident victims are doing in the criminal case in federal court in Texas, if not harder.

This is not a reason either to dismiss, or to claim decisivenesss of, any particular legal reasoning here. It is instead recognition that reasoning which points to the request for visual separation and then the failure to maintain it as the basic cause of the accident will produce a very unpleasant legal case. Think of the Army units assigned to this sort of duty, how they are trained to treat "continuity of governement" and transport of highly important (presumably) officials as a kind of higher calling - at least that's the impression given by several statements or articles. And one set of their fellow servicemembers are put in the position of being blamed, and not present even to try to explain what happened. And that's in addition to usual strident reluctance to assign responsibility to aviators in situations where things go wrong.

Over the past several days, it has become clearer that the airspace environment was indeed so compromised that, as SLF/attorney without technical expertise or even knowledge about airspace design, management and operation, it would be best to stop trying to refine an understanding of the causes and effects and instead leave the puzzle-solving aside until the NTSB report is completed and released. That said, the way Sen. Cruz pressed witnesses last week suggests that waiting for the report will be a difficult task.

I appreciate any and every acknowledgement of efforts to make positive contributions to this forum - thank you for your post!

As other posts have admitted I am biased against assigning responsibility in situations such as this one to any aviator. There additionally may be a somewhat unique factor in this case too (involving some personal history about Army aviation maintenance training circa 1975, enlistment as an alternative to dead-end mindless jobs, and studying German in high school and for a couple of semesters in college so that if I ever went to Germany in the Army . . . ).

NTSB chair pointing out the horizontal position of the helicopter during last weeks testimony.
The altitude is still uncertain because of difference between jet and heli values and destruction of the heli altimeter. So work on that is continuing with a focus on other sources.
But note the 75 ft separation is a maximum. So if the heli was at 200ft then it was on the glide slope.




Another interesting point is that mixed heli and fixed wing is forbidden in the yellow zone (permanently), and ADSB mandatory in the red zone. With routes 4 and 6 cut.

See post below

I tend to agree with ATC Watchers take on this.
Some people are making out that if the Helicopter had ADSB-out switched on/ activated, then this would never have happened.
Someone correct me if I am wrong but if the Blackhawk has ADSB-out switched on then nothing changes for the CRJ on that night. The TCAS behaves the same, there is no display of the Blackhawk on the CRJ\x92s Nav display\x85..nothing changes. The CRJ crew are still conducting an approach that requires a lot of fast mental processing close to the ground, at night onto a short runway while ensuring checklists/configuration etc is correct. ie they have a high workload. During this high workload phase, \x91the system\x92 has seen fit to allow a single Human ( the helicopter Captain) to be responsible for the separation of the two aircraft visually, at night, in a busy environment while conducting a check, on NVG\x92s.
Is it likey that a single Human, with the sole responsibility, will make a mistake? It\x92s not just likely, it\x92s inevitable, regardless of how sharp and well trained they are, if you run the program long enough their vision, or their SA will fail them and we get what we got here.
The system should never have devolved to the point where one person accepted the responsibility for visual sep 6nm away, at night, in a busy traffic environment while dealing with their own high workload.
The Blackhawk crew had a high workload, the CRJ crew had a high workload, the ATC had a high workload, there was no fat left in the system. Humans make mistakes and any good system will be tolerant of those mistakes.
The system was not tolerant of a mistake, ergo, the system is at fault.

Hi layman54 , I think it's much more subtle than that. As you say, other bits of the system may put the pilots into danger but you then need to fully understand why the Pilot(s) didn't save the day. You sort of start off with the premise that the crew of PAT25 took off that evening and certainly didn't want to fly into the CRJ - so, why did they?

To say so-and-so got it wrong is often obvious ........ but why did they get it wrong? That's often very complex and can involve a lot more people and a raft of other factors and that's where the really valuable lessons are to be found. That's the real reason behind any "bias" - it's so we don't simply stop at that first person (or persons) who got something wrong, but look at what led to them doing what they did and what other factors contributed to the end result . That is the real way Safety is improved. You can then look at appropriate mitigation to try and prevent that same scenario from setting up another crew to fail in the same way at a later date.

As others have said, height and track is a red herring TBH as the deal with ATC was for PAT25 to "see and avoid" so they could have quite safely passed behind the CRJ at the same altitude or even above it - but not too close due to things like wake effects. If you can't manage "see and avoid" safely, you need to build in much, much bigger safety margins - such as holding PAT until the CRJ had landed. Many, including me, have asked how on earth the PAT25 crew (or, indeed, anyone) could reliably be expected to pick out the CRJ in that scenario especially at that range. For vertical/horizontal separation, relying on a few 10's of feet up/down or left/right is simply worthless given errors with altimeters and piloting accuracy in such a high-workload situation where it's "eye's out" navigating and looking for traffic all at a couple of hundred feet above land/water which is quite unforgiving if you get too low (I know ex helo crew who are no longer here because they inadvertently hit the sea) - not to mention any issues with NVGs (no idea, never used them!). What the NTSB implied was that, by suggesting that such a set-up as Route 4 passing under the approach to 33 was intrinsically safe through vertical/lateral separation, was madness. The route was pulled almost immediately pretty much on that basis.

So, for example, based on the difficulty in picking out the correct aircraft from the inbound stream, one of the many questions I've been asking myself is "Why were the PAT25 crew so willing to say they had the CRJ in sight (twice they said that) in that environment?". Had that become "normalised" on the Sqdn, or were the risks of miss-IDing a/c not being adequately highlighted in Local Orders, particularly given the geometry of that specific set-up? There may be several reasons - that's for the NTSB to dig out. I used to do a lot of visual separation stuff Commercially and I was nervous as hell - and that was in wayyyyyyyy simpler scenarios in way better conditions usually involving just one other aircraft. ATC were the same - they were very pointed in making sure I'd really seen the a/c in question. Any doubts in my mind or the ATCs mind and it was either an orbit till traffic was well clear or, if busier, it was "Contact Approach ....... lets chat again when they hand you back to me on the ILS.". OK, the ILS bit is not applicable to PAT25 but you get my drift!

There is no one reason why this accident happened - there will be quite a list with each one contributing to the final outcome. Any one of those things, had they been different decisions by those involved on the night, or, for example, by those who designed and approved Route 4 way back when, would have saved the day. So correct not just the 1st issue you find, find out and correct ALL the issues! That's what we really need to do to stop similar things happening again, not just at DCA, but anywhere.

Anyway, hope the above helps with the context of the word "bias". It was not that long ago it was "Hang the crew! Erm, oh no! Someone else has done it now! Hang them too!" Rinse & repeat! Thankfully, we are much better at digging out all the issues these days. But we have to constantly remind ourselves to "Look for everything, not just the 1st thing you find!". Cheers, H 'n' H

This raises the question of what fraction of helicopter crews in that situation asked for visual separation. And how often did ATC grant it? According to posts above sometimes helicopters were held at Hains Point so apparently visual separation wasn't universal.

Yep, that question .......... and loads more.

One thing I mentioned earlier is that airlines also have a responsibility for conducting safe operations; safe for their crews, their pax and by-standers. For eg, airlines often have additional rules for certain airfields (eg some require specialist training before crews can operate in there due to say, terrain issues on the approach). As has anecdotally been reported on here, if there have been an above "average" (and someone will need to figure out exactly what that means) number of issues with this particular approach in terms of TA's, irrespective of the outcomes, 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. Sadly, even that doesn't guarantee the right decision was reached ...... but at least they'll have formally assessed it. Trouble is, landing on 33 seems to have cut taxi time = fuel = $'s.......

Anyway, just some thoughts! You know, I can be a right cynic at times but, having a background in Safety Engineering in a previous life, that's par for the course!!! Cheers, H 'n' H

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.

Who knows, you may be right. I think AA rocking up at DCA and stating that, as "policy", they'd never ever use the sidestep to 33 due to their own safety assessment flagging it up, esp if based on TCAS evidence, would have led to interesting discussions at senior levels. As you say, how that would have ended is anyone's guess. Bit academic anyway as there was no AA ban and the AA flight accepted it when offered it and the next AA asked for it on initial contact ..... not realising what had just happened! That's why I had a $ sign in my earlier post! The cynic that I am........

Apart from the IMC non-issue, the cause-and-effect chain of events and omissions in this accident is still under investigation. But I'll try to give some answer to your post - although I doubt my mind will latch onto anything new compared to the volume of this thread to date.

There are unknowns at this point about what information the Army PAT25 crew had in front of them about the altitude at which they were operating. There also are unknowns about the Army crew's visual scan (which, as a non-aviator, sounds to me like a complex subset of facts; I do work on maintaining strong visual scan plying limited access highways and even local streets and roads in my car but the instrument panel of my vehicle is, shall we say, somewhat limited in comparison). Add in the relatively fixed attributes of the physical environment, the background lights of the city and surrounding areas, the river, and so forth. Plus, NVGs, plus experience using same by the particular crew.

Then with all those factual matters still subject to fairly significant unknowns (at least as I am able to follow the developments), your question(s) turn to the acts or omissions of ATC. I am fairly strongly inclined to "stay in my lane" - meaning, there is a lot more about how ATC functions are performed that I don't know, compared to what I might actually have picked up from forum threads and other sources. It stands to reason that the visual separation set-up is subject to formal written rules and procedures, but I don't know to what extent these presumed rules and procedures reach down to very specific operational details. Beyond that, the signal-to-noise ratio of what more I might say would not be too especially good.

I'm reminded of the old saw that some one or another fairly well-versed individual has already forgotten more about a given subject than some smart-aleck will ever be able to master about such subject. I don't want to trip over that . . . altitude restriction.

One other perhaps non-trivial item I can add is that the attorney whose office has filed the preliminary claim (as required pursuant to the federal statute) is very accomplished in this field. I've met him at professional (Aviation Law) conferences. I have enough respect for other members of the bar who have amassed vastly larger public records of accomplishment - even those records which prompt lawyer-bashers to decry the profession and all who practice in it - not to try to pass off forum talk as the equivalent, or even merely reflective of, the serious legal thinking going on in that attorney's conference room. And many other law firm conference rooms. The issues in this matter aren't going to be simple, neat, or pleasant. Perhaps the air has been deflated out of the emotional shock-balloon the midair collision visited upon many folks; it is still my view that this was a catastrophe, wrenching in many respects the NAS all the way back to the skies over New York City in 1960 and the midair which ultimately gave rise to the formation of PATCO. And the strike, which led to, with respect to controller staffing . . . . .

As earlier mentioned, TAs (Tower and TCAS) may among other incidents and excursions find their way into databases including ASIAS. Once the NTSB dug into the databases, it came up with a long history of losses of separation at a frequency that makes one wonder that such an accident hadn't happened earlier. I suspect that this is not solely a DCA problem.

But who should be watching the data for trends - individual regionals, individual majors, local military, local ATC, individual airport authorities, FAA, NTSB?

The IP radioed "traffic in sight" which clearly showed that they had the wrong plane, if any in sight and lost both situational awareness. If have no idea why the helicopter had not its ADSB turned on. Training for real sneaking at night through DCA is idiotic as we know now with 20/20 hindsight. Visual separation with several planes in the area is challenging in daylight, let alone at night. You easy miss one.

Both crews were set up to fail. Considering the near monthly DCA conflicts between helos and fixed wing over a number of years, the surprise is that a midair didn't happen sooner. The data was accumulating, but nobody caught on in time. Not transmitting ADS-B Out in busy airspace and flying in that airspace with night vision goggles restricting view is a major factor. The lack of ADS-B In in the cockpits is another. Then there's the FAA approval of a helo route with inadequate vertical separation from the 33 approach slope along with a lack of ATC procedure to ensure positive separation between helos and aircraft on approach to 33.

Somehow I doubt that all those responsible for those lapses in oversight were female - quite possibly they were all male.

I really struggle to comprehend why the helicopter not transmitting ADS-B Out is relevant to the accident. What benefit would the other two parties - the CRJ and the TWR Controller gained?
The CRJ didn't have ADS-B IN, and the ATC Surveillance system (radar) doesn't process the data.

DM as required to convince me otherwise.

It would appear that while DoD reevaluates its helicopter operations inside the Beltway, it has shifted training flights to outside the Beltway. The only exception appears to be the USCG MH65s as they are based at DCA but even those are now flying more outside the Beltway.

If Route 5 is not being used (and Route 4 is shutdown), how are military helicopters accessing JPN?

Prior to the DCA accident, I don\x92t know that I\x92d ever seen a UH-60 out my way on Route 9 in nearly 3 decades. Now PAT UH-60s are almost a daily occurrence on Route 9 (saw/heard 4 yesterday). The ADW-based UH-1Ns are also flying Route 9 more frequently.

I maintain the the DC helicopter routes (including Route 4) interior to the Beltway are not inherently unsafe if used with appropriate restrictions and ATC-applied separation.

action is taking place with changes on the routes : (source Ops group Briefing ).

Pretty clear the Army helicopter was too high, a little off course, and certainly did not have the plane in sight the controller wanted them to have in sight. Controller busy and separation left to helicopter crew.

So may 'what ifs' could change the outcome. A "caution - VFR helicopter traffic below - southbound along river" call out to the CRJ crew by ATC could of made the difference. The helciopter crew staying at or below 200 could of made the difference.

Its amazing that this was considered "the norm" in that area.