4 ms·

Doesn't matter what they could and could not see - the ceiling for helicopters there is 200 feet. They were flying at 300. Make whatever conclusions you like fr

by ein0p 2y ago

Doesn't matter what they could and could not see - the ceiling for helicopters there is 200 feet. They were flying at 300. Make whatever conclusions you like from that, I've made mine.

fwipsy 2y ago
Excerpts from the article: "(According to investigators, this altitude data was rounded to the nearest 100.)" [...] "At over 100 miles an hour, the helicopter could have risen to 300 feet from 200 in seconds, because of winds or other factors. Such anomalies are not unusual and can be quickly corrected." I read your comment as implying that you've concluded it's pilot error. I don't disagree, but a good system should be robust against human error. Perhaps the permitted flight paths were too close together? I'm not an expert, but a commercial jet making a landing approach 100 feet above a helicopter doesn't seem safe or normal to me.
- ein0p 2y ago
  [flagged]
- heelix 2y ago
  NTSB did release some follow up data. They have the bottom of the jet at 325', +/- 25'. Helicopters add a tough element to any airport operation and DIA is one of the more challenging airports with the extra restrictions on routing. (Never flown into that one as not an ATP. I'd never be able to get closer than College Park. Even that was a non-trivial exercise in paperwork.)
  - stefan_ 2y ago
    What's complicated about it? Don't get within a mile. Some 250g drone can't, why should this thing?
    - bilbo0s 2y ago
      why should this thing? 'Cuz "National Security". End of discussion. /s You may laugh, but that's historically the argument in support of these practices. No one wants to go on record as questioning the practice. Maybe they will finally do something now? But it wouldn't surprise me if they don't.
  - dreamcompiler 2y ago
    DCA, not DIA. DIA is in Denver.
- geoduck14 2y ago
  > Perhaps the permitted flight paths were too close together? My understanding is that the helicopter was military and didn't need to submit a flight plan. They get to fly where ever they want
  - WillPostForFood 2y ago
    There is a difference between not needing to submit a flight plan, and flying wherever they want. They absolutely have rules to follow about where they fly.
  - atommclain 2y ago
    > They get to fly where ever they want Reminds me of the story of the Navy ship and lighthouse: https://en.wikipedia.org/wiki/Lighthouse_and_naval_vessel_urban_legend https://en.wikipedia.org/wiki/Lighthouse_and_naval_vessel_ur...
  - gosub100 2y ago
    I'm sure in a national defense scenario they have ways to "pull rank" and do what they need to do. But this would require a good reason. Like a VIP was on board and someone was attacking them.
    - jcgrillo 2y ago
      In that scenario civilian aircraft are all grounded.
      - bilbo0s 2y ago
        This is the thing people don't understand. Certain military and government aircraft can pull this kind of crap even when it doesn't seem necessary. (At least not to me as an outsider). Now it's easy to say, "Well, Bilbo0s, who are you to say it wasn't necessary?" That's true, but it's an argument that's closed onto itself. We can't probe any further 'cuz "National Security". So this unimaginably dangerous practice of allowing military and government pilots to do this sort of thing "if necessary" continues. We need to, at minimum, have a discussion about why the practice is necessary?
- wat10000 2y ago
  100ft isn't anywhere near an acceptable margin. The helicopter may bear the immediate blame due to going above the altitude limit, but ultimately the design of this corridor was completely nuts. This seems like a classic normalization of deviance. Reportedly there were literally a hundred automated collision warnings between airliners and helicopters in this area over the past decade. One such warning should raise eyebrows. Two should start people thinking there's a systemic problem. More than a handful should prompt an investigation to resolve the root cause of the conflicts. Instead, they (at least the system as a whole) seem to have decided that they weren't a real problem because nothing had happened yet.
  - imglorp 2y ago
    In other situations the normal vertical separation is 1000ft. In this situation ATC was depending on the visual conditions for the pilots to "see and avoid", but it's especially nuts if you factor in wind shear and wake turbulence that can change an altitude by 100ft in seconds.
  - pyrale 2y ago
    I wonder whether telling either the army to use cars, or that the airport should be moved further away from the city was doable for atc personnel, or even their higher ups.
    - mandevil 2y ago
      One of the missions of those helicopters was the immediate evacuation of personnel in the event of attack against Washington D.C. That requires the speed and range that a helicopter can provide but cars can't. To do that mission requires training and practice flying through the area, because as everyone in the military knows, you fight like you train, and so they need to be flying through DC regularly, both day and night. As for DCA itself, yeah, there have been people trying to close it for decades- that was originally the plan once they opened IAD in 1962. But DCA was so close and so convenient to the city and IAD (and later BWI) are so far away that no one has really wanted to pull the trigger on closing it, even as the airspace got more and more complex after the September 11th terrorist attacks.
mikhailfranco 2y ago
We should wait for the official report, but there is speculation the helicopter altimeter was miscalibrated. Apparently on the old avionics in the helicopter, the altimeter is calibrated by manual entry of barometric pressure to the nearest 0.1 inch Hg. So a rounding error could cause a 100 ft altitude discrepancy.
- xvinci 2y ago
  Thats the kollsman window and as far as i am concerned is pretty common also in modern avionics?
- loeg 2y ago
  > Apparently on the old avionics in the helicopter, the altimeter is calibrated by manual entry of barometric pressure to the nearest 0.1 inch Hg. That's how it's done in all aircraft.
  - rlpb 2y ago
    All US aircraft. The rest of the world uses modern units :-)
    - dghlsakjg 2y ago
      The thoroughly modern Pascal system from the 1600s?
      - rlpb 2y ago
        The metric system. "The name pascal was adopted for the SI unit newton per square metre (N/m2) by the 14th General Conference on Weights and Measures in 1971"
    - loeg 2y ago
      inHg, hPa, it doesn't change that the input is manual.
- dghlsakjg 2y ago
kevin_thibedeau 2y ago
100 ft. of separation is an idiotic safety margin.
- loeg 2y ago
  Yes -- 500 ft is considered inadequate in general.
- b_t_s 2y ago
  The combined height of a blackhawk and a large jet is about 60ft. The combined length is a bit over 300ft, and since neither aircraft is unlikely to be level, some portion of that length gets contributed to their effective height while flying. Just given the size of the aircraft, I wouldn't be surprised if they can potentially overlap even if their altimeters are 100ft apart.
- dghlsakjg 2y ago
  That wasn't the safety margin. That was the altitude discrepancy that was left after the Helo disregarded or misinterpreted ATC directions and flew where they specifically were told to avoid.
  - kevin_thibedeau 2y ago
    If the airplane was on the correct approach at 300 ft. and the Blackhawk was restricted to 200 ft. the margin is 100 ft.
    - dghlsakjg 2y ago
      No, The Blackhawk was supposed to be at a different altitude AND a different location. The loss of separation was not primarily because of the Z axis, but because the Blackhawk was in the wrong spot on the X,Y axis. The controller said, paraphrasing ATC speak, "Do you see that plane? You are cleared through the airspace as long as you see and avoid that plane by going behind it. You are responsible for separation if you accept this". The BH pilot responded, "I see the plane, I can and will avoid it. It is my responsibility to go behind it, and I will do that." The collision would have been narrowly avoided if the Blackhawk was at the right altitude, but that was the last in a long line of piloting errors that caused this midair. If they were at the correct assigned altitudes it still would have been an incident because the loss of separation wasn't about the altitudes, it was about the errors made long before then. They weren't cleared to be where they were, and no controller would allow an altitude only separation of 100ft. Simply put, that helicopter pilot was specifically not supposed to be where they were, and the standard separation was violated before the altitude became an issue. If you narrowly miss someone driving down the wrong side of the highway after crossing the medain, the margin of safety isn't the distance that you missed that car by, it is the median.
dehrmann 2y ago
The main conclusion is flying helicopters this close to a commercial airport approach at night is a bad idea. I'm sure it's much safer, but ever seen the approach into SJC? https://www.youtube.com/watch?v=bpT1wjwlL3Q&t=254s&e=270 https://www.youtube.com/watch?v=bpT1wjwlL3Q&t=254s&e=270

by ein0p 2y ago

Doesn't matter what they could and could not see - the ceiling for helicopters there is 200 feet. They were flying at 300. Make whatever conclusions you like from that, I've made mine.

fwipsy 2y ago

Excerpts from the article: "(According to investigators, this altitude data was rounded to the nearest 100.)" [...] "At over 100 miles an hour, the helicopter could have risen to 300 feet from 200 in seconds, because of winds or other factors. Such anomalies are not unusual and can be quickly corrected." I read your comment as implying that you've concluded it's pilot error. I don't disagree, but a good system should be robust against human error. Perhaps the permitted flight paths were too close together? I'm not an expert, but a commercial jet making a landing approach 100 feet above a helicopter doesn't seem safe or normal to me.

ein0p 2y ago
[flagged]
heelix 2y ago
NTSB did release some follow up data. They have the bottom of the jet at 325', +/- 25'. Helicopters add a tough element to any airport operation and DIA is one of the more challenging airports with the extra restrictions on routing. (Never flown into that one as not an ATP. I'd never be able to get closer than College Park. Even that was a non-trivial exercise in paperwork.)
- stefan_ 2y ago
  What's complicated about it? Don't get within a mile. Some 250g drone can't, why should this thing?
  - bilbo0s 2y ago
    why should this thing? 'Cuz "National Security". End of discussion. /s You may laugh, but that's historically the argument in support of these practices. No one wants to go on record as questioning the practice. Maybe they will finally do something now? But it wouldn't surprise me if they don't.
- dreamcompiler 2y ago
  DCA, not DIA. DIA is in Denver.
geoduck14 2y ago
> Perhaps the permitted flight paths were too close together? My understanding is that the helicopter was military and didn't need to submit a flight plan. They get to fly where ever they want
- WillPostForFood 2y ago
  There is a difference between not needing to submit a flight plan, and flying wherever they want. They absolutely have rules to follow about where they fly.
- atommclain 2y ago
  > They get to fly where ever they want Reminds me of the story of the Navy ship and lighthouse: https://en.wikipedia.org/wiki/Lighthouse_and_naval_vessel_urban_legend https://en.wikipedia.org/wiki/Lighthouse_and_naval_vessel_ur...
- gosub100 2y ago
  I'm sure in a national defense scenario they have ways to "pull rank" and do what they need to do. But this would require a good reason. Like a VIP was on board and someone was attacking them.
  - jcgrillo 2y ago
    In that scenario civilian aircraft are all grounded.
    - bilbo0s 2y ago
      This is the thing people don't understand. Certain military and government aircraft can pull this kind of crap even when it doesn't seem necessary. (At least not to me as an outsider). Now it's easy to say, "Well, Bilbo0s, who are you to say it wasn't necessary?" That's true, but it's an argument that's closed onto itself. We can't probe any further 'cuz "National Security". So this unimaginably dangerous practice of allowing military and government pilots to do this sort of thing "if necessary" continues. We need to, at minimum, have a discussion about why the practice is necessary?
wat10000 2y ago
100ft isn't anywhere near an acceptable margin. The helicopter may bear the immediate blame due to going above the altitude limit, but ultimately the design of this corridor was completely nuts. This seems like a classic normalization of deviance. Reportedly there were literally a hundred automated collision warnings between airliners and helicopters in this area over the past decade. One such warning should raise eyebrows. Two should start people thinking there's a systemic problem. More than a handful should prompt an investigation to resolve the root cause of the conflicts. Instead, they (at least the system as a whole) seem to have decided that they weren't a real problem because nothing had happened yet.
- imglorp 2y ago
  In other situations the normal vertical separation is 1000ft. In this situation ATC was depending on the visual conditions for the pilots to "see and avoid", but it's especially nuts if you factor in wind shear and wake turbulence that can change an altitude by 100ft in seconds.
- pyrale 2y ago
  I wonder whether telling either the army to use cars, or that the airport should be moved further away from the city was doable for atc personnel, or even their higher ups.
  - mandevil 2y ago
    One of the missions of those helicopters was the immediate evacuation of personnel in the event of attack against Washington D.C. That requires the speed and range that a helicopter can provide but cars can't. To do that mission requires training and practice flying through the area, because as everyone in the military knows, you fight like you train, and so they need to be flying through DC regularly, both day and night. As for DCA itself, yeah, there have been people trying to close it for decades- that was originally the plan once they opened IAD in 1962. But DCA was so close and so convenient to the city and IAD (and later BWI) are so far away that no one has really wanted to pull the trigger on closing it, even as the airspace got more and more complex after the September 11th terrorist attacks.

mikhailfranco 2y ago

We should wait for the official report, but there is speculation the helicopter altimeter was miscalibrated. Apparently on the old avionics in the helicopter, the altimeter is calibrated by manual entry of barometric pressure to the nearest 0.1 inch Hg. So a rounding error could cause a 100 ft altitude discrepancy.

xvinci 2y ago
Thats the kollsman window and as far as i am concerned is pretty common also in modern avionics?
loeg 2y ago
> Apparently on the old avionics in the helicopter, the altimeter is calibrated by manual entry of barometric pressure to the nearest 0.1 inch Hg. That's how it's done in all aircraft.
- rlpb 2y ago
  All US aircraft. The rest of the world uses modern units :-)
  - dghlsakjg 2y ago
    The thoroughly modern Pascal system from the 1600s?
    - rlpb 2y ago
      The metric system. "The name pascal was adopted for the SI unit newton per square metre (N/m2) by the 14th General Conference on Weights and Measures in 1971"
  - loeg 2y ago
    inHg, hPa, it doesn't change that the input is manual.
dghlsakjg 2y ago

kevin_thibedeau 2y ago

100 ft. of separation is an idiotic safety margin.

loeg 2y ago
Yes -- 500 ft is considered inadequate in general.
b_t_s 2y ago
The combined height of a blackhawk and a large jet is about 60ft. The combined length is a bit over 300ft, and since neither aircraft is unlikely to be level, some portion of that length gets contributed to their effective height while flying. Just given the size of the aircraft, I wouldn't be surprised if they can potentially overlap even if their altimeters are 100ft apart.
dghlsakjg 2y ago
That wasn't the safety margin. That was the altitude discrepancy that was left after the Helo disregarded or misinterpreted ATC directions and flew where they specifically were told to avoid.
- kevin_thibedeau 2y ago
  If the airplane was on the correct approach at 300 ft. and the Blackhawk was restricted to 200 ft. the margin is 100 ft.
  - dghlsakjg 2y ago
    No, The Blackhawk was supposed to be at a different altitude AND a different location. The loss of separation was not primarily because of the Z axis, but because the Blackhawk was in the wrong spot on the X,Y axis. The controller said, paraphrasing ATC speak, "Do you see that plane? You are cleared through the airspace as long as you see and avoid that plane by going behind it. You are responsible for separation if you accept this". The BH pilot responded, "I see the plane, I can and will avoid it. It is my responsibility to go behind it, and I will do that." The collision would have been narrowly avoided if the Blackhawk was at the right altitude, but that was the last in a long line of piloting errors that caused this midair. If they were at the correct assigned altitudes it still would have been an incident because the loss of separation wasn't about the altitudes, it was about the errors made long before then. They weren't cleared to be where they were, and no controller would allow an altitude only separation of 100ft. Simply put, that helicopter pilot was specifically not supposed to be where they were, and the standard separation was violated before the altitude became an issue. If you narrowly miss someone driving down the wrong side of the highway after crossing the medain, the margin of safety isn't the distance that you missed that car by, it is the median.

dehrmann 2y ago

The main conclusion is flying helicopters this close to a commercial airport approach at night is a bad idea. I'm sure it's much safer, but ever seen the approach into SJC? https://www.youtube.com/watch?v=bpT1wjwlL3Q&t=254s&e=270 https://www.youtube.com/watch?v=bpT1wjwlL3Q&t=254s&e=270