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Short summary: the two planes were very close, “200 feet vertical and 0.2nm horizontal,” and according to the article the main reason the incident happened is d
by yladiz 7y ago
Short summary: the two planes were very close, “200 feet vertical and 0.2nm horizontal,” and according to the article the main reason the incident happened is due to miscommunication and oversaturated communication channels.
Initially the Wizz Air plane was supposed to descend to FL300, but missed the first instruction, and the second one was incorrectly given and confirmed (read back by the crew means confirmed?) as FL200. The Air Europa flight was at FL290, and the Wizz Air plane got to FL292 (200 feet from FL290) before being instructed to ascend. The cause of the miscommunication was that the frequency used to communicate from the air traffic control to the planes was saturated and many communications collided, meaning multiple communications happened at the same time and were impossible to differentiate, necessitating repeating.
Edit: wasn’t misheard, instruction was incorrectly given.
- tombh 7y ago'nm' is 'nautical mile', for anyone wondering
- SirHound 7y agoYeah I did a double take. Close but surely not that close.
- rzzzt 7y agomissed by a whisker -> 90,000 nanometers apart
- acvny 7y agoClearly a mistake. Abbreviations for nautical mile are M NM or nmi. I guess the author has not heard about nanometer
- backspace_ 7y agoI guess you could take the context of the article. There would be no way to measure in nanometers in that situation. So if someone does not know that nautical miles was implied, it should be easy to infer that nm was not nanometer.
- StavrosK 7y agoI did infer that, but was extremely confused because I didn't know what else it could be.
- ogre_codes 7y agoThe source isn't really intended for general consumption. It's a briefing intended for pilots and others in the industry. The goal of these kind of documents is to help pilots and air traffic controllers to learn from their mistakes.
- mirimir 7y agoSure, but that didn't stop me from thinking "nanometer" whenever I saw it. Initially, I was wondering what font screwup could turn "km" into "nm".
- HeWhoLurksLate 7y agoSame! I was wondering A) how in the world they managed to get that closr and B) how they managed to measure it.
- _-___________-_ 7y agoIn an aviation context, `nm` is almost universally used for (and understood to mean) nautical mile.
- gdxhyrd 7y agoNM or nmi, but not nm. Confusion in units is never a good thing.
- nradov 7y agoThe FAA uses "NM" (capitalized) in federal regulations.
- nwallin 7y agoI don't think I've ever seen someone use M, NM, or nmi for nautical mile. I've only ever seen nm. I used nautical miles a lot in a previous career, in the context of aircraft mission planning. Telling people in the industry to use nmi or NM seems a lot like telling computer people to use MiB or GiB instead of MB or GB, or to pronounce gif "jiff". They're just not going to change.
- gdxhyrd 7y agoIt is going to change. I use MiB and GiB. I also use the ISO standard for dates, etc. Precisely because they are now standard. Saying it is not going to change is what makes things harder.
- burke 7y agoThe aviation industry: not exactly sticklers for metric usage.
- rovolo 7y agoThe Apollo flights used NM on their screens for nautical mile. [pic (right-most screen)] https://cdn.arstechnica.net/wp-content/uploads/2012/10/liebergot-eidophor1.jpg https://cdn.arstechnica.net/wp-content/uploads/2012/10/liebe... [article] https://arstechnica.com/science/2019/12/apollo-flight-controller-101-every-console-explained/ https://arstechnica.com/science/2019/12/apollo-flight-contro...
- semi-extrinsic 7y agoAlso "KFPS", presumably for "thousands of feet per second"
- solarkraft 7y agoThanks. 2 nanometers of distance would indeed be a bit low.
- analog31 7y agoIt's only a problem if the planes are both fermions.
- syncsynchalt 7y agoNautical miles are a fun unit. They are one minute of arc of the earth's surface (idealized), so it makes sense why they took hold in the two forms of travel that regularly travel great circle routes.
- anymane 7y agoNot nano meter :)
- raverbashing 7y agoIt was not misheard, the controller got confused and said FL200 instead of FL300
- yladiz 7y agoThanks, I updated my comment.
- phkahler 7y agoDont they have ADSB in on the commercial flights? They could have known another plane was so close?
- cjbprime 7y agoYes.
- flyinglizard 7y agoI believe that’s how TCAS (Traffic Collision Avoidance System) works; ADS-B broadcasts aircraft data which is received by other aircraft, and an “advisory” is issued to the crew if a potential for collision is detected. This system operated in this case, for the lower aircraft of the two.
- cjbprime 7y agoI think the parent commenter is pointing out that the descending aircraft could (and arguably should) have refused the descent clearance on noticing that it would lower them into FL290 traffic that they could see via ADS-B display in the cockpit, long before TCAS fired.
- bkor 7y ago> read back by the crew means confirmed Read back does not mean confirmed, it's basically a double check. What pilots do when they get an instruction they'll respond with the same instruction (but abbreviated). Example: ATC: Descend and maintain FL300 Pilot: Cleared for FL 300, XZ 123 Whereby XZ 123 indicates the flight. By reading back the instructions ATC should notice if the pilot heard everything correctly. That's entirely different than "confirmed". With confirmed there's no double check. Further, unless there's an emergency AFAIK the pilot must follow ATC so no need to "confirm".
- CapacitorSet 7y agoFractions of nanometers close? That's some insane precision.
- benhurmarcel 7y ago> 200 feet vertical and 0.2nm horizontal So that's 375m (1230ft) total for anyone wondering.
- hnarn 7y agoWhat do you mean by 375 meters "total"? They were 0.2 nautical miles apart vertically, which is 370.4 meters, and additionally they were separated horizontally by 200 feet, which is ~61 meters.
- marcosdumay 7y agoYou can't really compare horizontal and vertical distances.
- mannykannot 7y agoThis is correct, and it is implicitly recognized in the vertical separation intervals being less than the horizontal ones. What matters even more than distance, however, is time, and in this case, fortunately, the aircraft were travelling in the same direction and so had a low closing speed (it was actually negative, I believe.)
- mlyle 7y agoPlanes aren't spherical and don't change directions in all ways as easily... so taking the straight line distance isn't as helpful as you'd think.
- GordonS 7y agoWow, usually when there are reports of "near misses" the planes are relatively far apart (still potentially dangerously close, of course) - I don't think I've seen a report with the planes this close to each other before.
- dragontamer 7y agoPlanes don't actually have to strike each other to cause issues. The turbulence from the engines is enough to cause issues for the next plane. Enough so, that turbulence alone can cause a crash, even if the airplanes never actually touch. https://en.wikipedia.org/wiki/Wake_turbulence https://en.wikipedia.org/wiki/Wake_turbulence
- dsfyu404ed 7y agoThis is only really an issue for planes of highly disparate sizes and I've never heard of it causing issues (a crash or near miss) with a commercial airliner (edit: in good mechanical condition where the pilot does not make things worse from the get-go) sized craft being on the receiving end.
- cjbprime 7y agoWake turbulence was the cause of the second deadliest air crash in US history: https://en.wikipedia.org/wiki/American_Airlines_Flight_587 https://en.wikipedia.org/wiki/American_Airlines_Flight_587 And involved in this one, though the situation is harder to assess: https://en.wikipedia.org/wiki/USAir_Flight_427 https://en.wikipedia.org/wiki/USAir_Flight_427
- dsfyu404ed 7y ago>Wake turbulence was the cause of the second deadliest air crash in US history: >https://en.wikipedia.org/wiki/American_Airlines_Flight_587 https://en.wikipedia.org/wiki/American_Airlines_Flight_587 Funny you mention 587. That was actually the first thing I thought of. That was the one where the pilot slammed the pedals lock to lock in response to turbulence and ripped the vertical stabilizer off. Aircraft of similar size take off similar distances behind 747s all the time. The pilot really reacted badly in the case of 587 though his training was partly at fault. From wikipedia: "The first officer repeatedly moved the rudder from fully left to fully right... The resulting hazardous sideslip angle led to extremely high aerodynamic loads that separated the vertical stabilizer. If the first officer had stopped moving the rudder at any time before the vertical stabilizer failed, the airplane would have leveled out on its own, and the accident would have been avoided" >And involved in this one, though the situation is harder to assess: >https://en.wikipedia.org/wiki/USAir_Flight_427 https://en.wikipedia.org/wiki/USAir_Flight_427 427 was a hydraulic failure and any source of turbulence (e.g. weather) requiring rudder movements could have raised that issue. IT was part of a larger issue. https://en.wikipedia.org/wiki/Boeing_737_rudder_issues#Second_accident https://en.wikipedia.org/wiki/Boeing_737_rudder_issues#Secon... I originally said "Thank you from changing the wording from "implicated" to "cited" because they mean very different things." but you since edited your comment to say "cause" and "involved" which IMO is as accurate on average as "implicated" but with greater standard deviation.
- SomeHacker44 7y ago1nm is just over 6000 feet, so that is about 1200 feet horizontally. 1nm is also about 15% more than an sm (statute mile), the thing we usually call a mile outside of aviation or nautical circles.
- desertrider12 7y agoSo that means the planes were intended to be at levels 300 and 290. Is it normal to have only 1000 feet of vertical separation? It seems like the higher plane could easily lose 1000 feet in a few seconds before ATC could tell the lower plane to move away.
- _s 7y agoYup; https://en.m.wikipedia.org/wiki/Reduced_vertical_separation_minima https://en.m.wikipedia.org/wiki/Reduced_vertical_separation_... A plane can ascend/descend fast, but generally stick to either 500 or 1000ft/min.