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DIBO
February 01, 2025, 21:52:00 GMT
permalink Post: 11819330

Quote:

Originally Posted by RatherBeFlying

4. The CRJ crew was left out of the information loop. I have a dedicated traffic display on the top of my glider panel which shows ADS-B and Flarm traffic. A similar display would have enabled the CRJ crew to monitor traffic and get the hell out of the way when necessary.

In addition to previous post on the differences of TA & RA's (which were inhibited at that moment), No they were not left 'out of the loop', but they use their TCAS displayed info, as much as you use your Flarm display when on short final.
From the 'Mil' thread:

Quote:

Originally Posted by 212man

I take it you are unfamiliar with glass cockpits and Navigation Displays? A couple of examples of the CRJ ND - the TCAS Traffic Advisories are the blue diamonds, with altitude difference:

Subjects ADSB (All) CRJ TCAS (All) TCAS RA

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DIBO
February 02, 2025, 01:39:00 GMT
permalink Post: 11819437

Or all three?? As one of them did not follow ATC instructions ("cross behind")

Subjects ATC

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DIBO
February 02, 2025, 21:47:00 GMT
permalink Post: 11820136

Easy Street
from https://asn.flightsafety.org/wikibase/474365

Quote:

KDCA 300152Z 30014G23KT 270V330 10SM CLR 10/M07 A2990 RMK AO2 PK WND 30033/0108 SLP126 T01001072
KDCA 300052Z 29015G25KT 10SM CLR 11/M07 A2987 RMK AO2 SLP114 T01061072

Subjects KDCA

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DIBO
February 03, 2025, 22:46:00 GMT
permalink Post: 11820975

Quote:

Originally Posted by spornrad

Unlikely. The helicopter crew was told about the CRJ approaching 33. At the moment of that initial traffic advisory it meant, the CRJ would first cross their flight path from right to left, and then later on final (circle to land) from left to right. Did they simply expect still the former, seeing the second jet, misjudging the timing / distance as to the CRJ, and therefore turning right to pass behind / give way to an approaching aircraft espected to cross their path from right to left?

If people (and even 'reliable Youtubers') would stick to the available facts, instead of complicating things
No crossing of 'Route 4' prior to ...

Subjects CRJ Circle to Land (Deviate to RWY 33) Pass Behind Pass Behind (All) Route 4

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DIBO
February 03, 2025, 22:57:00 GMT
permalink Post: 11820985

Quote:

Originally Posted by YRP

Tower could have passed it on the hotline but it is probably normally more efficient to just have the a/c say.

Efficient? I call that sloppy...

Last edited by Senior Pilot; 4th February 2025 at 04:18 . Reason: Remove thread drift

Subjects: None

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DIBO
February 03, 2025, 23:26:00 GMT
permalink Post: 11821010

Quote:

Originally Posted by framer

I have never flown in the United States so am not sure, but if this was Australia the controller couldn\x92t give the helicopter a vector while it is below the minimum vectoring altitude anyway. I would be surprised if the controller in DC was able to legally issue a heading instruction to the Blackhawk while it is at or below 200ft at night. Can one of the American readers correct me if I am wrong?
Thanks

not an American readers, but was thinking the same couple of days ago, so I found this:

Quote:

Vector aircraft: At or above the MVA or the minimum IFR altitude except as authorized for radar approaches, radar departures, special VFR, VFR operations , or by paragraph 5-6-3 , Vectors Below Minimum Altitude.

https://www.faa.gov/air_traffic/publ...section_6.html

Subjects ATC Blackhawk (H-60) IFR Radar VFR

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DIBO
February 03, 2025, 23:29:00 GMT
permalink Post: 11821012

VHF, UHF, .... the important fact is that pilots were on different frequencies...whatever spectrum band they were on, is less relevant.

But for those rebuking any mentioning of a VHF Heli frequency, please provide some proof as any reference I find on VFR sectionals, is a VHF Heli-frequency.
IFR charts only have the regular VHF+UHF TWR freq.

Subjects IFR VFR

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DIBO
February 04, 2025, 00:35:00 GMT
permalink Post: 11821049

Well I only replied to the CRJ not crossing "Route 4" as some people paint on screenshots...

Quote:

Originally Posted by MikeSnow

And, looking at the radar replay, the A319 did actually turn right for a bit, to align to 01.

the A319 was adjusting a few degrees left and right, but wouldn't call that 'turning' (but of course its position would make it an ideal target for misidentification)

Quote:

Originally Posted by MikeSnow

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

Well, it's probably my worn out eyes, but I don't see really any reliable evidence of the helo turning right ... remember it came out of Route 1 which ends in one big right-hand turn until joining Route 4 which only after passing KDCA airfield, has a very slight course adjustment to the left.

And the "amateur MLAT" tracking of the helo, is only a rough indication of the trajectory with a wide margin of position error and should be interpreted more like the right side hereunder:

Subjects CRJ KDCA Radar Route 4

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DIBO
February 04, 2025, 00:46:00 GMT
permalink Post: 11821058

Quote:

Originally Posted by SAM 2M

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

indeed relevant to this accident (except for the V / UHF aspect), but at least you understand half of what is said on the other frequency. What about all these countries where you don't understand a word from what is being said to half or more of the other traffic....

Subjects Situational Awareness

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DIBO
February 04, 2025, 21:40:00 GMT
permalink Post: 11821727

Quote:

Originally Posted by BrogulT

Hains Point

so that we are all on the same page:

Subjects: None

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DIBO
February 04, 2025, 22:48:00 GMT
permalink Post: 11821767

matching the info from the NTSB transcript briefing to the ADS-B trajectory:

Quote:

Originally Posted by Sailvi767

Regardless the TCAS almost certainly gave them a traffic alert while above 500 feet

exactly at 500ft it seems

Quote:

Originally Posted by Sailvi767

and displayed the traffic all the way to impact for the RJ crew.

to put "all the way" into context, 18 seconds is what they had

Subjects ADSB (All) NTSB TCAS (All)

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DIBO
February 05, 2025, 00:05:00 GMT
permalink Post: 11821822

Quote:

Originally Posted by airplanecrazy

the helicopter ground speed appears to be closer to 80 kts.

I think we can take this (radar recorded) data-source as pretty reliable, it matches (rounded) the ADS-B reported CRJ speed of 121kts at 375ft (QNE)

I think the confusion comes from the "amateur MLAT" tracking, which calculates the GS based on the multilaterated position calculations, which have a (relatively) large margin of error:

And probably PAT25 was doing initially something in the region of 100kts GS (edit: averaging all but last calculated GS, gives 105kts as average - and over more datapoints, longer trajectory, calculated average GS becomes more reliable)

but at the end it seems there might possibly have been a decreasing GS trend:

Last edited by DIBO; 5th February 2025 at 00:10 . Reason: added calculated average GS

Subjects ADSB (All) CRJ PAT25 Radar

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DIBO
February 07, 2025, 00:03:00 GMT
permalink Post: 11823326

Quote:

Originally Posted by artee

It would be interesting to know what percentage of time the military helos request (and presumably get) VFR.

... "request Visual Separation", not VFR (helicopter routes can only be flown VFR)
I wouldn't be surprised it's a high percentage of the Heli route1 & 4 traffic that requests "Visual Separation".

Have been listening to a few of LiveATC recordings. On the recording combining TWR & Heli frequencies, you can hear all transmissions (which sometimes overlap), however overall quality is poor. Nevertheless, I get the impression "request Visual Separation" is a common thing.
On the recording of the TWR VHF-frequency only, quality is good, but you don't get the requests/replies from the Heli's, so it's not always clear what was being requested/approved.

Subjects Separation (ALL) VFR Visual Separation

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DIBO
February 07, 2025, 22:21:00 GMT
permalink Post: 11823972

As I had it anyway, I might as well put it here in view of the previous posts; just for info, a few examples in the hours before the accident:

Subjects: None

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DIBO
February 10, 2025, 17:56:00 GMT
permalink Post: 11825641

Quote:

Originally Posted by deltafox44

how can you tell for sure which is the one "just south of Wilson Bridge" ?

well, that's the one that should be starting to drift to the East, as the side-stepping/dogleg starts around Wilson.

But that is easier said that done.... much easier....

Subjects: None

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DIBO
February 10, 2025, 21:47:00 GMT
permalink Post: 11825733

Quote:

Originally Posted by RatherBeFlying

I suspect the NYTimes simulation did not adjust the helicopter heading for crosswind drift correction

I think most of the visual presentations made on this forum and elsewhere, are to be taken more as an artist impression, rather than a scientific fact.
For the first NYT simulated helicopter view, there was (is) no reliable/precise tack info publicly available, the MLAT track that has been overly (ab)used, is a very rough indication only. And the planned Route1->4 transition trajectory is a curved one, anyway.

But it was a good attempt to provide a visualization of what the UH60 pilots were (most likely) confronted with, and a very good attempt at countering public reactions as " how can you miss a landing airliner on a clear night "

Subjects New York Times

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DIBO
February 11, 2025, 00:58:00 GMT
permalink Post: 11825797

Quote:

Originally Posted by BFSGrad

The situation was actually more visually complicated.

And I think you can drop the "visually".
For the ATCO, there wasn't only the flow of arrivals, but a good number of (no delay) departures, all this on intersecting runways and, not shown on the screenshot, in the seconds (a few dozens of...) prior to the accident, the ATCO was handling at least 3 helicopters (Mussel7 / Medevac / PAT25), even not counting the police helicopter working in the SW corner as depicted in the screenshot.

And all this on three* separate frequencies, not fully cross coupled, so TWR was receiving on several occasions, simultaneous/parallel incoming R/T calls (* based on info from other posters in both threads here on pprune & NTSB info - but I still have doubts PAT25 was on UHF, although 3 or 2 freq's, doesn't really matter in this accident's context)

And simulations by VASAviation and the likes, are heavily edited (as they correctly indicate in their comments), so they easily give the impression that traffic and R/T comm's were relatively light...

Subjects ATCO NTSB PAT25

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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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DIBO
February 14, 2025, 21:03:00 GMT
permalink Post: 11828208

Quote:

Originally Posted by deltafox44

Just heard NTSB briefing. It seems that the scapegoat will not be any of the humans involved, nor even the procedures, but the altimeter system of the black hawk (a 100 ft discrepancy) and the radio ( they did not hear "circling" and "pass behind" )

(my bold in quote) well.... that doesn't surprise me.
For a couple of days now, was thinking about posting something on an "extra noise" I keep hearing in the R/T comms, when TWR gives the ' pass behind ' instruction. Was wondering whether TWR's Tx wasn't stepped over by someone.
My first impression was that the extra noise came from an radio call from a turbine helicopter (given the typical background noise often heard in radio calls from turbine helicopters). And was wondering if it wasn't PAT25 that started replying to TWR's first ' in sight? ' call, effectively blocking part of TWR's second call, the ' pass behind ' part of the instruction.

In attached mp3 (in .zip per forum attachment requirements) around 00:05 I hear this 'extra noise'.

Edit:
well, this seems to confirm my initial impression:

Quote:

Originally Posted by parabatix

Briefing the RT comms, NTSB stated that a portion of the ATC instruction to the BlackHawk to 'pass behind the CRJ' was received in the Blackhawk (according to the CVR), truncated due to the BlackHawk keying the mic at the same time. Apparently, the words 'pass behind the' were missing from the BlackHawk CVR.

Attached Files

KDCA1-Twr-Midair - PAT25 pass behind.zip (89.1 KB, 20 views)

Last edited by DIBO; 14th February 2025 at 21:07 . Reason: last posts with NTSB info seem to confirm my suspicion

Subjects ATC Blackhawk (H-60) CRJ NTSB PAT25 Pass Behind Pass Behind (All)

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DIBO
February 14, 2025, 22:35:00 GMT
permalink Post: 11828263

Quote:

Originally Posted by blind pew

There have been many accidents which might have been avoided if a duplex radio system had been used

Well, not duplex, but the existing simplex with 'stepping over' protection, was something I read about in Flight Int'l some 40 odd years ago, which at that time was being discussed in some ICAO (??) workgroup, but nothing ever came out of this.
In the following decades, I've been more than once frustrated with hundreds of 'stupid' stepping-over's, causing so much confusion (luckily nothing more serious that I witnessed), which all could have been prevented if that mechanism would have been standardized.

Subjects ICAO

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DIBO February 01, 2025, 21:52:00 GMT permalink Post: 11819330	Quote: Originally Posted by RatherBeFlying 4. The CRJ crew was left out of the information loop. I have a dedicated traffic display on the top of my glider panel which shows ADS-B and Flarm traffic. A similar display would have enabled the CRJ crew to monitor traffic and get the hell out of the way when necessary. In addition to previous post on the differences of TA & RA's (which were inhibited at that moment), No they were not left 'out of the loop', but they use their TCAS displayed info, as much as you use your Flarm display when on short final. From the 'Mil' thread: Quote: Originally Posted by 212man I take it you are unfamiliar with glass cockpits and Navigation Displays? A couple of examples of the CRJ ND - the TCAS Traffic Advisories are the blue diamonds, with altitude difference: Subjects ADSB (All) CRJ TCAS (All) TCAS RA 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.
DIBO February 02, 2025, 01:39:00 GMT permalink Post: 11819437	Or all three?? As one of them did not follow ATC instructions ("cross behind") Subjects ATC 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.
DIBO February 02, 2025, 21:47:00 GMT permalink Post: 11820136	Easy Street from https://asn.flightsafety.org/wikibase/474365 Quote: KDCA 300152Z 30014G23KT 270V330 10SM CLR 10/M07 A2990 RMK AO2 PK WND 30033/0108 SLP126 T01001072 KDCA 300052Z 29015G25KT 10SM CLR 11/M07 A2987 RMK AO2 SLP114 T01061072 Subjects KDCA 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.
DIBO February 03, 2025, 22:46:00 GMT permalink Post: 11820975	Quote: Originally Posted by spornrad Unlikely. The helicopter crew was told about the CRJ approaching 33. At the moment of that initial traffic advisory it meant, the CRJ would first cross their flight path from right to left, and then later on final (circle to land) from left to right. Did they simply expect still the former, seeing the second jet, misjudging the timing / distance as to the CRJ, and therefore turning right to pass behind / give way to an approaching aircraft espected to cross their path from right to left? If people (and even 'reliable Youtubers') would stick to the available facts, instead of complicating things No crossing of 'Route 4' prior to ... Subjects CRJ Circle to Land (Deviate to RWY 33) Pass Behind Pass Behind (All) Route 4 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.
DIBO February 03, 2025, 22:57:00 GMT permalink Post: 11820985	Quote: Originally Posted by YRP Tower could have passed it on the hotline but it is probably normally more efficient to just have the a/c say. Efficient? I call that sloppy... Last edited by Senior Pilot; 4th February 2025 at 04:18 . Reason: Remove thread drift Subjects: None 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.
DIBO February 03, 2025, 23:26:00 GMT permalink Post: 11821010	Quote: Originally Posted by framer I have never flown in the United States so am not sure, but if this was Australia the controller couldn\x92t give the helicopter a vector while it is below the minimum vectoring altitude anyway. I would be surprised if the controller in DC was able to legally issue a heading instruction to the Blackhawk while it is at or below 200ft at night. Can one of the American readers correct me if I am wrong? Thanks not an American readers, but was thinking the same couple of days ago, so I found this: Quote: Vector aircraft: At or above the MVA or the minimum IFR altitude except as authorized for radar approaches, radar departures, special VFR, VFR operations , or by paragraph 5-6-3 , Vectors Below Minimum Altitude. https://www.faa.gov/air_traffic/publ...section_6.html Subjects ATC Blackhawk (H-60) IFR Radar 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.
DIBO February 03, 2025, 23:29:00 GMT permalink Post: 11821012	VHF, UHF, .... the important fact is that pilots were on different frequencies...whatever spectrum band they were on, is less relevant. But for those rebuking any mentioning of a VHF Heli frequency, please provide some proof as any reference I find on VFR sectionals, is a VHF Heli-frequency. IFR charts only have the regular VHF+UHF TWR freq. Subjects IFR 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.
DIBO February 04, 2025, 00:35:00 GMT permalink Post: 11821049	Well I only replied to the CRJ not crossing "Route 4" as some people paint on screenshots... Quote: Originally Posted by MikeSnow And, looking at the radar replay, the A319 did actually turn right for a bit, to align to 01. the A319 was adjusting a few degrees left and right, but wouldn't call that 'turning' (but of course its position would make it an ideal target for misidentification) Quote: Originally Posted by MikeSnow At around the same time, the helo starts turning right. I agree that these are just guesses, but the alternative seems to be that the helo just drifted to the right randomly, for no specific reason, which seems unlikely. Well, it's probably my worn out eyes, but I don't see really any reliable evidence of the helo turning right ... remember it came out of Route 1 which ends in one big right-hand turn until joining Route 4 which only after passing KDCA airfield, has a very slight course adjustment to the left. And the "amateur MLAT" tracking of the helo, is only a rough indication of the trajectory with a wide margin of position error and should be interpreted more like the right side hereunder: Subjects CRJ KDCA Radar Route 4 Links are to this post in the relevant subject page so that this post can be seen in context. 5 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DIBO February 04, 2025, 00:46:00 GMT permalink Post: 11821058	Quote: Originally Posted by SAM 2M - Any policy that permits 'band-boxing' of UHF and VHF radio communication frequencies should be reviewed, especially as it does not enable the crew of the UHF and VHF aircraft to hear the transmissions of the other crew. This reduces flight crew situational awareness (SA). indeed relevant to this accident (except for the V / UHF aspect), but at least you understand half of what is said on the other frequency. What about all these countries where you don't understand a word from what is being said to half or more of the other traffic.... Subjects Situational Awareness 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.
DIBO February 04, 2025, 21:40:00 GMT permalink Post: 11821727	Quote: Originally Posted by BrogulT Hains Point so that we are all on the same page: Subjects: None 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.
DIBO February 04, 2025, 22:48:00 GMT permalink Post: 11821767	matching the info from the NTSB transcript briefing to the ADS-B trajectory: Quote: Originally Posted by Sailvi767 Regardless the TCAS almost certainly gave them a traffic alert while above 500 feet exactly at 500ft it seems Quote: Originally Posted by Sailvi767 and displayed the traffic all the way to impact for the RJ crew. to put "all the way" into context, 18 seconds is what they had Subjects ADSB (All) NTSB TCAS (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.
DIBO February 05, 2025, 00:05:00 GMT permalink Post: 11821822	Quote: Originally Posted by airplanecrazy the helicopter ground speed appears to be closer to 80 kts. I think we can take this (radar recorded) data-source as pretty reliable, it matches (rounded) the ADS-B reported CRJ speed of 121kts at 375ft (QNE) I think the confusion comes from the "amateur MLAT" tracking, which calculates the GS based on the multilaterated position calculations, which have a (relatively) large margin of error: And probably PAT25 was doing initially something in the region of 100kts GS (edit: averaging all but last calculated GS, gives 105kts as average - and over more datapoints, longer trajectory, calculated average GS becomes more reliable) but at the end it seems there might possibly have been a decreasing GS trend: Last edited by DIBO; 5th February 2025 at 00:10 . Reason: added calculated average GS Subjects ADSB (All) CRJ PAT25 Radar 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.
DIBO February 07, 2025, 00:03:00 GMT permalink Post: 11823326	Quote: Originally Posted by artee It would be interesting to know what percentage of time the military helos request (and presumably get) VFR. ... "request Visual Separation", not VFR (helicopter routes can only be flown VFR) I wouldn't be surprised it's a high percentage of the Heli route1 & 4 traffic that requests "Visual Separation". Have been listening to a few of LiveATC recordings. On the recording combining TWR & Heli frequencies, you can hear all transmissions (which sometimes overlap), however overall quality is poor. Nevertheless, I get the impression "request Visual Separation" is a common thing. On the recording of the TWR VHF-frequency only, quality is good, but you don't get the requests/replies from the Heli's, so it's not always clear what was being requested/approved. Subjects Separation (ALL) VFR Visual Separation 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.
DIBO February 07, 2025, 22:21:00 GMT permalink Post: 11823972	As I had it anyway, I might as well put it here in view of the previous posts; just for info, a few examples in the hours before the accident: Subjects: None 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.
DIBO February 10, 2025, 17:56:00 GMT permalink Post: 11825641	Quote: Originally Posted by deltafox44 how can you tell for sure which is the one "just south of Wilson Bridge" ? well, that's the one that should be starting to drift to the East, as the side-stepping/dogleg starts around Wilson. But that is easier said that done.... much easier.... Subjects: None 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.
DIBO February 10, 2025, 21:47:00 GMT permalink Post: 11825733	Quote: Originally Posted by RatherBeFlying I suspect the NYTimes simulation did not adjust the helicopter heading for crosswind drift correction I think most of the visual presentations made on this forum and elsewhere, are to be taken more as an artist impression, rather than a scientific fact. For the first NYT simulated helicopter view, there was (is) no reliable/precise tack info publicly available, the MLAT track that has been overly (ab)used, is a very rough indication only. And the planned Route1->4 transition trajectory is a curved one, anyway. But it was a good attempt to provide a visualization of what the UH60 pilots were (most likely) confronted with, and a very good attempt at countering public reactions as " how can you miss a landing airliner on a clear night " Subjects New York Times 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.
DIBO February 11, 2025, 00:58:00 GMT permalink Post: 11825797	Quote: Originally Posted by BFSGrad The situation was actually more visually complicated. And I think you can drop the "visually". For the ATCO, there wasn't only the flow of arrivals, but a good number of (no delay) departures, all this on intersecting runways and, not shown on the screenshot, in the seconds (a few dozens of...) prior to the accident, the ATCO was handling at least 3 helicopters (Mussel7 / Medevac / PAT25), even not counting the police helicopter working in the SW corner as depicted in the screenshot. And all this on three* separate frequencies, not fully cross coupled, so TWR was receiving on several occasions, simultaneous/parallel incoming R/T calls (* based on info from other posters in both threads here on pprune & NTSB info - but I still have doubts PAT25 was on UHF, although 3 or 2 freq's, doesn't really matter in this accident's context) And simulations by VASAviation and the likes, are heavily edited (as they correctly indicate in their comments), so they easily give the impression that traffic and R/T comm's were relatively light... Subjects ATCO NTSB PAT25 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.
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 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.
DIBO February 14, 2025, 21:03:00 GMT permalink Post: 11828208	Quote: Originally Posted by deltafox44 Just heard NTSB briefing. It seems that the scapegoat will not be any of the humans involved, nor even the procedures, but the altimeter system of the black hawk (a 100 ft discrepancy) and the radio ( they did not hear "circling" and "pass behind" ) (my bold in quote) well.... that doesn't surprise me. For a couple of days now, was thinking about posting something on an "extra noise" I keep hearing in the R/T comms, when TWR gives the ' pass behind ' instruction. Was wondering whether TWR's Tx wasn't stepped over by someone. My first impression was that the extra noise came from an radio call from a turbine helicopter (given the typical background noise often heard in radio calls from turbine helicopters). And was wondering if it wasn't PAT25 that started replying to TWR's first ' in sight? ' call, effectively blocking part of TWR's second call, the ' pass behind ' part of the instruction. In attached mp3 (in .zip per forum attachment requirements) around 00:05 I hear this 'extra noise'. Edit: well, this seems to confirm my initial impression: Quote: Originally Posted by parabatix Briefing the RT comms, NTSB stated that a portion of the ATC instruction to the BlackHawk to 'pass behind the CRJ' was received in the Blackhawk (according to the CVR), truncated due to the BlackHawk keying the mic at the same time. Apparently, the words 'pass behind the' were missing from the BlackHawk CVR. Attached Files KDCA1-Twr-Midair - PAT25 pass behind.zip (89.1 KB, 20 views) Last edited by DIBO; 14th February 2025 at 21:07 . Reason: last posts with NTSB info seem to confirm my suspicion Subjects ATC Blackhawk (H-60) CRJ NTSB PAT25 Pass Behind Pass Behind (All) 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.
DIBO February 14, 2025, 22:35:00 GMT permalink Post: 11828263	Quote: Originally Posted by blind pew There have been many accidents which might have been avoided if a duplex radio system had been used Well, not duplex, but the existing simplex with 'stepping over' protection, was something I read about in Flight Int'l some 40 odd years ago, which at that time was being discussed in some ICAO (??) workgroup, but nothing ever came out of this. In the following decades, I've been more than once frustrated with hundreds of 'stupid' stepping-over's, causing so much confusion (luckily nothing more serious that I witnessed), which all could have been prevented if that mechanism would have been standardized. Subjects ICAO 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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