[HN Gopher] The 2002 Uberlingen midair collision
___________________________________________________________________
The 2002 Uberlingen midair collision
Author : vinnyglennon
Score : 190 points
Date : 2023-08-14 12:41 UTC (10 hours ago)
(HTM) web link (admiralcloudberg.medium.com)
(TXT) w3m dump (admiralcloudberg.medium.com)
| stall84 wrote:
| Posts like this painfully push me to finish setting up my blog
| where I'm going to mostly opine on and outline aviation incidents
| like this..
|
| But I can disseminate at least two flying maxims you can take
| away from this tragedy:
|
| 1: Do what TCAS is telling you to do.
|
| 2: Air Traffic Control does NOT have the final responsibility for
| your plane, you do.
|
| - The TCAS system had already resolved the safe and correct
| conflict avoidance maneuvers for both of the transceivers
| involved (on both aircraft).
|
| - As amazing and professional as our air traffic controllers are
| (and they are), they to, just like you the pilot are prone to
| error, and they in fact are not inside your aircraft, nor are
| they the pilot in command.
|
| I've seen especially in new pilots and people that want to learn
| to fly this urge to defer to ATC (I even asked a friend who's a
| huge Flight Simulator enthusiast, of which I was too when young,
| what he'd do in a purely technical flight situation, and he
| responded he'd "ask ATC what to do"...).
|
| While yes, Air Traffic Control 'controls' certain air space, they
| don't control your aircraft or its occupants. FAR 91.3 says it
| all, I'll let you look it up, it's 2 very brief (thank you
| FAA/congress) sentences that spell out the end of this
| discussion. You might get a fine, you might lose your license,
| etc etc, if you're reasoning for having to deviate from ATC rules
| aren't sufficient..
|
| But hey in this case would those pilots on those 2 planes in this
| incident have rather lost their licenses (potentially) or have
| what happened happen.
|
| Of course this incident is nuanced, as they all are. Flying
| safely involves mitigating and accepting certain levels of risk.
| TCAS was a system specifically designed and implemented to
| resolve collision situations. You test your equipment at regular
| intervals and pre-flight so that you can be confident they are
| working properly so that when you get into a situation where TCAS
| is telling you to do something, you do it.
|
| But the reality is stress, human behavior isms' like maybe say
| flying in from an eastern european country and wanting to not
| 'piss off' the Swiss controllers, so deferring to their every
| direction instead of following your own instruments. << That's a
| real thing .. when you fly into busy airspace in the US, you
| quickly realize you just 'don't want to piss anyone off' .. All
| of these factors influence what should have been a cut and dry
| collision avoidance dictated by the TCAS system. And this is the
| cost of human flight.
| stavros wrote:
| FAR 91.3:
|
| (a) The pilot in command of an aircraft is directly responsible
| for, and is the final authority as to, the operation of that
| aircraft.
|
| (b) In an in-flight emergency requiring immediate action, the
| pilot in command may deviate from any rule of this part to the
| extent required to meet that emergency.
|
| (c) Each pilot in command who deviates from a rule under
| paragraph (b) of this section shall, upon the request of the
| Administrator, send a written report of that deviation to the
| Administrator.
| genewitch wrote:
| as an aside i once called the FCC to get a definitive answer
| about a part 97 rule, and they put me on hold, and gave me
| the answer i was suspecting they would, which i am nearly
| positive is the wrong answer.
|
| In the context of your post, if asked, i wonder if the FAA
| (or whoever) would say "the pilot has final authority, even
| if it goes against what the ATC commanded", even with the
| nuance and additional information that would be required in
| 91.3c.
|
| for the record, it was 47 cfr 97.405
| https://www.ecfr.gov/current/title-47/section-97.405 - and it
| states clearly:
|
| (a) No provision of these rules prevents the use by an
| amateur station in distress of any means at its disposal to
| attract attention, make known its condition and location, and
| obtain assistance.
|
| (b) No provision of these rules prevents the use by a
| station, in the exceptional circumstances described in
| paragraph (a) of this section, of any means of
| radiocommunications at its disposal to assist a station in
| distress.
|
| My question was simple - one has a radio what can transmit
| clearly on a police frequency, that is, if one pushes
| transmit, police radios and scanners in the area can hear the
| audio being transmitted. Can one use said radio in an
| emergency, if they are a licensed part 97 operator?
|
| FCC: "no"
|
| me: "yes, obviously."
| JimtheCoder wrote:
| "1: Do what TCAS is telling you to do.
|
| 2: Air Traffic Control does NOT have the final responsibility
| for your plane, you do."
|
| I wonder if there is some human bias that preferences human
| directions/instruction over technologically manufactured ones
| (TCAS).
|
| Especially when it's a stressful, fast paced situation.
| stall84 wrote:
| Yes this definitely is a thing. Like I mentioned, there is a
| real desire 'to be liked' by ATC from the pilot. It happens
| to me, it happens to many pilots.. They give you an
| instruction and you want to show how quickly and efficiently
| you can execute it. The hardest part is when your own flying
| intuition tells you to not do what they're requesting, or
| even worse when it merely makes you question the
| instruction.. leaving you in a decision paralysis.
| bombcar wrote:
| 2 is very hard to keep in mind, because in a stressful
| situation we seem to naturally want someone "to tell us what
| to do".
|
| This is one of the reasons that if you're trained in
| emergency situations they tell you things like "don't yell
| 'someone call 911' but instead point directly at someone and
| say 'call 911'".
| xattt wrote:
| On the contrary, EKGs are well-known to have a machine
| interpretation line often called the "Idiot Box".
| FreshStart wrote:
| It's ultimately a culture war of neuro-types, controllfreaks
| and those who yearn for irresponsibility in some underling
| caste vs idealistic humanists dreaming of everyone being
| there own company,master and commander. These characters and
| their constructs collided that night with two planes. How to
| plan and prepare for this? No, idea.
| jandrese wrote:
| The article put it best. If the TCAS is going off then then
| ATC has already failed at their job.
| bfeynman wrote:
| I find this type of writing compelling, so if you write a blog
| I think you would get people to read it. One thing I've seen
| after the fact is the schism between media and evidence which
| adds an extra dimension here with the air traffic controller's
| story. The post mortem investigation usually takes a long time,
| and by then the media has completely moved on. Reminds me of
| the Boeing MCAS incidents, which interestingly I had a few
| airline industry friends, and internally according to them
| almost incidents were due inadequate training of pilots, but no
| one would say that since there is a nationalistic aspect to it.
| kingofpandora wrote:
| At the time there was no guidance to pilots on whether to
| follow TCAS or ATC.
|
| That guidance to always follow TCAS came in because of this
| incident.
| gen220 wrote:
| According to the article, there were actually conflicting
| guidelines.
|
| The FAA said always follow TCAS ("any guidance from TCAS
| overrides guidance from ATC"), whereas other regulators were
| either vaguely non-committal to which had overriding priority
| or assigned priority to ATC.
|
| It also notes that the Russian pilots were not accustomed to
| TCAS (which was not common in Russia, at the time). Even
| further, to the extent they were familiar with it, Russian
| regulations noted that the ATC's guidance superseded all
| other guidance systems.
| krisoft wrote:
| > 1: Do what TCAS is telling you to do.
|
| Other similar maxim is "In case you are intercepted by a
| fighter jet, and ATC and the fighter jet issues seemingly
| conflicting instructions follow what the fighter jet
| says/signals, and inform about this fact the ATC."
|
| People with missiles trained on you have command priority for
| all the obvious reasons.
| omnibrain wrote:
| The plane crash storyline in Breaking Bad seems to be in part
| inspired by this event.
|
| Having lived in the are and going to school in Uberlingen at the
| time it is not something I'm ever going to forget.
|
| I did not notice the crash itself (I'm a deep sleeper) but heard
| about it in the radio at morning. First I thought I must have
| misheared. Being a vonlunteer firefighter in our village I
| wondered, why I did not get an alarm. On my way to the train
| station I stopped at our local fire station but saw only a small
| transporter was missing, so I figured they may have alarmed only
| a few people.
|
| There was some sort of "fog of war". Nobody knew anything for
| sure. There were rumours, that one of the planes crashed into the
| lake. The crash site being at Hohenbodman did not help because
| there is a village named Bodman on the other side of the lake.
|
| Waiting for the train and on the train there was nothing else we
| could talk about. Arriving in Uberlingen, we (a classmate and I)
| went straight down to the lakeside of the city to see if we can
| catch a glimpse of anything. The atmosphere in the city was
| surreal.
|
| The route from the city center and train station to our school
| went over the yard of the city's fire station. And there it hit.
| Dozens of firefighters, police, red cross, etc. swarmed the
| place. A search dog unit just arrived. The facial expressions of
| everybody.
|
| At school there was no lessons of course. Everybody just talked
| about the crash and the newest rumours. Some classmates arrived
| by bus and their bus drove straight by the crashsite. They saw
| corpses under cloth and smoking debris. A few hours later people
| from the local newspaper arrived to distribute a special issue
| with the most comprehensive compilation of available information
| at the time.
|
| (... a few months later ...)
|
| We had local festivities and I helped. It was bigger festivities
| and we spent days building everything and had to gather stalls,
| building material and tools from various storage areas,
| companies, etc. To fetch something I went with someone to a local
| building company. We went into their warehouse and an
| overwhelming stench of kerosene hit me. The warehouse was filled
| with transport container trays full of excavated ground that was
| contaminated with kerosine (and small debris) from the crash. The
| guy I went with just mentioned this in a very non-chalant way.
| leipert wrote:
| I was on vacation at Lake Constance that night. We didn't hear
| anything consciously, but _everyone_ (four people) was awake at
| the time of the crash (unlikely, right?) and heading to the
| toilet/grabbing a water.
|
| Next day we knew why we all were awake at the same time.
| Surreal.
| alistairSH wrote:
| ATC communication is fascinating to me. I go down the Youtube
| rabbit hole a few times a month.
|
| A few things that always stand out to me... - the calm demeanor
| shown by both ATC and pilots. Even in situations that make me
| cringe sitting at my laptop, everybody involved is steady. I know
| it's their job, but it still amazes me.
|
| - the complexity of airport operations at a major international
| is mind-boggling. Hand-offs from ground to tower to departure...
| and then back again if something goes wrong. And doing that for
| dozens of planes at a time. Some crewed by pilots with thick
| accents or static-y radios.
|
| - that air travel is the safest form of transit given the
| complexity of engineering and human processes involved is truly
| astounding. I know today's successes are the result of all
| previous tragedies; it's still something else.
|
| I live under the main international approach to IAD. Watching the
| heavies fly in makes me smile. Especially the A380. It's a shame
| the A380 didn't find a long-term market - looking up, it
| shouldn't be able to fly, but there it is.
| jcranmer wrote:
| > the calm demeanor shown by both ATC and pilots. Even in
| situations that make me cringe sitting at my laptop, everybody
| involved is steady. I know it's their job, but it still amazes
| me.
|
| It's actually probably not as amazing as it seems. I was just
| on a high ropes course, and it's similar to ATC in that if
| things go pear-shaped, there is just nothing that you can do.
| So when I saw something going wrong [1], the instinct I had to
| immediately run and try to help was suppressed, and instead I
| (and everybody else) was essentially in the same calm-and-
| collected mood.
|
| [1] Admittedly, this is wrong in the "abnormal operation"
| sense, not "immediate risk to life" sense.
| reddit_clone wrote:
| What is amazing to me is how do Pilots stay calm when their
| own lives are under imminent threat?
| stall84 wrote:
| I've had just one definite emergency experience and it's
| only 1 data point to draw on, and it's definitely not going
| to be the same for everyone flying..
|
| You drill for emergency situations during training, and you
| should drill repeatedly afterwards. Any ATP rated pilots do
| so regularly whether in actual flight or in simulators.
|
| But one flight very early, before I had my pilot's license,
| flying on a student's permit.. I ran out of fuel during
| cruise flight.. It was dumb, it was a case of me being a
| poor just-out-of-college student, and trying to do some
| very risky calculus with the flight planning and fuel
| required. There were extenuating factors including the
| (small) plane's fuel gauges malfunctioning sporadically ..
| having to 'stick the tank' on the ground (measure the fuel
| in the plane's wings by using a ruler and chart for how
| many inches equaled gallons).
|
| .. excuses aside. I ran out of gas at 8000 feet above
| Columbus Georgia ..
|
| What I remember happening is the engine abruptly lurching,
| then stopping, sending a massive amount of adrenaline
| through me.
|
| But almost immediately I started looking for a runway to
| land at. I knew I had at least 1, maybe 2 airports in range
| of a glide, and one was relatively in front of me, so I
| decided on it, and called ATC in Atlanta who were following
| my flight at that time & declared a 'pan-pan' (step below a
| mayday .. meaning you have a serious situation on board &
| require priority attention if available, but you are still
| in control of the aircraft). They confirmed the vector to
| the (abandoned, but still in decent condition) airport a
| few miles in front of me.
|
| Now.. Your original question is probably answered at this
| point... Basically as long as you can continue to have
| things to _do_ .. As long as you can envision and work
| toward a goal (landing the f 'n plane safely) .. The stress
| of the situation tends to just fuel the focus on getting to
| that goal.
|
| I can't say its going to be the same for every pilot, and
| maybe it isn't . I did grow up obsessed with flying (after
| being absolutely horrified by it as a child), and so I had
| kind of gone over in my mind and in training over and over
| again this potential type of situation occurring and I
| wasn't about to let the moment get to big.
|
| This kind of thing does worry me a little bit with our
| recent explosive need for pilots as commercial aviation
| expands rapidly. A lot of pilots are going through "0 to
| ATP" courses to get a good paying job, rather than because
| they're actually obsessed with flying itself.. Because in
| those cases, I'm not sure what is going to happen
| psychologically for those pilots. Again though, this is why
| you are constantly drilled and trained on these situations,
| so that you have almost muscle-memory of things _to be
| doing_ in an emergency situation so that there is _no_ time
| for you to sit passively and become a victim of
| circumstance.
| alistairSH wrote:
| _A lot of pilots are going through "0 to ATP" courses to
| get a good paying job..._
|
| Are those "0 to ATP" graduates landing quality jobs? Has
| pay at the smaller regionals actually moved up into "good
| paying" ranges (used to be $20-$40k/year starting, and
| that's usually after $50k+ in tuition/fees to get first
| set of pilot credentials)?
|
| Last time I checked (10+ years ago), landing a job at a
| major airline still required years of experience at a
| regional OR some special combination of
| degree/networking/military service. And the regionals
| didn't pay well and had pretty crap working conditions
| (getting better post-Colgan Air crash, but still not
| great).
|
| I see United has an in-house "0 to ATP" program now, but
| it's still more than $70k and a few years to graduate,
| and then the pilot still spends time at a regional
| United-affiliate before having the chance to move to
| United itself.
|
| Really just curious what conditions are like for new
| pilots today (vs roughly the Colgan Air disaster era).
| And what the pipeline looks like post-COVID.
| pc86 wrote:
| As they say, every regulation is written in blood. An
| exaggeration for sure, but not by much. Many regs can point to
| a specific, not always fatal crash or series of incidents as
| the reason it exists.
| JackFr wrote:
| Another great expression I've heard is 'tombstone technology'
| for pieces of hardware created in response to a particular
| tragedy.
| BrentOzar wrote:
| > the calm demeanor shown by both ATC and pilots
|
| My ex-wife was a US air traffic controller, and the training
| they go through is stunning. They're tested continuously for
| _years_ , with something like an 80% wash-out rate.
|
| During testing, they get 1-2 tests per week, working a shift
| just like a controller would, with fake pilots on the radio,
| and real computer systems. If they let airplanes get even
| _remotely_ close to each other, they fail. If it happens twice,
| they 're out of the FAA, immediately, permanently. One of the
| instructors told me, "It's my job to make sure your wife has
| the worst week of her career, every week, during training - so
| that when she's actually on the job, every week will seem easy
| no matter what she's facing."
|
| Even just in training, you could see the stress take its toll
| on the candidates over the years.
| reddit_clone wrote:
| Good to know. I am glad it is such a strenuous
| training/testing. It has to be, given the price of failure.
|
| Hmm.. Are there incidents that were caused by Controller's
| error? (most common seem to be equipment failures, pilot
| errors, bad weather and bad luck with bird strikes etc.)
| krisoft wrote:
| > Are there incidents that were caused by Controller's
| error?
|
| There is a nice wikipedia list here: https://en.wikipedia.o
| rg/wiki/Category:Aviation_accidents_an...
|
| Of course I don't think it is correct to say that an
| incident were caused by controller error. It makes it sound
| like a single controller error was the only thing which
| went wrong. It is probably more correct to say that
| controller error contributed to the outcome of some
| incident.
| throwaway34655 wrote:
| Tell me you didn't read the article without telling me you
| didn't read the article :)
| reddit_clone wrote:
| Guilty as charged :-)
|
| Like many others (I am sure) I read the comments first
| and read article later (if I read).
|
| I was responding to the informative comment about the
| rigorousness of Controller training. As a nervous flier
| myself, that made me feel a bit better.
| PetitPrince wrote:
| As the article highlights with the Japan near-miss, "Regulations
| are written in blood". What a tragic story for everyone involved.
| jandrese wrote:
| That anecdote about the Japanese 747 near miss that required a
| dive so hard it sent a drink cart _through the ceiling_ and
| injured nearly a quarter of the crew and passengers is also
| shocking. That 's the reason you keep your seatbelt on even
| when the captain turns off the sign.
| pwesner wrote:
| Did not expect this story on hackernews. I witnessed the crash.
| It was such a surreal moment...
|
| Its the first time I read an article about all the details.
| Thanks for the writeup!
| distortionfield wrote:
| You witnessed the crash? Care to elaborate on that? Sounds very
| interesting!
| pwesner wrote:
| I was in a boarding school close by (just 400m close to
| location 7 from the map showing the impacts). I did not see
| the crash in the sky (some did see an explosion). I heard a
| noise like a thunder but it did not stop. It was burning
| parts falling from the sky. The noise was from the flames. My
| first guess was that it will hit us so I rushed and woke up
| anybody I could grab. Back to my window I noticed that we are
| save - not by much. After falling to the ground it exploded
| with a gigantic fireball. We had our own firefighter devision
| at the school. They where the first on site. The week
| afterwards was very stressful. Constant helicopter and
| fighter jet noises. Press calling us, etc...
|
| At one point we realised that these where young students like
| us... And all our firefighters where tasked to help find all
| those bodies...
| throwawaylinux wrote:
| Sorry to hear that. Must be be a heavy thing to carry.
| gok wrote:
| If you'd like to feel extra uncomfortable next time you get on an
| airplane, read a bit more about limitations of TCAS that still
| exist today. For example, it doesn't actually model aircraft
| performance, so TCAS occasionally issues resolution advisories
| that are not physically possible. It also does not integrate with
| terrain awareness, so sometimes to avoid a collision with an
| aircraft it may suggest flying into a mountain (pilots are
| instructed to ignore TCAS RAs in this situation).
| Retric wrote:
| Fixing either of those comes at significant risk because you
| are making the TCAS system significantly more complicated and
| it needs to work across multiple manufacturers and equipment
| build decades apart.
| pc86 wrote:
| This is a real issue, especially for GA aircraft in hard IMC at
| low altitudes, but airliners almost never receive RAs because
| they're almost never close enough to, especially enroute.
| ilyt wrote:
| In this case it appears it would've worked just fine
| Sebb767 wrote:
| > pilots are instructed to ignore TCAS RAs in this situation
|
| I like that you explicitly pointed out that flying into a
| mountain is not the recommended course of action for pilots.
|
| Humor aside, this crash also includes a lot of broken down
| communication, so in most cases, even if TCAS fails, a crash is
| not inevitable. A pilot aware of the priority TCAS has will
| definitely communicate a failure to abide by its orders.
| FabHK wrote:
| Have these limitations ever been a problem in practice? As long
| as one plane climbs and the other doesn't, the conflict should
| be resolved, no?
| rossdavidh wrote:
| Admiralcloudberg is, you know, never really a pick-me-up story
| kind of place, but this one is particularly grim.
|
| Among many other things, a reminder that software upgrades need
| to be carefully planned, with an assumption that other stuff
| might go wrong while the system is offline.
| FabHK wrote:
| What is somewhat encouraging while reading the (grim)
| narratives of aviation accidents is this: how much has to go
| wrong for things to go seriously wrong (compare James Reason's
| Swiss Cheese model of accidents), and how most similar cases
| end well.
|
| In this case, things that went wrong - and any one of them not
| going wrong might have averted the disaster:
|
| 1. Kids missed the original plane and had to get on this
| special charter flight instead. 2. Skyguide had just the
| previous year reduced staff from 3 to 2 controllers at night,
| and 2'. One of the controllers took an unofficial break. 3.
| There was an unexpected delayed A320 coming in, distracting the
| single controller. 4. The Tupolev was equipped with TCAS - if
| it hadn't been, TCAS on the other plane would not have issued
| an RA, and they might have stayed level or climbed instead of
| descending, as instructed by TCAS. (Though without TCAS it
| would not have been allowed to fly in Europe, probably.) 5. ATC
| happened to tell the Tupolev to descend, and TCAS happened to
| tell the 757 to descend. 6. That ATC instruction came exactly
| at the same time as the TCAS instruction on the 757, so the 757
| crew didn't hear the ATC instruction to the Tupolev. 7. The
| Tupolev crew did not acknowledge that ATC instruction (which
| the 757 crew might have heard). 8. A bit later ATC repeated the
| instruction, and exactly at the same time TCAS on the 757 also
| repeated the instruction, so again they didn't hear the ATC
| instruction to the Tupolev. 9. Just then, the delayed A320
| called ATC again, so the controller was distracted and did not
| monitor that his instruction to descend resolved the conflict
| successfully. 10. The copilot in the 757 had to go to the
| toilet just 18 seconds before all this happened. 11. It was
| night, making visual separation harder, possibly. 12. The 757
| crew was trained to prioritise TCAS > ATC, the Tupolev crew was
| more or less trained to prioritise ATC > TCAS. 13. The Tupolev
| crew following ATC over TCAS received an ATC instruction that
| was in line with their right-of-way rules (left plane climbs,
| right plane descends), so it must have seemed more plausible.
| 14. The Tupolev crew had a first officer that suggested
| following TCAS instead, but he was not sitting in the RHS
| because there happened to be an extra Instructor Captain on
| that flight in the RHS who chose to follow ATC. 15. There
| happened to be a software upgrade at Zuerich ATC that night
| that disabled the Short-Term Conflict Alert light. 16. That
| software upgrade also disabled the phone lines, forcing the
| controller to waste time with the phone when trying to call
| Friedrichshafen for the delayed A320, and also prevented
| Karlsruhe ATC from warning Zuerich ATC of the problem. 17. ATC
| made a small, per se inconsequential, mistake of confusing "at
| your 2 o'clock" with "at your 10 o'clock". 18. The 757 crew
| waited 23 seconds to tell ATC that they were in a TCAS RA
| descent, by which time ATC was busy with the delayed A320. 19.
| The Tupolev crew was too busy/distracted to hear and understand
| that 757 TCAS RA descent call. 20. The ATC radar updated only
| every 12 seconds and did not yet reflect the 757's descent when
| ATC decided to instruct the Tupolev to descend. 21. The serious
| incident earlier in Japan with ATC/TCAS mismatch had not yet
| filtered through to all crews worldwide.
|
| It's just so unlikely.
| Maxion wrote:
| You forgot the karlruhe controllers who saw it all, and tried
| to call but the phone lines were down. They obeyed protocol
| and didn't contact the planes that weren't in their
| sector,even though they could have.
| rossdavidh wrote:
| It's a tough call. If they had contacted them, they also
| could have talked over instructions from the other sector's
| controller, for all they knew, which is presumably the
| reason for the protocol? Tough decision.
| laydn wrote:
| Anyone know why the TCAS only instructs the two approaching
| aircraft to change altitude only, but not heading?
| lisper wrote:
| Good answers in sibling comments, but for those who don't want
| to grovel through a lot of stackexchange answers here is the
| TLDR: There are two reasons:
|
| 1. When TCAS was originally developed, the direction
| information to the other aircraft was not very accurate, being
| obtained only via the TCAS antenna. Nowadays GPS information is
| transmitted via ADS-B and so it's much more accurate, but
| taking advantage of this would require a major redesign. It may
| happen eventually, but...
|
| 2. Aircraft can change altitude faster than they can change
| heading. Also, most aircraft can change pitch faster than they
| can roll, and they are longer and wider than they are high. So
| effecting enough altitude change to avoid a collision can be
| done faster than effecting enough heading change to do so.
| rootusrootus wrote:
| I have to imagine that if there was a #3 on that list it
| would be that introducing a random heading change adds
| follow-on complexity that could be dangerous itself. Now the
| planes are not just at different altitudes, but pointed who-
| knows-where.
| pdonis wrote:
| I don't think the GP was asking about changing heading
| _instead of_ altitude; I think they were asking about
| changing heading _in addition to_ altitude. Sure, the
| altitude change is going to achieve better separation faster,
| but a heading change _in addition_ to the altitude change
| will act as a backup in case for some reason something goes
| wrong with the altitude change.
|
| In this particular accident, it seems like commanding a
| heading change (to the right for the Tupolev and to the left
| for the DHL flight) in addition to an altitude change would
| have avoided the collision.
| lisper wrote:
| This is fallacious reasoning. "X would have prevented Y,
| and Y was a bad outcome, therefore we must do X." You can
| plug in many things for X which reveal this to be an
| unsound argument.
|
| Yes, intuitively being able to change headings seems like a
| good thing except that 1) it adds expense and complexity,
| and thus produces new potential points of failure and 2)
| it's not necessary. The problem was not that an altitude
| change was insufficient, the problem was that two sources
| of command authority (TCAS and ATC) contradicted each
| other. The solution is simply to add a new rule: if TCAS
| and ATC disagree, go with TCAS.
| pdonis wrote:
| _> This is fallacious reasoning. "X would have prevented
| Y, and Y was a bad outcome, therefore we must do X."_
|
| I never said we _must_ do X. It 's a _suggestion_ which
| might or might not be worth considering. From the article
| it appears that the TCAS system was designed with the
| assumption that pilots would always immediately do what
| it said. This accident obviously violated that
| assumption. The question is how best to respond to that
| as far as the design of TCAS is concerned; the eventual
| tradeoffs might lead to the answer "do nothing to TCAS"
| but that doesn't mean it isn't worth considering possible
| changes.
|
| _> it adds expense and complexity_
|
| Yes, this is always a tradeoff with safety systems. But
| the heading change rule would be even simpler than the
| altitude change rule (which requires negotiation of
| possible conflicts between the TCAS systems in the two
| aircraft): the heading rule is simply "turn away from the
| other aircraft", i.e., if the other aircraft is to your
| right, turn left, if it's to your left, turn right. That
| seems like logic that could be implemented, checked, and
| verified fairly easily, if it were decided to do so.
|
| _> it 's not necessary_
|
| When it comes to safety systems, "necessary" is always a
| judgment call. Yes, cases in which adding a heading
| change to TCAS instructions would be helpful are rare
| (like this crash was). But _all_ aircraft accidents are
| rare. No rule gets followed exactly as it 's given 100%
| of the time. Taking that into account when deciding on
| what safety systems to implement is perfectly justified.
|
| _> The solution is simply to add a new rule: if TCAS and
| ATC disagree, go with TCAS._
|
| Or more precisely, to explicitly make that a rule
| worldwide, instead of just in the US as it was before
| this accident.
|
| Yes, this is the response the system settled on, but
| this, too, involves a tradeoff: this rule has to be
| implemented by humans, and humans are less reliable than
| automated systems. The international air safety system
| evidently decided that humans were reliable enough in
| this case for this rule to be sufficient; but that
| doesn't mean they didn't make a tradeoff.
| sokoloff wrote:
| ADS-B is not guaranteed to be available from all aircraft in
| most of the airspace below 10K feet MSL. (Basically, if a
| transponder used to be optional before, ADS-B out is also
| optional.) Mode-C (altitude encoded transponder replies) are
| also not required, but the equipage rate is very high at this
| point, which is less the case for ADS-B among GA aircraft.
|
| https://www.aopa.org/go-fly/aircraft-and-
| ownership/ads-b/whe...
| lisper wrote:
| > ADS-B is not guaranteed to be available from all aircraft
| in most of the airspace below 10K feet MSL.
|
| Sure, but so what? The lack of universality is not an
| impediment to implementing a new TCAS system that uses
| ADS-B data when it's available. (And BTW, the places where
| ADS-B is not required are generally places where traffic is
| sparse and so the risk of a collision is pretty low to
| begin with.)
| sokoloff wrote:
| If the expense and lead time for the redesign now that
| more reliable and precise position (and first derivative
| thereof) are available from GPS via ADS-B are to be
| considered, it's fair to ask "well, what are the
| downsides as compared to using altitude for separation as
| today?" and one of them is "a higher percentage of
| aircraft are transmitting mode-C than will be
| transmitting ADS-B out".
|
| Given that the clear priority is now to follow a TCAS RA
| (resolution advisory) over an ATC instruction, I think
| that the current TCAS approach is good enough to cause
| aircraft to miss each other and that a GPS-based redesign
| is unlikely.
| ceejayoz wrote:
| https://aviation.stackexchange.com/questions/36451/why-does-...
| MerelyMortal wrote:
| I met someone who says he helped develop TCAS, and that it
| decides which one to climb or descend based on the registration
| number.
|
| I'm guessing that it does not issue turn instructions because
| it only gives a Resolution Advisory when a collision is
| imminent (otherwise they would be giving RAs all the time). At
| altitude, where the air is thinner, it is much easier for a
| plane to immediately climb or descend, planes turn _very
| slowly_ when the air is thin.
| ceejayoz wrote:
| That's only partially true, in the case of a tie.
|
| https://aviation.stackexchange.com/questions/92495/how-
| does-...
|
| > But what if the other aircraft is "thinking" the same
| thing? That's the heart of this question. The answer is,
| whichever TCAS makes a decision first, and then in case of a
| tie, the lower Mode S address "wins":
| jll29 wrote:
| Thanks for answering my question, namely how does the
| collision resolution in TCAS work? (Different from, say,
| TCP, which uses randomness)
|
| EDIT: FAA PDF on TCAS 7.1 - https://www.faa.gov/documentlib
| rary/media/advisory_circular/...
|
| This story is a moving example of the self-improvement
| going on in global air traffic industry; perhaps sometimes
| slowly, but definitely self-improving. The following book
| compares the transparency of the air traffic industry with
| the lack of transparency that currently exists in the
| medical sector, where errors are denied:
|
| https://www.amazon.com/Black-Box-Thinking-Psychology-
| Paperba...
| ogig wrote:
| Ok, last week or so it was posted another long read blog post
| from Admiralcloudberg. Somebody commented that the rest of her
| posts were very nice. So true, I went into rabbit hole mode, been
| reading the rest avidly, just a few to go. Be warned!
|
| PS: Tonight I dreamt of a surreal MD-80 crash.
| TravisLS wrote:
| I came here to say the same thing. I've read about 20 of them
| in the past few days and they're absolutely captivating. The
| TWA 800 post got me started and is a must-read:
| https://admiralcloudberg.medium.com/memories-of-flame-the-cr...
| dav_Oz wrote:
| While TCAS priority was the technical point of failure, I feel
| that the transition phase from public to private of the Swiss air
| traffic control services in 2001 seems to be the greatest
| disruption of this finely coordinated ATC.
|
| Under the new management of _Skyguide_ which led to the obvious
| cut in labor cost like reducing the night shift from 3 to 2
| controllers. The private company still tolerated the extended
| break convention during night shift from before but leaving only
| _one_ person responsible, now. And guess what? Maybe a software
| update to make some efficiency steps when we are at it. The
| single one controller was then informed during the update taking
| place what was still functioning and not which was very little.
|
| > _Part way through Nielsen's shift, a group of technicians
| arrived to install the update, and he was informed that his work
| station's main computer would have to be shut down, causing his
| displays to operate in fallback mode -- a secondary condition in
| which several features provided by the main computer became
| unavailable. In fallback mode, the system which automatically
| correlated an aircraft's radar return with its filed flight plan
| would not work, forcing him to enter the information manually,
| and the Short-Term Conflict Alert light, which illuminates when
| the system predicts that two planes will pass too close, would be
| rendered inoperative. But Nielsen had no idea what features would
| be lost in fallback mode, nor did he have any obvious way of
| finding out. And as if that wasn't enough, a few minutes later
| the technicians informed him that they would also have to
| disconnect the control center's direct telephone landline to
| neighboring centers_
|
| For me also surprisingly shocking that back in Karlsruhe multiple
| (!) controllers had to literally watch the obvious horror unfold
| while the one controller responsible was not available because of
| ... _maintenance_ work.
|
| > _Heartbreakingly, controllers in neighboring Karlsruhe saw the
| collision coming, but they did not have the authority to speak to
| planes in another sector without permission from the responsible
| controller. The Karlsruhe controllers tried several times to call
| Nielsen in the minute before the crash, but the landlines were
| down and they couldn't get through. By the time they gave up on
| this effort, it was too late to prevent the crash even by
| breaking the rules. The controllers were forced to watch,
| helpless, as the two planes collided and then disappeared from
| radar, knowing that dozens of people were dying before their
| eyes, and that there was nothing they could do to save them._
|
| Edit: According to this article [0] and this verdict [1] the
| controllers in Karlsruhe had the full authority but were
| illegally instructed otherwise by DFS (German ATC) management
| which had an informal agreement with Skyguide (Swiss ATC) over
| this border region.
|
| In the end the heavily traumatized and retired controller Nielsen
| was brutally stabbed because the modern diffusion of
| responsibility of companies only operates on the culture of
| financial compensation and is blissfully ignorant of a desperate
| man losing his whole family trying to restore his honor. So, no
| apology before everything is _settled_ accordingly.
|
| [0]https://www.dw.com/de/deutschland-haftet-f%C3%BCr-fehler-
| der...
|
| [1]https://research.wolterskluwer-
| online.de/document/2ceee0e8-5...
| kergonath wrote:
| > In the end the heavily traumatized and retired controller
| Nielsen was brutally stabbed because the modern diffusion of
| responsibility of companies only operates on the culture of
| financial compensation and is blissfully ignorant of a
| desperate man losing his whole family trying to restore his
| honor.
|
| Well yeah. I'd still take innocent until proven guilty over any
| of the blood debt and honour killing cultures. Particularly
| when the victim sacrificed to restore someone's "honour" is not
| responsible. Desperation is no excuse, and of course we should
| not base our judicial systems on it.
|
| As usual, the real culprits got nothing. As usual, this is
| unacceptable and, as usual, nothing has been or will be done to
| change this.
| stavros wrote:
| Why was TCAS priority the point of failure? As I understood it,
| the TCAS said the correct thing to both aircraft, but the ATC
| overrode it in one, resulting in the accident.
| dav_Oz wrote:
| > _Official guidance from the International Civil Aviation
| Organization, or ICAO, which signatory nations use to create
| their own regulations, did not say what to do if TCAS and ATC
| issued conflicting avoidance instructions. Similarly,
| European regulations failed to cover this scenario._
|
| Technical in the sense of giving priority one over the other;
| the priority was clear in the US but at the time not strictly
| set in Europe or Japan (a near miss happened one year before
| because of conflicting instructions) and in Russia the
| opposite (highest priority ATC) was true with TCAS being a
| new thing obligatory for flights to Europe, of the five crew
| members only one pilot seemed to be aware that the two TCAS
| are tightly coordinated (CLIMB/DESCEND) for a last resort,
| but nobody listened to him.
| Sebb767 wrote:
| Minor nitpick, but
|
| > The single one controller was then informed during the update
| taking place what was still functioning and not which was very
| little.
|
| According to the text you quoted, it's worse:
|
| > But Nielsen had no idea what features would be lost in
| fallback mode, nor did he have any obvious way of finding out.
|
| Nielsen never knew which systems were out of order. Given the
| apparent workload he was under, knowing that the collision
| warning was out of order probably would not have helped, but it
| seems that he didn't even know for sure that the system was
| down.
| antihero wrote:
| Is there not a point where ignoring what you're allowed to do
| and doing what's best if it prevents massive human catastrophe
| is the correct option regardless of personal consequences?
| Nobody is going to jail for saving hundreds of lives. The media
| outcry would likely prevent any job loss...or was it that their
| systems wouldn't allow them?
| Chris2048 wrote:
| > Nobody is going to jail for saving hundreds of lives
|
| Given that Edward Snowden isn't a free man, I doubt this..
| where is the "media outcry" there?
| rootusrootus wrote:
| He is a free man, he is a citizen of Russia living in
| Russia. We can speculate on whether he would have been
| successfully prosecuted and would still be in prison today
| had he not left the US, but he is definitely not in jail.
| dav_Oz wrote:
| > _By the time they gave up on this effort, it was too late
| to prevent the crash even by breaking the rules._
|
| There was too little time. And I imagine it is hard to be
| that quick and lucid in breaking the rules of ATC.
|
| Edit: I've looked it up and according to this article [0]
| there was only an informal agreement between Skyguide and the
| German counterpart DFS regarding this border region. Since
| ultimately only Germany is solely responsible for their
| airspace no such an agreement can exist and therefore the
| federal government (Bund) is partly to blame for the
| accident.
|
| Indeed the controllers in Karlsruhe had the obligation to
| intervene asap even without informing the Swiss counterpart
| but they were instructed otherwise although _there had been
| no legally binding transfer of the sovereign task_ ( "weil es
| keine rechtlich verbindliche Ubertragung der hoheitlichen
| Aufgabe gegeben habe"); so this was illegal. In both cases a
| management issue.
|
| [0]https://www.dw.com/de/deutschland-haftet-f%C3%BCr-fehler-
| der...
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