Posts about: "CRJ" [Posts: 363 Page: 8 of 19]ΒΆ

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photonclock
February 02, 2025, 00:21:00 GMT
permalink Post: 11819407
Just finished watching the NTSB briefing, which stated that the CRJ was at 325 feet AGL, and helicopter max allowed altitude is 200 feet.

Assuming the CRJ was at an expected/typical altitude at that point in it's approach, if the helicopter was at 200 feet, or lets say for their benefit 175 feet, then they would have avoided collision by a mere 150 feet of vertical separation if everything else about the position of the two aircraft remained the same.

Is 125 feet of vertical separation (with no horizontal separation) considered acceptable?

If the CRJ movement is controlled by ATC, and the helicopter is responsible for avoiding all other aircraft, then there is no question the helicopter was at fault here as the primary cause, and ATC as the secondary.

Given the collision course these aircraft were clearly on, why wouldn't ATC have diverted one of them prior to impact? Does ATC have any reason to believe that the helicopter sees everything with the same degree of detail and accuracy as ATC? This is not a sarcastic question. I'm genuinely curious. Would ATC, hearing the helicopter twice affirming visual separation, have had any plausible reason to doubt that the helicopter was unaware of the impending collision?

What's the point of having Air Traffic "Control"...if they're not actually in control?

Subjects ATC  CRJ  NTSB  Separation (ALL)  Vertical Separation  Visual Separation

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Denflnt
February 02, 2025, 00:48:00 GMT
permalink Post: 11819416
Originally Posted by photonclock
Just finished watching the NTSB briefing, which stated that the CRJ was at 325 feet AGL, and helicopter max allowed altitude is 200 feet.

Assuming the CRJ was at an expected/typical altitude at that point in it's approach, if the helicopter was at 200 feet, or lets say for their benefit 175 feet, then they would have avoided collision by a mere 150 feet of vertical separation if everything else about the position of the two aircraft remained the same.

Is 125 feet of vertical separation (with no horizontal separation) considered acceptable?

If the CRJ movement is controlled by ATC, and the helicopter is responsible for avoiding all other aircraft, then there is no question the helicopter was at fault here as the primary cause, and ATC as the secondary.

Given the collision course these aircraft were clearly on, why wouldn't ATC have diverted one of them prior to impact? Does ATC have any reason to believe that the helicopter sees everything with the same degree of detail and accuracy as ATC? This is not a sarcastic question. I'm genuinely curious. Would ATC, hearing the helicopter twice affirming visual separation, have had any plausible reason to doubt that the helicopter was unaware of the impending collision?

What's the point of having Air Traffic "Control"...if they're not actually in control?
125'? God no.

The helo should have been told to hold some half mile away and wait for crossing traffic to clear.

The NTSB is going to have a field day with the FAA on this.

Subjects ATC  CRJ  FAA  NTSB  Separation (ALL)  Vertical Separation  Visual Separation

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photonclock
February 02, 2025, 00:50:00 GMT
permalink Post: 11819419
Originally Posted by Lead Balloon
That's assuming perfect equipment accuracy. My understanding is that the tolerance of e.g. an IFR altimeter in the USA is 75'. If that's correct, one IF aircraft with a 'legal' altimeter indicating 325' could in fact be at 250' and another IFR aircraft with a 'legal' altimeter indicating 175' could in fact be at ... 250'. I'm hoping that the avionics in the aircraft involved in this terrible tragedy were more accurate than that, but I always exercise caution in taking numbers out of avionics and ATC systems as 'gospel truth' to the foot. The altitudes on RADAR displays don't increase and decrease in 1 foot increments; nor do the outputs of aircraft transponders. RADALT is different.
Of course. So lets assume the readings to be at the outside of the envelope to the benefit of both aircraft, ie, CRJ at 350 (325 +/- 25 as stated by NTSB), and 200 +/- 75 for the helicopter, so 125. That's 225 feet of vertical-only separation. Is that considered acceptable? If not, why did ATC allow it?

Subjects ATC  CRJ  IFR  NTSB  Separation (ALL)

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Denflnt
February 02, 2025, 00:57:00 GMT
permalink Post: 11819424
Originally Posted by Bratchewurst
Couldn't the same result be achieved by landing on RWY 01 and (assuming 15/33 is not in use) simply taxiing off 01 onto 33? It wouldn't be slower, there'd be no hazard from landing or departing traffic on 01, and, as the ground track would be shorter and one engine could be shut down to taxi, quite possibly more fuel-efficient.
The CRJ was diverted to 33 because of traffic. No other reason. The pattern was congested, so ATC diverted them to relieve those issues for them at the time. The CRJ could have declined the ATC's request, but they would have had to circle for another approach to R1. From what I have seen, the CRJ adapted to that request professionally and ATC should have made sure that they were safe. Instead, ATC put the onus on the helo crew to maintain a safe airspace. That't the ATC's job, especially given the situation.

Ws should expect more.

Subjects ATC  CRJ

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artee
February 02, 2025, 01:26:00 GMT
permalink Post: 11819432
Originally Posted by Denflnt
The CRJ was diverted to 33 because of traffic. No other reason. The pattern was congested, so ATC diverted them to relieve those issues for them at the time. The CRJ could have declined the ATC's request, but they would have had to circle for another approach to R1. From what I have seen, the CRJ adapted to that request professionally and ATC should have made sure that they were safe. Instead, ATC put the onus on the helo crew to maintain a safe airspace. That't the ATC's job, especially given the situation.

Ws should expect more.
My understanding is that the helo crew requested VFR, which ATC accepted. So essentially the helo crew requested the onus. Whether ATC should have accepted is a valid question, but it seems to have been commonplace. Normalisation of deviance?

Subjects ATC  CRJ  VFR

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aox
February 02, 2025, 01:32:00 GMT
permalink Post: 11819434
Originally Posted by photonclock
Assuming the CRJ was at an expected/typical altitude at that point in it's approach, if the helicopter was at 200 feet, or lets say for their benefit 175 feet, then they would have avoided collision by a mere 150 feet of vertical separation if everything else about the position of the two aircraft remained the same.

Is 125 feet of vertical separation (with no horizontal separation) considered acceptable?
Put it this way

If two aircraft passed that close in some other part of controlled airspace, and they'd seen each other, would one or both have filed an air miss report?

Subjects CRJ  Separation (ALL)  Vertical Separation

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B2N2
February 02, 2025, 01:50:00 GMT
permalink Post: 11819439
You don\x92t put a descending aircraft in the path of a level aircraft with 100-150\x92 vertical separation.
That is insane.
The CRJ likely wasn\x92t flying VNAV vertical guidance as it\x92s an LNAV only MDA for 33 and they were coming out of a left base to final turn flying visually on a 3 degree PAPI.
Which means they\x92re hand flying and no one can guarantee they won\x92t be slightly slow to slightly fast or slightly high or slightly low.
\x93Three red on the PAPI correcting\x94
0.01 on the altimeter is 25\x92, that\x92s already 10%
Plus inherent altimeter inaccuracy,
For a shorter taxi or one departure.
Its madness.

Subjects CRJ  Separation (ALL)  Vertical Separation

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adnoid
February 02, 2025, 01:53:00 GMT
permalink Post: 11819441
Originally Posted by photonclock
Just finished watching the NTSB briefing, which stated that the CRJ was at 325 feet AGL, and helicopter max allowed altitude is 200 feet...
That speaker had more patience than I would after being asked the exact same question over and over. His first explanation was clear. Sheesh.

Subjects CRJ  NTSB

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YRP
February 02, 2025, 01:59:00 GMT
permalink Post: 11819443
Originally Posted by arc698
A red collision alert was flashing at this point on the controllers screen, the instruction should\x92ve been for the CRJ to go around, not wasting time on the helicopter pilots.

Secondly, why shouldn\x92t we criticise the controller? Imho his actions need to be criticised. Not the individual but the environment, procedures and training he operated in. The mission of ATC is to prevent exactly this from happening and they failed in their mission.
It is Conflict Alert not Collision Alert. It notifies the controller that two targets might get close, in case they weren\x92t aware.

It would happen all the time with visual separation. It\x92s nothing like the RA must-follow-without-question alert. Issuing a go around would often be the exact wrong thing to do.

In this case the controller was aware they were close.

The accepted procedures look like quite likely the culprit here. They seem to allow a single mistake (misidentifying visual traffic) to become catastrophic.

The controller\x85 he\x92s required to use the accepted procedures. If the procedure after safety analysis is to allow helicopters to visually separate from jets, he can\x92t just say not on his shift. He can double check of course, and imho that\x92s what his \x93still got \x91em in sight\x94 call was about, since it clearly concerned him.

Anyway my point about not criticizing him was just that my post was not intended that way. I don\x92t have access to listen to the full conversation. If you do, then go ahead.

And certainly the environment/procedures/etc are all in question here.

Subjects ATC  CRJ  Separation (ALL)  Visual Separation

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PuraVidaTransport
February 02, 2025, 02:27:00 GMT
permalink Post: 11819458
Watching the wrong aircraft??
If the Army pilots mistook another aircraft for the CRJ they were warned of at least three times, can someone look at the radar and explain which aircraft they thought was the CRJ? I see none they could have possible been watching instead. Considering the distance from one warning to the next and the Army pilot's assurance of seeing the CRJ both times, I don't see how any light on the ground could have been their focus either.

Subjects CRJ  Radar

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Denflnt
February 02, 2025, 02:53:00 GMT
permalink Post: 11819469
Originally Posted by artee
My understanding is that the helo crew requested VFR, which ATC accepted. So essentially the helo crew requested the onus. Whether ATC should have accepted is a valid question, but it seems to have been commonplace. Normalisation of deviance?
The helo was always always flying VFR. ATC's job was protecting the CRJ.

Subjects ATC  CRJ  VFR

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Easy Street
February 02, 2025, 02:56:00 GMT
permalink Post: 11819470
Originally Posted by PuraVidaTransport
If the Army pilots mistook another aircraft for the CRJ they were warned of at least three times, can someone look at the radar and explain which aircraft they thought was the CRJ? I see none they could have possible been watching instead. Considering the distance from one warning to the next and the Army pilot's assurance of seeing the CRJ both times, I don't see how any light on the ground could have been their focus either.
AAL3130 on final to runway 1. The diagram at my #432 shows how there was only 12 degrees difference in bearing between it and the CRJ. Someone else did a reconstruction showing that the differences in height and range made the elevation angles similar too. It's very difficult to judge distance at night (and impossible on NVGs). And unlike the CRJ, the AAL was pointing directly towards the helo so its landing lights would have looked brighter.

I suspect the helicopter's gradual turn to the right was a result of the pilots fixating on AAL3130 and instinctively flying to pass just behind it, without realising how far away it was.

Edit: this is the reconstruction which shows the similarity in elevation. Captain Steve and Juan Browne have put forward the same theory on their channels but without quite the same compelling graphics.





Last edited by Easy Street; 2nd February 2025 at 03:09 .

Subjects CRJ  Night Vision Goggles (NVG)  Pass Behind  Pass Behind (All)  Radar

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Denflnt
February 02, 2025, 03:02:00 GMT
permalink Post: 11819477
Originally Posted by PuraVidaTransport
If the Army pilots mistook another aircraft for the CRJ they were warned of at least three times, can someone look at the radar and explain which aircraft they thought was the CRJ? I see none they could have possible been watching instead. Considering the distance from one warning to the next and the Army pilot's assurance of seeing the CRJ both times, I don't see how any light on the ground could have been their focus either.
OK, let's go down that route, as dumb as it is. How many times was the CRJ warned of traffic? I don't recall hearing them being alerted at all, though on short final, low and configured for landing there wasn't much they could do at that point. It is ATC's job to ensure separation for controlled aircraft. If ATC relied solely on the helo to keep from hitting the CRJ, that is a big effing problem.

Subjects ATC  CRJ  Radar  Separation (ALL)

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galaxy flyer
February 02, 2025, 03:04:00 GMT
permalink Post: 11819478
Originally Posted by Denflnt
The helo was always always flying VFR. ATC's job was protecting the CRJ.
In Class B, all aircraft are separated, it might visual, it ATC is required to provide separation, IFR or VFR traffic. This standard goes back to the original TCA in 1972.

Subjects ATC  CRJ  IFR  Separation (ALL)  VFR

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gretzky99
February 02, 2025, 03:10:00 GMT
permalink Post: 11819482
Originally Posted by Denflnt
If ATC relied solely on the helo to keep from hitting the CRJ, that is a big effing problem.
As soon as the helo reported the traffic in sight, that's exactly what happened, and it's exactly how the system is designed.

Yes it's a "big effing problem". But it's a "big effing problem" of the system, not the specific ATC on duty at the time.

Subjects ATC  CRJ  Traffic in Sight

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Lead Balloon
February 02, 2025, 03:23:00 GMT
permalink Post: 11819488
Originally Posted by photonclock
Of course. So lets assume the readings to be at the outside of the envelope to the benefit of both aircraft, ie, CRJ at 350 (325 +/- 25 as stated by NTSB), and 200 +/- 75 for the helicopter, so 125. That's 225 feet of vertical-only separation. Is that considered acceptable? If not, why did ATC allow it?
ATC didn't "allow it".

The procedures allowed the controller to hand responsibility for separation to the helo pilot, once the helo was instructed to pass behind an aircraft which the helo said it had identified (twice I think?). However, it seems that the helo identified the wrong aircraft. That's hardly surprising when it's night, there's lots of stationary and moving lights around, and one of the apparently stationary lights is in fact bolted to an aircraft with which you're on a collision course.

Subjects ATC  CRJ  NTSB  Pass Behind  Pass Behind (All)  Separation (ALL)

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JRBarrett
February 02, 2025, 03:43:00 GMT
permalink Post: 11819495
Originally Posted by Lead Balloon
That's assuming perfect equipment accuracy. My understanding is that the tolerance of e.g. an IFR altimeter in the USA is 75'. If that's correct, one IF aircraft with a 'legal' altimeter indicating 325' could in fact be at 250' and another IFR aircraft with a 'legal' altimeter indicating 175' could in fact be at ... 250'. I'm hoping that the avionics in the aircraft involved in this terrible tragedy were more accurate than that, but I always exercise caution in taking numbers out of avionics and ATC systems as 'gospel truth' to the foot. The altitudes on RADAR displays don't increase and decrease in 1 foot increments; nor do the outputs of aircraft transponders. RADALT is different.
The maximum allowable altimeter error between sea level and 1000 feet is +/- 20 feet, and even a simple stand-alone barometric altimeter has to be able to meet that requirement. The RVSM-certified Air Data Computers on something like a CRJ are typically much more precise than that - more like +/- 5 feet at almost all altitudes. I would assume the air data system on a Blackhawk would be equally precise at low levels.

Subjects ATC  Barometric Altimeter  Blackhawk (H-60)  CRJ  IFR

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Lead Balloon
February 02, 2025, 04:12:00 GMT
permalink Post: 11819502
Originally Posted by JRBarrett
The maximum allowable altimeter error between sea level and 1000 feet is +/- 20 feet, and even a simple stand-alone barometric altimeter has to be able to meet that requirement. The RVSM-certified Air Data Computers on something like a CRJ are typically much more precise than that - more like +/- 5 feet at almost all altitudes. I would assume the air data system on a Blackhawk would be equally precise at low levels.
Thanks JRB. Regulatory reference? I'm not saying you're wrong. But I can't find anything other than the 75'. (The acceptable 'split' between 2 on board altimeters is a different tolerance, I believe.)

Subjects Barometric Altimeter  Blackhawk (H-60)  CRJ

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JRBarrett
February 02, 2025, 04:47:00 GMT
permalink Post: 11819512
Originally Posted by Lead Balloon
Thanks JRB. Regulatory reference? I'm not saying you're wrong. But I can't find anything other than the 75'. (The acceptable 'split' between 2 on board altimeters is a different tolerance, I believe.)
Appendix \x91E\x92 of FAR 43, which contains the minimum standards that all altimeters must meet. It includes a table of allowable error at altitudes between sea level and 50,000 feet. Most air data computers on jet aircraft are far more precise than the minimum standards in FAR 43. RVSM certified altimetry systems must meet additional accuracy requirements set forth in Appendix \x91G\x92 of FAR 91 - but that only applies at altitudes between FL290 and FL410.

The Blackhawk air data system would not be RVSM certified as it could not fly high enough to need it, but the CRJ definitely would be. The CRJ has independent dual digital air data computers, and I assume the Blackhawk does as well.

The \x9375 foot\x94 requirement does not come from a specific FAR, but from the Airman\x92s Information Manual (AIM), which states that if the current barometric pressure is set on the ground, that the altimeter should read within 75 feet of the known field elevation at the aircraft\x92s location or the \x93altimeter accuracy should be suspect\x94.

In the US, the altimeters of all civil aircraft that fly under IFR must be tested for required accuracy every 24 months. I assume military aircraft have to meet the same requirement.

FAR 43 Appendix \x91E\x92 is the basic standard for accuracy, but in the case of something like the CRJ, the AMM (Aircraft Maintenance Manual) Chapter 34 will have additional tests to perform which have much more stringent accuracy requirements set forth than FAR 43.
Last edited by JRBarrett; 2nd February 2025 at 04:59 .

Subjects Blackhawk (H-60)  CRJ  IFR

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photonclock
February 02, 2025, 05:47:00 GMT
permalink Post: 11819528
Originally Posted by Lead Balloon
ATC didn't "allow it".
The procedures allowed the controller to hand responsibility for separation to the helo pilot,
Well, that's interesting. You seem to be saying that "the system" worked as designed? FDR notes immediately before your reply:

Originally Posted by fdr
7.2.1 VISUAL SEPARATION
a.2. Pilot-applied visual separation.
(a) Maintain communication with at least one of the aircraft involved and ensure there is an ability to communicate with the other aircraft.
(b) The pilot sees another aircraft and is instructed to maintain visual separation from the aircraft as follows
(1) Tell the pilot about the other aircraft. Include position, direction, type, and, unless it is obvious, the other aircraft's intention.
(2) Obtain acknowledgment from the pilot that the other aircraft is in sight.
(3) Instruct the pilot to maintain visual separation from that aircraft.
Did ATC do all of that? Having listened to the ATC comms (including the UHF) a few times, I believe they did, for the most part? They mentioned CRJ (of what use is mentioning the type at night, I have no idea, but they did), they mentioned where it was and where it was headed, and they received two acknowledgments...

So that means this collision occurred entirely within all established protocls?

These aircraft crashed, as per the system specifications.

So the system is, to put it plainly...FUBAR?

That's not good.

Subjects ATC  CRJ  Separation (ALL)  Visual Separation

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