NIST's Cases

[Kevin Fenton]

According to the NIST computer simulation and its best estimates should the towers have fallen over at all?

NIST considered two variants (which it calls cases) for each tower. The cases are known as A and B for the North Tower and C and D for the South Tower. Cases A and C are known as the base cases – they represent NIST’s best estimates about the various factors which affected the collapses, for example the amount of combustibles in the towers, although there is reason to believe that some of these numbers are high-end estimates. Cases B and D represent NIST’s best estimates of the factors increased by a few percent to make the computer model produce more damage and instability. For example in Table 6-4 on page 106/160 we can see that NIST thinks United 175 hit WTC 2 at 542 miles an hour (plus or minus 24 mph). On page 107/161 in Table 6-5 Input Parameters for Global Impact Analyses we can see that this speed was used in Case C (base case), but Case D (severe case) used a speed of 570 mph, even though NIST clearly thought the plane was travelling at a lower speed. Table 6-5 also shows that some other parameters were altered to increase the amount of impact damage, for example the weight of both planes was increased by 5%. In Table 6-6 Values of WTC Fire Simulation Variables, NIST increased the tenant fuel load for cases B and D by a whole 25% (from 4 lb/ft2 to 5 lb/ft2), in addition to other unjustified alterations to make the fires in the simulations worse.

Further, the NIST subdivided each case into impact damage and thermal loads sections. So you can combine, for example Case A impact damage with Case B thermal loads and vice versa. This gives us four options for each tower (for example AA, AB, BA and BB for the North Tower). Again I would emphasise that Cases AA and CC represent NIST’s best estimate of the factors influencing the tower’s performance.

What happened when the case factors were fed into the model?
“In WTC 1, the core was stable under Case A (base case) impact damage, but the model could not reach a stable solution under Case B (more severe) impact damage.”
“The WTC 1 core became unstable under Case A impact damage and Case B thermal loads as it leaned to the northwest (due to insulation dislodged from the northwest corner column); the core model was restrained in horizontal directions at floors above the impact zone half way through the thermal loads.” (Page 99/153)

But what happened in Case AA? If NIST’s best estimates were correct, should the North Tower have fallen over at all?

OK, does the South Tower look any better?
“The WTC 2 core was stabilized for Case C (base case) by providing horizontal restraint at all floors representing the restraint provided by the perimeter wall to resist leaning to the southeast. A converged, stable solution was not found for Case D (more severe) impact damage.
The WTC 2 stabilized core model for Case C impact damage was subjected to Case D thermal loads.” (Page 99/153)

I should point out that Case C impact damage includes 5 severed core columns and four heavily damaged ones – this was the lowest estimate they considered. (Page 113/167)
Again, we have to ask what happened in case CC? According to NIST’s best estimates, should WTC 2 have fallen down?
The sentence, “The WTC 2 stabilized core model for Case C impact damage was subjected to Case D thermal loads” begs the question ‘What happened then? Did the building fall over or not?’

Why Is NIST Using Severe Cases Anyway?
Shouldn’t it just use its best estimates and then call it as it sees it?
NIST argues that Cases B and D better produce on the computer the phenomena that were observed in real life, so they should be used in preference to Cases A and C, even though NIST thinks that A and C are theoretically more accurate. However, this is not entirely true, for example on page 114/168 it describes the agreement between the computer model simulation for Cases A and C impact damage and the photographs of the damage and says that the “overall agreement with the observed damage was very good. The agreement for Cases B and D was slightly lower.”
NIST says that some of the other factors, for example the debris that were ejected from the buildings, indicate that Cases B and D are better matches, but, for example, when Case D impact damage was first run, the starboard engine of United 175 did not even penetrate the building (it must have hit a floor slab), forcing NIST to “tweak” Case D to get the starboard engine to pass through the tower. Would it not be also possible to “tweak” Cases A and C to get the debris to emerge, thus making them better matches?

I cannot help but feel that the most important phenomenon from NIST’s point of view that Severe Cases B and D match, but Base Cases A and C do not is the actual collapse of the buildings.

It seems that, based on NIST’s best estimates (AA and CC), the towers should not have fallen down. But they bumped the numbers up by a few percent and ‘persuaded’ them to go.

[pox americana]

1. This is to make us think it was close. It wasn't.

The NIST report is full of phony assumptions passed off as fact, like those "bracket clips," which totally misrepresent how the floors were attached to the columns. And who knows what's in their computer "model."

Meanwhile, Enron continues to show record profits for investors...

[hack89]

2. I guess that's why every engineering society in the world..

is vocally criticizing the report, its methodology and its results!

You do realize that the NIST report is a draft that was posted for public comment, don't you? Have you given your comments to NIST?

[janedoe]

3. Funny that you mentioned that. Why would NIST ask for public comments?

Why would NIST ask the public for help in finishing their report? What does this say about their competency?

Is it that they don't trust their abilities and are asking for help?
Are they that incompetent?
Or... perhaps they are trying to test just how much they can get away with?

The CAIB took about 6 months to research the cause of the Shuttle disaster, write the report, and publish it -- and without asking for public "approval" for their final report. Public comments were requested in the early part of the investigation. Also, the public's help was requested in gathering evidence, such as the scattered debris. But, unlike the NIST "investigation," the CAIB investigators borrowed video recorded by the public, made copies, and returned the camera and video back to the owner! (Imagine that!)

The CAIB didn't publish a "draft report" and ask the public if they were on the right track, or even to check their numbers!

In view of what the CAIB did, the NIST investigators look unbelievably incompetent.

[petgoat]

4. A discussion period is only courteous, since their findings contradict the

prevailing MIT theories.

MIT/Eagar said the external truss "clips" failed and the external
columns, deprived of their lateral support, buckled outward. This was
the dogma for three and a half years.

Now NIST says the external truss "clips" are sooooooooo strong, that
sagging floors from fire damage pulled the external columns inward and
buckled them.

I can't wait to see if MIT defends its theories. Or will they just roll
over and show their belly to Authority?

And given that every piece of steel had a stamped ID number, why wasn't
the buckling issue settled with crash-zone steel samples long before
today?

[hack89]

5. They haven't so far..

so I guess its safe to assume they concur.

[petgoat]

8. " safe to assume they concur."

If their information was so wrong that they said the external clips
failed and the external columns buckled outward, do they just accept
that the real information says the clips held and the trusses buckled
inward, and accept without complaint the proposition that they got bad
information and NIST got reliable information? Don't you think that's
wierd?

[Kevin Fenton]

9. Obvious

If it's so obvious that the fall of the towers was not caused by explosives, how come the engineering/scientific community can't agree why they fell?

There's been all sorts of theories: trusses, columns, angle clips, pancakes, zippers and God knows what else. Why can't they agree?

[petgoat]

10. "Why can't they agree?"

I am very curious to see whether the MIT contingent defends its theory
or simply bows to NIST's authority. But more important to me than the
conflicting theories is the deliberate destruction of evidence--at the
orders of a former federal prosecutor who should have known better.

[hack89]

11. Perhaps because there are so many possible causes..

that don't require explosives. You have hit on the key point - no one has listed explosives as a plausible cause.

[petgoat]

13. "there are so many possible causes.."

Right, but the fact that one requires spectacularly weak external truss
"clips" and the other requires spectacularly strong ones is an
indication that even the officials are speculating becauese they don't
have the data they need--for instance the blueprints are suppressed and
the steel was destroyed.

[hack89]

16. But not one is even considering explosives..

which is a telling statement. They have access to all the same "convincing" videos and photos that you have and no one agrees with you.

[petgoat]

17. Van Romero said it looked just like a controlled demolition. He

offered the opinion that fire could not have brought the towers down.
A week later he changed his mind about the fire, but he never changed
his mind about the fact that it looked just like a controlled
demolition.

Did NIST test their steel samples for explosive residue? Why not?
Was the FEMA Appendix C metallurgical study continued? Why not?

[hack89]

18. One guy who later recanted...

not the strongest case you must admit.

[petgoat]

21. Did you even read my post? Van Romero recanted his opinion that

fire could not have brought down the towers. He never recanted his
opinion that it looked just like a controlled demolition, and never
recanted his opinion that it would not take a whole lot of explosives to
do the job.

[hack89]

31. Are you sure?

"Certainly the fire is what caused the building to fail," said Van Romero, a vice president at the New Mexico Institute of Mining and Technology.
The day of the attack, Romero told the Journal the towers' collapse, as seen in news videotapes, looked as though it had been triggered by carefully placed explosives.

Subsequent conversations with structural engineers and more detailed looks at the tape have led Romero to a different conclusion.

Romero supports other experts, who have said the intense heat of the jet fuel fires weakened the skyscrapers' steel structural beams to the point that they gave way under the weight of the floors above. That set off a chain reaction, as upper floors pancaked onto lower ones.
Romero said he believes still it is possible that the final collapse of each building was triggered by a sudden pressure pulse caused when the fire reached an electrical transformer or other source of combustion within the building.

But he said he now believes explosives would not have been needed to create the collapse seen in video images.

http://www.public-action.com/911/jmcm/ABQjournal/

[stickdog]

47. Yes, it's certainly telling. What it tells us is that only certain flavors

of blind speculation have been allowed at the "scientific investigation" table.

I'm still waiting for you (or NIST or MIT for that matter) to produce a SHRED of hard physical evidence that ANY pieces of ANY WTC tower were heated enough before collapse to cause significant weakening of ANY steel support structure.

[Kevin Fenton]

23. Perhaps?

Do you think there were or weren't "so many possible causes that don't require explosives" or not?

How come the experts all contradict each other? For example some think the angle clips were the weakest part and failed first, whereas others think they were real strong. There's no consensus in the scientific community about what happened and that's one of the reasons I have a hard time accepting it was a "natural" collapse.

The NIST report was supposed to end the debates, but some of its numbers are so bad you could call them fictional. How come in Cases B and D they added 15 tons of combustibles to each fire-affected floor? These combustibles weren't there, as NIST found, so what's the point of adding them in the model?

[hack89]

24. Before the investigation and modeling, etc...

there were many possible theories put forth. Through collaborative government and academic studies these theories were tested and the most likely cause was determined. You do understand the scientific method don't you? Show me a lack of consensus now.

All I see is untrained amateurs like you questioning the numbers - that leads me to believe you are simply unfamiliar with engineering studies and models. Show me a valid criticism from real engineers and we will take it from there.

[Kevin Fenton]

25. Criticism

A criticism is valid if it's valid, no matter who makes it.

NIST says:
"NIST estimated the fuel loading on these floors to have been about 4 lb/ft2 (20 kg/m2), or about 60 tons per floor." (Page 76/130)

My question to you is, what was the fuel loading on the floors? Do you agree with the above quote, or disagree with it? Why?

[hack89]

30. You are wrong...

if you do not have the education and/or experience to evaluate the situation. We are talking about a very technical field - how can a non-engineer offer anything else but a superficial analysis? How are you able to determine the validity of a technical criticism?

As for the fuel loading - fire prevention is a science with decades of data, observations and experiments. Look here for info on fuel loading in office buildings:

http://fire.nist.gov/bfrlpubs/fire96/PDF/f96080.pdf

Unless you can show that the WTC office buildings were radically different from a typical office building, I think you either have to accept the NIST figures or find some other source. When you consider that NIST has always been responsible for determining fire safety and building standards I would put my money on NIST.

[Kevin Fenton]

32. Do you agree with the NIST estimate or not?

I asked you a straight-forward question. Do you agree with the quote on page 76/130 that the fuel loading of the two towers was about 4 lb/ft2 or not?

If you don't want to say why, a simple "yes" or "no" will suffice.

[hack89]

33. I was trying to let you study and learn something..

if you had read the NIST fire loading studies you would understand why yours is an unnecessary question as it is obvious that NIST's estimates are well within the measured norms for office buildings. Believing that NIST is an organization that has studied fire safety and science for years, I have no technical reason to question their figures.

[Kevin Fenton]

34. You are so gracious

Can I take that as a yes?

The 4 lb/ft2 is only an approximate figure. How approximate do you think it is, for example if I ran the NIST model with a value of only 3 lb/ft2 and the towers didn't fall down, would this be meaningful, or would the deviation (-25%) be outside what I'll call "reasonable limits"?

[hack89]

35. You seem much more knowledgeable about modeling then me..

so perhaps you can tell me. My entire point, if you haven't figured it out yet, is that neither one of us is capable of questioning the NITS report on technical terms. I'm sorry but your views are not convincing as they are not backed up any in depth insight into the subject - all you have is questions which in and of themselves prove nothing. The minute you are backed up by a competent engineer or scientist then I will be willing to entertain the thought that you have something. Nothing personal you understand.

[Kevin Fenton]

46. I'll ask again

If I ran the NIST simulation with a figure of 3 lb/ft2 of combustibles in the WTC (instead of the 4 lb/ft2 NIST claims) and the towers did not become unstable, would you accept this as evidence that NIST's theory about why the towers fell may be incorrect or would you say, "You can't alter it by 25%, that makes it meaningless."

My entire point, if you haven't figured it out yet, is that both of us are capable of questioning the NIST report to a certain degree. I have to admit defeat at a certain point, but that doesn't mean I don't understand it at all or that I shouldn't try.

[stickdog]

49. Anyone with a brain can see that NIST's theory is based on

ZERO pieces of hard, physical evidence.

ZERO.

And you find that impressive?

[stickdog]

48. Where is a SHRED of hard physical evidence supporting the

ridiculously contrived theories you laughably call "scientific"?

Please produce some actual EVIDENCE or kindly restrain your indefensible enthusiam.

[hack89]

6. Nice evasion..

no one has criticized the report to date - if they don't I guess it is safe to assume the engineering community has no problems with it.

[pox americana]

7. It's never safe to assume.

Here's why: it's unwise to kill the goose that lays the golden eggs, in this case, the federal agencies that sponsor all those grants, research projects, cushy jobs, conferences, publications, etc etc.

Recall that the "financial community" didn't exactly blow the whistle on Enron either, at least until after it stopped laying golden eggs.

[hack89]

12. So French, Chinese and Russian engineers...

depend on federal funding? How are they being kept quiet?

[pox americana]

14. Do you read French, Chinese, and Russian journals?

How would you know what they're saying? Or are you waiting for Fox News to let us know if they raise any objections?

p.s. if you really care what the rest of the world is thinking, start by reading some German journals, or Arabic.

[hack89]

15. So the French, Russian and Chinese press would ignore..

an major story like this? Wouldn't it be big news?

Are you saying that German and Arab engineers are disputing the NIST report - if so do you have a link?

[hack89]

19. What about all those retired American engineers...

who are no longer on the federal gravy train? How are they being kept quiet?

[pox americana]

36. Why don't you ask some, instead of making a lot of ridiculous assumptions?

Assuming that because no engineers have personally contacted you the NIST report must be accurate amounts to faith-based denial.

[hack89]

37. No...

it is clear that no engineer disagrees with the NIST report because you have been completely unable to find one.

My assumption is very simple: the NIST report is good science and there is no significant disagreement in the engineering and scientific communities.

Your assumption, on the other hand, is the the US government has coerced almost every engineer in the world to ignore a blatant whitewash that is clearly poor science. And your proof is exactly the same as mine - no one is stepping out to question the NIST report!

Don't you find it curious in this age of digital anonymity, not a single leak has come out of NIST? There are a lot of Clinton era scientist working there - won't they be inclined to undermine a neocon plot? Do you really believe that everyone at NIST is so cowardly as to allow themselves to become complicit in mass murder? You have such a dark view of mankind that I cannot accept - I have to believe that most men and women are moral and good.

[pox americana]

38. Yes, I understand that you "cannot accept" what you wish weren't true.

I wish it weren't true too. But here's were we differ: I don't care what other engineers say or don't say because I can do my own analysis of the available evidence, which is manifest, and it's entirely consistent with explosive demolition.

On the other hand the collapse theories produced by the brand-name yahoos you put so much faith in, or as you put it "the engineering and scientific communities," are absolute bad-faith hogwash. Period.

[hack89]

39. But what are your qualifications?

you have displayed absolutely no knowledge of in depth engineering concepts. Why should your opinion matter one iota to me? I have no problem with you expressing an opinion - what I object to is the attitude that every opinion is created equal and I cannot question it. You are a liberal creationist - holding your opinion in the face of overwhelming opposition from the scientific community.

[pox americana]

40. Reread my last post until you understand it. I don't think you did. n/t

[hack89]

41. No I understood it very well...

you have made up your mind and nothing will change it. Have a good evening - bye.

[pox americana]

42. My judgment is based on evidence, yours is based on propaganda.

Big difference.

[hack89]

43. If you say so. n/t

[Make7]

44. But what are your qualifications? ( n/t )

[pox americana]

56. A pair of eyes is all anybody needs. (n/t)

[stickdog]

50. I guess nobody at the Pentagon has a problem with neocons,

either, right?

And the fact that "no one" questioned that the sun revolves around the earth for about 1000 years made that theory unassailable, right?

[hack89]

55. True but completely irrelevant...

why are you so evasive? A simple answer for a simple question is all I am asking for. But that's the rub isn't it? The entire engineering and scientific community appears to reject your position and you have no recourse but to put out a smokescreen to try to deflect and distract. Good effort but it didn't work.

[stickdog]

58. Just because doubts aren't highly publicized doesn't mean

they don't exist.

What would any engineer or scientist have to gain by drawing attention to fact that NIST's report is questionable, shoddy and highly speculative?

[LARED]

20. You used the word estimate 10 times in your post

That is an important clue to understanding modeling. No one know precisely what happened in the towers. The models are used to develop insight into how the towers likely collapsed in order to determine ways to make buildings safer.

No one, when the model fails to simulate the observed collapse under a given set of conditions is scratching their head thinking maybe some one planted explosives because I have to tweak a variable or two a few percentage points. They know the base conditions are an estimate and as such know that the real life various variable interact in ways not entirely predicable, which is one reason they need to tweak the model.

The towers were incredibly complex from an analytical perspective. The collapse variables are manifold. Also everyone that has ever build designed or analyzed anything remotely complex know the theoretical and the practical are seldom a perfect match.

[Kevin Fenton]

22. Best estimates

My argument is that NIST should use its best estimates, especially for the things it can objectively verify. It didn't. It seems that when NIST input its best estimtes the towers didn't fall down, so it altered its estimates to make the towers unstable in the models. This is cheating. There is a good argument for using a case-based approach, but such an aproach is only valid when applied to "unknowables" such as the distribution of combustibles from the plane, the degree of rubblization of combustibles in the towers, etc. It shouldn't be applied to knowables like the angles the planes hit, their speed, the amount of combustibles in the towers, etc.

If NIST had come out and said, "We don't really know why the towers fell over, they're really complex and we just can't figure it out based on the extermely small amount of evidence we have. How the hell are we supposed to estimate fire temperatures based on photos and videos?" then I'd respect them. They didn't, their conclusions are bullshit and their methodology is duplicitous.

How can they justify altering the plane speeds? They were determined using the video analysis. You can find my post on the plane speeds here: http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=125x53659

[LARED]

26. That's why it's called modeling

My argument is that NIST should use its best estimates, especially for the things it can objectively verify. It didn't. It seems that when NIST input its best estimtes the towers didn't fall down, so it altered its estimates to make the towers unstable in the models. This is cheating.

No, that's not cheating. That's called modeling.

At the end of the day you have two choices if your model does not behave as expected.

You tweak the variables to see if changing them can get your expected outcome (within reasonable parameters). Or you go back and redo the model. It is obvious to me (and seemingly the engineering community at large) that the model was close enough to meets it purpose.

The purpose of the model is what drives these decisions. The purpose of the model is to find out likely failure modes to improve building designs in order to make buildings safer. It is not to indulge in the fantasies of a extremely small group of people that believe the model should show the towers could not fail without a controlled demolition

[Kevin Fenton]

27. Tweaking variables

Whether it's cheating depends on what you are altering and by how much.

If, for example, they had doubled the planes' speed or said there were only 20 core columns in each tower, then this would be a clear case of cheating.

If NIST had merely altered by a few percent a few "unknowable" parameters like the degree of rubblization of the combustibles or where the fuel was spilt, then I would accept that as a fair use of modeling.

However, whilst I think it is obviously acceptable for NIST to model, the way they do it is (in many cases) improper. My argument is that many of the tweaks are not "within reasonable parameters". For example, the plane speed (of United 175) in Case D is 570 miles an hour. The plane speed can be determined from the video evidence and it isn't 570 miles an hour. IMHO it's approx. 500 mph. This has a knock-on effect in the form of how many core columns are damaged and severed. If I took the model, input a plane speed of 430 mph into it and the South Tower didn't collapse because, say, only 1 core column was severed, would this outcome have any probative value, or would it be meaningless?

What is "within reasonable parameters"?
I think it depends on the variable being measured.
Some numbers cannot be legitimately altered at all, for example the wingspan of the aircraft, the height of the towers, etc.
Some numbers cannot be known precisely, but a central figure and a range (plus or minus, say, 5%) can be estimated. Here, the plus or minus range tells us what the reasonable parameters for tweaking are.
We don't really have a clue about some numbers (like the distribution of combustibles from the plane, which is too complicated to be accurately simulated on computer), so any reasonable estimate can be taken and the plus / minus range has to be a lot larger here.

In your opinion, how many core columns were severed in the South Tower?

[LARED]

28. Can you clarify something

Is your concern really over a 4 MPH difference?

For example in Table 6-4 on page 106/160 we can see that NIST thinks United 175 hit WTC 2 at 542 miles an hour (plus or minus 24 mph). On page 107/161 in Table 6-5 Input Parameters for Global Impact Analyses we can see that this speed was used in Case C (base case), but Case D (severe case) used a speed of 570 mph, even though NIST clearly thought the plane was travelling at a lower speed.

542 MPH +/- 24 is 518 on the low end and 566 on the high end. They used 570 to create a collapse. This strikes me as being well within good engineering judgement for tweaking a parameter and hardly can be called cheating.

Is this your concern or have I missed something?

[Kevin Fenton]

29. Not just one variable

I think United 175 was travelling at 500 mph and I give my reasons here:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=125x53659
The difference between what I think and Case D is therefore 70 mph (14%). I don't think that is "within reasonable parameters". The difference between Case C (5 core columns severed) and Case D (10 core columns severed) is 5 severed core columns and I think that Case C is an extremely high-end estimate - I'd say United 175 severed 2 core columns (+/-2) - what would you say? Are you happy with 10 core columns?

Also, it's not just the plane speed, it's other variables as well - the vertical approach angle, plane weight, plane failure strain, tower failure strain, live load weight and contents strength were altered in Cases B and D, sometimes by as much as 25%. In every single case they were "tweaked" to make the towers more unstable in the model. If they'd only tweaked a couple of them by 5% of so, I wouldn't bother, but all of them, and by so much?

A similar criticism can be made of the fire simulation variables, which you can find in Table 6-6 on page 124/178.

[stickdog]

51. Where is the HARD EVIDENCE? Did NIST have the fucking debris

to examine or not? If not, why not? If so, why did they rely on inaccurate estimates and ridiculously strained models rather than hard physical evidence?

Finally, why doesn't a shred of the physical evidence that they did examine confirm their completely speculative modeling?

[LARED]

52. Is inaccurate estimates

an oxymoron?

Also what in the world is speculative modeling and how is it somehow complete?

[stickdog]

53. It's telling that you choose to linguistically deconstruct my

questions rather than answer them.

[hack89]

54. I think he is politely telling you that you make no sense n/t

[petgoat]

57. stickdog makes perfect sense.

To estimate the distance from NYC to Omaha at 1300 miles when the
available evidence says it's 1269 miles is an accurate estimate. To
estimate the distance at 3000 miles when the available evidence says
it's 1269 miles is an inaccurate estimate.

None of the NIST core steel shows heating above 250 degrees C. Of all
the perimeter steel, less than 1% shows heating above 250 degrees C.

stickdog is complaining that the steel samples do not support NIST's
estimates and computer models, and questioning why not. Given that
the steel was all numbered, why didn't they pull out the pieces from
the strike zone that showed what happened? How did they miss it and
let the steel be shipped away to recycle? Or must we pose yet another
"incompetence theory" to explain the investigation?

[philb]

45. The majority of firemen at WTC in position to observe the "collapses"

observed explosions or thought explosions were involved. They seem to have had a lot of propaganda and pressure to overcome in supporting their observations and impressions of 9/11, but many still reported what there was clear pressure not to report.
And what was the reason that the firemen statements were suppressed?
and not taken into account or followed up on by 9/11 commission?
Similar for the suppressed NY Police statements.
Why did it take a FOIA suit to get them released?

See firemen statement thread or
http://www.flcv.com/firemen.html
http://www.flcv.com/nypolice.html

Is N.Y. considering an investigation of all these reports? If not, why not? how much evidence does it take to result in investigation?

Its clear there has been major suppression of evidence, no legitimate independent investigation of events and causes, and a major cover-up by 9/11 Commission.
http://www.flcv.com/coverup.html