Posts by user "Luc Lion" [Posts: 16 Total up-votes: 31 Page: 1 of 1]ΒΆ

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Luc Lion
January 30, 2025, 15:04:00 GMT
permalink Post: 11817309
In my understanding, the minimum safe separation in altitude is 500 feet.
As the approach to R33 crosses IDTEK (over the East bank of the river) at about 490 feet MSL, there is no way another aircraft can safely pass underneath at 200 feet MSL.
Thus, I think, the helicopter route RT 4 must be closed whenever an approach (visual or RNAV) to R33 is underway.
If a southbound traffic request a clearance for RT 4 in such a circumstance, they should be ordered to hold at Hains Point or North of it, or be redirected via routes RT 2 and RT 3 to Wilson Bridge.

And the helicopter route chart precedes the route descriptions with the comment "ALL ROUTES MAY BE ALTERED AT PILOT'S REQUEST OR AS DIRECTED BY ATC".


Last edited by Luc Lion; 30th January 2025 at 15:12 . Reason: more info

Subjects ATC  Separation (ALL)

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Luc Lion
January 30, 2025, 17:10:00 GMT
permalink Post: 11817417
Originally Posted by SASless
which would make me ask the question what height the CRJ should have been at at the point it collided with t he helicopter.
Between 229 and 263 feet above runway TDZ whose altitude is 14 feet MSL, if the plane was spot on the visual glide slope indicated by the PAPI.

Originally Posted by SASless
Was the CRJ Crew using Glide Slope information as part of their VFR Approach procedure for the designated runway?
Yes, there is a PAPI or VGSI (a set of lights on the ground near the TDZ whose colours indicate if the plane is on the glide slope).
I couldn't find any NOTAM that would have signaled a non-functioning PAPI and, in a clear night, any trained pilot would follow the PAPI indication out of force of habit.

Originally Posted by SASless
The other question is at what point would the CRJ Crew have benefit of visual glide slope lighting for the RWY 33?
The circling approach for RW33 after an ILS RW01 follows more or less the same path as the RNAV approach for RW33 and the final segment of this RNAV approach is an Extended Visual Segment
starting at the Visual Guidance Fix (VGF) IDTEK which is overhead of the motorway I-295 (if I am not mistaken).
I think that it is reasonable to assume that the pilot would have aimed at passing overhead IDTEK at 490 feet MSL as specified in the RNAV procedure.
IDTEK is about at 1.4 nm or 8500 ft from the threshold or about 9600 ft from the TDZ.
With a published PAPI glideslope of 3.00\xb0, the glideslope path is at about 500 ft MSL at IDTEK

Originally Posted by SASless
Can one derive a reasonable height above ground for the collision point....and/or a distance from the Touchdown Point of RWY33 for comparison to what seems to be the height and distance from the TD point?
Yes. The radar tracks show the collision above the eastern side of the river on the runway extended centerline. That makes the collision point between 1000 m and 1200 m from the threshold.
And the distance TDZ - threshold is about 330 m for this runway.
With some trigonometric calculation, you end up with a height between 229 and 263 feet above runway TDZ, under the assumption that the plane was spot on the glide.


Subjects CRJ  Circle to Land (Deviate to RWY 33)  Radar  VFR

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Luc Lion
January 30, 2025, 17:32:00 GMT
permalink Post: 11817444
EFHF , the glideslope starts from the TDZ, not from the threshold.

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Luc Lion
January 30, 2025, 19:53:00 GMT
permalink Post: 11817598
As many others said earlier, it is unfair to blame an individual, pilot or ATCO, who made a honest fatal mistake when the system allows that very mistake to have catastrophic consequences.

Adding an additional slice of cheese in the sandwich is very easy: just state that when 2 tracking routes provide less than 500 ft of separation, then they are mutually exclusive.

A clearance for route RT4 and a clearance for an approach RW33 cannot be active at the same time.
If an approach is underway, the route is closed. And if a clearance for the route has been issued, then the approach to RW33 is not available.

And the FAA would be well inspired to investigate all other similar conflicts across the USA and implement the same principle.

Subjects ATCO  FAA  Separation (ALL)

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Luc Lion
January 31, 2025, 10:10:00 GMT
permalink Post: 11818067
Originally Posted by Diff Tail Shim
The aircraft that was on a vectored approach to land. it was night so VMC rules do not apply. it was IMC. Is it standard approach into Reagan on ILS with LOC capture or a free for all? Every aircraft I have ever flown in as a civvy engineer is AP/YD engaged well into DH accepted AP disconnect unless MEL applied. So on a set course and trajectory that is the same everywhere else in the world. Long final, Short final, little difference. Whom gives way?
What planet are you from?

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Luc Lion
January 31, 2025, 13:18:00 GMT
permalink Post: 11818194
Rarife , the planned separation is more like 0-100 ft than 100-200 ft.
When overflying the eastern side of the Potomac, the planes aligned with RW33 are between 220 and 270 ft MSL
Basically, route RT4 is designed to place the helicopters at the same height as planes approaching to land on RW33.
I believe that this corridor altitude was rather planned to avoid conflicts with RW01 approaches.
And, in my view, this corridor is incompatible with approaches to RW33.

By the way, the situation with approach to RW19 is marginally better: approaching planes are overflying the helicopter corridor RT1 up to the Franklin Roosevelt memorial where their paths diverge and, at that point, the planes are supposed to be at 420 ft and the helicopters at or below 200 ft.
The CNN article mentions several near-misses that happened with approaches to RW19.

I think that the RT1 between Memorial Bridge and Hains Point and the RT4 between Haines Point and Wilson Bridge should be operated by ATC as roads crossing 2 bascule bridges and the bridges open to let respectively approaches RW19 and approaches RW33 pass through.
Last edited by Luc Lion; 31st January 2025 at 13:34 .

Subjects ATC  CNN  Separation (ALL)

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Luc Lion
January 31, 2025, 13:57:00 GMT
permalink Post: 11818229
Kenny, I respect your experience with landing in KDCA 15 years ago but, either the 3.00\xb0 published angle of the PAPI is a lie, or Google map scaling is wrong, or your memories are distorted.
As per Google map, the distance from the TDZ to the eastern bank of the Potomac is 1635 m and, with 3.00\xb0 angle, the glide path is supposed to be at an height of 85.5 m, or 280 ft at that point.
Reversely, a height of 500 ft above TDZ is on the glide at a distance of 9540 ft or 2908 m from the TDZ. Google map shows that overhead the northbound lane of I-295.
I think that it's plausible that you aligned your plane with RW33 centerline over the Potomac's East bank if you were flying a steep VFR approach, not a night IFR approach.

Note: 450 ft overhead the eastern bank gives you a 8.4% slope or 4.8\xb0 to the TDZ.
Last edited by Luc Lion; 31st January 2025 at 14:29 . Reason: grammar

Subjects IFR  KDCA  VFR

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Luc Lion
January 31, 2025, 14:20:00 GMT
permalink Post: 11818247
Originally Posted by ;11818231
but equally describing a fast developing potential collision situation in terms referencing local bridges (was the pilot local ?) is (at least with hindsight) inadequate and something 'far more alarming' could have been said in time.
Jetstream67, "Memorial Bridge", "Hains Point", "Capitol Street Bridge" and "Wilson Bridge" are the names of visual reporting points (VRP) displayed on the "Helicopter Route Chart, Baltimore-Washington". Further, the routes' altitude constraints make reference to these points.
https://aeronav.faa.gov/visual/09-05...-Wash_Heli.pdf

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Luc Lion
January 31, 2025, 14:24:00 GMT
permalink Post: 11818249
Originally Posted by slfool
I've heard conflicting reports about whether the collision was head on, or the helicopter hit the RHS, do we know which it was? I'm asking because there's also been comments about the difficulty of picking out lights from an aircraft that's approaching head on against a background of city lights.
From the available videos, (particularly the CNN ones) the difference in heading looks close to 90\xb0. Maybe 110\xb0.

Subjects CNN

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Luc Lion
January 31, 2025, 16:30:00 GMT
permalink Post: 11818345
@ NIBEX2A this list is appalling.

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Luc Lion
January 31, 2025, 16:45:00 GMT
permalink Post: 11818351
Originally Posted by kap'n krunch
My understanding is the helo involved was UHF and that the audio presented on various internet sites was manually combined with the normal Live ATC VHF communications.
Originally Posted by adnoid
That is exactly what VAS Aviation did for the SECOND Youtube video - spliced together the VHF and UHF recordings. His first video only had the VHF.
Originally Posted by Lascaille
What's your source on that? You're suggesting that the civilian ATC controller was talking to the helo on UHF and separately talking to the civ traffic on VHF?
Because it's clearly the same controller voice. What's the published UHF frequency for the civ traffic controller to use?
His first video had responses from the helo, just not all of them... The civ ATC is sending to the helo on VHF and receiving on UHF? Is that mentioned anywhere on the VAS Aviation channel? Because the LiveATC recordings page has clips which include all the audio with no mention of splices being made.
This endless discussion about UHF/VHF frequencies is a bit disturbing.
Please read the helicopter route chart.
https://aeronav.faa.gov/visual/09-05...-Wash_Heli.pdf
There is a DCA tower frequency dedicated to helicopters: "134.35 (HELI)".
And it looks VHF to me.

Edit: Sorry, didn't see that skwdenyer had already answered

Subjects ATC  DCA  Frequency 134.35

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Luc Lion
January 31, 2025, 22:24:00 GMT
permalink Post: 11818577
Originally Posted by pax britanica
Where else does 200ft vertical get classed as separation on top of which the CRJ was obviously descending as well .as it was on final approach .
200 ft is not the separation between the 2 aircrafts, it's the maximum altitude allowed in the helicopter corridor. As the airplane on approach is supposed to be at about 250 ft when crossing this corridor, there is no way a 200 ft separation could ever have been achieved.

Subjects CRJ  Separation (ALL)

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Luc Lion
January 31, 2025, 22:36:00 GMT
permalink Post: 11818582
Originally Posted by SAR Bloke
Whilst I agree giving avoidance instructions would possibly be a sensible thing to do, I can't see that explicitly written in the FAR AIM if pilot-applied visual separation has been approved.
Granting a visual separation clearance at night in a context like this is a bit like removing all slices of cheese but one. (Context being conflicting paths on same low altitude, one aircraft on a constrained track)
It works most of the time until you run out of luck.

Subjects Separation (ALL)  Visual Separation

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Luc Lion
February 03, 2025, 13:58:00 GMT
permalink Post: 11820556
I am surprised with the NTSB statement that the CRJ was at 325 ft altitude: the collision appeared to have taken place over the water (the helicopter had a track parallel to the bank and its hull splashed in the water) and, even if computed overhead the river bank, 325 ft gives a glide slope with an angle of 3\xb0 and 28 minutes. This is between 3 and 4 whites on the PAPI (the angle separating 3 and 4 whites is 3\xb0 and 30 minutes). And the videos show that the CRJ was lined up at least 9 seconds prior to impact.

Edit: after correcting the calculation with the fact that the PAPI is 350 ft before the TDZ, the angle for 325 ft altitude is rather 3\xb0 48 minutes, well into the 4 whites range.
Last edited by Luc Lion; 3rd February 2025 at 14:35 . Reason: correction

Subjects CRJ  NTSB

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Luc Lion
February 03, 2025, 14:29:00 GMT
permalink Post: 11820584
Originally Posted by island_airphoto
So you are saying the plane would have been even LOWER had it been right on glideslope, making the whole plan even WORSE?
Yes. I posted the calculation several times earlier in the thread.
If we assume that the collision occurred over the water close to the eastern bank, that gives a distance to the TDZ of 4900 ft.
And the PAPI is even closer than the TDZ.
If we then assume a plane spot on the glide of 3.00\xb0.
4900 ft * tan(3\xb0) = 257 ft
257 ft + 13 ft (TDZ altitude) = 270 ft AMSL

However, as several posters have highlighted, the plan was NOT to have the helicopter route underneath the CRJ.
Last edited by Luc Lion; 3rd February 2025 at 14:40 .

Subjects CRJ

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Luc Lion
February 07, 2025, 14:19:00 GMT
permalink Post: 11823680
Originally Posted by 51bravo
I really run out of an idea what ATC would clear if the PAT25 crew didnt ask for "visual separation"...
Maybe something like continue route RT1 up to Pennsylvania Avenue, then route RT2 to Woods Corner, then route RT3 to Wilson Bridge.
There is also route RT6 from Bolling to Woods Corner, but I don't think that the steep climb from Hains Point 200ft to Bolling 1400ft is reasonable.

Subjects ATC  PAT25  Separation (ALL)  Visual Separation

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