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probes
17th May 2012, 21:26
Thought I'd ask about the Polish government plane crash here, not to upset the pros up there. A new guy to investigate technical aspects, a US professor (the link from rumorous news):


Binienda specializes in fracture mechanics, a highly technical field that analyzes how and why materials break under stress. His focus is the lightweight stuff – aluminum, titanium and exotic polymers –used in aviation and aerospace. He often works with NASA and jet engine manufacturers. He is no stranger to aircraft structures.
The wing-tree impact became the target of his inquiry. It didn't make sense to Binienda that, after a collision that severed a third of the wing, the jet would be able to climb almost 100 feet in altitude before crashing, as the Russian investigators had concluded. Robbed of lift and momentum, the damaged plane should drop like a stone.
To study the wing-tree impact, Binienda created a computer model using a software program called LS-DYNA (http://www.lstc.com/products/ls-dyna). He and other engineers routinely use LS-DYNA to simulate complex fracture situations with lots of rapidly changing conditions, like when a loose, high-speed chunk of insulating foam bashed into the space shuttle Columbia's (http://www.google.com/url?sa=t&rct=j&q=ls-dyna%20columbia&source=web&cd=1&ved=0CCQQFjAA&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload% 3Fdoi%3D10.1.1.76.5872%26rep%3Drep1%26type%3Dpdf&ei=lAGbT879Ls_wggfX1fCVDw&usg=AFQjCNHtGlA2k58y6iAkYDBis-tmvffPvQ&cad=rja) wing during a 2003 launch, fatally damaging the orbiter.
With LS-DYNA and information from the crash reports, Binienda could input the strength, density and other properties of the wing and the tree. That allows a computer to calculate the impact forces and create a second-by-second, realistic 3-D animation (http://www.youtube.com/watch?v=fbJ29pGJLNU) of what happened.
Even when Binienda intentionally under-represented the wing's strength and over-estimated the tree's, the simulations still showed the wing slicing off the treetop while suffering only minor damage. The tree impact couldn't have broken the wing, his model showed. Something else must have done that, and something else must have snapped off the treetop. (For the latter, Binienda suspects it was the powerful backwash from the jet's engines as they passed overhead.)
Binienda's simulation also showed that, for the wing tip to have landed where it did, the break must have happened at a higher altitude and closer to the runway than where the birch tree was located.



Binienda's computer modeling of the tree impact is an unconventional approach to an aircraft crash analysis, said Greg Phillips (http://viterbi.usc.edu/aviation/bios/phillips.htm), a veteran former NTSB investigator who's now an aviation safety instructor at the University of Southern California. Still, "it sounds like the guy has all the credentials that would certainly set off the alarms that we really need to listen hard to this."



Whether the birch tree fractured the wing or not is a moot point, said Paul Czysz, an aircraft design expert and professor emeritus at St. Louis University's Parks College of Engineering, Aviation and Technology (http://parks.slu.edu/). "If that tree didn't do it, there are about 50 others in front of it that could have," said Czysz, who thinks pilot over-confidence caused the crash. "The fact that he hit the tree that far from the end of the runway means that unless he got that airplane up right away, he was dead. And very few pilots have the reactive skills to get that airplane up."


So someone has to be wrong. How can an investigation be so totally controversial about hard evidence? After all, it's not a Hollywood crime (about which someone had mentioned 'twas really hard to prove the guy had committed suicide because of the knife in his back).


Binienda knows his high-profile position raising doubts about the crash's official cause could jeopardize his professional reputation.
"If they show that I made an obvious error, it would be a tremendous blemish on my career," he said. But "if I would hesitate to look for truth just because of my career, that would be a pretty bad scientific approach. I hope at a minimum I can bring people to ask questions, and at the end they will do the investigation and show that my work was incorrect or correct. Either way, I don't mind."


graphics:

http://media.cleveland.com/science_impact/photo/29cgcrashjpg-767747a599d80284.jpg

probes
17th May 2012, 21:38
P.S and his work - formulae, graphs, maps, photos etc.

http://www.ecgf.uakron.edu/~civil/people/binienda/Parlament%20November%202011%20-%20English.pdf

Tankertrashnav
18th May 2012, 09:16
Probes, by "up there" I take it you mean the thread on this crash on 'Rumour and News'. I have trawled through a fair proportion of the 1800 plus posts on that thread and I reckon that there is so much tosh on it (as well as some very thoughtful posts) that I would be surprised if your intrusion with an informative post would "cause offence"

If it did it would probably be to some 700 hour first officer who can't accept that anyone not currently employed as a pilot has any valid opinion on aviation matters. There are quite a few of them "up there".

OFSO
18th May 2012, 11:11
anyone not currently employed as a pilot has any valid opinion

Tanker, you have a very valid point there. Sometimes the training, qualifications or intensive experience narrows one's view or enforces a certain mindset. Mrs OFSO and I work in completely different subjects (sculpting/international civil service law) but ask each other's opinions on matters and it's surprising how often comments are very useful.

When I was writing procedures in the space industry I would frequently go and find a colleague who knew nothing about the subject and ask him to read my work and make comments. Far more useful than asking someone who knew what I was writing about.

probes
18th May 2012, 12:05
Probes, by "up there" I take it you mean the thread on this crash on 'Rumour and News'.
yes, and I've read most of them posts, but that's something new, and also there's been speculation and just 'noise' (because of the political whatnot) and alternative theories and of course the official report has been published, and that's why I didn't ask there (the link is from there, but the article is long and I quoted the technical aspects only). I thought maybe the engineers around here could comment on the wing-thing. That the wing-tip could not have been ripped off by the birch.

lomapaseo
18th May 2012, 15:40
bring this thread into the technical forum and I may have a go at it

I'm withe Greg Phillips :ok:

probes
27th Jun 2012, 11:08
Uh, oh, one should have been more keen on physics when younger.
So, a new 'independent report', lots of photos, formulae etc, and a thing I was wondering about and is too naive to ask probably, but...
Elastic properties of the soil should act somewhat like a shock absorber, reducing the peak vertical acceleration of the fall. There were no obstacles in addition to trees, which could have significantly slowed down the machine. The effect should not be much larger, then then driving a car into the shrubbery of a grove at a speed of 150-250 km/h, which is the estimated speed at the time of impact. (At such a supposed grove, thin trees would need to be quite thin, as we compare the plane of a length of about 50 m to a car, less than 5 m).
isn't it about the 'strength of material' of the objects as well, not only length or size?
www.simulate-events.com/getdata.do?source=3&id=23 (http://www.simulate-events.com/getdata.do?source=3&id=23)

Lonewolf_50
27th Jun 2012, 15:22
yes, probes, strength of materials is an important factor. That said, he has in the early third of the slide show an analysis of the comparative strengths of the aluminum and the wood.