The scope being used by the controller working both the American Eagle flight and Army Blackhawk helicopter that collided Thursday in Washington, D.C. showed the helicopter about 125 feet lower than the CRJ700 it met over the Potomac River. At a press briefing on Saturday, NTSB member Todd Inman said the flight data recorder and ADS-B data put the regional jet at 325 feet AGL at the point of impact, plus or minus 25 feet while the controller's console showed the helicopter at 200 feet, the ceiling of the flight corridor it was flying at the time. Inman said the discrepancy would likely be reconciled Sunday when results of FDR analysis from the Blackhawk are complete but he did note that radar altitude displays have less fidelity than the recorders.
Why did it take an additional day to release her name? And raw ads-b data shows the helicopter over 300 feet at the crash, when the corridor clearly is marked and known for an altitude restriction of 200 feet. The controllers alert sounded for a conflict. So why would a controller allow a helicopter to fly “under by 100 feet” an airliner on final anyway…stupid.
ATC recordings clearly show the controller asking the helo pilot if she had the CRJ in sight, then directing the helo to pass behind the jet. Given the proximity of the approach path and VFR corridor, I would imagine this scenario is not uncommon. It seems to me the Army should reconsider the times it allows VFR operations in this corridor. Perhaps limiting operations to times when airline operations are fewest.
On a different note, if I were the helo pilot I might balk at flying directly behind and below an airliner, even a relatively small one like a CRJ.
Her body had not yet been found. Her family had made the request, probably to avoid the press assault that would had happened to them while they were grieving the loss with the additional stress of their daughter still missing, and finally none of us including press had a need to know. My opinion.
Bingo, putting a helo directly in the wake of a jet should have raised red flags for everyone. A simple “hold position” for the helo would have reduced all the risks.
ADS-B altitudes are not accurate to the foot, nor are radar altitudes as reported by the transponder. I have seen them off by nearly 200 feet even when the transponder is functioning correctly and the altimeter setting is correct. While it does appear that the helicopter was higher than it should have been, I’d want to wait for the official report before conclusively saying it was off altitude.
As for passing behind and below a CRJ, the course of both aircraft were at 90 degrees and it is not uncommon for two aircraft to cross as they did. I have had similar crossings happen to me, and while not ideal, the aircraft usually passes beyond where the wake turbulence is fairly quickly.
It’s also not as simple as telling the helicopter to hover in position out of ground effect and hold. For one, the helicopter can’t come to a stop instantly, and for another a quick stop like that would mean a pretty high pitch attitude and the crew would lose a lot of forward visibility momentarily.
I have also had ATC issue me instructions to pass behind other traffic and I think I have the correct traffic in site but the realize the traffic I was actually looking for was somewhere else closer. Fortunately I’ve always identified the other traffic in time, but controllers to some degree have to take the pilot at their word when they say the have the traffic in sight. And in this case, it appears the controller did have reason to suspect the helicopter didn’t have the correct traffic in sight and queried the helicopter pilot. The official investigators will get to the actual sequence of events, so all I’m really saying is that in the actual moment in real-time, the perception of what was going on was not as we see it now after the fact, knowing what happened.
As a UAV development/support engineer I have been involved with troubleshooting faulty air data systems, achieving RVSM, programming transponders, building an autotakeoff and land system, and building a detect-and-avoid system. From the standpoint of setting up for success, the idea of putting that helicopter route crossing under a final approach path, that close to touchdown, is mind-boggling.
I don’t understand why they think they can get away with that without ever having this kind of crash happen.
Just my two cents, based on trying to keep people from getting killed for over three decades.
There are also system delays for radar and ADS-B to account for…radar sweep (antenna rotation rate) and though ADS-B out provides more frequent reports out, still potential for processing delays…when traffic is miles from each other and crews are using info to build SA, the visual search cues are close enough, but in-close where geometry is rapidly changing, delays may cause extra looks in wrong sector (i.e. distraction akin to when every warning chime/light goes off in a multi-issue emergency…good intent, but another layer to wade thru).
Delays may be a factor in the differing altitude readouts. Random delays/ghost self reporting during maneuvering are why I only glance at ADS-B for help with pattern SA approaching field, but don’t let it distract when visually tracking in busy/in-close geometry, all that said to address opinions that ADS-B solves in-close scenario (yes, ground sorting of taxi traffic works ok because closure rates are slow enough to not create rapid geometry changes).
My uninformed opinion that using 2 runways with 2 different approach paths didn’t help, helo looking down river vs looking for traffic popping out of lights of Anacostia/Boling…perhaps a reduction in traffic enough to unload ATC will also minimize need for multiple approaches.
My least favorite aviation explanation is “we’ve always done it that way”
It seems likely the helo crew had the wrong traffic in sight, but I don’t think switching the approach to just a single runway would necessarily have helped. How many times have any of us thought we had the correct traffic in sight, but didn’t actually, even when operating at an airport with only a single runway in use?
As with most aviation accidents, there wasn’t just one thing that went wrong that lead to the mid-air; there were multiple things going wrong at the same time.
In the area I regularly fly in, there are two common issues with ADS-B. Many times I will see a target following me on the display. It’s me, rather an ADS-B ghost. I only use ADS-B as an indication that there MAY be traffic in the immediate area. Also targets may be on the display one minute and gone the next or be static for a while then jump in position several miles. Don’t know if this is my equipment or the ground ADS-B infrastructure. Then there are the military aircraft that operate in the area. Very rarely are they emitting ADS-B. I’m not so concerned about the helicopters, they are slow and easy to see. Fighters go between a nearby MOA and a Restricted area. Usually, they are hauling arse down low. Very hard to see.
I am surprised nobody has mentioned a remote possibility for this crash cause. Looking at the radar track, and considering the actual position of the mid-air as being somewhere between 200 and 400 agl, and the progressive radar altitude readouts of the Blackhawk and its progressive gound track, and looking to be about a 1 mile final for runway 33, this could actually be intentional. I wonder if the army/FBI/CIA is doing a deep dive? I have not been able to find a chart that depicts that route, but seems obvious that the Blackhawk shoud not have been there at any altitude for any reason. Just total lack of situational awareness of all three of the crew??
ATC is required to separate VFR aircrat from IFR aircrafft by 1.5 miles, unless visual separation is applied. Once a pilot accepts the responsibility for visual separation, they can apply whatever separation interval they want, including ducking 100’ below another aircraft. And ATC will shrug off the consequences. That’s the point.
ADS-B reports altitude in 25-foot increments - ATC displays altitude in hundreds, without the trailing zeroes (e.g., 9,500 displays as “95”). Additionally, ATC displays the altitude from an aircraft’s mode-C transponder which can be erroneous if the altimeter is not set correctly. ADS-B altitude is a mathematical calculation based on the position of the satellites being used to determine position and is not available to ATC.
VFR corridors often follow highways and rivers to lessen the noise impact. There will be pushback if anyone suggests moving training corridors over populated areas. No neighborhood is going to rise up and declare, “we want to contribute to the safety of the NAS near DCA. Please fly the aircraft over our houses.”
The clock positions provided by ATC are in relation to the aircraft’s track, not the direction the nose is pointed in. If you’re crabbing down final and alerted to traffic at your twelve o’clock, you should be looking down the final, not past the nose of your craft. If ATC tells you in your moving aircraft at an unfamiliar airport, at night, about traffic on a 3-mile final, they assume you know exactly where to look just like they do from their stationary position that they work every shift. The majority of controllers have never been in the cockpit of an aircraft. Consequently, they often don’t know how unhelpful many of their advisories are.
Let’s get the DC NIMBYs face to face with the Congress-critters that have pushed to keep so much air carrier traffic at DCA instead of IAD so they can get in and out of DC quicker and see who wins. I’d pay to see that fight!