The Hangar

Farhan

02:08

@BretCopeland How much for eleven Minutes?

Federico

09:00

Engine flight-data readout for the crashed #TransAsia ATR 72: #GE235 http://t.co/yUjyMWDRVE

Tweeted by FlightDKM on February 6, 2015 at 8:18 AM

do you think is a realiable source? got retweeted by fr24

falstro

@Federico I'll treat it as reliable when it shows up here: avherald.com/h?article=48145bb3&opt=0

Reading the updates to the avherald post it almost sounds like a repeat of the kegworth disaster, that is shutting down the wrong engine

in which case it wasn't a Vmc, but an engine out stall/spin

the sad part in that case is that from the looks of it they might even have made the river upright if they maintained airspeed. That's just speculation of course, hard to judge from the videos.

Federico

09:23

what I do not understand is that they say that the RH engine auto-feathered, while in the videos it seems the LH to be feathered (see still images on avherald)
let's wait for the interim report

falstro

shutting down an engine will feather it, so if they shut down #1 it would be feathered. It might be an illusion that #1 is more feathered than #2. Or they were trying to get #2 running, thinking that was the better of the two

@Federico it's up on avherald now as well, so it appears to be genuine

Federico

@falstro seen that. also, several aviation news outlets are saying that it comes from the Taiwan authorities, but I cannot find a single link

ratchet freak

maybe directly leaked from them to the new distribution?

it would be nice to know what each line was the cryptic abbreviations aren't really helping

Federico

09:46

from top to bottom, the ones I know:
- main gear (I'd say is clear)
- master warning
- CLA (no idea)
- Beta (aka sideslip)
- bleed valve
- PLA (power lever angle, aka throttle lever position)
- ITT (inter turbine temperature, http://www.pprune.org/archive/index.php/t-191771.html)
- NP (propeller speed)
- fuel flow
- TQ (torque)
- NL (low pressure rpms)
- NH (high pressure rpms)
- oil pressure

what is not clear to me are those dotted lines, if the labels are blue and green, what the hell the dotted line means?!?

ratchet freak

unless the dotted is the blue

Federico

would make sense

ok, found that CLA on ATRs is "Condition Lever Angle", trying to find out what it is

flightsim.com/vbfs/…

I think that the "beta" might be the one of the props, with 90° indicating feathering

falstro

@Federico beta usually means that the prop is in beta range, i.e. reverse thrust

ratchet freak

10:01

so engine 2 activated thrust reversers?

Federico

@falstro in the plots is an angle in degrees

falstro

... so assuming beta 90° means feather seems reasonable to me :)

ratchet freak

10:15

Tell me if I'm wrong

but it looks like master warning flame in engine 2 happened

then a few seconds later the power lever for engine 1 was pulled back

then engine 1 was shut down

and then it was doomed

falstro

11:37

@ratchetfreak yeah, it does look suspiciously like a kegworth repeat

(in the sense that they shut down the wrong engine)

Kegworth air disaster

The Kegworth air disaster occurred on 8 January 1989 when British Midland Flight 92, a Boeing 737-400, crashed onto the embankment of the M1 motorway near Kegworth, Leicestershire, UK. The aircraft was attempting to conduct an emergency landing at East Midlands Airport. Of the 126 people aboard, 47 died and 74, including seven members of the flight crew, sustained serious injuries. == History == The aircraft was a British Midland operated Boeing 737-400, registration G-OBME, on a scheduled flight from London Heathrow Airport to Belfast International Airport, Northern Ireland, having already flown...

falstro

11:59

@ratchetfreak what I'm reading is eng2 flame out waster warning lit up, and the #2 prop autofeathered. This is further confirmed by the drop in ITT and fuel flow on #2. For some this reason prompted a power reduction by the crew on the #1 engine while the #2 remained at full power. That #1 lost power is also evident from the #1 prop governor reducing the pitch to remain on the set RPM.

The power is further reduced in steps (while also increasing #2 power) and eventually the condition lever is pulled to fuel shut-off and the #1 prop feathers.

It's interesting to see that it appears the #1 was just being relit as they crashed, but #2 prop was coming out of feather (not #1)

The question remains why did they confuse the engines, it could even be a wiring issue that the engine flameout warnings were reversed.

also what's "objective TQ"?

it jumped from 90 to 100% on the #1 before #2 flamed out

heh. "waster warning" should be "master warning" :p

Federico

@falstro torque, see my list :P

the "objective" one might be a normalization of some sort

falstro

yeah, I'm asking about the "objective" part

Federico

12:15

Normal takeoff torque is also known as ìobjective torque.î

fosterweb.com/atr-notes/atrnotes.pdf

falstro

so, if objective tq 1 increases, but tq 1 stays the same/decreases, what does that tell us?

Federico

no idea, I am simply googling around, reporting what I find

falstro

I'm guessing it's some switch or lever position

Federico

here might be the answer: scribd.com/doc/61626807/ch-2#scribd

falstro

but 90%-100% makes no sense :)

it appears to be a torque bug setting

it's there on page 2

ratchet freak

12:25

@falstro or the thrust levers were cross wired

I think the connections to the display have incompatible left-right connections to prevent cross wiring

falstro

@ratchetfreak depends on the avionics I suppose

I'd be surprised if the old school bulbs couldn't be crosswired

and even so, they could be cross wired internally from production

you never test just one of the warning lights

ratchet freak

the kegsworth 737 had incompatible left-right display wirings

falstro

@ratchetfreak then the condition lever would have to be cross wired too

ratchet freak

at least according to NGC's aircraft investigation

falstro

@ratchetfreak I know, but this is an ATR 72

ratchet freak

12:30

In that same episode they said a previous incident had them cross wired and that would probably be the reason for the incompatibility

falstro

@ratchetfreak but that was a wiring harness, not a single bulb connector

ratchet freak

I'm fairly certain that they would test for crosswires when putting in the wiring harness

falstro

I don't know how the ATR 72 is wired, so it may be the same there, I don't know

@ratchetfreak the thing is, on the 737, there was one big connector with all kinds of stuff, one for the left and one for the right engine

it might well be the case that the master warning light is separate, and just a single wire, and that it doesn't have the same kind of mix-up-safe connector

but I mean it could be a whole bunch of other reasons

ratchet freak

Master warning light is a giant OR of issues it can indicate

falstro

ranging from actual double engine failure (of which only one was a flame out and the other was some other kind of failure) to simple pilot stress/incompetence

it could even be a wiring problem in the FDR :)

@ratchetfreak yeah, I think if it's called "master warning: eng flameout" it would not indicate anything but an engine flameout ;)

ratchet freak

12:37

Then to diagnose which engine you have to scan the engine gages

that takes more than a few seconds

falstro

well, as it says in the FDR graph, it's called "Master Warning:ENG 2 Flame Out", don't know if it's a separate bulb, or an ECAM message or what.

ratchet freak

see if you can find the light... airliners.net/photo/FedEx-Feeder-%28Mountain/…

falstro

I'm guessing the warning light bay?

underneath the backup AI

on the left side

but it's hard to read when they're not lit up :)

ratchet freak

and it also depends on whether the plane has gages or a display

falstro

12:53

yeah, that's what I meant. Don't know what kind of avionics was in this one, it was pretty new, but that doesn't necessarily mean it's a glass cockpit

ratchet freak

according to planespotters.net delivered apr last year

CGCampbell

13:07

I was about to add another comment to the why is first class up front ... but realized I should ask it here first...

Given that the mass of cow class is generally in the rear, and they (the majority) use the rear lavatories, could weight distribution of crap be a factor, or is it not 'weighty enough' to matter as far as CG distribution? :cD

Federico

lavatory waste ends up all in the same place, afaik (IIRC even on the A380)
factors are: noise ("wealthy" passengers prefers a quieter trip and usually in the back you have all the engine turbulence that is not really helping) and quick access to doors at arrival (in particular when using fingers)

ratchet freak

and first class doesn't need to move through the cow stable

CGCampbell

yep, ok, so first on first off and nicety of ride :d) thanky

ratchet freak

@CGCampbell actually I'd say last on

Would you as a high paying passenger like to see the plebs migrating passed you dragging infants?

Federico

@ratchetfreak depends on airline germanwings (ok, a kinda-lowcost) lets passengers in row 1-3 and families with infants in first

CGCampbell

13:21

well, I'm a bad example. I try to board as late as absolutly possible, regardless of my seating, but that's just me....I guess I assumed that first class = privileged to get on first

ratchet freak

@Federico but that is infants

Federico

@ratchetfreak and families with infants

falstro

14:43

heh. random failures in xplane can be weird. On the third touch and go it decided my control locks where still in :)

Farhan

15:03

@falstro I thought you were planning to for flying in a real plane.

falstro

@Farhan I did, the winds didn't want me to.

Farhan

@falstro Weather is affecting your flights a lot recently, isn't it?

falstro

@Farhan yeah, this winter sucks

haven't flown the TB10 since september, and after that I had one hour BFR in the katana in late november

Farhan

@falstro Katana is DA20?

falstro

yeah

this one is a DA20-A1 to be exact

Farhan

15:58

@falstro $V_{mc}$ looks prettier than V<sub>mc</sub>.

stupid markups

falstro

@Farhan I did $v_{mc}$ everywhere, didn't I?

besides it's usually a lower case v, but that's nitpicking ;)

Farhan

@falstro Yup, that's what I was trying to show you, but chat didn't let it happen.

Is it MathJax?

falstro

yeah, mathjax

ratchet freak

@Farhan yup

and it's disabled on chat for reasons™

Farhan

Luckily, it worked in the question title (HTML doesn't):

4

Q: What is a $V_{mc}$ roll?

Many aviation discussions of the TransAsia GE235 accident include comments like "that was a $V_{mc}$ roll". What is a $V_{mc}$ roll and how should you avoid it and/or recover from it?

Oh com'on, desktop chat is making me look bad

falstro

16:07

:)

Federico

17:54

how the hell do you make image to be clickable? (this question: aviation.stackexchange.com/questions/12474/explain-the-fdr-plot)

fooot

@Federico It's just linked like text

[![TransAsia GE235 FDR plot][3]][4]

Federico

18:19

@fooot yeah, I found out and I was sure I wrote it here, but the message is not here O_o

but thanks anyway

I was trying to make the image clickable, if you see the edit is mine

in the meanwhile I discovered why my landing simulation was wonky: the nose gear was "attached" in the opposite way -_-

casey

@falstro mathjax wont render in chat, or in titles or comments on the mobile SE app.

falstro

@casey @farhan I think this was for you :)

casey

18:35

if i clicked the wrong little arrow, oh well :)

falstro

:)

I figured you were on mobile and siri messed up your autocomplete :)

voretaq7

@casey <sup> and <sub> don't render in title bars either. I prefer them for superscript/subscript though because they're defined HTML entities (search engines understand them) - they may not understand MathJax

falstro

19:00

@voretaq7 everyone should understand, live and breathe LaTeX!

@BretCopeland I've just about finished typing up the cover letter (I'm slow at writing letters... my excuse is that I put a lot of thought into them), ;) should I send it your way or would it be better to submit it via the web interface?

Bret Copeland

@falstro send me an email. bret@so

or @se, whatever. I think @askubuntu.com even works.

Oh, it's @askpatents.com that works.

voretaq7

@falstro All typesetting systems should be Turing-complete!

falstro

19:16

@BretCopeland otw

@voretaq7 I do all my programming in PS

voretaq7

@falstro import universe

Pondlife

19:33

@voretaq7 Interestingly, searching for this question title on Google gives aviation.SE as the first hit (already), but searching for "what is a Vmc roll" doesn't find this one. Perhaps we should avoid MathJax in titles so as not to mess up Google indexing?

voretaq7

@Pondlife I avoid it everywhere it isn't needed for that reason. If HTML can do the job I use it.

Pondlife

19:45

@voretaq7 It looks like some other sites have chosen to avoid it in titles for the same reason: meta.stackexchange.com/questions/228881/…

Federico

I was discussing the FDR plot from the transasia flight with my father. He was surprised in seeing NH from the faulty engine to remain at ~80% even with no fuel (and actually that the faulty engine got more fuel than the shut-off one in the last minute)

Farhan

@Pondlife I didn't know that. In fact, the title was ~~messed up~~ not so nice looking on Twitter too.

rolled back

Pondlife

@Farhan Thanks, that's put it up to the #3 hit in Google already, they're fast... :-)

Farhan

@Pondlife No problem. I initially used the HTML tags, but MathJax looked so pretty.

FreeMan

20:50

@Farhan But it makes it hard to read, especially on smaller screens

Shalvenay

23:12

o/ @voretaq7

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