A Question for Avionics Techs  RE Recent DC crash. - Page 1
Forum section: electronics / general

author: LaserSteve
author_rank: Super Contributor
timestamp: February 03, 2025, 03:57:59 pm
content: OK,What is the displayed resolution, actual resolution, accuracy and precision of a well-made military grade radar altimeter? Specifically in the low altitude regime, ie under 1000 ft.Same question for a Barometric Altimeter.What is the transmitted resolution of a Mode C transponder with respect to altitude?Does the Mode C data suffer from "Bit Bobble" ? Is there Kalman filtering or just the instrument's own lag for smoothing?In other words, what is in the PID loop other then a human? I'm guessing the rotorcraft had a stability augmentation system.I know from flying with private pilot friends a long time ago that the desired tolerance when flying a bug smasher was +/- 50 feet of assigned altitude.I'd like some sane tech data, as too many videos, journalists, bloggers, etc have already assigned blame in the recent crash, which I think is a bloody shame till we have tapes and analysis.This is not the right place to debate the merits of the flight route, location of the glide slope, airport placement, etc,I'm well aware that without sensor fusion the radar only updates every 12.5 seconds if you use a simpleton style rotation-based explanation, and ignore beamwidth, PRF, decode times etc. I'm willing to concede that the DC area has sensor fusion, but what data actually makes it to the presentation on a BRITE display these days?Which leads to another question, how fast does ADSB update?Let's stick to determining technical tolerance / error bands, shall we? I'm sure EEVBLOG would appreciate it if we keep the emotions and opinions out of this.A long-ago childhood visit to the back rooms of a TRACON with an on-site ASR has me wondering about human expectations vs technical reality. I'm seeking a bettersystem model. I'm thinking that "Tolerance Stacking" may make obtaining an actual cause determination very difficult.Steve

author: Kerlin
author_rank: Regular Contributor
timestamp: February 03, 2025, 10:37:39 pm
content: Hi SteveI will qualify this answer is from my perspective.I am an Aussie, this is an Aussie form. So my observations relate only that situation.I rarely get on forums as those from the land whose biggest single export is anxiety can surface.After an investigation I found that the university I went to told me that they do still train and run avionics courses.Incredibly they could not give me the course name or number, no one could.I went to there on open day and asked the question in person.After hours of waiting and talking with heads of departments and lecturers I found one fellow who knew.Avionics is done as part of aircraft mechanics. They are only taught briefly what the systems provides and how to do a quick go/no go test, that's it.Most were previously taught by our defense organizations but they stopped doing that decades ago.So locally it would be hard to get answers. The industry here finds it impossible to fill such positions.There are almost no publications on the subject. In my life I have found only one, cant remember it.Those who can answer those questions are under strict contracts not to discuss or divulge that stuff, certainly defense related.Another feature of forums is those who get their Jollies by googling others questions to provide answers.On that note I have googled some of your queries to see if I can get an answer.Here is an example -The resolution of that a Mode C transponder provides is set by the aircraft's height encoder.I did google "what is the resolution of a height encoder" and got a good answer, you will need to specify the number of bits, try 12 bits.I have also found at least partial answers on google and Gemini.I found some time on spent there will reveal some reasonable results you are after, even defense related.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 03, 2025, 11:00:55 pm
content: I went to my once awesome big city library looking for the avionics books of my youth. The tech section is gutted. Somebody decided a library once worthy of a city of sixty thousand people with defense contractors and tire and chemical companies didn't need all the highly detailed electronics and materials science books any more.So they moved a few classics to the reference section. The rest went to the Friends of the Library book sale. The FAA in the US has always been cryptic, not because the data is classified. There are hundreds of thousands of open source FAA documents, but digging through them is futile. Most of them are about system upgrades and research that was never implemented.Local University is winding down, about to be defunded. From 22,000 students to less then 10k in six years. Since I was downsized in the second staff let-go I don't have access to the cool but expensive online pubs any more.I live in the rust belt.Much of this isn't classified, it's just so old it's "BI", before internet. They literally closed the University Science Library and used it to house the guidance counselors. There went the Government Depository Library.A a public use 3D printer and a public use laser cutter now fills much of the space where the thirty or so huge shelves of tech stuff went at what was one of the best public libraries of the cold warera. Glorious, ain't it!You Aussies host the best "World Wide" forum. Far less adverts and crap here then elsewhere.I'll have to drive about an hour and a quarter and hit the remaining good library that still has the Depository section.That is, unless some kind person chimes in.Steve

author: Benta
author_rank: Super Contributor
timestamp: February 03, 2025, 11:17:50 pm
content: Quote from: LaserSteve on February 03, 2025, 03:57:59 pmCorrect. And the "Project" section is the totally wrong place for your post in an electronics engineering forum."General Techincal Chat" might apply, but pprune.com could be more appropriate.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 03, 2025, 11:21:28 pm
content: PPrune is asking the same questions I am. So is the Mil aviation bunch.Steve

author: jpanhalt
author_rank: Super Contributor
timestamp: February 03, 2025, 11:25:38 pm
content: FAR regulations specify barometric altimeter requirements. Basically, they are in Part 91, but Part 121 (scheduled airliners) may be more rigorous. Part 91 specifies ±20 ft for 1000 ft and below. I didn't check on what transponders must report.Military is not controlled by the FAA, but generally it is at least as rigorous. One would expect for helicopters following the terrain low and at night that the requirement would be at least as rigorous for radio/radar altimeters. Elevation of DCA is about 13 ft, and barometric setting from the airport automated information service should have been used. Even then, assuming 325 and 200 feet, allowing only 125 ft separation is ridiculous. It's not clear so far as I have read whether the helicopter was at 200 ft or whether that was its assigned altitude.

author: Benta
author_rank: Super Contributor
timestamp: February 03, 2025, 11:26:55 pm
content: Quote from: LaserSteve on February 03, 2025, 11:21:28 pmYou're still in the wrong place. Geddit?Thread reported.

author: Konkedout
author_rank: Frequent Contributor
timestamp: February 04, 2025, 05:19:23 am
content: Quote from: Kerlin on February 03, 2025, 10:37:39 pmIf you are an Aussie, wouldn't all of the altitudes be negative?

author: moffy
author_rank: Super Contributor
timestamp: February 04, 2025, 05:38:49 am
content: Quote from: Konkedout on February 04, 2025, 05:19:23 amNo, we're the ones that have positive altitudes.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 04, 2025, 06:18:54 am
content: Quote from: moffy on February 04, 2025, 05:38:49 amThat's a matter of perspective. Your altitudes may be positive, but you fly upside down.

author: Kerlin
author_rank: Regular Contributor
timestamp: February 04, 2025, 11:11:49 pm
content: Haha Actually we use an attitude type altimeter meter.It uses a prominent attitude reference location, for example, say trump towers and then subtracts the diameter of the earth.The resulting calculation is the height below the earth which gives us our local altitude.

author: Analog Kid
author_rank: Super Contributor
timestamp: February 05, 2025, 01:07:06 am
content: Quote from: Benta on February 03, 2025, 11:26:55 pmOh, c'mon, give us an effing break!What are you, your neighborhood cop?

author: bdunham7
author_rank: Super Contributor
timestamp: February 05, 2025, 01:56:46 am
content: Quote from: LaserSteve on February 03, 2025, 03:57:59 pmI'm not an avionics tech, but:IDK about "military grade" but from what I know, radio altimeters will have a resolution of 1 to 10 feet and are pretty accurate but somewhat susceptible to errors from the oriention of the aircraft and the nature of the surface. No idea how they behave over water.Barometric altimeters are supposed to be 20 feet but they don't always quite measure up to that, especially if you set them by the ATIS broadcast baro reading vs dialing in the airfield elevation before taking off. You obviously can't do the latter enroute so sometimes they're going to be a bit off when you land.LSB of Mode C is 100 feet. THere's no filtering AFAIK, this is a pretty old standard and was in use well before any sort of microcontroller--or even macrocontroller--would have been practical. So I suppose if you were near the threshold you might see a 1-bit "bobble". The system was never intended to be read that way, sort of like people looking at the last digit of their 6.5-digit meter and wondering why it isn't steady. I don't know much about more modern systems that may be operating in parallel with Mode C/S. ADS-B has more information and the system behind what the ATC sees is beyond me--since I'm not an avionics tech.+/- 50 feet would be a performance goal for pilots, not a standard for the altimeter.What PID loop are you referring to?

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 05, 2025, 02:40:17 am
content: Quote from: jpanhalt on February 03, 2025, 11:25:38 pmYes, a compliant altimeter at these altitudes should largely have no problem distinguishing clearly between 200ft and 325ft, if that was the underlying question. So, unless there was a technical failure, this can't be due to an instrument just not being accurate enough. But we can't rule out that there was indeed a technical failure.In this accident, the report so far shows that the helicopter was flying too high, at 325ft when 200ft was the max. allowed in this area for helicopters. So it should have been at 200ft or below (in which case, the accident wouldn't have actually happened). This max altitude of 200ft in the defined area for helicopters guarantees the safety of planes approaching or leaving the airport on the defined routes with normal ascent/descent rates.No one knows why it was flying above the allowed altitude so far, the investigation will probably tell. But flying safely at <= 200ft with a Blackhawk near an airport is not trivial, it takes serious training.

author: tom66
author_rank: Super Contributor
timestamp: February 05, 2025, 11:29:13 am
content: Not a helicopter pilot (or any other pilot), so apologies if this is a stupid question, but is the altitude of the helicopter entirely controlled by the human pilot throughout the flight? Typically, the plane will be on an autoland approach, or following an ILS glideslope, so its altitude should be pretty consistent. If the helicopter is manually piloted even through these critical areas, it's easy to imagine task saturation (looking for that aircraft that ATC just mentioned) causing momentary disorientation, and a slow increase in altitude.

author: hwasti
author_rank: Contributor
timestamp: February 05, 2025, 12:40:14 pm
content: Pilot and avoinics designer here...There is some reporting that this was a relatively old BlackHawk and had original analog gauges. The pictures I have seen online of that cockpit setup does not show a radar altimeter, only standard pressure altimeter.Down low, a pressure altimeter should be within +/- 25 feet,ASSUMINGthe barometric pressure is set correctly.Down low, an error of 0.1" in the altimeter pressure setting produces and error of about 100 feet in the altitude.IFthe BlackHawk was indeed operating off the pressure altimeter, then it isPOSSIBLEthat the operators may have entered an incorrect pressure, off by 0.1" from the actual pressure.IFthis happened, then when the altimeter showed 200 feet in the cockpit, they would actually be at 300 ft +/-25 ft, which overlaps with the aircraft's altitudes.How could both pilots enter the wrong pressure? SeveralPOSSIBILITIES:They used an old setting.One pilot listened to the ATIS (Automatic Terminal Information Service: An automated broadcast with the current information about the airport), heard incorrectly and relayed that incorrect setting to the other pilot.They asked the controllers for the altimeter setting and the air traffic controller relayed the incorrect pressure setting.Again, this is allSPECULATIONabout whatCOULDhave happened.We will have a really good idea ofwhathappened in a couple of weeks when the NTSB releases its preliminary report. We will have to wait another 12 to 24 months forwhyit happened, when the NTSB releases its final report.

author: hwasti
author_rank: Contributor
timestamp: February 05, 2025, 01:17:55 pm
content: Quote from: bdunham7 on February 05, 2025, 01:56:46 amAccording to Wikipedia, Mode C was published as a specification in 1968 under ARINC-572The Mode C pressure is broadcast in a gray code, so only 1 bit changes when there is a 1 bit change in the value.Each bit of the code represents 100 feet and the reported pressure is referenced to -1200 feet. The typical accuracy is +/-20 feet and the worst case is +/-50 feet.The old (circa 1970's and 1980's) Mode C pressure encoders contained a pressure sensor, op-amps, a dual-slope ADC, and a ROM. The output of the dual slope ADC was used as the address of the ROM and the ROM's data was the gray code, or Gillham code. While 12 bits are defined in the standard to achieve more than 120,000 feet, most low altitude encoders used only 9 bits for a maximum altitude of 30,700 feet.The altitude encoder has to be recertified every 2 years.One of the most common altitude encoders was ACK Technologies A-30. For calibration, it had 2 pots that had to be adjusted successively to adjust the offset and span. The process was supposed to be repeated until it reported the correct altitude at +50 feet and the maximum altitude -50 feet.The A-30 is still manufactured. The manual is currently on "Mod 59." Looking at pictures of the current production hardware, it looks like it is using a single chip micro and reporting the pressure using RS232 outputs as well as the legacy 9-bit Gray Code.This is for the civilian world. I do not know what the military uses.

author: bdunham7
author_rank: Super Contributor
timestamp: February 05, 2025, 03:17:26 pm
content: Quote from: tom66 on February 05, 2025, 11:29:13 amIDK for sure, but I tend to doubt that the helicopter would have AP engaged in these circumstances. In any case, it was not on an ILS or any other external guidance and AFAIK would have relied on its own instruments alone for navigation. The other plane was not on an ILS at all, it was a visual approach circling to land from the approach to another runway.

author: bdunham7
author_rank: Super Contributor
timestamp: February 05, 2025, 03:20:39 pm
content: Quote from: hwasti on February 05, 2025, 01:17:55 pmSo where is the threshold for indicating say 300 feet? Is it exactly 300 feet (so a 300 indication would be valid for actual altitudes from 301 to 400, plus the allowable error) or is it 251 feet orIOW, if I see it flickering from 200 to 300, where am I most likely to actually be at?

author: hwasti
author_rank: Contributor
timestamp: February 06, 2025, 07:46:32 am
content: Quote from: bdunham7 on February 05, 2025, 03:20:39 pmI do not have the formal specification for the Blind Encoder. I do have the specification for air data computers (AS8002), which is responsible for converting static pressure into a digital value for display on the primary flight display in the cockpit.According to Table 1 of AS8002:At the real altitude of 0 feet, the indicated altitude must be within 0 feet +/-25 feetAt the real altitude of 1,000 feet, the indicated altitude must be within 1,000 feet +/-25 feetASSUMINGBlind Encoder specifications are identical, when the encoder outputs 300, it can be anywhere from 225 to 375 feel, which is 300-50-25 to 300+50+25. Yes, I am ignoring the pesky question of whether 250 should be reported as 200 or 300. I am sure it is specified in the formal specification; I just don't have it in front of me.For normal flight operations, air traffic controllers are supposed to keep aircraft 1000 feet away from each other vertically if they are closer than I think 3 miles laterally. This means if one aircraft is indicating high and the other is indicating low, they are still 850 feet from each other vertically.This system was never designed to separate aircraft by 100 feet, or even 200 feet vertically.The caveat is that if a pilot reports that they have the other aircraft in sight, the controller can allow them to get as close to the other aircraft as the pilot is comfortable doing, with the responsibility of separation solely on the shoulders of the pilot who accepted responsibility of separation. This system falls apart when a pilot mistakenly identifies the incorrect aircraft to avoid, which is likely what happened here.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 06, 2025, 09:20:33 am
content: Yes, there may have been an issue with the altimeter calibration, but additionally, it appears more and more likely that they weren't looking at the right plane and there was severe miscommunication with the ATC.

author: tom66
author_rank: Super Contributor
timestamp: February 06, 2025, 09:34:47 am
content: YT shorts warning, but Scott Manley posted this, it models how much view each pilot would have had of the other...https://www.youtube.com/shorts/g1eXQJBOpycIMO a visual approach here (especially at night) was bound to result in a collision at some point. Especially as heli pilots would be wearing NVGs which reduce FoV and particularly impact peripheral vision.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 07, 2025, 04:01:41 pm
content: A retired Blackhawk factory engineer chimed in on another forum. Rad Alt antenna is on the bottom of the armor pan, static ports are higher up. Rad Alt switches virtual display "Tape" presentation at 200 FT. RAD ALT is 16.4 FT below the Rotor top. Reference datum is thus the bottom of the hull.The display flipping modes at or near assigned altitude is interesting. I doubt it "Blinks" rapidly between modes, but that is hopefully something the pilots are used to.Having designed a few visual interfaces before, and having did some display upgrades on half dome AATD Simulators ( for one off applications), I would appreciate the need for a display resolution switch but would have had a course and fine display present.Having flown the sims, having a display mode flip would be something welcome but annoying, to me.Steve

author: Stray Electron
author_rank: Super Contributor
timestamp: February 07, 2025, 05:41:56 pm
content: The US Army is now saying that a"critical safety system onboard the Blackhawk was turned off"and all of the pilots were wearing NVGs when the collision occurred. But to me it's very notable that they not saying what types of NVGs or what safety system. They've also had the black box from the Blackhawk for over a week now and I'm sure that by now they know exactly what altitude it was at but they're not saying. They also saying that the helicopter flight was related to "transportation" and not to a COG training.Also a few days ago the head of the NTSB (not the investigators but the head guy) came on the news and said that he has ORDERED the Pentagon to drastically reduce the number of helicopter flights over Washington DC and around the civilian airports. He even made the remark that if the Generals wanted to get around DC that they should get in their Hummers and drive to their destination instead of taking a helicopter ride. You could plainly see that he was very angry when he made that announcement.Last night's news revealed that the two shorter runways (33 and another that generally runs in the same direction) have been closed and that only the longer, main runway that runs North South is still open. And that it is over congested so they (the FAA) have ordered that it only be used up to 26 times per day instead of the current 28 times per day. In other words, the flights thathad to cross the Potomac river, like the one involved in the collision, are no longer allowed and they have cut back on the number of flights that use the one remaining runway. So it looks like the FAA might be in the process of shutting down that airport or at least severely cutting back it's usage.

author: bdunham7
author_rank: Super Contributor
timestamp: February 07, 2025, 06:13:56 pm
content: Quote from: Stray Electron on February 07, 2025, 05:41:56 pmWe all know what altitude it was at and I'm fairly sure every single indicator available from the Blackhawk (Mode S/radio altimeter/baro altimeter) will agree to within the relevant margin of error. The "altitude discrepancy" is a red herring here.QuoteWho was this? Link? The NTSB doesn't actually have the legal authority to order much of anything at all. And the head of the NTSB is a woman. Was it the Defense Secretary, Pete Hegseth? He's the only one other than Trump who can give such orders.QuoteThat's a reduction from 28 to 28arrivals per hour, not per day, and that doesn't include departures. There will be 5 to 10 planes stacked up waiting to depart between arrivals and that main runway is going to be seeing a plane every minute or so. DCA is still very busy. Thankfully I don't need to go there anytime soon.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 07, 2025, 09:15:51 pm
content: Short of Dave doing a teardown, this is a good start. May not be the model in the crash, but a good start. Accuracies of instruments are in the TECH manual for the most part, not the Pilots basic manual. I know there are newer models with MFDs, but still gives you an idea of the capability and complexity of the beast.https://aviation-assets.info/wp-content/uploads/tm1-1520-237-10-operators-manual-for-uh-60al.pdfRather complex aircraft.GPS LDG is interesting in how it changes the displays in the A/L.Here's an "M"https://live.staticflickr.com/3067/2644574569_a015a24497_b.jpgIf the RAD ALT was working, calibrated, and readable in the NVGs, it is very mission capable resolution wise. Range is 0-1500 feet, and accuracy is +/- 2 feet. The A model altitude hold system resolution is 50 FT working off the Baro altitude.The RAD ALT display mode flips at 200 feet.Of course they were not flying full IFR, so all the neat gadgets in the world are not going to help you if your looking OUT.lSteve

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 07, 2025, 11:51:34 pm
content: Quote from: Stray Electron on February 07, 2025, 05:41:56 pmYes, its ADS-B:https://en.wikipedia.org/wiki/Automatic_Dependent_Surveillance%E2%80%93BroadcastIt's possible that it's "routine" for some training flights (which it was) to disable this to simulate "stealth" conditions. The investigation will tell.

author: tautech
author_rank: Super Contributor
timestamp: February 08, 2025, 09:38:36 am
content: Quote from: SiliconWizard on February 07, 2025, 11:51:34 pmIn a controlled airspace ?The US is nuts to allow for ADS to be disabled in peace times for ANY military aircraft let alone one flying in the hours of darkness when IFR applies.Further, in controlled civilian airspace transponder systems with collision avoidance should be mandatory at all times....especially so when IFR applies.Here in NZ all civis know of restricted airspace rules where the controllers are god but it seems this don't apply to US military.Daughter is a civilian Captain.......

author: iMo
author_rank: Super Contributor
timestamp: February 08, 2025, 09:56:37 am
content: Usually military (anywhere in the world) do not provide details (or make up a coverup) when something like that happens.It is sad what happened with the crash, but that is how it works (the military will always stay P1, otherwise you will stay without the military willing to follow the orders)..

author: hwasti
author_rank: Contributor
timestamp: February 08, 2025, 10:20:29 am
content: Quote from: tautech on February 08, 2025, 09:38:36 amNight VFR is not only allowed but very common in the USA. There is no requirement for IFR only in the hours of darkness here.My understanding is that this is not how most of the rest of the world operates. By now you should have figured it out that that alone is reason enough for us to do it this way

author: tautech
author_rank: Super Contributor
timestamp: February 08, 2025, 10:55:21 am
content: Quote from: hwasti on February 08, 2025, 10:20:29 amVFR or IFR, take your pick but you should be rated and comply with the one that applies.Not to do so putseveryonein airspace at risk.

author: jmelson
author_rank: Super Contributor
timestamp: February 09, 2025, 01:07:35 am
content: Quote from: jpanhalt on February 03, 2025, 11:25:38 pmEncoding altimeters have a "Kollsman window" where you can dial in the local sea level pressure, but that ONLY affects the reading displayed on the clock hands. The encoder wheel only reports a digital version of pressure altitude. So, mis-setting of the local pressure will not affect the altitude reported on transponder or ADS-B.Jon

author: EPAIII
author_rank: Super Contributor
timestamp: February 09, 2025, 05:12:31 am
content: Well, thanks for posting a video that can't be viewed. Even after going full screen so that the stupid vertical format can be fully seen, the advertisement for HIS CHANNEL is on top of the video with no way to make it go away.Thanks for NOTHING!Quote from: tom66 on February 06, 2025, 09:34:47 am

author: m98
author_rank: Frequent Contributor
timestamp: February 10, 2025, 04:37:05 pm
content: I really wonder why there was no TCAS resolution advisory? Were they flying in controlled airspace without transponder?

author: tom66
author_rank: Super Contributor
timestamp: February 10, 2025, 05:25:41 pm
content: Quote from: EPAIII on February 09, 2025, 05:12:31 amWorks fine for me. Take up the shorts format with Mr Manley, not me.

author: tom66
author_rank: Super Contributor
timestamp: February 10, 2025, 05:33:44 pm
content: Quote from: m98 on February 10, 2025, 04:37:05 pmTCAS advisories are inhibited below 1000ft AGL, because there's a risk an RA could lead to controlled flight into terrain.

author: janoc
author_rank: Super Contributor
timestamp: February 10, 2025, 05:51:39 pm
content: Quote from: m98 on February 10, 2025, 04:37:05 pmThere was TCAS traffic advisory ("Traffic! Traffic!") warning onboard of the ERJ. It is in the published transcript of the data recorder. The crew even reacted to it and started to climb but it was too late.However ...TCASwill notissue resolution advisory ("Climb/Descend!") when below 1000ft - that is by design. Those warnings are inhibited because that low to the ground it could drive the plane into the terrain. Imagine what would happen if the TCAS ordered the heli to climb and the ERJ to descend ... In this case the conflicting traffic will be marked on the screens in the cockpit but no voice alert will be given. And given that the crew was likely looking outside because they were flying the circling approach visually they wouldn't have seen the alert until too late. Circling to land is a normal, albeit difficult procedure, esp. in the dark with lot of distracting lights and in a very difficult airspace - you fly instrument approach to one runway and then visually hand fly to switch to another where you actually land.And for folks who were getting incensed about ADS-B being apparently off on the Blackhawk. ADS-B is not the same thing as the transponder or TCAS. Those are different systems (see e.g.https://www.avionix-tech.com/blog/Difference-between-TCAS-and-ADS-B/) and the helicopter definitely had both transponder and most likely even TCAS on. Without the transponder the controller wouldn't even see them on his display (secondary radar), which certainly was not the case.Technology didn't fail here. The fail is why there is an approved helicopter route passing right through the arrival corridor of the extremely busy airport - and why visual separation is allowed there, instead of having the controllers to clear the helis into the airspace only when it is safe. Just a day before this disaster there was an almost identical near miss in the same spot. It was a disaster waiting for happen.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 10, 2025, 11:09:39 pm
content: ADS-B is relatively recent and not required for all aircrafts in all conditions in the US.Not having that obviously doesn't make the aircraft invisible to the ATC.But it does improve overall safety quite a bit (which is why it's been deployed and progressively made mandatory) and in particular *situational awareness* for the aircraft crews themselves.And given what happened and the trajectory/altitude of the helicopter, this definitely looks like a problem of situational awareness.So could it have helped if it were on? Possibly. That doesn't mean that it's the "cause". Just an additional safety feature. To draw a parallel, it's a bit like, say, a car accident in which the driver sees a pedestrian at the last second, brakes hard but hits them, then investigation finds out that the ABS was off when this happened. Is the lack of ABS the cause of the accident? Nope. Could it have been avoided with it on? Maybe.Remains to be determined why it was off (maybe again it's something routine for these helicopters, but then one may wonder why they would bother equipping them with it if it stays off).It's just one piece of the puzzle, maybe an insignificant one. Investigation will tell. Aviation accidents are most often multifactorial and certainly the odd routes that are currently defined in the vicinity of this airport will have to be reconsidered.

author: tautech
author_rank: Super Contributor
timestamp: February 11, 2025, 12:13:01 am
content: One might expect commercial aviation will take a long hard look at airports where the military regularly fly in civilian aircraft controlled airspace and drop routes where public safety is compromised.......at least until the investigation is complete and released.