Posts about: "ADSB (All)" [Posts: 130 Page: 2 of 7]¶

Subjects ADSB (All)  TCAS (All)

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Subjects ADSB (All)  ADSB In  ADSB Out  Blackhawk (H-60)  CRJ  TCAS (All)  TCAS RA

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Subjects ADSB (All)  ADSB Out  ATC  DCA  TCAS (All)

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Subjects ADSB (All)  ADSB Out  DCA  TCAS (All)

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Quote:

Originally Posted by ATC Watcher

I was taking Military , and here in DC airspace Class B you had one aircraft without ADS-B. out.( not that it would have changed anything ,) but if you want to devise /create a performant CAS using ADS-B it starts there .
Then there is the question of the C150s, you raised , of course no TCAS, we are talking ADS-B out, but even then, do you really want to have them anywhere near the approach path of a major busy airport airspace to start with ?

The military somehow exempted themselves with the results we see now.
I was a frequent visitor to DCA in C-150s and C-172s pre 9-11, it was a nice way to get to the city for dinner from the island I live on. Unless the airlines start buying their own private airports there is no sorting out of airplanes like that, public airports are for everyone with an airplane (9-11 bullcrap excepted). They would do "river tours" back then too, you got a trip up and down the Potomac with some great sightseeing. Back then airplane ramp fees were less than you could end up paying to park a car

Subjects ADSB (All)  ADSB Out  ATC  DCA  TCAS (All)

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Blancolirio says at his latest update that the helicopter should have been told to hold before crossing the approach patch of 33. My post saying the same was deleted. I dont know why our very senior pilot is adamant that an army crew in a combat ready chopper cannot stop. Me, just a lowly private R22 driver, had to perfom quick stops on my examination flight for the PL(H) licence and we were trained to avoid and/or get out of a possibly ensuing vortex ring state. If I could do it in this wobbly contraption of Robinsons, anybody else can, because I am not Top Gun.
We used this quite often when parachute jumpers crossed our approach path to the homebase (from above of course ). We could have done a 360 , but then we would have lost sight of our vertical traffic and a quick stop is more fun.
I my country we widely use a wonderful device called FLARM. It is sort of a pour man's TCAS, using a similar protocol as ADS-B but on a free to use frequency. Shows traffic of other live FLARMS and warns if a Mode-S transponders is approaching (using field strength) . It has another optional feature: a database of low strung cables, power lines and other obstructions our country is infested with. Guess what we had to do in a heli when this alarm went of? Indeed, a quick stop and then a good lookout for cables!

Your deleted post said nothing of the sort; it was “ Blow your nose and you might be 100 ft higher (or splash) in a powerful heli at 130kts” and nothing else.

Senior Pilot

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Last edited by Senior Pilot; 5th February 2025 at 07:33 . Reason: Add actual deleted post

Subjects ADSB (All)  TCAS (All)

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Quote:

Originally Posted by clearedtocross

Blancolirio says at his latest update that the helicopter should have been told to hold before crossing the approach patch of 33. My post saying the same was deleted. I dont know why our very senior pilot is adamant that an army crew in a combat ready chopper cannot stop. Me, just a lowly private R22 driver, had to perfom quick stops on my examination flight for the PL(H) licence and we were trained to avoid and/or get out of a possibly ensuing vortex ring state. If I could do it in this wobbly contraption of Robinsons, anybody else can, because I am not Top Gun.
We used this quite often when parachute jumpers crossed our approach path to the homebase (from above of course ). We could have done a 360 , but then we would have lost sight of our vertical traffic and a quick stop is more fun.
I my country we widely use a wonderful device called FLARM. It is sort of a pour man's TCAS, using a similar protocol as ADS-B but on a free to use frequency. Shows traffic of other live FLARMS and warns if a Mode-S transponders is approaching (using field strength) . It has another optional feature: a database of low strung cables, power lines and other obstructions our country is infested with. Guess what we had to do in a heli when this alarm went of? Indeed, a quick stop and then a good lookout for cables!

The R-22 is (in)famous for having low momentum to the point they were crashing before that was addressed specifically in training, so slamming on the brakes is going to work WAY better than a big heavy helicopter.

Subjects ADSB (All)  TCAS (All)

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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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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:

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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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Quote:

Originally Posted by clearedtocross

Blancolirio says at his latest update that the helicopter should have been told to hold before crossing the approach patch of 33. My post saying the same was deleted. I dont know why our very senior pilot is adamant that an army crew in a combat ready chopper cannot stop. Me, just a lowly private R22 driver, had to perfom quick stops on my examination flight for the PL(H) licence and we were trained to avoid and/or get out of a possibly ensuing vortex ring state. If I could do it in this wobbly contraption of Robinsons, anybody else can, because I am not Top Gun.
We used this quite often when parachute jumpers crossed our approach path to the homebase (from above of course ). We could have done a 360 , but then we would have lost sight of our vertical traffic and a quick stop is more fun.
I my country we widely use a wonderful device called FLARM. It is sort of a pour man's TCAS, using a similar protocol as ADS-B but on a free to use frequency. Shows traffic of other live FLARMS and warns if a Mode-S transponders is approaching (using field strength) . It has another optional feature: a database of low strung cables, power lines and other obstructions our country is infested with. Guess what we had to do in a heli when this alarm went of? Indeed, a quick stop and then a good lookout for cables!

Quote:

Originally Posted by Torquetalk

And Top Gun wouldn’t try and do it either, because getting rid of the energy in an R22 at 70 KIAS is an entirely different prospect to getting rid of the energy in a Blackhawk at 140 KIAS.
like they say in the industry: “you don’t know what you don’t know”
Trying to quick stop at night as a means of collision avoidance is just dumb anyway.
And fwiw: if you understand VRS training as necessary to recover from mismanaged quick stops, then you need more training.

R-22 v UH-60L/MH-60 etc.. yes they are absolutely different, have different paint n everything, different spelling and all. The relationship of inertial vs aerodynamic forces on the rotor system. generally referred to as the Lock number are worlds apart. It may seem like a meaningless number but it is what gives the characteristics of the harmonic control that you, the rotary pilot are actually controlling. It also uses similar factors that determine the tip path plane of the rotor for different conditions and the relationship between control input, swash plate plane and the tip path plane of the rotor.

During a quick stop, your instructor was correct to prepare you for what follows rapidly thereafter with respect to your heading and your need to be ready for some footwork, and to be aware of the torque demand that follows where the wake influences your aircraft. This isn't however vortex ring state, nor is it settling with power, it is a transient related to your wake. The R-22 has adequate but not fantastic tail rotor authority, the UH-60 has an excellent tail rotor befitting a damned fine tactical/combat helicopter.

You can get through a complete aviation career in helicopters without opening up any books beyond your training manuals. Helicopters also bite back hard if you.step out of line, so my suggestion is that you may frame Torquetalk's comment: “you don’t know what you don’t know” , and enjoy reading about your machines physics.

Spoiler

 

 

dont start with Wayne Johnson unless you love matrices and integrals and vector math, Ray Prouty is always a good read, but it can jam your seat track in a B777, Gareth Padfield is clear, Gordon Leishman's work is clear, Seddon & Newman are good reading, Walt Wagtendonk is an easy starting point. If you just want a great read and an insight into some testing stuff, Shawn Coyles series are fun reading. Shawn sadly recently passed away, leaving a vacuum in the Ray Prouty lecture series.

Subjects ADSB (All)  Blackhawk (H-60)  TCAS (All)

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Quote:

Originally Posted by JohnDixson

Dibo/fdr: keep wondering why the Hawk crew made that last correction to the right.

I don't think it make a significant turn right, and I believe that what you are seeing is positional inaccuracy due to MLAT position limitations in the ADS-B Exchange data. According to Flightradar24, " MLAT position calculations have a general accuracy of 10-100 meters and 1000 meters in the worst cases." Given that, I believe this previous post from MikeSnow AA5342 Down DCA represents our best current understanding of the actual helicopter track and its relation to Route 4 (until we get more information from the NTSB). I generated my own zoomed overlay and got essentially the same results



The position of the collision shown in the radar data overlay is consistent with the position of the RJ as shown in ADS-B Exchange at the time of the collision (approximately 01:47:59Z according to the NTSB timeline). See this link from DIBO for the RJ Track with timing AA5342 Down DCA In my experience, times in ADS-B Exchange are generally accurate to within 2 seconds. Given all that, I believe that the Black Hawk was within the horizontal bounds of Route 4 at the time of the collision and that it did not make the right turn we see in the ADS-B Exchange map.

Edit: Corrected route number and helicopter

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Last edited by airplanecrazy; 6th February 2025 at 01:24 .

Subjects AA5342  ADSB (All)  Blackhawk (H-60)  DCA  NTSB  Radar  Route 4

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Subjects ADSB (All)

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Quote:

Originally Posted by Cobraguy

I've not read the entire chain of thoughts and comments, so please excuse me if my thinking has already been brought out:

Spoiler

 

 

Seems to me that the collision altitude is reasonably well established.

Further, seems to me that the helicopter was reporting 200 feet via the IFF (transponder), probably from the AAU-32 Baro altimeter instrument in the cockpit.

I now understand that the H-60 had an ADS-B capable black box upgrade in place of the original basic IFF (APX-100?), and that the extended (ADS-) squitter message was turned off on the subject flight.

I think it is worth a close review of the static line plumbing to the AAU-32 which is the source of the 29.92 altitude report.

If, for example, the static line became disconnected, then cockpit ambient pressure might influence (bias) the AAU-32's reading.

I'd check the records to see if a pitot-static leak set had been performed in the recent past, and I'd inspect the remnants of cockpit plumbing if practical

Second... I'd check the upgraded ADS-B capable IFF/Transponder to see if it used aircraft static altitude sensed values as it reported "altitude" , and not (ever) use any other value such as altitude above geoid.

Long-shot thoughts, but perhaps worth considering.

How refreshing. Someone with a technical insight. Thanks.

Subjects ADSB (All)

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Quote:

Originally Posted by Cobraguy

I've not read the entire chain of thoughts and comments, so please excuse me if my thinking has already been brought out:

Seems to me that the collision altitude is reasonably well established.

Further, seems to me that the helicopter was reporting 200 feet via the IFF (transponder), probably from the AAU-32 Baro altimeter instrument in the cockpit.

I now understand that the H-60 had an ADS-B capable black box upgrade in place of the original basic IFF (APX-100?), and that the extended (ADS-) squitter message was turned off on the subject flight.

I think it is worth a close review of the static line plumbing to the AAU-32 which is the source of the 29.92 altitude report.

If, for example, the static line became disconnected, then cockpit ambient pressure might influence (bias) the AAU-32's reading.

I'd check the records to see if a pitot-static leak set had been performed in the recent past, and I'd inspect the remnants of cockpit plumbing if practical

Second... I'd check the upgraded ADS-B capable IFF/Transponder to see if it used aircraft static altitude sensed values as it reported "altitude" , and not (ever) use any other value such as altitude above geoid.

Long-shot thoughts, but perhaps worth considering.

Quote:

Originally Posted by Lonewolf_50

How refreshing. Someone with a technical insight. Thanks.

CG, (& LW), thanks for cutting through the noise.

There is graphic evidence that the fuselage of the 60 went under the nose of the CRJ700, and they hit is probably established beyond reasonable doubt on this forum, if not in the evidence of the wreckage in the Potomac. The flight path of the CRJ is well established, up until the moment that the aircraft struck. That should itself have put to bed the matter of height in the analysis.

It is highly probable that the 60 was on altitude on their instruments, and the causal factor being misidentification of a visual target beyond 5nm at night, landing on RWY01, while the CRJ is not pointing at the helicopter, it is presenting the red navlight on the port wingtip to the helicopter drivers, along with occasional strobes against a night sky. The vector of the CRJ across the visual sector of the helo crews was a slow translation to the right, and then from off around 10 o'clock the CRJ intersects the RWY33 finals and becomes a stationary target well off the main scan of the helicopter crew. When asked to confirm they are passing behind the CRJ traffic, they have the RWY01 traffic off to their right, and they are reasonably expecting that to be their traffic. If they don't have a breadcrumb trace of the traffic on their ND of tac display, while the outcome is unfortunate, I would argue that misidentification of a target in a condition where misidentification is a high probability is not the primary causal factor, it is a consequence of the practice of mixing crossing LL traffic with landing and TO traffic.

My concerns are not future risk from this condition occurring, failure to place spak filler over the cracks in this practice would be naughty. My concern is the system scapegoating a US Army flight crew doing a task that is arguably unreasonable. The fact that some may consider it just normal practice done badly does not answer the fact that physiological limitations and the kinetics of this situation make a mid air a near certainty, the obvious evidence being they did hit, the day before there was a near-miss/loss of separation.

It is time for command to assume responsibilities that go with their post, and not blame those beneath them that travel in harms way on the implicit faith that command is competent and cares for the crews safety, and the national resource that they represent. To do otherwise is conduct unbecoming.

The CRJ crew were having a normal day, until they were killed. The passengers on board could also reasonably expect that our industry cares enough to actually do what we say we are doing, and to MANAGE SAFETY , if that is not too much to ask for. Managing safety does not equate to box ticking, it is the very fact we have devolved into considering safety in a stochastic system to be assured by compliance that we get to this sorry saga.

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Last edited by fdr; 7th February 2025 at 20:23 .

Subjects ADSB (All)  CRJ  Separation (ALL)

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Subjects AA5342  ADSB (All)  NTSB  PAT25  Situational Awareness  TCAS (All)

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Subjects AA5342  ADSB (All)  ATC  Blackhawk (H-60)  CRJ  DCA  NTSB  PAT25  See and Avoid  Situational Awareness  TCAS (All)  VFR

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Subjects AA5342  ADSB (All)  CRJ  NTSB  PAT25  TCAS (All)

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Subjects ADSB (All)  ICAO  Radar  Separation (ALL)

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Subjects ADSB (All)  ICAO  Radar  Separation (ALL)  Vertical Separation

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Subjects AA5342  ADSB (All)  NTSB  Night Vision Goggles (NVG)  PAT25  Situational Awareness  TCAS (All)

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