AA5342 Down DCA

[ATC Watcher]

Originally Posted by BFSGrad

3. PSA Captain/PF expressed to PM a preference for continuing to runway 1 but accepted runway 33. Media will make a big deal out of this. I don’t think it is.

Agee, but always the pressure not to say " negative " or " unable " even when not feeling comfortable with an ATC request.

What is likely to make a media deal is the wrongly calibrated ( or QNH setting) of the PAT altimeters which might open discussion on the real issue : the initial 100 feet procedural separation

[ozsmac]

I found the summary of day 1 of the hearings on the NTSB Newstalk podcast to be quite insightful. The discussions around altimeters, SOPs and charts was insightful (overblown by a few of the folks asking the questions).

https://www.aviationnewstalknetwork....ntsb-news-talk

[ATC Watcher]

Originally Posted by ozsmac

I found the summary of day 1 of the hearings on the NTSB Newstalk podcast to be quite insightful. The discussions around altimeters, SOPs and charts was insightful (overblown by a few of the folks asking the questions).

https://www.aviationnewstalknetwork....ntsb-news-talk

A must read/listen . The holes in the cheese layers were quite big
just a few :
-UH60-L Heli altimeters accuracy .80 -130 ft systemic error due position of the static sensors affected by rotor blades in cruise
-80 ft error deemed within acceptable tolerance by Army pilots
-flying at 300ft targeting 200ft is "acceptable" by the Army
-200ft restriction on the chart is a only a "recommended target" in VFR not a hard restriction i unless instructed by ATC ..
-Lack of regulatory oversight by FAA despite many previous incidents .
-FAA (bureaucratic) refusal to put a 'Hot spot" symbol on routes crossings.
-Lack of ADS-B compliance on Army helis, due maintenance documentation errors during installation
-lack of experience of heli pilots on specific areas due frequent rotation of staff and lack of training hours in general.
-Lack of continuity in of DCA ATC operations supervision , 10 managers in 12 years and 5 in last 5 years.

In fact on some of the Reason's layers there were more holes than cheese.

[Lonewolf_50]

Originally Posted by ATC Watcher

-flying at 300ft targeting 200ft is "acceptable" by the Army
-200ft restriction on the chart is a only a "recommended target" in VFR not a hard restriction i unless instructed by ATC ..

Something smells wrong about some of this.
(I need to see a bit more of the documentation on the difference between the hard altitude (200') that I was under the impression was on that route, as opposed to the "recommended altitude" statement made there...maybe it will make more sense to me then).
As to altimeter errors.
The UH-60L has a radalt.
Are you trying to tell me that the alleged acceptable error for a rad alt is 80'-130'?
I think not.
I doubt that the rules have changed that much since I was last flying a Blackhawk. (yes, it has been a while).
Will do a bit more reading, thanks.

[MechEngr]

Depending on radalt for this flight mode is a problem when flying over buildings or terrain when one wants to maintain an absolute altitude relative to a common datum. If done perfectly radalt would be hammering back and forth with every chimney and tree and park and car. I'm sure they use smoothing to give something for the crew to read, but it doesn't tell how high the terrain is that the measurement is made from - it only reports clearance to the terrain when one wants clearance to other aircraft.

For TF/TA radalt is the go-to instrument, but for coordinating multiple aircraft to maintain vertical separation, barometric altitude is more suitable. The problem being that barometric altimeters are subject to a lot of measurement and reporting errors.

I am sure that GPS-RTK could be used to fix the absolute altitude with great precision, but I am also sure that depending on an easily denied measurement source on a military aircraft is not going happen.

The correct solution for operating in a civilian airspace is to use ADS-B In/Out for all manned aircraft to provide appropriate and timely situational awareness. While ADS-B is also subject to denial, it offers far greater benefit in civilian airspace over GPS-RTK in that it tells the pilots where all the other aircraft are rather than simply being more precise about where their own aircraft is.

It is clear that the helicopter crew not knowing where the passenger jet was was the primary cause of the collision.

Arguments about the error in the altimeter readings are suitable to emphasize that depending on them in a crowded airspace is a fool's choice and should have been spotted a long time ago as insufficient to provide clearance.

[WillowRun 6-3]

With respect to the Army aviation helicopter unit, and the other VIP transport helicopters in the National Capital Region, the reason stated for not using ADS-B is that these missions include continuity of government functions, which is significantly more critical than day-to-day transport of very high-level officials (as important as that transport may be).

Law enforcement and med-evac helicopter flights also are involved in the DCA airspace problem. Further, besides the Army unit, reference was made - if I understood correctly - to a unit of USAF. Perhaps this was a reference to the helicopter unit assigned specifically to the White House and was left unclear on purpose.

[albatross]

If the Blackhawk’s pressure altimeters had been both reading correctly and they had maintained 200 ft they would of passed only 75 feet under the RJ.
That is “nuts”.
Even if they had maintained 100 feet over the river that would still be classified as a very near miss.

A terrible case of Swiss Cheese holes lining up for a multitude of reasons.

An error of 100’ ft from field elevation during preflight would be out of limits and snagged in my civilian experience. Shouldn’t military aircraft that operate at very low altitudes at night have even tighter restrictions?

[BFSGrad]

Originally Posted by WillowRun 6-3

Further, besides the Army unit, reference was made - if I understood correctly - to a unit of USAF. Perhaps this was a reference to the helicopter unit assigned specifically to the White House and was left unclear on purpose.

1st Helo operating out of ADW, call sign MUSL.

[Lonewolf_50]

Originally Posted by MechEngr

Depending on radalt for this flight mode is a problem when flying over buildings or terrain

They were flying over the river, not the built up areas. Not sure how much time you have flying in a Blackhawk, but if you are over the water at night at 200' your radalt is giving you better indications of how far you are above water than your bar alt. If the two disagree, which one do you think you'll be using?
(Same is true in the Seahawk).

As to your point on the cause of the accident, yes, they were not aware of the traffic coming into 33 (for reasons beaten to death already).

I'm going to offer a contributing cause that I think merits consideration: there was mention made early on of there being 1, not 2, tower controllers on duty at the time when apparently 2 is the normal number.
Had there been two, the helicopter might have been handled differently, but we'll never know.

Spoiler

 

 

Spoiler

 

 

The youtube vid some months back had a pilot who had flown in that unit, and he mentioned often getting "do a left 360 for spacing" in the past.
That would have sufficed in this, and other, cases where traffic comes into 33.





[WillowRun 6-3]

Originally Posted by BFSGrad

1st Helo operating out of ADW, call sign MUSL.

Thank you for clarifying this information.

[BFSGrad]

Originally Posted by Lonewolf_50

They were flying over the river, not the built up areas. Not sure how much time you have flying in a Blackhawk, but if you are over the water at night at 200' your radalt is giving you better indications of how far you are above water than your bar alt. If the two disagree, which one do you think you'll be using?
(Same is true in the Seahawk).

My recollection from the CW3 Roth (former 12th AB pilot) interview was he said the opposite; i.e., due to the frequent bridges/islands in the river, PAT25 would have been flying referenced to baro for route 1 and 4 altitude limits.

[dragon6172]

Originally Posted by Lonewolf_50

They were flying over the river, not the built up areas. Not sure how much time you have flying in a Blackhawk, but if you are over the water at night at 200' your radalt is giving you better indications of how far you are above water than your bar alt. If the two disagree, which one do you think you'll be using?
(Same is true in the Seahawk).

As to your point on the cause of the accident, yes, they were not aware of the traffic coming into 33 (for reasons beaten to death already).

I'm going to offer a contributing cause that I think merits consideration: there was mention made early on of there being 1, not 2, tower controllers on duty at the time when apparently 2 is the normal number.
Had there been two, the helicopter might have been handled differently, but we'll never know.

Spoiler

 

 

Spoiler

 

 

The youtube vid some months back had a pilot who had flown in that unit, and he mentioned often getting "do a left 360 for spacing" in the past.
That would have sufficed in this, and other, cases where traffic comes into 33.





I have flown that route a handful of times during my time in the Marine Corps (admittedly it's been more than 20 years ago). I recall being asked to do a 360 turn over the Wilson Bridge for spacing (we were northbound) for traffic landing on 33.

In regards to your other comment about them not seeing the CRJ, I have believed from the time that the radio traffic was public that the controller was not specific enough when he asked PAT 25 "do you have the CRJ in sight?" Something along the lines of "PAT 25, CRJ on final for RWY 33 is at your 10 o'clock less than a mile, pass behind that traffic" should have drawn the helo crews eyes to the left to hopefully see the traffic. Even better would have been to have the helo do a left 360 over Hains Point.

[nachtmusak]

Originally Posted by ATC Watcher

What is likely to make a media deal is the wrongly calibrated ( or QNH setting) of the PAT altimeters which might open discussion on the real issue : the initial 100 feet procedural separation

My impression was not that they were wrongly calibrated, but that they were simply bad. It sounds like the barometric altimeters in the helicopter type in question might not be taking the helicopter's own backwash/downwash into account.

[ST Dog]

Originally Posted by BFSGrad

My recollection from the CW3 Roth (former 12th AB pilot) interview was he said the opposite; i.e., due to the frequent bridges/islands in the river, PAT25 would have been flying referenced to baro for route 1 and 4 altitude limits.

And I forget who, but there was mention of RADALT varying with the depth of the water.

[BFSGrad]

Originally Posted by ST Dog

And I forget who, but there was mention of RADALT varying with the depth of the water.

Don’t recall hearing that. Roth referred to the river clutter causing the radalt to bounce around.

To complicate further, the Army Day 1 witness, CW4 Lewis, indicated she would have flown route 1/4 using radalt as her altitude reference. She also offered that she had zero DC route experience.

[MechEngr]

No matter, radalt only gives the altitude above some actual thing, not a shared pressure altitude that all air vehicles can agree on. AA5342 was not on a radalt path. AA5342 was flying over buildings.

EDIT: I also appreciate the arriving jet was on a geometric glide slope and that radalt under the glideslope could have been sufficient, but if one is expecting that vertical separation is sufficient then there needs to be certainty to that altitude and clearly that isn't possible on barometric altimeter and should never have been accepted by anyone.

[ST Dog]

Originally Posted by BFSGrad

Don’t recall hearing that. Roth referred to the river clutter causing the radalt to bounce around.

Once the recording/transcript is available I'll try to find it. I remember it struck me as odd.

To complicate further, the Army Day 1 witness, CW4 Lewis, indicated she would have flown route 1/4 using radalt as her altitude reference. She also offered that she had zero DC route experience.

Was it her that later said she'd use baro since the route was MSL not AGL?

Again need to recheck against the transcript. my memory may be fuzzy. I was doing 3 different things at the time.

I have several things I want to revisit from the 2 days so far.

[island_airphoto]

Originally Posted by ST Dog

Once the recording/transcript is available I'll try to find it. I remember it struck me as odd.



Was it her that later said she'd use baro since the route was MSL not AGL?

Again need to recheck against the transcript. my memory may be fuzzy. I was doing 3 different things at the time.

I have several things I want to revisit from the 2 days so far.

MSL and AGL are hardly different at KDCA, the airport is 14 feet above sea level. Now if you are only missing by 75 feet on a good day, maybe 14 feet DOES matter

[ATC Watcher]

Originally Posted by Lonewolf_50

I'm going to offer a contributing cause that I think merits consideration: there was mention made early on of there being 1, not 2, tower controllers on duty at the time when apparently 2 is the normal number.
Had there been two, the helicopter might have been handled differently, but we'll never know.

Spoiler

 

 

Spoiler

 

 

The youtube vid some months back had a pilot who had flown in that unit, and he mentioned often getting "do a left 360 for spacing" in the past.
That would have sufficed in this, and other, cases where traffic comes into 33.





Yes , but for me more important is the fact that a single controller was handling 2 frequencies that were not really coupled, the CRJ did not hear the RAT and vice versa, both only heard what the controller said not the questions asked , The single controller was also busy doing 2 jobs and quite busy with Runway 1 OPS , so probably that is why he did not find the time top pass essential traffic info to the CRJ . 2 controllers might have changed something, yes, but only " might" because in that case , both would have been on 2 separate frequencies , if traffic info was not passed to the CRJ , the result could have been the same .

For me the key point of this accident is the 100 ft procedural separation planned between a Heli route and a non precision ( e.g visual) approach path . The rest are just more holes in the cheese.

[YRP]

Originally Posted by ATC Watcher

For me the key point of this accident is the 100 ft procedural separation planned between a Heli route and a non precision ( e.g visual) approach path . The rest are just more holes in the cheese.

Yes, that does seem nuts. It is as if they decided to ignore all the tolerances (altimeter accuracy, pilot accuracy, etc) and pretend everything is spot on.

There's a reason for the normal 500' or 1000' separation between traffic, eg enroute cruising altitudes. Someone once worked out the tolerances and margins.