Posts about: "INLINE_IMAGES" [Posts: 88 Page: 3 of 5]¶

Quote:

Originally Posted by spornrad

NYT has attempted a reconstruction of the visual picture from the Blackhawk at the time of the first traffic alert, with the CRJ just south of Wilson Bridge.
They could only later identify the correct light spot by following its trajectory according to their mental image of the approach to 33.

The original NYT article thanks to the Internet Archive (archive.org) .

Subjects Blackhawk (H-60)  CRJ  New York Times

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Quote:

Originally Posted by DIBO

so that we are all on the same page:

Quote:

Originally Posted by moosepileit

Only to Rwy 33, not Rwy 1. Yuge differenxe.

1.5Nm is longer than Rwy 1. Any traffic on the runways basically knocks out helicopters within a circle more or less encompassing Memorial Bridge, Capitol St Bridge, the sewage treatment plant, and Route 5. The approach paths to the two runways are pretty close together compared to a 1.5Nm separation.

Anything approaching Rwy 1 should be below ~700ft anywhere north of the sewage treatment marker; use the Wilson Bridge for a bit of headroom because not all aircraft are going to be perfectly on glideslope.

The river is far narrower than 1.5Nm so clearly a southbound helicopter on Route 4 can never cross a northbound aircraft approaching runway 1 north of the Wilson Bridge.

You'd have to hold a southbound helicopter north of either the Memorial or Capitol St Bridges until previous traffic had landed. Then have a sufficiently large gap with no arrivals (or departures until south of the runways) for the helicopter to reach the Wilson St Bridge before the next arrival crosses that bridge.

That's the preceding aircraft covering ~3Nm at 140kt (~80s), followed by the helicopter covering ~6Nm at ~100kt (another 3.5min), and accurately timing the next arrival so it doesn't cross the Wilson bridge until after the helicopter, or it needs to do a go-around.

Subjects Route 4  Route 5  Separation (ALL)

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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:

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Quote:

Originally Posted by BrogulT

There's a designated holding point on the route. IDK exactly what that means, but it must mean something, right?

The river is 4000 feet wide just south of that designated point. I imagine there is a procedure otherwise what would be the point?

The other option is that they would have to have the landing traffic go around.

If I've read the chart legend correctly, that triangle at Hains Point is a "Non-Compulsory Reporting or Holding Point".
...

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Quote:

Originally Posted by Lead Balloon

If I've read the chart legend correctly, that triangle at Hains Point is a "Non-Compulsory Reporting or Holding Point".
...

Interesting also that the legend clearly describes the \x93Route Altitudes\x94 as \x93Recommended\x94 (not compulsory), therefore PAT25 being at 300\x92 while not being recommended, was not breaking any rules.

Subjects PAT25

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Quote:

Originally Posted by Ant T

Interesting also that the legend clearly describes the “Route Altitudes” as “Recommended” (not compulsory), therefore PAT25 being at 300’ while not being recommended, was not breaking any rules.

The route description on the chart says "ROUTE ALTITUDES ARE MAXIMUM". Routes 1 and 4 are described as follows:

Subjects PAT25

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Quote:

Originally Posted by Bogner

Not meaning to pick on you individually, it’s just that you have a great line to quote!
I think the point may be that in those 50yrs you may actually have made a mistake identifying an aircraft, but we don’t have the data. Just because you didn’t have a collision or Airmiss you can’t say for certain that everything worked perfectly.
If you mistakenly identify the wrong aircraft, but don’t realise and don’t actually hit anything and the other party also don’t notice/report, then the error is never recognised, nor recorded. Are we suggesting that this scenario has never happened in the history of aviation?
A flight that doesn’t end in a crash does not mean it was perfect.

+1
I think many pilots would have made a mistake indentifying : seen from the helo, there are 3 aircraft in final, plus 1 on take-off, at the same bearing, how can you tell for sure which is the one "just south of Wilson Bridge" ?

Quote:

Originally Posted by spornrad

NYT has attempted a reconstruction of the visual picture from the Blackhawk at the time of the first traffic alert, with the CRJ just south of Wilson Bridge.
They could only later identify the correct light spot by following its trajectory according to their mental image of the approach to 33.

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Last edited by Senior Pilot; 10th February 2025 at 21:20 . Reason: Image source

Subjects Blackhawk (H-60)  CRJ  New York Times

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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....

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Quote:

Originally Posted by deltafox44

+1
I think many pilots would have made a mistake indentifying : seen from the helo, there are 3 aircraft in final, plus 1 on take-off, at the same bearing, how can you tell for sure which is the one "just south of Wilson Bridge" ?

Quote:

Originally Posted by spornrad

NYT has attempted a reconstruction of the visual picture from the Blackhawk at the time of the first traffic alert, with the CRJ just south of Wilson Bridge.
They could only later identify the correct light spot by following its trajectory according to their mental image of the approach to 33.

This simulation, if correct, is harrowing. The accident aircraft is actually almost superimposed over the following aircraft AA3130 at exactly the time of the tower's first notification of traffic to the helicopter. The helicopter's response is so quick, so reflexive. Then when the second notification is received, even though PAT25 knows he has just asked for visual separation and been granted he asks again, further suggestion that this is reflexive behavior.

At the same time the accident aircraft peels off to the right to swing around and line up to 33, thus taking his (smaller) lights out of the helicopter's direct line of vision and leaving 3130's (brighter) lights still heading to 01 to decoy the pilot. The reflexive nature of the helicopter's responses suggest to me that the full implication of 'circling to 33' in the tower's first call was missed, and also sort of implies that the helicopter could not conceive that following (nearly) the published heliroute could lead him into conflict with an aircraft on final. Me neither.

Quote:

NOTAM 5/1069 for DCA, valid from 07 Feb 0200 UTC until 31 March 2359 UTC

I'd push the expiry date of that one out a little.

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Last edited by Senior Pilot; 10th February 2025 at 21:22 . Reason: Quote

Subjects Blackhawk (H-60)  CRJ  DCA  New York Times  PAT25  Separation (ALL)  Visual Separation

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Quote:

Originally Posted by deltafox44

+1
I think many pilots would have made a mistake indentifying : seen from the helo, there are 3 aircraft in final, plus 1 on take-off, at the same bearing, how can you tell for sure which is the one "just south of Wilson Bridge" ?

The situation was actually more visually complicated. Screenshot below is about 5 seconds prior to collision with red arrow pointing at 5342 turning into 33. There are 5 aircraft on final for 1 with a 6th joining the parade. AAL 3130 is over the Wilson Bridge and as I recall, UAL 472 next with a couple more JIAs in the stack. Adding to the background against which PAT25 is target hunting is National Harbor with some lesser contribution from the Naval Research Lab and Blue Plains.

Subjects PAT25

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Quote:

Originally Posted by henra

First of all: I can largely follow your Maths. In a straight line the PAPI is a bit less than1550m from the Eastern bank of the Potomac on a straight 328\xb0 course. At 3\xb0 this would be 270ft altitude when crossing the -east bank. Both aircraft ended up in the Potomac. When looking at the point of impact of the Blackhawk in the Potomac in these videos I end up with a spot ~1450m from the PAPI.
On the other hand the collision will have somewhat altered trajectory of both aircraft, so maybe the collision had still occured over land and due to the lateral energy transfer the Helicopter was thrown off its original course towards the West and into the river. We will get this information finally.
And in the end it doesn't really make that much of a difference wrt the level of lunacy of this whole setup.

I think the collision was closer to 1250m (4100') from the PAPI. I base that upon the NTSB statement " At 8:47:58, the crew had a verbal reaction, and FDR (flight data recorder) data showed the airplane beginning to increase its pitch. Sounds of impact were audible about one second later," That puts the collision at about 8:47:59 (01:47:59Z). ADS-B Exchange data at that time puts the ground distance to the PAPI between 1200-1280m (3900-4200'). My assumptions are that the NTSB statement is correct and that the ADS-B Exchange data is accurate (which in my experience, the times are generally less than 0.2 seconds later than the timestamps on data collected by the FAA, and the reported NACp (position accuracy) was estimated at < 10m). Here is the graphical representation I generated of my estimated collision position vs. PAPI.


Collision Altitude vs PAPI

Quote:

Originally Posted by galaxy flyer

Having been in a mid-air collision with similar geometry, I would bet it was only normal input to approach path. FDR’s are incredibly sensitive recorders. I have a vague memory of the other plane’s wing flashing by. It looks slow in the videos, but it’s incredibly fast.

If my depiction is accurate, it's hard to see why they would pitch up as normal input to approach path. I think their inputs would have been focused on getting down.

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Last edited by airplanecrazy; 11th February 2025 at 06:30 . Reason: Problem with picture. Awkward phrasing

Subjects ADSB (All)  Blackhawk (H-60)  FAA  NTSB

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This kind of smells like a "gentleman's agreement" to me, if not implied threats of retaliation.

Speculation : The helicopter crews know that if they don't report traffic in sight as soon as it's called, they'll be slowed down and deprioritised by ATC and eventually held back until they either do report the traffic, or there's a substantial gap in arrivals - see the LH A380. That makes them unpopular with their passengers and/or superiors, so they are very flexible with what 'in sight' means.

ATC likewise knows that if they push helicopter crews too hard on altitude busts, report anything involving a helicopter, or hold up either kind of traffic, they might get people breathing down their neck and certainly nothing good comes of it.

Calling traffic immediately and not enforcing separation too strictly allows both parties to 'get on with their jobs' while looking more-or-less by-the-book - until an incident like this happens.

I'm hopeful I'm wrong, but given there seems to be a long history of near misses and altitude busts this seems like the obvious conclusion. No-one high-up wanted to hear about it or change anything , because no-one had died yet.



On a slightly different note, I'm curious whether anyone is familiar with the Hierarchy of Controls by NIOSH? It doesn't map 1:1 to aviation, but it codifies some things that are 'obvious' in hindsight:


Broadly speaking, some controls are more effective than others. Wherever possible, you should attempt to use more effective controls in place of less effective ones. More effective means not just that it reduces the risk the most, but also the most reliable over time and most resistant to having rules bent, being left broken, being ignored due to alarm fatigue, or 'normalisation of deviation'. Procedures that assume everything is working perfectly and everyone is 100% competent will fail; see MCAS and a great number of other accidents.

Elimination is rarely possible but substitution (radar vs visual) and isolation (separate helicopters from other traffic) amongst other engineering controls are potentially more feasible, and much higher up the hierarchy than a glorified instruction not to crash (the very bottom of administrative). Engineering a problem out of existence is far superior to having a procedure to fix it in the QRH.

I list things like TCAS, GPWS, RSAs, and crash-proof seating as broadly being under PPE: they're nice to have and certainly worth pursuing, but unless there is no other alternative, they should never be your primary protection. Something has gone wrong if they get used.

Subjects ATC  Close Calls  Radar  Separation (ALL)  TCAS (All)  Traffic in Sight

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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.

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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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Quote:

Originally Posted by airplanecrazy

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.

"...FAA depicted width of a helicopter route is governed by the following doc: https://www.faa.gov/air_traffic/flight_info/aeronav/iac/media/IAC15/IAC-15-22AUG2022-complete.pdf "

I think that the "width" that you are referring is for the chart maker but not the actual width of a helicopter route.

I can't find in any FAA document a definition of the lateral extent of a helicopter route. Is there one?

There are inconsistencies between the "DESCRIPTION OF ROUTES AND ALTITUDES" and the charts themselves. The Merriam-Webster's 11th Collegiate Dictionary definition of "BANK 2 : the rising ground bordering a lake, river, or sea or forming the edge of a cut or hollow."
for example "RT. 4: ... VIA EAST BANK OF POTOMAC RIVER..." while the chart depicts RT. 4 over the POTOMAC RIVER not over the ground bordering the river.
while "RT. 15: ... ALONG THE WESTERN SHORE OF THE CHESAPEAKE BAY AND PATAPSCO RIVER..." and the chart depicts RT. 15 over water.

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Last edited by airman1900; 11th February 2025 at 22:33 . Reason: punctuation and quote

Subjects DCA  FAA  NTSB

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Quote:

Originally Posted by BFSGrad

The situation was actually more visually complicated. Screenshot below is about 5 seconds prior to collision with red arrow pointing at 5342 turning into 33. There are 5 aircraft on final for 1 with a 6th joining the parade. AAL 3130 is over the Wilson Bridge and as I recall, UAL 472 next with a couple more JIAs in the stack. Adding to the background against which PAT25 is target hunting is National Harbor with some lesser contribution from the Naval Research Lab and Blue Plains.

I would like to ask if it is known number of aircraft at TWR Frequency( ies) at the moment of collision?
One ATCO, worked , at three separate frequency, three runways, 6 aircraft for arrival 01, one a/c 33, plus three helicopter, plus how many departures ( both active and approaching/crossing active runways) ?
Plus active estimate for a few aircraft more?
Ground vehicles, any?

Subjects ATCO  PAT25

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I just saw that the National Transportation Safety Board will hold a media briefing on Friday, Feb. 14 at 2 p.m. Eastern time.

FWIW, this is my take on the layout of the crash scene:


Crash Scene


Zoom on helicopter

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Last edited by airplanecrazy; 14th February 2025 at 07:49 . Reason: Fixed pictures

Subjects: None

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...
I was recently watching a video on the highlights of Oshkosh, the relevance of which will hopefully become clear shortly.

One part of the video was some POV footage from the cockpit of one of the Blue Angels. I had a 'double-take' and triple rewind to confirm what I thought I saw on the glareshield: I think I saw a piece of portable avionics that is very, very familiar to me.

Is any expert able to confirm what that white block on the glareshield is?

I've been in a discussion about the complexity of avionics upgrades to military flying machinery, the discussion precipitated by the differing terminology about "fitted with" and "equipped with" and "carried". And I suggest that even if the helo was "fitted with" an ADS system, at the altitude the aircraft were operating at the time of the collision any alerts may have been suppressed.

Subjects: None

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Quote:

Originally Posted by dbcooper8

The L model radar altimeter indicators each contain a pointer that indicates altitude on a linear scale from 0 to 200 feet (10 feet per unit) and a second-linear scale from 200 to 1500 feet (100 feet per unit). In other words 300 feet could easily be misread as 210 feet for the uninitiated. Worth noting the pointer is the width between 200 feet and 300 feet. Also, was the bug in use and if so what altitude was it set to?

Disconcerting that the PAT 25 crew, about to descend and fly less than 200 feet AGL , would not have investigate the discrepancy of 100 feet between their respective altimeters...

Details of instrumentation here:
https://apps.dtic.mil/sti/tr/pdf/ADA409934.pdf
Not completely obvious in the photo is the digital display of radar altitude just underneath the annotation ABS ALT. The technical manual also mentions a three digit radar altitude displayed on the HUD.

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Last edited by Stagformation; 15th February 2025 at 23:01 .

Subjects HUD  Radar

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Quote:

Originally Posted by airplanecrazy

Spoiler

 

 

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.

Quote:

Originally Posted by Wide Mouth Frog

So this just cracks me up. He's in the middle of the river where the route says it's up the East bank, and that's OK because the routes are not defined with no procedural separation from landing traffic. He's instructed to pass behind the CRJ, but that would involve him either holding short or deviating over the city at 200ft at night, but instead he chooses to plow right on. The helicopter is out of his standard altitude, and the jet is way above the glideslope, and ATC encourages them to sort it out themselves. And the helicopter crew are wearing NVGs. What could possibly go wrong.

The diagram shows the route up the east ~half of the river, solidly over water. The inset seems to show it within perhaps the east quarter, but still 100% over water. Asking crews to follow the riverbank therefore seems to be a direct contradiction.

You could reasonably define the bank as the water's edge, and therefore expect crews to fly along an infinitesimally narrow path. Or as the space between the water's edge and the [edge of the flood plain | first flat area | something else], which would imply that the western boundary changes with the water level. Both imply the route is substantially above land.

Neither are useful for precise navigation, but the map and the description are probably 'close enough' if they are only needed for general route guidance and knowing that structures on the east bank need to be NOTAMed for helicopters, but probably not the west bank.

A good reminder that measurements/specifications without tolerance are often worse than useless.

Quote:

Originally Posted by galaxy flyer

KDCA 01 visual to 33 (note: not circle, 121 carriers are not circling authorized in the US)

If it quacks like a duck... this kind of "It can't be an X because we can't do it, so we'll call it a Y" leads to a culture that gets used to massaging the truth for convenience. Did we hear more on the Alaska door plug that was an 'opening' not a 'removal'?

Subjects ATC  CRJ  DCA  FAA  KDCA  NTSB  Night Vision Goggles (NVG)  Pass Behind  Pass Behind (All)  Separation (ALL)

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This one got deleted because it was connected to a previous post that was deleted. I do think it's an important part of the record so I've reposted it here with appropriate modifications. Hope that's OK.

Quote:

Look at this excellent analysis below. If its right, you can see that if the CRJ was on glide slope it would have been at about 240ft and indeed anywhere in the PAPI range. The actual altitudes on the day brought about where the crash actually occurred, but it was the route design that brought them there in the first place, and nearly did on many other days in the past decade or so that we know about.

If everyone had been flying at the prescribed altitudes, the CRJ should have passed 40ft over the Blackhawk, I can't believe that would have been OK.

I was very surprised also to hear Jennifer tell us that the heliroutes have no lateral boundaries, which is a bit bizarre given that the Route 4 in the notes on the chart is described as following the East bank of the Potomac which is about on the left end of the diagram. Doesn't matter though, same problem there. Routes shouldn't be designed so that aircraft can infringe on landing (or any other kind) of passenger jet traffic.

Subjects Blackhawk (H-60)  CRJ  Route 4

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