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Armchair air crash investigator

momav.me

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Re: Armchair air crash investigator

#71

Post by momavujisic »

JonFish85 wrote: post #64

I don't really like when people post these sort of "arm-chair" hypotheses. As much as it's fun to try to figure things out, there is always the danger of people jumping to conclusions based on bad or incomplete data. It reminds me a lot of the reddit people immediately following the Boston Marathon bombings. It's definitely an interesting read, but I don't want to take it for much more than just idle speculation.

Idle speculation and having a bit of fun trying to play air crash investigator, is exactly what this article is. I hope that I was able to convey that this is about "what I think" happened and not "what happened".

Re: Armchair air crash investigator

#72

Post by VLM »

momavujisic wrote: post #69
VLM wrote: post #57

Earlier quoted context omitted.

It gives a pretty good estimate of the error involved in the descent rate reporting. Probably accurate +/- 200 FPM or so. The airspeed encoder is probably from the same system that displays the pilot instruments, indicated airspeed IAS. I thought it odd that the analysis of conditions didn't think 125 and 98 were ridiculously low airspeeds, but claimed that an approach around 130 knots was a "fast approach". However…

About the speed, you're correct – 130 kts for a 777 is not fast, I was mistaken. In fact the NTSB just said the target approach given by the pilots was to be 137 kts. I should have chose one of the higher airspeeds given but I did not want to give a high estimate. I am not familiar with 777 speeds and should of done some more research in that regard. I did however, write that I found the sub-100 speeds to be extremel…

I read sometimes you can get a Vref under 120, great density altitude, sea level, winter, no pax cargo and low on fuel, but yeah when the IAS is reporting 98 you're pretty much screwed under any conditions. Maybe it was already on the ground at that point, if it wasn't.. it going to be on the ground real soon...

I would imagine some of the flightsim people I know are flying the approach under identical conditions right now. Would be interesting to hear at what point they found it unrecoverable. 98 kts is unrecoverable, but I wonder when it went unrecoverable. One problem with sims is if you know how its supposed to turn out, that screws up your actual reaction if you sim it 20 times trying different things. All you need is a cockpit distraction to totally screw up an approach. Maybe a false alarm of some type at just the wrong moment.

Re: Armchair air crash investigator

#73

Post by rdl »

VLM wrote: post #67
rdl wrote: post #29

NY Daily News is reporting that VASI was down as well ( http://www.nydailynews.com/news/national/expert-runway-guida... ) Which appears to be due to someone incorrectly reading a post-crash NOTAM which is about the aids being gone due to the crash, so there's no particular reason to think VASI was down before the crash. I really don't think I'd trust SF city government to run an airport, even under FAA regulations. L…

The short version is there are multiple things on a runway that emit light and I think they're being confused. "Which appears to be due to someone incorrectly reading a post-crash NOTAM which is about the aids being gone due to the crash" OK first of all VASI has been obsolete since I was a kid in the 90s, its all PAPI now. (edited to add, in the USA) Much like people still call the AWOS an ATIS because it does about…

It looks like they mount stuff on CA-92/San Mateo Bridge (http://www.flysfo.com/web/export/sites/default/download/abou...) and then from there along the approach. The main issue seems to be the two parallel runways. From when I took photos of the airfield, there were a lot of lights and other things sticking out of the bay on the approach path. Decision Bar is supposed to be 1000' off the threshold so that was probably it.

I'm not a pilot; once I have spare money and time (and enough to fly monthly to keep current), probably.

It's interesting reading about stuff like the "No Transgression Zone", though.

Re: Armchair air crash investigator

#74

Post by shin_lao »

jevinskie wrote: post #39
cjrp wrote: post #24

Earlier quoted context omitted.

Pilots will actually very rarely use the autoland functionality (apart from when weather, e.g. low visibility, requires it, and also to ensure that they're current with the procedure). They'll use the autopilot for the initial part of the approach, but then when visual with the runway will often disconnect it in order to fly the actual landing manually (still following the indications on the flight director, which ar…

Why is this? Can they do a better (in terms of passenger comfort) job landing manually?

They are bound by regulations to do a certain number of landings every year.

Re: Armchair air crash investigator

#75

Post by lisper »

snom380 wrote: post #61
lisper wrote: post #45

Earlier quoted context omitted.

No, autoland is pretty good. But there are two factors that cause pilots to land manually most of the time: 1) pilots think they are better at handling last-minute unexpected contingencies like wind sheer or bird strikes (and they may well be right about that) and 2) pilots don't want to give the Powers that Be any additional data to suggest that they aren't actually needed to fly a plane at all. The fact of the matt…

I don't find it likely that pilots hand-fly approaches to make a point. Isn't it more likely that this is codified in airline operation instructions? As for completely autonomous, do you seriously think we have the technology available today to make an autopilot handle any conceivable situation without a human being present and ready to take over? (non-IR PP here)

It isn't "just to make a point". It's also to stay proficient, or to make the job less tedious. But whether to hand-fly an approach is always the pilot's discretion (as far as I know -- I'm a just a private pilot so I could be wrong about that).

And no, automation can't handle "every conceivable situation", but neither can humans. Furthermore, humans screw up more often than autopilots. Pilot error is currently the single biggest contributor to the overall accident rate.

Mind you, I'm not advocating fully autonomous aircraft. I like having a human in the loop, but that's in part because I am the human in the loop. It's far from clear that human pilots are a net win for safety.

Re: Armchair air crash investigator

#76

Post by VLM »

rogerbinns wrote: post #62

There is an excellent posting with graphs comparing the Asiana flight to a United 777 that landed 10 minutes before. The graphs compare height, speed and importantly energy. http://flyingprofessors.net/what-happened-to-asiana-airlines... As most have hypothesized, it was an unstabilized approach and they should have done a go around (barring unknown technical/mechanical factors).

Looking at the graphs the plane was ahead of them by about 5-10 seconds. That usually doesn't turn out too well. Gotta be ahead of the plane, not the plane ahead of you. Usually a noob mistake (on the ground system failure, hard to fix) OR hopefully extensive extenuating circumstances (on the plane system failure, easy to fix).

Re: Armchair air crash investigator

#77

Post by [deleted] »

snom380 wrote: post #61
lisper wrote: post #45

Earlier quoted context omitted.

No, autoland is pretty good. But there are two factors that cause pilots to land manually most of the time: 1) pilots think they are better at handling last-minute unexpected contingencies like wind sheer or bird strikes (and they may well be right about that) and 2) pilots don't want to give the Powers that Be any additional data to suggest that they aren't actually needed to fly a plane at all. The fact of the matt…

I don't find it likely that pilots hand-fly approaches to make a point. Isn't it more likely that this is codified in airline operation instructions? As for completely autonomous, do you seriously think we have the technology available today to make an autopilot handle any conceivable situation without a human being present and ready to take over? (non-IR PP here)

[deleted]

Re: Armchair air crash investigator

#78

Post by hga »

joejohnson wrote: post #68

Does anyone know if they've released the information about where the people who died/were severely injured were sitting in the plane? I'd love to see a seating chart that shows the safest and least safe seats on a 777.

It really depends on the type of accident (skim Wikipedia on ones with survivors) ... and after looking at the CNN supplied video https://news.ycombinator.com/item?id=6003232 right now I'm thinking "Major miracle" and "If it's ain't Boeing, I ain't going", although I'm sure it's a lot more of the former than the latter.

Re: Armchair air crash investigator

#79

Post by jrockway »

avree wrote: post #22
madiator wrote: post #12

Sorry to go offtopic here, but the images seem to be used without any credits. The first one was taken by David Eun ( https://path.com/p/1lwrZb )

Well, the whole blog design is very gray-area 'theft' of Medium's design.

I don't know what Medium is, but ... a white page with a title on the top? This is just as much a 'theft' of the default Apache "It works!" page.

Re: Armchair air crash investigator

#80

Post by bajsejohannes »

Lusake wrote: post #4

Here is graphical comparison of safe landing and Asiana crash: https://pbs.twimg.com/media/BOhIDCWCUAApHFV.jpg:large . Also it appears that runway was modified: http://metabunk.org/sk/HL7742_777_Crash%2C_Korean_Asiana_Air...

This is comparing one single safe landing to a crash landing. Does that gain us new insights? Not really. For that, we'd need the crash landing compared to the average landing, and also to other (safe and unsafe) extreme landings of the past.

And to get all Tufte of the graphics: Most of this is chart junk. The 3d view only serveres to hide information, and overlaying the paths (in 2d) would actually let us compare more accurately.

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