Posts about: "ATC" [Posts: 614 Page: 20 of 31]¶

Listening to the tower and helo local controller audio files, here\x92s what I come up with from shortly before up to the time of the accident:

Fixed wing
AAL1630, departed 1, waiting handoff to departure
JIA5305, holding short 1, #2
DAL832, holding short 1 #3
JIA5342, cleared to land 33
AAL3130, cleared to land 1
AAL472, cleared visual 1
JIA5347, cleared visual 1, requested 33

Rotary wing
PAT25
helo, Zone 4
helo, callsign Blackjack 1, freq change approved just prior
helo, callsign Muscle 12, handed off to ADW prior
helo, request Route 3, Zone 6
helo, Zone 7
Medevac AirCare helo, proceeding to Inova Fairfax

Some of the helo\x92s on above list may be duplicates due to poor audio quality.

At the time of the accident, runway 4/22 was not in use.

Long version of Wall Street Journal article about changing DCA airspace use rules, from WSJ website (summary in print edition Feb. 12):
__________

Federal air-safety officials want to permanently keep helicopters away from commercial jets taking off and landing at a busy Washington, D.C., airport after the deadliest U.S. aviation accident in more than two decades.

The move, under consideration by senior Federal Aviation Administration officials, would be part of a long-term plan to improve safety at Ronald Reagan Washington National Airport, according to people familiar with the discussions.

Helicopters have been temporarily barred from flying in a corridor used by the U.S. Army Black Hawk that collided on Jan. 29 with an American Airlines regional jet, killing 67 people. The chopper routes have been used to ferry senior military officials around the region and to train for a \x93continuity of government\x94 mission in the event American political leaders need rapid evacuation from Washington. Other government agencies have also used the routes.

Federal officials have said they would revisit the helicopter restrictions once the National Transportation Safety Board issues a preliminary report on the accident in the coming weeks. Preliminary indications from the probe point to multiple factors potentially contributing to the crash, including the design of the airspace, as well as actions by the helicopter pilot and air-traffic controller, according to people familiar with the investigation.

The NTSB said it would examine how far apart planes and helicopters are supposed to be while flying in the airspace.

Transportation Secretary Sean Duffy has criticized the Pentagon\x92s operation of helicopters near the airport. \x93If we have generals who are flying in helicopters for convenience through this airspace, that\x92s unacceptable,\x94 he said last week. \x93Get in a damn Suburban and drive. You don\x92t need to take a helicopter.\x94

The Army said it would continue to comply with FAA requirements and restrictions to enhance flight safety. The service said it was reassessing its aircraft operations near the airport and that it gave priority to the safety of the public and military personnel. The current restrictions allow certain critical flights.

Duffy also suggested certain military missions can be done at a different time of night. The Jan. 29 crash occurred around 9 p.m. Eastern time.

Defense officials have assumed that the helicopter routes would be closed in the coming months amid several ongoing investigations, but have privately said that the routes should be reopened. Adjustments under consideration if routes are reopened include limiting hours for training and test missions.

Reagan\x92s convenient location, a few miles from Capitol Hill, has made the nearly 84-year-old airport a favorite among politicians, business executives and tourists.

Space is tight at the airport. Reagan\x92s longest runway, Runway 1, is the nation\x92s busiest, airport officials have said, and it has two smaller runways. Routes into and out of the airport are constrained by no-fly zones around sensitive government buildings.

The FAA has said it is also reviewing airspace around airports aside from Reagan that also have high volumes of helicopter and airplane traffic.

Discussions about Reagan airport have also focused on a small runway known as Runway 33, people familiar with the matter said. The American Airlines regional jet was attempting to land there when it collided with the Army helicopter. Some government and industry aviation officials believe that there isn\x92t a problem with planes using the runway if helicopters aren\x92t near the traffic lanes.

Warning signs existed for years about risks facing commercial passengers, with planes sharing the skies closely with helicopters zipping up and down the Potomac River.

The path the American Airlines regional jet took toward Runway 33 required it to turn toward the right and then bank left to line up for its landing. That route crosses over a lane for helicopters at a relatively low altitude.

There have been at least 35 events involving conflicts between helicopters and flights into and out of the airport that have been flagged since the 1980s, according to a Wall Street Journal analysis of anonymous reports to a system overseen by the National Aeronautics and Space Administration.

In one instance, in July 2018, a helicopter and small plane came within roughly 580 feet of each other while the plane was approaching Runway 33. The helicopter pilot had to maneuver to avoid the plane and questioned the air-traffic controller about it after, according to an internal FAA report on the incident viewed by the Journal.

Neither aircraft had received traffic advisories or safety alerts, the report said. The helicopter pilot reported the incident as a near midair collision. \x93I\x92m sorry for the confusion,\x94 the controller told the helicopter pilot, according to an audio recording of air-traffic-control communications following the incident.

Nearly two weeks after the deadly crash over the Potomac, the FAA has lifted some of the constraints put on Reagan airport in the wake of the accident.

The FAA on Tuesday boosted the airport\x92s arrival rate from 26 to 28 aircraft an hour, after temporarily reducing it to ease the strain on controllers still dealing with the aftermath of the crash, according to an email viewed by the Journal and earlier reported by other news outlets. The current rate is still lower than the airport\x92s typical maximum of 32 arrivals an hour.

Reagan\x92s two smaller runways, which had been closed due to search and recovery efforts, have been reopened.
________

I am not a US controller but as I understand it their conflict alert is not a last minute save in the way TCAS is.

TCAS RA says that a collision is imminent (within the accuracy of the system, ie it probably means the system can\x92t prove the planes won\x92t hit).

Conflict alert is to notify the controller well in advance \x97 maybe a few minutes for en-route. It isn\x92t a loss of separation, it is so they can avoid a loss of separation (3 or 5 miles for radar).

I would say that TCAS is designed to issue guidance on a projected loss of separation, not necessarily an imminent collision (although it does that too). A highly simplistic explanation would be that it projects a nested set of egg-shaped volumes around the aircraft, which if it looks like they will be infringed can generate a TA or RA, depending on where the intruder is projected to make its closest approach. These volumes have nothing whatsoever to do with ATC separation standards.

The problem with conflict alerting is that in mixed-use airspace you will get a lot of warnings; I hesitate to say false as they are defined by preset parameters that may or may not be relevant to the potential conflict. Talking to controllers in the UK, they often turn this feature (STCA) off as GA traffic happily avoiding each other by visual and/or electronic means can fill the screen with so many alerts it distracts from the main job, especially if you are not in communication with either aircraft.

I would expect, given the traffic density around DCA, that CAs are so commonplace they have become unremarkable, indeed expected. Twice the controller was told that the traffic was in sight, so in their mind they are applying visual separation (no minima, just don\x92t collide). The takeaway has to be that IFR/VFR separation at night by visual means is inherently risky and so a questionable pursuit.

ATC Watcher, Full Wings and YRP,
Thanks for the clarification on STCA ops.
I have done a few Tower visits but the game changes over time.
In no way is an implicit criticism of the controller intended...
I'll be keen to see what recommendations might be made after the investigation.
B

I just can\x92t help compare the general situation to London, where it\x92s again very busy airspace, and the helicopter routes generally follow the river. You have Heathrow at western end and London City at the eastern end.

ATC do a fantastic job of managing the flow, basically by issuing helicopter traffic clearance limits based on the VRPs - usually based on Thames bridges. The Eastbound clearance limit is usually the Isle of Dogs\x85. Before London City Tower take over to manage traffic closer to the airport. At the Western end the heli routes go nowhere near the LHR approaches due or traffic density.

ATC will not in my experience clear any helicopter traffic to visually proceed behind airline traffic based on the helicopters visual perception. Day or night. They do a great job of keeping both airline and rotary traffic advised about each other, and prioritise air ambulance and police helicopters as required. But, they keep control over the overall traffic flow and it works.

I just fail to see why the FAA couldn\x92t employ a similar system, where helicopter traffic is issued a clearance limit - pending a gap in traffic - either a natural one or an ATC created gap. Before being cleared to continue.

I have also been in the situation having started engines at London City and police helicopter then was tasked to something going on off the departure end of the runway. All departures and arrivals suspend. Indefinite delays. It\x92s part of the bigger picture. CAVOK day but no possibility of visual separation. So the London system gives priority to helicopters where appropriate. But seems infinitely safer for both airline and helicopter traffic.

deltafox44
Not at all. The briefing indicated there may be a possibility that the altimeter in the BlackHawk displayed an inaccurate altitude reading and that the discrepency was in the order of approx 100' given the height at which the collision is known to have occurred.
Briefing the RT comms, NTSB stated that a portion of the ATC instruction to the BlackHawk to 'pass behind the CRJ' was received in the Blackhawk (according to the CVR), truncated due to the BlackHawk keying the mic at the same time. Apparently, the words 'pass behind the' were missing from the BlackHawk CVR.

(my bold in quote) well.... that doesn't surprise me.
For a couple of days now, was thinking about posting something on an "extra noise" I keep hearing in the R/T comms, when TWR gives the ' pass behind ' instruction. Was wondering whether TWR's Tx wasn't stepped over by someone.
My first impression was that the extra noise came from an radio call from a turbine helicopter (given the typical background noise often heard in radio calls from turbine helicopters). And was wondering if it wasn't PAT25 that started replying to TWR's first ' in sight? ' call, effectively blocking part of TWR's second call, the ' pass behind ' part of the instruction.

In attached mp3 (in .zip per forum attachment requirements) around 00:05 I hear this 'extra noise'.


Edit:
well, this seems to confirm my initial impression:

I'm not sure they did say that about the altimeter, they said that there was bad pressure altitude data recorded on the FDR. That's not the same as saying the altimeter display was wrong, although it does mean that it's going to be hard to infer what was actually displayed on the Baro Alts. I would have thought a military crew would be pretty solid on altimeter cross checks though so I think that's all a bit of a red herring. The Potomac is (give or take the tide) at sea level so I think we can be pretty confident that the RadAlt figure of 278ft is good for an altitude too.

Barometric altitude is the only reading that all participants can share. Trying to avoid terrain? Radalt makes sense. Trying to comply with a corridor, barometric altitude. If there is a problem that the radalt is way too low for the barometric, that should be a call to the ATC to find out what the reading is at the airport.

but for this accident, this was all close to irrelevant, as QNH was very close to std.pressure (18ft. diff), Potomac AGL was almost MSL (3ft diff), even airfield/TDZ elevation is only 14ft / 13ft. So baro alt., encoding & radalt all should have been very close. Equipment rounding was even larger (or less small), with the UH60's mode C apparently even reporting rounded to the nearest 100ft (and TWR's BRITE displaying in 'hundreds' only).

It appears from the NTSB's most recent press conference that the instruction "pass behind the CRJ" was not heard in the helo's CVR and, therefore by inference, not heard by the crew. Am I correct in assuming that there is no requirement to readback an instruction like that in the USA? ATC appeared not to expect one.

The Aeronautical Information Manual lists a number of instructions that should be read back, but there are none that must be read back (unless the controller specifically requests). "Pass behind..." is not even one of the "should" be read back instructions, so ATC wouldn't be bothered by not getting a read back. Frankly, if there was a requirement to fully read back all things like "Pass behind..." the frequency would be constantly full. In any case, whether PAT25 heard the "Pass behind" or not, it had already said that it was providing its own visual separation, so not hearing an instruction to pass behind does not take away the requirement to maintain separation.

I think we're flogging a dead horse with this altitude thing, we already know that the aircraft collided from the video.

The most reliable information from the helicopter indicates they were at 278ft above the water. Likewise we're told that the CRJ was at 313ft 2 seconds before impact. The CRJ is 20ft tall, more with landing gear extended. The UH60 is 16ft tall. There is no more information to be gleaned from this.

The CRJ was a passenger jet on finals to land and there is no way on earth anything else should be on a collision track. The helicopter should never have been allowed to be that close to landing traffic, no matter what the legal and procedural niceties of ATC communication were.

And the fact that there were numerous reports of similar close calls of this kind over the previous decade or so is a damning (some might say criminal) indictment of the safety management systems of the authorities involved.

+1 to everything you and Wide Mouth Frog said.

I sincerely hope the NTSB can avoid being distracted by the distractions of altimetry and the missing ATC words on the Blackhawk CVR.

Upthread, Luca Lion calculated the 3 degree PAPI approach path as crossing the eastern riverbank at 270ft. If that's correct, then the CRJ's 313ft radar height 2 seconds before collision puts it at least 43ft above the approach path, so the Blackhawk's radio height deviation of 78ft would have contributed only about 35ft to the erosion of any intended "procedural separation" (*) between the aircraft. Or, to put it another way, the same outcome would have resulted if the Blackhawk had been at 235ft radio and the CRJ on the glide. Height keeping of plus or minus 35ft can only be achieved by instrument flying, which is obviously not compatible with visual separation (or indeed VFR) so cannot be reasonably cited as part of a safety case for the procedure. And of course a landing aircraft could easily be below the glide. Altimetry and height keeping are not the cause of this accident.

Missing the word "circling" wouldn't have influenced the helo crew getting visual with the CRJ at the time of the trasnmission. At best, it would have given them an extra nudge that "runway 33" (which was audible) meant the CRJ would be taking an easterly flight path. Missing "pass behind" with only a few seconds to collision was irrelevant if, as seems likely, the helo crew did not see the CRJ at that point.

(*) The quotes around "procedural separation" are intended to convey a tone of disgust and sarcasm.

Following "5*why", keep asking...
Why did the did miss part of the message
Why was the incomplete read back missed
Why does missing a few words lead to this disaster within seconds.

Does this lead an answer like: helicopter in a very busy airspace, busy controllers (insufficient time to be fully focused on full read backs) being by default too close to (and even needing to cross) the glideslope.
​​​​​​

I hadn't intended to go all the way along the causal chain in my post. But since you ask, I think your answer only goes one step further. There are more steps to take.

Helicopters in busy airspace are not a problem if a safe system exists for separating them from airline traffic.

There is no evidence yet of the controller having made a mistake. He was undoubtedly busy, but that was not his fault. What could be done about it? The answers to that question take us another step along the causal chain:

1. The FAA could have provided more controllers. We know the helicopter controller position was unoccupied, and it's likely that closer monitoring and earlier intervention could have changed the outcome (notwithstanding point 3).
2. Controller workload could have been reduced by implementing effective procedural separation . If the DCA ATC rulebook allowed this segment of Route 4 to be in simultaneous use with Runway 33 landings, then procedural separation did not exist , however much anyone thought it did. At least 1.5nm or 500ft between flight paths would be needed to meet the least restrictive FAA separation standards, and this would have forced constraints to be applied to Route 4 or Runway 33 utilisation.
3. Regulations allowed the helo pilots to assume responsibility for separation. This is what happened, with the consequences which flow from the inherent difficulty of identifying and separating visually at night (especially while wearing NVG).

The authorities (by which I mean FAA and DoD) have questions to answer on all three points. Why was the helicopter controller position vacant? Did the ATC rulebook or staffing requirements rely on a false assumption that procedural separation existed? How did any such assumption remain in place after previous near misses? Is visual separation between helicopters and airline traffic a reasonable thing for regulations to permit, at night and using NVG? Ultimately it seems to have routinely been used as a release valve for the pressure building in the system due to the failure to address points 1 and 2.

Hopefully the investigation will be bold enough to ask these questions, which expand the potential scope of responsibility well beyond the individual controller and pilots.

Whilst these are valid observations, it is also micro-managing a procedure whose altitude separation was always totally flawed. I cannot personally attribute any blame to ATC or either pilot when the scenario was so badly devised ... and that means not only the infamous Route 4 but the concept of visual separation in the dark.

It was doomed to fail, eventually, but sadly someone [other than those directly impacted] never saw it coming. THEY are the culprits.

MPN11, former Mil ATCO

Pretty much it, everyone had to be lucky every time, gravity only had to be lucky once. The altimeter issues are a red herring at best, the helicopter crew were not trying to go directly under the airplane.

I agree that the DC controllers should not be scapegoated. At the same time, the concept of professionalism must be addressed. The concept that professionals in a field must alone (without management, without lawyers, without the public) maintain the best practices of the given professional discipline.

In the US, physicians who work for "Health Maintenance Organizations" are asked to practice medicine, at times, in a "basically unsafe" manner...to keep patients moving. On occasion, such practices will bite a patient (and sometimes the physician). As a whole, HMO physicians do not enjoy the best reputation.

From my perspective, there is practically no difference between the plight of an American air traffic controller and an American HMO physician. Both are expected to "squeeze one more in." Both fields are staffed by above-average capable individuals who thrive on challenges. Both are managed in such a manner that they cannot say "no" and also keep their job. In this regard, at least physicians have job portability.

But the take home point is that one cannot admit to knowing a practice is fundamentally unsafe, yet do it anyway. The public, rightfully, should not accept this. I have no solution except more staff and/or more airports (and not some next-gen whizzbang computer system).