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Armchair air crash investigator

momav.me

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Re: Armchair air crash investigator

#61

Post by snom380 »

lisper wrote: post #45
jevinskie wrote: post #39

Earlier quoted context omitted.

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

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)

Re: Armchair air crash investigator

#62

Post by rogerbinns »

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).

Re: Armchair air crash investigator

#63

Post by rogerbinns »

momavujisic wrote: post #50
bdirgo wrote: post #2

I heard a reporter on TV reporting that the airplane was doing cartwheels on the runway, and I pictured the semi-truck being flipped over in Batman. And then I thought what the hell could have done that? Fishtailed makes more sense, thanks for the clarification.

CNN just released video footage they have of the actual crash. The plane (from what I see) after crashing does a near 360-degree turn with the right wing high up – in fact you can see that the plane is almost nose down-tail up which almost makes it look like it was cartwheeling. Very surprising revelation, I really did not expect an airframe to remain as intact as it did after going through that.

http://edition.cnn.com/video/?/video/us/2013/07/07/vo-plane-...

Re: Armchair air crash investigator

#64

Post by JonFish85 »

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.

Re: Armchair air crash investigator

#65

Post by JshWright »

neurotech1 wrote: post #41
joshbaptiste wrote: post #14

Earlier quoted context omitted.

indeed, which will take ~2 years

They'll make a preliminary, primarily "factual" report within days, or weeks. This will be based on the FDR, Quick Access Recorder, statements by crew, passengers and witnesses to the NTSB investigators. Even though I'm a former pilot, I've not made any posts prior to this one, because I didn't want to speculate.

The recently released video (which I'm sure the NTSB already had) should be helpful as well (and appears to support the author's speculation).

Re: Armchair air crash investigator

#66

Post by dmourati »

austenallred wrote: post #3
bdirgo wrote: post #2

I heard a reporter on TV reporting that the airplane was doing cartwheels on the runway, and I pictured the semi-truck being flipped over in Batman. And then I thought what the hell could have done that? Fishtailed makes more sense, thanks for the clarification.

There were a lot of reports like these that were complete assumption based on the fact that one witness said the airplane had flipped over. It actually hadn't.

O RLY? http://www.cnn.com/2013/07/07/us/plane-crash-main/index.html...

Re: Armchair air crash investigator

#67

Post by VLM »

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 the same thing. I'm not just picking nits, if you try researching this, you'll find the VASI has been outta service probably since the 90s, you want the PAPI. Its all the same anyway, white you're light, red you're dead. VASI is before my time but I'm told it was the same arrangement?

If you want NOTAMs you can just go to FAA's pilotweb, this link might work or you can search. Holy cow SFO has a lot of NOTAMS to read about.

https://pilotweb.nas.faa.gov/PilotWeb/notamRetrievalByICAOAc...

!SFO 07/047 SFO RWY 10R/28L CLSD WEF 1307062309

!SFO 07/046 SFO RWY 28L PAPI OTS WEF 1307062219

The PAPI (precision approach whatever indicator or something) was marked out on the 6th at 2219 and the runways (not all listed above) formally closed at 2309. I think that is after the crash UTC time?

Now according to this NOTAM

!SFO 06/003 SFO RWY 28R ALS OTS WEF 1306011400-1308222359

They've been screwing around with the ALS lights for like 5 weeks now as per the daily news story. The ALS is mostly to light the place up at night, make sure you can line up on the correct runway (L or R) and most importantly in the USA this has the decision bar, if the weather is so poor that you can't see the decision bar, its too poor to continue the approach. I'm told the weather was beautiful during the crash, so I don't think the decision bar being rebuilt or whatever had much if anything to do with the crash.

Something I don't understand about ALS on an airport by an ocean (not exactly a problem where I live) is how they mount the decision bar and its little friends. Its going to be quite a distance from the end of the runway and some runways seem to go right up to the sea, so piers out in the ocean or something? If they hit the SFO ALS that would imply the plane would be well offshore under water.

The ALS, aside maybe from some wiring, is probably not any more or less messed up by the crash than anything else's power wiring. I could imagine a plane running off the runway into the PAPI and that would be about the end of that PAPI, or at least it'll have to be aligned.

Re: Armchair air crash investigator

#69

Post by momavujisic »

VLM wrote: post #57
lukecampbell wrote: post #15

Earlier quoted context omitted.

I've never flown a B777 or any heavy aircraft so I can't comment on their typical flares, but in a Cessna 172 the flare doesn't induce a positive rate of climb, it simply slows the vertical descent speed to something manageable for touch down, a positive vertical speed seems counterintuitive to me as a good flare. What I want to know is what his IAS (indicated air-speed) at the decision altitude. Again the only thing…

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 extremely slow, even suggesting that it's most likely below stall speed – which seems to be correct as the NTSB says the stick shaker went off some 4 seconds before impact.

Re: Armchair air crash investigator

#70

Post by VLM »

RockyMcNuts wrote: post #56
RockyMcNuts wrote: post #36

Earlier quoted context omitted.

like this link better than the OP which is fairly uninformed speculation ...

some video of the crash - kind of looks like it was skimming the waves in ground effect trying to go around http://www.cnn.com/video/?/video/us/2013/07/07/vo-plane-sf-p... I stand by the parent having some useful data and analysis, and the OP being totally speculation, and in many respects uninformed. - number 1, if you say 'loss of power', makes sense as a possible cause. if you say 'icing in the FOHE', it's like sa…

"- number 4, pilot error/bad approach, can't argue with that. the story is what's interesting"

Pilot induced oscillation on a really big scale. Coming in way too hot, slam down, whoops way over corrected, now coming in too low, whoops ran outta air and time to correct. Coming in way too hot, now are you better off trying to salvage or go around and get fired? Different nations airlines have differing policies on this...

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