NIST Petition Demands Corrections

[Mancman]

First of all, that's not formed as a question.

But I'll make what I can out of it.

Okay, some facts first from the NIST Report;

Partial main landing gear (tire, wheel, brake assembly and hub) exited WTC 1 at an estimated speed of 105 mph after breaking through the opposite perimeter wall.pg344 NIST NCSTAR 1-2B, WTC Investigation.

Another piece of landing gear debris, (from WTC 1) shown in Figure 9–123, was found embedded in what is postulated to be the panel containing columns 329, 330, 331, running from the 93rd to the 96th floors.

As little other damage had been documented on the south face of WTC 1, it is postulated that the landing gear debris that landed at the corner of Rector St. and West St. also exited through this panel location.
pg344-45 NIST NCSTAR 1-2B, WTC Investigation.

So, NIST is saying we are dealing here with 2 separate pieces of landing gear debris exiting the WTC 1.

They are postulating that the piece shown in the photograph of Figure 9-123, removed the perimeter panel containing columns 329, 330, and 331.
Based on limited damage documentation for the south face of WTC 1, they are then postulating that the partial main landing gear (tire, wheel, brake assembly and hub) noted first, exited through the opening created by the panel removal.

Do you understand yet?

As already noted, the partial main landing gear (tire, wheel, brake assembly and hub) exited WTC 1 at 105 mph and as NIST acknowledges, it was not the same landing gear debris you are arguing took out the perimeter panel containing columns 329, 330, and 331.

Do you understand yet?

Thanks for answering.

But you totally missed the point I made and just posted some excerpts from the report which I have read numerous times.

The landing gear was captured in the core in the simulation, but other heavy debris hit the south wall. In reality, the situation was reversed. Ie. the debris that hit the wall in the simulation would have damaged the core in reality. Thus the landing gear exit is inconsequential because the damage is equal overall.

Simple as.

Moving on to your other previous question that I lost in the flood.

I can see now that I probably skipped your question because I thought I had adequately responded to it in previous replies to other posts, and indeed you quote the answer in this post you want answered.

NIST admits that minor aircraft entry corrections would significantly improve the match with the video and photographic record.

"None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower. However, the impact behavior suggests that only minor modifications (lowered 1-2 ft.) would be required to achieve this response." NIST NCSTAR 1-2B, WTC Investigation pg353.

I actually said in my post that you cannot swap the narratives for the WTC1 landing gear and WTC2 engine around like that. The situations are very different. You've done it again.

All I was looking for was the admission that NIST may well have to produce an ungodly number of simulations to get the landing gear to exit WTC1. And that conducting that many would be ridiculous based on the path of landing gears in a highly complex event.

Obviously, the landing gears would have been negotiating much more structure than the WTC2 engine, and many more simulations would have to be run to perfectly match reality.

Addressing your single piece of debris and it's importance to the validity of the NIST WTC simulation.

There is debris that is inconsequential and then there is debris that is quite consequential.

Most of each aircraft's non-fuel components were comprised of relatively weak materials that fragmented upon passing through the first perimeter wall. At high velocity, they sprayed the interior of each tower but were unable to focus enough energy transfer to damage the core columns.

The most damaging aircraft components were the heavy titanium steel engines and landing gear that would have remained largely intact after passing through the first perimeter wall of each tower.

The amount of damage they did to the core columns was critical to the collapse initiation outcome.

We know 2 separate pieces of landing gear debris exited WTC 1.


But the NIST Report states;
“No portion of the landing gear was observed to exit the tower in the simulations, but rather was stopped inside, or just outside, of the core.”
(NCSTAR 1-2B, p.345)

We know 1 separate piece of landing gear debris exited WTC 2.
We know an entire engine exited WTC 2.

But the NIST Report states;

“No landing gear debris exited the building in either the base case or the less severe simulations.” (NCSTAR 1-2B, p.353)

“None of the three WTC 2 global impact simulations resulted in a large
engine fragment exiting the tower.” (NCSTAR 1-2B, p.353)

So in both towers, we have these destructive titanium steel components from the impacting aircraft wrongfully doing damage in the NIST simulation, when in reality, they should not be involved.

The 2 aircraft effectively representied 8 major destructive components, 4 sets of landing gear and 4 engines.

The successful NIST collapse initiation simulations used all 8 destructive components in order to match what happened on 9/11.

In reality, only 4 of these destructive components should have been used in the simulation, 1 set of landing gear and 3 engines.

I hope you understand?

MM

The 2 aircraft effectively representied 10 major destructive components, 6 sets of landing gear and 4 engines.

The successful NIST collapse initiation simulations used all 10 destructive components in order to match what happened on 9/11.

In reality, only 6 of these destructive components should have been used in the simulation, 3 sets of landing gear and 3 engines.

It never pays to rush a reply.

MM

You can add the fuel to the list of major destructive components. Check NIST NCSTAR 1-2B to see the difference between an empty plan wing and a fuel laden plane wing hitting the building.

And no, the simulations did not use 'all 10 destructive components'. In the WTC2 simulation (more severe case) a landing gear exited the building within a couple of columns of where it exited in reality. It did not exit in the less severe or base case. It did not have any contact with the core.

Plus, the engine in WTC2 did not exit the building in the simulations, but it did not damage the core either. It was nowhere near it. By the end of the simulation it had slowed to under 100mph as it destroyed workstations.

So that's already down to 8, you say 6 should have been used. But it doesn't matter because, as has been stated several times to you, other debris capable of knocking free a south wall column panel in WTC1 (thus NOT lightweight, inconsequential debris) did indeed hit the wall and not the core, when in reality that debris would have damaged the core. So the situation is balanced. Easy

 

[Belz...]

So, which one of the three scenarios is a best fit, MM ?

 

[Miragememories]

Part 2

A continuation of my reply to R.Mackey.

Originally Posted by Miragememories
I think NIST definitely erred in using a homogeneous model. It unfairly describes the aircraft, and when combined with the model failing to confirm the only major observable criteria, the exiting engine and landing gear, it raises justifiable concerns when only their extreme case scenario succeeded in a collapse initiation.

Several problems with reasoning here as well, all of them brought up by me as early as the first page of this thread.

NIST had no choice but to use a homogeneous model. We accept and declare this as a limiting assumption. I note that your early complaints did not include this, but rather you are echoing my acknowledgement of it.

Regardless, whether or not that assumption is a flaw depends on a sensitivity analysis of the results. This is precisely why NIST ran three cases, and varied the ductility of the aircraft considerably (+/- 25% in the case of WTC 1) to see the effects. What they found was that ductility had only a minor effect on the overall results. The damage in all three cases is driven by the pitch angle of the aircraft, and other factors such as speed, weight, and material strength have only a slight effect. This is evidence that, contrary to your assertion, the homogeneous assumption is valid. It does not introduce a significant amount of uncertainty when compared to the other, irreducible uncertainties in the model. I was surprised to find this, but I accept NIST's conclusion in this respect.

Another major reasoning error is that you refer to engine and landing gear exit above as "the only major observable criteria," which they are not. I explained to you at length in this post the wide range of selection criteria, and among them NIST considers the final disposition of engine and gear fragments to be a relatively (but not completely) unimportant observable.

And, as explained back on Page 1, recall that the non-exit of such components means they were stopped by the core, and that means the core suffered less damage than it did in reality. Therefore, any simulation that does not end with those fragments exiting stage right is an underestimate. This, again, biases us towards the more severe simulations. Yet somehow, you conclude the exact opposite.

Regarding "ductility", you are entitled of course to accept any NIST conclusion you wish. From my observations, it's primary relevance was the effect on the initial impact perimeter wall which I have the least issue with.

Regarding our disagreement about selection criteria, yes you did explain at length and I replied. I did reply here; http://72.32.2.238/forumlive/showthread.php?t=79311&page=10

This is how I addressed your point about "the wide range of selection criteria";

We have selection criteria;

: Impact on the outer walls can be substantiated by the
video and photographic record.

Agreed.

: Travel of debris through the structure.

Not substantiated by video or photographic record. Requires extrapolation based on "little hard data".

: Distribution of of aircraft debris and furniture after impact.

Not substantiated by video or photographic record. Requires extrapolation based on "little hard data".

: Initiation locations and spread of fires.

Partially substantiated by video or photographic record. Requires some extrapolation based on "little hard data".

: Total moment added to WTC 2 (WTC 1 was not filmed
with enough precision to estimate oscillation after impact).

Not substantiated by video or photographic record. Requires extrapolation based on "little hard data".

: Disposition of floor damage and bowing after evolution.

Partially substantiated by video or photographic record. Requires some extrapolation based on "little hard data".

: Evolution of the exterior after fire simulation.

Partially substantiated by video or photographic record. Requires some extrapolation based on "little hard data".

: Predicted collapse time of each tower.

Requires extrapolation based on "little hard data".

"And, as explained back on Page 1, recall that the non-exit of such components means they were stopped by the core, and that means the core suffered less damage than it did in reality."

No it means the in-the-simulation non-exit of such components means they were stopped by the core, and that means that in-the-simulation, the core absorbed these impacts and subsequent damage, while in reality, these components (3 landing gear and 1 engine) exited the towers, were never stopped by the core, and therefore, never damaged the core!

That reasoning of yours truly baffled me. Exiting debris indicates less core damage though an obvious increase in perimeter damage.

So to continue, a second into the approximately 3600 second and 4200 second aircraft crash to tower initiation collapse simulation timelines, for WTC 2 and WTC 1 respectively, the simulated core absorbs this additional damage and the rest of the running simulation's timeline deals with the effects of the tower fires on this impact damage that occurred in the first second.

If the simulated fires had been working on less simulated core damage, as they should have, in my opinion, less harm could have resulted than simulated fires working on more core damage.

If the simulation had been running on the less core damage scenario as it should, the towers would have either taken longer to reach collapse initiation, or they would have not reached collapse initiation at all. In either case, we would end up with results that would not agree with what was observed!

In light of the fact that only the most extreme case scenario reached a threshold that resulted in a simulated collapse initiation, the importance of additional simulated core damage that should not have existed in any of the case scenarios, is particularly significant.

To quote the NIST Report;

"The magnitude of damage to the core columns and core beams was important because this damage affected the residual strength of the tower. This strength was a critical input to subsequent structural stability and collapse analyses. The overall model for the core structure and calculated impact damage to the core is shown in Figure E–30. The figure shows that the core had significant damage in the region close to the impact point. The columns in line with the aircraft fuselage failed on the impact side, and several of the core beams were also severely damaged or failed in the impact zone."
pg.lxx NIST NCSTAR 1-2B, WTC Investigation

Originally Posted by Miragememories
I disagree that the jet fuel, even at 570 mph, as in the extreme case scenario, had enough concentratible momentum to cut the towers steel perimeter columns.

I'm not familiar with the word "concentratible" when speaking of momentum.

I disagree with your disagreement. The work of Purdue University confirms that, in aircraft impacts, the blow dealt by the aircraft structure is secondary compared to the effect of the fuel inside.

Furthermore, the NIST NCSTAR1-2B also discusses the fuel impact, in its simplified core analysis in Chapter 10. Please turn to the P-I chart, figure 10-5, on page 374 (180 of the PDF). The impulse provided by the fuel is seen to be enough to fail core columns, not just the weaker perimeter columns.

Unless you can support your disagreement, these analyses stand.

This thread is about the basis for the NIST Petition, and not a Purdue Petition or a Pentagon Petition.

Concentratible is a word of my own devising that merely refers to the ability to concentrate.

After penetrating the perimeter tower wall, where I agree it's momentum significantly effected that area of damage, the fuel inside the aircraft wings could no longer concentrate it's momentum behind the now shredded aluminum skin that previously 'contained' it. It would rapidly disperse and tend to splash against rather than damagingly pummel the core columns.

The fuel impact loads used in the above example were an upper bound on the damage that could be produced by the fuel at the core since the fuel was still assumed to be in a solid rectangular section at full density. In reality, the impact with the exterior wall broke up the wing structures, and the fuel cloud spreads out to some extent prior to reaching the core columns. The impact with the internal building contents also reduced the severity of the fuel impact at the core.
pg.376-77 NIST NCSTAR 1-2B, WTC Investigation

The comparison shows that an expanded fuel cloud did not produce sufficient loading to fail a core column with the exception of points close to the wing root at the highest impact speeds considered. A more realistic fuel cloud dispersion would have included lateral and longitudinal spreading, as well as removal of some fuel from the cloud as a result of impact with the outer wall and building contents. Under these conditions, it is expected that the fuel cloud alone would not be sufficient to fail core columns.
pg.376-77 NIST NCSTAR 1-2B, WTC Investigation

Hmm...sounds like NIST disagrees with you.

That argument may have merit when debating the downward forces acting on the towers at the point of collapse initiation but I feel it is less compelling when dealing with these lateral "slicing" forces.

As above, you have not supported why you find it "less compelling." NIST has described in detail why material strength of impacting materials is not the deciding factor. As shown above, the fuel itself, having virtually zero material strength, is capable of inflicting enormous structural damage.

Again, you've failed to prove that's true about the fuel!
Rather, the aircraft fuel SPH particles tended to bounce off of internal structures.The physics of fuel impact and dispersion in this type of impact event is complex and no appropriate validation data could be found. The fuel starts as a continuous fluid within the tanks and ends up distributed both on the tower structures and as small droplets that interact with the atmosphere surrounding the impact zone. No single analysis technique is currently available that can analyze this full range of fuel dispersion without significant uncertainties.
NIST NCSTAR 1-2B, WTC Investigation pg219

Originally Posted by Miragememories
Yes trajectory of course factors into what lines up with what, and therefore will determine where the relatively clear paths to the exit perimeter wall lay. The major stopper for large, heavy, materially strong objects prior to a clean exit, is of course the heavy steel core columns. Certainly they had the capacity to stop engines and landing gear, while obviously sustaining significant damage to themselves in the process. The fact that a jet engine and landing gear did in fact break through the opposite steel perimeter walls and exit the towers at over 100+ mph indicates a lot of core damaging aircraft components failed to do what the NIST simulation indicates they must have done.

Emphasis added for clarity. That's exactly correct, but it supports my conclusion, not yours. The NIST less severe and baseline cases indicated the core columns etc. stopped those large fragments. Therefore, those cases either underestimated the severity of impact, or overestimated the strength of those elements. In either case, it means we must prefer the more severe simulations over the less severe ones. That's precisely what I've been saying this whole time.

One of us has a blindspot on this particular aspect of the simulation.

For the WTC 2 only! as you point out, we have;

extract "a chunk of simulated landing gear exited at a velocity higher than, but not impossible compared to, the estimates of the real event (230 MPH simulated vs. 102 MPH estimated real-world, pp. 350-351 or 155-156 of the part 2 PDF). There was no exit of landing gear in the baseline or less severe cases, though there was substantial exit of other debris in the baseline case."

A chunk? We've had particles, debris, partials, portions etc. and now we have a simulated 'chunk' of landing gear leaving WTC 2 at an estimated speed over twice that of the one that existed in the 'real world'; "A 'portion' of the landing gear of UAL 175 exited WTC 2 and landed on the roof of 45 Park Place.
pg352 NIST NCSTAR 1-2B, WTC Investigation

You are again ignoring the virtually complete engine or "large engine fragment" as NIST likes to call it, that exited WTC2.
NIST NCSTAR 1-2B, WTC Investigation pg359
Calling that damaged engine a fragment calls anyone's objective credibility into question?
“None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower.” (NCSTAR 1-2B, p.353)..calls again NIST's judgment into question when evaluating evidence.

For WTC 2, what we have is the less extreme, baseline and extreme case scenarios showing no engine components exiting WTC 2.

We have only the less extreme and baseline scenarios showing both no landing gear and no engine components exiting WTC 2.

In the extreme case scenario only, we have "a chunk of simulated landing gear exited at a velocity higher than, but not impossible compared to, the estimates of the real event.."

I guess you see this lone simulated "chunk" as like an escape valve that argues because the extreme case collapsed, even though it appears to simulate less damage than the less severe and baseline scenarios? Does this simulated "chunk" moving at a velocity over twice that of the observable, compensate for the damage difference expected between the 'less severe and baseline scenarios' and that injected by application of the extreme case's more severe parameters. If the simulated exit reduces the core impact damage load by say 5%, but from the baseline to extreme case scenario the core impact damage is actually increased by say 10% or more, then that would nullify this simulated chunk exit for WTC2.

For WTC 1, what we have is the less extreme, baseline and extreme case scenarios showing no landing gear and no engine components exiting WTC 1.

For WTC 1, the argument holds without the need to answer for any simulated exits.

Originally Posted by Miragememories
You are arguing energy totals as the key ingredient and I disagree. Certainly the total energy is something to be considered and given a large enough energy budget, the landing gear and the engines could be ruled out as inconsequential in the greater scheme of things.

I'm not saying the landing gear and engines are inconsequential. I'm saying they are indistinguishable in the model. Whether it's those specific fragments or other fragments, so long as the energy total is the same, we expect the model results to be valid.

Here I strongly disagree with you.

Don't you say in your next comment "The energy budget isn't really the issue, it's where that budget goes."

The NIST collapse initiation argument is based on 2 key energy-related events.

Impact Damage: Initially we have the energy transfer damage caused by the aircraft impacts on the towers.

Fire Damage: Followed and via a the slower energy transfer fire, weakened the steel which lead to NIST's collapse initiation belief.

Fire damage was critically dependent on the amount of impact damage, otherwise no collapse initiation. Therefore, since only the extreme case simulation of impact damage resulted in a successful fire damage collapse, any unwarranted impact damage was very significant.

As NIST has stated, "The magnitude of damage to the core columns and core beams was important because this damage affected the residual strength of the tower. This strength was a critical input to subsequent structural stability and collapse analyses"
pg.lxx NIST NCSTAR 1-2B, WTC Investigation.

Because the model mishandled these "non-inconsequential" aircraft components, the impact damage was simulated to be greater than it was, which improved the success potential for the fire damage.

I'm arguing, that total energy transferred to the effected parts of the building is less consequential in this situation (core damage), than how the total energy was parceled and focused throughout the effected parts of the building (core damage).

The core was much more vulnerable to the effects of the concentrated energy transfer of heavy titanium steel aircraft engines and landing gear than it was to that of the softer debris field represented by fuel, plastics, glass, aluminum etc. Granted that debris field had a large amount of kinetic energy, but it was more easily absorbed as it was dispersed against the heavy steel core columns.

I'll conclude this part 2 reply to the R.Mackey post here and continue with a final Part 3 posting when I have enough time.

MM

 

[Miragememories]

Repost of Part 1 Reply to R.Mackey

Quote:
Originally Posted by Miragememories.
Is a large mass supposed to equate to a unified mass or just a large accumulation of aircraft particles? By saying that with a few tweaks, within the margin of observational error, that the mass could be the landing gear, do you mean it could have the equivalent mass or actually could be physically characteristic of the actual landing gear? It's a very important distinction.

Originally Posted by R.Mackey
Because the model is homogeneous, actually there is no distinction. Nevertheless, the simulation suggests that moving the point of impact a few feet horizontally or vertically, which is well within the margin of observational error, would make it possible for the "actual landing gear" to break loose. This is what NIST is saying on page 343 of NIST NCSTAR1-2B (page 149 of the PDF). Also, consider the different engine trajectories experienced with only slight vertical changes presented in Figure 5-19, page 107 (page 203 of the first half PDF). This demonstrates quite clearly how minute changes of input conditions give rise to significant differences in the evolution of individual components.

I understand what you are saying. The problem is we share different levels of faith in the acceptability of the model and the validity of the allowances it permits.

Originally Posted by Miragememories.
Again I apparently misquoted you about massive chunks of aircraft. You are very easy to misquote unfortunately..or slippery.

Anyway, in the more severe case "chunks" of something, apparently from the aircraft, was comparable in size to the landing gear or a wheel and that for you, this was in excellent agreement.

Originally Posted by R.Mackey
That's correct. Because the aircraft model is homogeneous, the source location of an individual piece of debris is far less relevant than the total amount of debris that passes through the building. As you have argued yourself, the principal issue is one of energy transfer. Since the total amount of debris pass-through in the baseline and more severe cases plausibly matches the actual event, whereas the less severe case shows virtually nothing making it across the core, let alone the whole structure, NIST (and I) conclude that the less severe case is the worst fit out of the three cases.

Yes I've adopted energy transfer explanations, though I continue to disagree with how energy transfer should be expressed and applied to the simulation. You agree with NIST that the "less severe case" should be ignored because it is the "worst fit of the three cases" as it fails to plausibly match the actual event as well as the baseline and more extreme case simulations.
You support this by pointing to the TOTAL AMOUNT OF DEBRIS PASS-THROUGH as it matched the "actual event".
My problem with that argument continues to be the generalization of how debris is handled.

Since NIST was unable to make direct observations, and have no records of the actual internal damage for each tower, following the aircraft impacts and prior to collapses, there is no mechanism to validate that the simulation got it right other than it generates a successful collapse initiation.

Treating similar sized pieces of debris as equals ignores the significances that are characteristic of different types of debris.

Originally Posted by R.Mackey
In the case of the WTC 2 simulation, in the more severe case, a chunk of simulated landing gear exited at a velocity higher than, but not impossible compared to, the estimates of the real event (230 MPH simulated vs. 102 MPH estimated real-world, pp. 350-351 or 155-156 of the part 2 PDF). There was no exit of landing gear in the baseline or less severe cases, though there was substantial exit of other debris in the baseline case.

I was unable to resolve what you meant by 155-156 of the part 2PDF?

I noted that there is a significant uncertainty in this estimate associated with the exit trajectory, aerodynamic effects, landing position rather than final resting position of debris, etc. pg352 NIST NCSTAR 1-2B, WTC Investigation.

Back to your point though about, "there was no exit of landing gear in the baseline or less severe cases" BUT, in reality; "a portion of the landing gear of UAL 175 exited WTC 2 and landed on the roof of 45 Park Place.

This is the landing gear that you refer to in your 102 mph example above. Very ODDLY, "No photographic evidence was available to document the size of the fragment and whether this was a nose or main landing gear." pg352 NIST NCSTAR 1-2B, WTC Investigation. It seems very strange that NIST would not have a photograph, or any documented description of this landing gear debris, yet they were able to clearly identify it and document it's discovery in their Report?

We also have a complete engine that exited WTC 2.
The residual velocity and mass of the engine after penetration of the exterior wall was sufficient to fail a core column in a direct impact condition. liv NIST NCSTAR 1-2B, WTC Investigation.

Note that each engine weighs 5 tons!

Another interesting statement from NIST;

"Eyewitness accounts of damage to stairwells and visible floor damage were also significant as they were the only available data on the damage to the tower interiors. That these observables were in good agreement adds greater credibility to the predicted damage to the tower interiors."NIST NCSTAR 1-2B, WTC Investigation pg363

This calls into question how loosely they use the assessment of "good agreement!", since a few survivor eye witness observations regarding "stairwells and visible floor damage" hardly constitutes a broad base of observation made by structural experts. It suggests that NIST finds "good agreement" in observations that suit their needs.

Originally Posted by R.Mackey
Therefore, if we were to follow your line of reasoning, you must conclude that, in the case of WTC 2, only the more severe case fits. WTC 1 is still blurry by your standard.

No, I don't think that's established merely because you have roughly simulated a landing gear debris exit for WTC 2 for just the extreme case. The complete engine exit is still ignored. “None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower.” (NCSTAR 1-2B, p.353)

Quote:
It's important because particles or groups of particles would not be as significant as a large object known to definitely come from the aircraft. As we know, the only aircraft components capable of remaining relatively intact were the heavy steel components like the titanium engine and landing gear. The rest of the aircraft and it's contents, due to lack of material strength would have become part of the debris cloud.

Originally Posted by R.Mackey
There are several errors of reasoning here. First, there are other structures in the aircraft that are both massive and with high material strength, such as the main spar, the RAT, and primary oxygen supply.

Second, being massive and high strength did not guarantee that those components would exit intact -- between the two aircraft, we have a total of four engines and six sets of landing gear, out of which only fragments of two engines and one landing gear passed through clealy, with another main gear fragment getting wedged into the exterior columns before falling free.

Third, the strength of components is not the dominant factor in damage estimation, as we will revisit below. As a brief example that I explained to you before, liberated fuel did plenty of damage, despite having virtually zero material strength. Momentum is the key, momentum that cannot escape the impact zone simply because the event is so large and so fast.

You are again ignoring the virtually complete engine or "large engine fragment" as NIST likes to call it, that exited WTC2.
NIST NCSTAR 1-2B, WTC Investigation pg359

Calling this a fragment calls anyone's objective credibility into question?
“None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower.” (NCSTAR 1-2B, p.353)..looking at what they term as a fragment, calls again NIST's supposed unbiased judgment into question when evaluating evidence.

Three pieces of landing gear!

Regarding the landing gear that was embedded in the exterior columns of WTC 1 and then 'fell free' as you put it. This piece of landing gear debris, (from WTC 1) shown in Figure 9–123, was found embedded in what NIST postulated to be the panel containing columns 329, 330, 331, running from the 93rd to the 96th floors. pg346 NIST NCSTAR 1-2B, WTC Investigation
As you can see by the photo, it remained embedded, it took the panel with it during it's high velocity exit (otherwise the MIST postulation below would make no sense (supposedly, it cleared a path for the 105 mph landing gear behind it to exit). That would suggest it had to be the nose gear.

NOTE: postulate = suggest or assume the existence, fact, or truth of

As little other damage had been documented on the south face of WTC 1, NIST postulated that the landing gear debris that landed at the corner of Rector St. and West St. also exited through this panel location (as above, Figure 9–123). pg344-45 NIST NCSTAR 1-2B, WTC Investigation. Partial main landing gear (tire, wheel, brake assembly and hub) exited WTC 1 at an estimated speed of 105 mph exiting through the opposite perimeter wall. pg344 NIST NCSTAR 1-2B, WTC Investigation.

The obvious conclusion is; NIST is saying we are dealing here with 2 separate pieces of landing gear debris exiting with significant velocity from the WTC 1.

They are postulating that the piece shown in the photograph of Figure 9-123, removed the perimeter panel containing columns 329, 330, and 331.
Based on limited damage documentation for the south face of WTC 1, they are then postulating that the partial main landing gear (tire, wheel, brake assembly and hub) noted first, exited through the opening created by that panel removal.

A portion of the landing gear of UAL 175 exited WTC 2 and landed on the roof of 45 Park Place. No photographic evidence was available to document the size of the fragment and whether this was a nose or main landing gear. 352 NIST NCSTAR 1-2B, WTC Investigation

Regarding the impact potential of the fuel;
The analysis of the impact response of the aircraft fuel cloud had several limitations. Smooth Particle Hydrodynamics (SPH) was used to model the fuel in the impacting aircraft, and approximately 60,000 SPH particles were used for the approximately 60,000 lb of fuel in each aircraft. Therefore, the particle size in the fuel cloud was approximately one pound. The air in and around the towers was not modeled, so the deceleration of the fuel particles in the cloud by aerodynamic resistance was not included. The contact algorithm for the fuel particles and tower did not include a sticking or “wetting” behavior so the fuel particles bounce off of components in the tower. The results of these limitations would spread the fuel cloud over a larger region in the simulation. Finally, the deflagration of the fuel was not modeled, and the resulting dynamic over-pressures in the tower from the combustion process were not included in the analysis.
pg.196 NIST NCSTAR 1-2B, WTC Investigation.

The aircraft fuel SPH particles tended to bounce off of internal structures.The physics of fuel impact and dispersion in this type of impact event is complex and no appropriate validation data could be found. The fuel starts as a continuous fluid within the tanks and ends up distributed both on the tower structures and as small droplets that interact with the atmosphere surrounding the impact zone. No single analysis technique is currently available that can analyze this full range of fuel dispersion without significant uncertainties.
NIST NCSTAR 1-2B, WTC Investigation pg.219

The fuel impact loads used in the above example were an upper bound on the damage that could be produced by the fuel at the core since the fuel was still assumed to be in a solid rectangular section at full density. In reality, the impact with the exterior wall broke up the wing structures, and the fuel cloud spreads out to some extent prior to reaching the core columns. The impact with the internal building contents also reduced the severity of the fuel impact at the core. pg.376-77 NIST NCSTAR 1-2B, WTC Investigation

Fuel damage due to the added momentum it gives the wing, would do most of it's damage to the perimeter. After passing through the perimeter wall, the wing would be shredded and the rapidly unconfined fuel would disperse in a cloud that would tend to bounce off of most solid structural components.

I'll stop my post here and continue the reply in a fresh post.

MM

 

[Miragememories]

Part 3 Reply to R. Mackey

Hopefully this 3rd post will finish my reply.

Originally Posted by Miragememories View Post
The fact that the less severe and base scenarios failed to create a collapse initiation indicates there wasn't an overwhelming energy budget available.

Originally Posted by R.Mackey
No, it does not. The eventual collapse involved additional steps, simulating the fires and their effects on the structure. At this stage of calculation, NIST evaluated the less severe and baseline scenarios against other observable evidence, and found they were not the best fit -- independent of the ultimate finding of the investigation.

Additionally, as remarked above, the biggest factor in the simulation is the pitch angle of the aircraft. The energy budget isn't really the issue, it's where that budget goes. If the aircraft is pitched down, as in the less severe case, it expends too much energy on floor slabs, which reduces damage on core columns and doesn't match the clear pictures we have of sagging floors, damaged but still attached and contributing to the collapse. Also, as Dr. Greening calculated, the aircraft had sufficent energy to completely destroy (pg. 10-11) an entire floor's worth of core columns, had it hit with the right geometry and avoided the other energy sinks present.

The primary energy budget was expended in step event No.1, the aircraft impact into the towers. Once that was over with and the towers stood firm, collapse was strictly dependent on whether the subsequent fires could generate enough heat and distribute it sufficiently, to weaken the steel to the point of collapse initiation.

The other observable evidence that NIST "evaluated against the less severe and baseline scenarios, and found to not be the best fit", was the fact that they would not lead to the observed collapse of the towers.

Doesn't your earlier statement "Whether it's those specific fragments or other fragments, so long as the energy total is the same, we expect the model results to be valid." conflict with this statement; "The energy budget isn't really the issue, it's where that budget goes."??

Dr. Greening may be right about the aircraft arriving with sufficient total energy potential to completely destroy an entire floor of core columns BUT, and this is a point your argument seems to consistently ignore, the energy would require the guidance of artificial intelligence AI, to sufficiently parcel and focus itself against all the heavy steel core columns. So while Dr. Greening's math my work in theory, in practice it defies the laws of probability.

Originally Posted by Miragememories
The columns were vulnerable to focused energy and less vulnerable to dispersed energy of the same amount. Think of a karate chop. The same amount of energy delivered with the flat of the hand (large surface area) vs. the side of the hand (small surface area), when striking a board is going to produce two different results. I won't insult your intelligence by explaining that further.

Originally Posted by R.Mackey
If you were to concentrate the entire impacting energy of the aircraft into a single point, it would be certain to slice clean through the building, but that doesn't mean distributed forces can be neglected. It's not true. Distributed forces were responsible for nearly all of the damage to the core columns. Again, read Chapter 10 of NIST NCSTAR1-2B.

Because the aircraft was severely damaged on impact, there are few solid masses left to deliver these "concentrated" blows. Because few solid masses flew out the other side, and those that did were decelerated considerably, we conclude those masses delivered nearly all of their energy.

Focusing the entire impacting energy of the aircraft into a single point, would blow a hole through the tower based on the diameter of the concentrated energy necessary to overcome the obstacles in it's path. The hole's diameter would steadily shrink due to energy loss while advancing through the major building structural steel components.

FROM CH.10
These data show that a solid section of fuel directly impacting the core columns at 430 mph or above would cause failure. The fuel impact loads used in the above example were an upper bound on the damage that could be produced by the fuel at the core since the fuel was still assumed to be in a solid rectangular section at full density. In reality, the impact with the exterior wall broke up the wing structures, and the fuel cloud spreads out to some extent prior to reaching the core columns. The impact with the internal building contents also reduced the severity of the fuel impact at the core.
The comparison shows that an expanded fuel cloud did not produce sufficient loading to fail a core column with the exception of points
close to the wing root at the highest impact speeds considered. A more realistic fuel cloud dispersion would have included lateral and longitudinal spreading, as well as removal of some fuel from the cloud as a result of impact with the outer wall and building contents. Under these conditions, it is expected that the fuel cloud alone would not be sufficient to fail core columns.
pg.376-7 NIST NCSTAR 1-2B, WTC Investigation

Chapter 10 does not appear to agree with your statement.

Originally Posted by Miragememories
"Aircraft debris external to the towers (landing gear for WTC 1 and landing gear and engine for WTC 2) as documented by photographic evidence."
xc NIST NCSTAR 1-2B, WTC Investigation

NOT engine fragments but the whole heavy titanium steel engine!

Which only serves to support my contention that NIST over compromised their Model!

Originally Posted by R.Mackey
Again, backwards. If NIST had overcompromised their model, their model would predict more debris exiting the structure, not less.

How is it backwards?

I'll state this as simply as I can;

I realize this is far from a full parameter illustration but the point I feel is valid;

A REAL Scenario;

1) We take a simple cardboard box that is precut so that it is supported internally by a mass of evenly spaced wood columns.

NOTE: We'll label it WTC 1 (to avoid the issue of the simulated debris exit in the NIST extreme case for WTC 2).

2) We throw piece of wood with 5 loosely-held heavy metal fasteners at the box.
3) We observe the piece of wood is completely absorbed by the box.
4) We observe 2 of the metal fasteners break out the other side of the box.
5) We observe the box remain standing.
6) Done.

The MODEL Scenario;

1) We create a computer Model of the same box.
2) We throw a simulated board with 5 metal fasteners attached at the model at 3 different speeds.
3) When the simulation is run, we observe for all 3 speeds low, medium and high.
4) The board is absorbed inside the box for all 3 speeds.
5) None of the fasteners break out the other side of the box for any of the 3 speeds.
6) For the fastest throwing speed, we observe the box collapse.
7) We remove 2 of the fasteners, reset the Model and repeat the simulation with the 3 speeds.
8) The box remains standing for all 3 speeds.

CONCLUSIONS:

The Model was able to absorb the damage caused by the low and medium speed impacts with the board and it's 5 loosely-held heavy metal fasteners.

The Model was not able to absorb the damage caused by the high speed impacts with the board and it's 5 loosely-held heavy metal fasteners.

The Model was able to absorb the damage caused by the low, medium and high speed impacts with the board and it's 3 loosely-held heavy metal fasteners.

The Model erred in it's simulation of the board and it's 5 loosely-held heavy metal fasteners, which proved fatal in the high speed scenario.

If the Model had simulated the board ejecting 2 of the loosely-held heavy metal fasteners, as occurred in the REAL Scenario, it is concluded, that even in the high speed scenario, the box would not have collapsed.

It is also concluded that in spite of it's error in not ejecting the 2 fasteners, the Model was sufficiently robust to remain standing when subjected to the low and medium speed scenarios but this threshold was crossed when subjected to the high speed, extreme case scenario.

As I said, I realize this is not a legitimate illustration of the NIST Model, but I do feel it is a legitimate examination of the flawed logic in ignoring or dismissing the importance of the observed exiting of a heavy titanium steel engine and 3 separate sections of landing gear.

I get the impression that you are basing your belief that I have it backwards based on the perimeter wall exit damage?
If so, I don't consider perimeter wall damage to be anywhere near as important, as damage to the core which was responsible for the primary support of the building.

Originally Posted by Miragememories
A complete heavy titanium steel engine in the case of WTC2, not just fragments which only lessens the apparent significance!

Originally Posted by R.Mackey
Ditto.

It's "engine and gear fragments" when in your reference to them which appears to have the intended the effect of diminishing their importance while attempting to elevate the strength of the counter argument.

Originally Posted by Miragememories
Not a big deal? Malcontents? Excuse me for not rolling over and accepting every word of the NIST conclusions. The global results of the NIST simulations are surprisingly accurate? I guess accuracy is based on the fact that sure enough, NIST tweaked the extreme case scenario and sure enough the towers fell. just like in reality..case closed.

Originally Posted by R.Mackey
Again, the global results of the NIST impact simulations were compared to numerous observations, none of which was whether or not the towers fell. That conclusion depends on other, later scenarios.

We know they were limited in what they had for observables.

Originally Posted by Miragememories
I'm sorry, it doesn't matter if 9,999 pages of the report are true, if one page of critical flaws remain.

Originally Posted by R.Mackey
That depends, but thus far you have not demonstrated a single flaw.

Flaw: a mistake or shortcoming in a plan, theory, or legal document that causes it to fail or reduces its effectiveness.

I think I have clearly revealed how the NIST document is flawed.

Originally Posted by Miragememories
Which makes their results and conclusions all the more subject to question!
I hope I haven't distorted your quotes this time.

Originally Posted by R.Mackey
I have no issue with questioning the NIST results. I encourage it. What I am endeavoring to counteract are misunderstandings of what those results are, and the illogical conclusions drawn from this misapprehension.

A laudable goal as long as you haven't closed the door to the possibility that the misunderstandings might be your own?

Originally Posted by R.Mackey
As I have asked you repeatedly, and you still have not answered, one of the three cases is the best fit to what we observed. We need to select one before we can proceed. NIST selected the most severe cases and justified their choices. I agree with them. You have not disagreed, instead you reject selecting any of the three.

And as explained above, the final distribution of landing gear is not the only proven observable, nor is it even the most significant.

I did answer or is any answer that doesn't fit your rigid criteria a non-answer?

Originally Posted by Miragememories
I am well aware that there was a "cloud" of objects moving at high velocity inside the towers once the aircraft disintegrated after punching through the perimeter wall.

Just because I isolated the effect of one object, does not negate my point about deformation damage as invalid.

Some of the objects were trapped inside the WTC and some of the objects punched the perimeter walls, making high velocity exits, carrying their remaining destructive potential with them.

Diffused energy due to a high velocity spread of small, relatively soft particles is not going to have the potential for deformation damage that large relatively intact titanium steel jet engines and landing gear will.

Originally Posted by R.Mackey
Again, you state this from personal incredulity. It is not true. The majority of impact damage in the core was due to "diffused energy," essentially a pressure load on the columns themselves. This is because the aircraft almost completely shattered as it smashed through the perimeter columns.

I base it on what I know about the existing conditions and how forces normally should behave in under those conditions.

SOURCE?

Not about the aircraft shattering upon breaking through the perimeter, I agree that occurred. I have no support for your argument; "The majority of impact damage in the core was due to "diffused energy," essentially a pressure load on the columns themselves." I believe we already covered this earlier, but if you have better information than Chapter 10 which I discussed, I'd like to hear it?

Originally Posted by Miragememories
Focused energy is more damaging to the core than distributed energy.

Originally Posted by R.Mackey
It isn't in this case because the focused energy was a very small fraction of the total. Had the aircraft been unloaded, empty of fuel, etc., the significance of the landing gear and engines would have been greater.

Well we disagree about how the core was damaged and how much the core was damaged. I attribute the damage primarily to the result of stopping heavy, materially strong objects like the 3 titanium steel engines and 3 sets of landing gear.

It is not my belief that the core was ever sufficiently compromised to allow the post impact fires to deliver the death blow.

The NIST simulation made it so but it took extreme case parameters and the addition of an engine and 2 or 3 sets of landing gear to reach the collapse initiation thresholds.

Originally Posted by Miragememories
I won't argue that liquid moving at high speed carries significant mass and thus significant force, momentum and transferable energy. Since the bulk of fuel is carried inside the wings, it's impact force will be significantly spread out while being further lessened by contact with office components and interior walls. I really question how much impact damage the jet fuel had on critical building structural members.

Originally Posted by R.Mackey
The NIST report answers this question.

Yes they do, and they seem to agree that the primary fuel load damage was done to the perimeter wall.

Fill a bag with water and swing it against people and other objects and the momentum created is quite powerful and damaging. Once that bag ruptures, it's a completely different story.

Originally Posted by Miragememories
No doubt in the volume of posts I have omitted replys to some of your questions. If my answers are important to you, I suggest you re-ask or move on.

Originally Posted by R.Mackey
I have asked my questions several times. I am also quite aware that you have seen them, because you replied to both of them without giving me an answer. However, I sympathize with the sheer weight of this discussion, although you did ask for clarity and thoroughness, which I have now delivered. Let me then restate the question, carefully and thoroughly:

The NIST impact model, captured in NIST NCSTAR1-2, is principally concerned with the state of the core columns immediately following aircraft impact. This is because the perimeter columns were photographed, allowing a direct assessment of their status, whereas the core was impossible to inspect. To this end, NIST created a simulation of each impact. Each impact had multiple uncertainties with respect to the state of the aircraft and the relative strength of both aircraft and structure.

NIST therefore created three cases for each simulation. The baseline contained the best guess for all of the uncertain parameters above. The less severe case contained a reasonable lower bound (think of this as "one sigma") for all uncertain parameters. The more severe case contained a reasonable upper bound (except for WTC 2, it was forced closer to the baseline). The results from all three trials were compared against each other to ascertain sensitivity, and to the catalogue of observations to determine which was closest to reality.

Before proceeding, NIST had to decide which one was the best fit. In both cases, NIST decided the more severe case was the best fit, and furthermore concluded it was in acceptable agreement with observations.

Here's the question: Which one do you think is the best fit? And why? Like NIST, you must choose one, and only one answer.

Thank you for your careful attention.

Again you are asking me a question, that if pick one of only 3 choices, I'm forced to support a NIST scenario that I'm in the least disagreement with. That's a negative option. The NIST simulation is based on too many assumptions that involve more than just aircraft speed, weight and trajectory.

In particular, I disagree with their assumptions about complete removal of fire proofing and the extent severity of the fires.

I'll halt here and await the inevitable.

MM

 

[R.Mackey]

Again you are asking me a question, that if pick one of only 3 choices, I'm forced to support a NIST scenario that I'm in the least disagreement with. That's a negative option. The NIST simulation is based on too many assumptions that involve more than just aircraft speed, weight and trajectory.

You will note, of course, that nowhere did I ask you to support any NIST scenario. I merely asked you to indicate which of the results, in your opinion, was the closest match to reality.

Nonetheless, that's fine. I won't ask this question again. I will simply acknowledge that you decline to give any answer. If you change your mind in the future, please feel free to give us your thoughts.

---

Let me try a new tack. Judging by your last three (!) replies, it seems clear that you and I are discussing too many topics at once. Furthermore, I will be away from my computer until next Monday. So instead of issuing a monolithic reply addressing the great many areas where you need help at once, let me tackle only a single issue.

Please understand that I have not ignored anything you have thoughtfully written above, and you have my word that I will return to address all of them.

---

Underlying your entire body of commentary in this thread is one fundamental misconception, namely the significance of exit or non-exit of substantial debris. I first pointed this out on the very first page of this thread. This time, I'd like to go back to this issue and not leave it until we reach an understanding.

Please consider the following figure, which describes the initial conditions of WTC 1. I copied this figure from NIST NCSTAR1-2, figures E-25(a) and E-26(a), found on pages lxxvi-lxxvii or 78-79 in your PDF reader. I then added two sets of three parallel lines, as follows: The first parallel line passes through the nose and tail of the aircraft, and is meant to represent the initial trajectory of the three sets of landing gear, which will be slightly below and centered, left, or right of the dotted line. The other two parallel lines have been offset to overlay the engines, and represents their approximate initial trajectory. In the upper figure, you can see the geometry of the core columns, and in the lower figure you can see the core columns and bolted/welded floor beams indicated by darker shading.



In your Part 2 post above, you describe your understanding of these three components as follows:

No it means the in-the-simulation non-exit of such components means they were stopped by the core, and that means that in-the-simulation, the core absorbed these impacts and subsequent damage, while in reality, these components (3 landing gear and 1 engine) exited the towers, were never stopped by the core, and therefore, never damaged the core!

Now, here's my new question for you:

Consider my figure above. Please explain, in the real-world scenario, how either engine or any of the three sets of landing gear could possibly have entered the building at figure left, then exited at figure right, without damaging the core. Tell me how you think this happened.

Once I have your answer to that question, I should be able to pinpoint the source of this fundamental misunderstanding, and we can continue from there. Again, thank you for your careful attention.

 

[Mancman]

We also have a complete engine that exited WTC 2.
The residual velocity and mass of the engine after penetration of the exterior wall was sufficient to fail a core column in a direct impact condition. liv NIST NCSTAR 1-2B, WTC Investigation.

Note that each engine weighs 5 tons!

Totally irrelevant because the engine missed the core in the simulation. You keep going on and on about this engine. When will you realise that the only damage it did to the simulation was to the perimeter.

[/B]Regarding the landing gear that was embedded in the exterior columns of WTC 1 and then 'fell free' as you put it. This piece of landing gear debris, (from WTC 1) shown in Figure 9–123, was found embedded in what NIST postulated to be the panel containing columns 329, 330, 331, running from the 93rd to the 96th floors. pg346 NIST NCSTAR 1-2B, WTC Investigation
As you can see by the photo, it remained embedded, it took the panel with it during it's high velocity exit (otherwise the MIST postulation below would make no sense (supposedly, it cleared a path for the 105 mph landing gear behind it to exit). That would suggest it had to be the nose gear.

That might 'suggest' it to be the nose gear. But it isn't.

76 NIST NCSTAR 1-5A, WTC Investigation
There are two types of retractable landing gear on a Boeing 767-200ER, a single nose gear formed by a support strut holding two wheels near the front of the main body of the aircraft and two sets of main landing gear on the wings consisting of four wheels attached to carriages mounted to heavy support struts. The wheels used on the two types of landing gear have different appearances. By comparing the configuration of the wheel embedded in the steel panel section with photographs of landing gear for a similar Boeing 767 provided to the Investigation (NIST NCSTAR 1-2B), it was determined that the wheel came from one of the main landing gear. This conclusion is based on the number and placement of the bolts in the wheel hub.

NOTE: postulate = suggest or assume the existence, fact, or truth of

I'm sorry, do you have a specific issue with the postulations of the NIST regarding the column panel? There is certainly visual evidence for the panel between floors 93-96, columns 329-331 being knocked free:

As little other damage had been documented on the south face of WTC 1, NIST postulated that the landing gear debris that landed at the corner of Rector St. and West St. also exited through this panel location (as above, Figure 9–123). pg344-45 NIST NCSTAR 1-2B, WTC Investigation. Partial main landing gear (tire, wheel, brake assembly and hub) exited WTC 1 at an estimated speed of 105 mph exiting through the opposite perimeter wall. pg344 NIST NCSTAR 1-2B, WTC Investigation.

A key point you seem to have missed here is the word 'partial'. Partial landing gear. This has been pointed out to you on this thread and at LCF.

The only pieces of debris we are certain came out of WTC1:

The single wheel embedded in the panel:

Wheel with hub and brake attached, and a cylindrical piece of metal:

The cylindrical pieces resembles the diagonal structure:

And er...that's it. There could have been other pieces lying around but we will never know for sure. So what do have, 2 wheels, one we know had a brake and hub attached and a 6ft long piece of metal next to it.

That is well under half of one of the main landing gears. Throughout this thread you have tried to pass off this debris as 2 landing gears.

The report states that the landing gears are estimated to have weighed 8,400lbs total. How much of that mass was lying on the streets? 1,000lbs? 500lbs? 200lbs?

I think you should revise the following statement. It should say NIST used 8 major components (WTC2 engine, landing gear could not have damaged the core) when it should only have used 7.5. Or 7.7. Maybe even 7.8.

The 2 aircraft effectively representied 10 major destructive components, 6 sets of landing gear and 4 engines.

The successful NIST collapse initiation simulations used all 10 destructive components in order to match what happened on 9/11.

In reality, only 6 of these destructive components should have been used in the simulation, 3 sets of landing gear and 3 engines.

It never pays to rush a reply.

MM

 

[Belz...]

Again you are asking me a question, that if pick one of only 3 choices, I'm forced to support a NIST scenario that I'm in the least disagreement with. That's a negative option. The NIST simulation is based on too many assumptions that involve more than just aircraft speed, weight and trajectory.

Irrelevant. Mack asked you which of the three scenarios was the best fit, according to you. It's not a negative option. He's asking you which one fits best. You're the one making it sound negative.

In any event, your inability to "cross over" and give a hypothetical response, at least, shows how you are unwilling to even consider other views than your own.

 

[Miragememories]

You will note, of course, that nowhere did I ask you to support any NIST scenario. I merely asked you to indicate which of the results, in your opinion, was the closest match to reality.

Nonetheless, that's fine. I won't ask this question again. I will simply acknowledge that you decline to give any answer. If you change your mind in the future, please feel free to give us your thoughts.

---

Let me try a new tack. Judging by your last three (!) replies, it seems clear that you and I are discussing too many topics at once. Furthermore, I will be away from my computer until next Monday. So instead of issuing a monolithic reply addressing the great many areas where you need help at once, let me tackle only a single issue.

Please understand that I have not ignored anything you have thoughtfully written above, and you have my word that I will return to address all of them.

---

Underlying your entire body of commentary in this thread is one fundamental misconception, namely the significance of exit or non-exit of substantial debris. I first pointed this out on the very first page of this thread. This time, I'd like to go back to this issue and not leave it until we reach an understanding.

Please consider the following figure, which describes the initial conditions of WTC 1. I copied this figure from NIST NCSTAR1-2, figures E-25(a) and E-26(a), found on pages lxxvi-lxxvii or 78-79 in your PDF reader. I then added two sets of three parallel lines, as follows: The first parallel line passes through the nose and tail of the aircraft, and is meant to represent the initial trajectory of the three sets of landing gear, which will be slightly below and centered, left, or right of the dotted line. The other two parallel lines have been offset to overlay the engines, and represents their approximate initial trajectory. In the upper figure, you can see the geometry of the core columns, and in the lower figure you can see the core columns and bolted/welded floor beams indicated by darker shading.

http://www.internationalskeptics.com/forums/imagehosting/thum_9193462ebc70ea182.jpg

In your Part 2 post above, you describe your understanding of these three components as follows:



Now, here's my new question for you:

Consider my figure above. Please explain, in the real-world scenario, how either engine or any of the three sets of landing gear could possibly have entered the building at figure left, then exited at figure right, without damaging the core. Tell me how you think this happened.

Once I have your answer to that question, I should be able to pinpoint the source of this fundamental misunderstanding, and we can continue from there. Again, thank you for your careful attention.

PLease note, ALL BOLDING (emphasis is added).

When I earlier said "these components", I was referring to those that were known to have exited the towers. WTC 1; 2 landing gear and WTC 2; 1 engine, 1 landing gear.

The remaining 3 engines and 3 landing gear I accept as stopped by the cores and I believe I've previously acknowledged that.

Okay, just to be clear, we are discussing WTC 1. Portions of 2 sets of landing gear were observed to exit this tower via the opposite wall from impact. In none of the 3 NIST simulated scenarios did this occur.

For WTC 1, the WTC Report states: “No portion of the landing gear was observed to exit the tower in the simulations, but rather was stopped inside, or just outside, of the core.”(NCSTAR 1-2B, p.345)
Landing gear was observed exiting the south side of WTC 1 at about 105
mph. (NCSTAR 1-2B, p.344).

The first NIST figure creates a line-up of the engines and landing gear with the core columns which would indicate a full stop expectation.

The second NIST figure shows the vertical and lateral approach angles, but both figures appear to make the assumption of perpendicular entry.

For all 3 scenarios, for the WTC 1 impact, NIST used zero degrees for aircraft Trajectory - yaw and Orientation - yaw.
Table E-6, Input parameters for additional WTC 1 global impact analyses. NIST NCSTAR 1-2B, WTC Investigation lxxxv

I also have to note that according to NIST; "Since no accurate orientation information could be derived from the video analysis, analysis of the damage pattern was critical in determining the aircraft orientation at the time of impact."
NIST NCSTAR 1-2B, WTC Investigation p167

In addition, according to NIST; "The calculated debris cloud included 17,400 lb of debris and 6,700 lb of aircraft fuel outside of the tower at the end of the impact analysis, either rebounding from the impact face (north wall) or passing through the tower (south wall). This amount might have been larger in the calculation since the exterior walls were not modeled with windows that would contain the fuel cloud and other small debris inside the towers."
lxxvi NIST NCSTAR 1-2B, WTC Investigation

My reason for noting the above items, is that they directly call into question the accuracy of the 2 NIST figures and thus could account for misalignments which would easily explain why the 2 sets of landing gear would have passed through WTC 1 without impacting the core columns.

That is my answer!

MM

 

[Miragememories]

The landing gear was captured in the core in the simulation, but other heavy debris hit the south wall. In reality, the situation was reversed. Ie. the debris that hit the wall in the simulation would have damaged the core in reality. Thus the landing gear exit is inconsequential because the damage is equal overall.

Comprehending the above statements is difficult, so I'll break it down (no pun intended).

In WTC 1, In reality the core stopped 2 engines and 1 complete set of landing gear while the other 2 sets of landing gear exited through the opposite perimeter wall partially intact. Possibly some landing gear debris remained behind or exited as smaller debris. Regardless, in the simulation, the core stopped it all, 2 engines and all 3 sets of landing gear.

The reference made to "other heavy debris hit the south wall" needs to be sourced and clarified for me to better understand and respond. I refer to the core stopping major aircraft components and landing gear exiting through the opposite perimeter wall.

I'm sure lots of 'heavy' debris hit the south wall but without explanation the statement has no meaning. If you're saying these are offsetting losses, it's necessary to prove that simulated exiting debris had the same core-destructive potential as the additional aircraft components stopped by the core in the simulation. Since NIST tagged the debris and knew in all 3 simulation scenarios for WTC 1, that no landing gear or engines exited and that they determined they were all stopped by the core, I don't know what simulated debris remained at the south wall that had the destructive potential to make your argument work?

Quote=Miragememories
NIST admits that minor aircraft entry corrections would significantly improve the match with the video and photographic record.

"None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower. However, the impact behavior suggests that only minor modifications (lowered 1-2 ft.) would be required to achieve this response." NIST NCSTAR 1-2B, WTC Investigation pg353.

Simple as.

I actually said in my post that you cannot swap the narratives for the WTC1 landing gear and WTC2 engine around like that. The situations are very different. You've done it again.

All I was looking for was the admission that NIST may well have to produce an ungodly number of simulations to get the landing gear to exit WTC1. And that conducting that many would be ridiculous based on the path of landing gears in a highly complex event.

Obviously, the landing gears would have been negotiating much more structure than the WTC2 engine, and many more simulations would have to be run to perfectly match reality.

The nose gear possibly could behave similarly, as possibly could main landing gear if 'sheared' by a core column during passage.

The fact is, reality found away for this to happen and it's a shortcoming of the model that it can't reproduce an important observable. It's especially important when there so few key reference observables.

You can add the fuel to the list of major destructive components. Check NIST NCSTAR 1-2B to see the difference between an empty plan wing and a fuel laden plane wing hitting the building.

I believe if you read my reply to R. Mackey, you'll observe that I have thoroughly addressed that question.

And no, the simulations did not use 'all 10 destructive components'. In the WTC2 simulation (more severe case) a landing gear exited the building within a couple of columns of where it exited in reality. It did not exit in the less severe or base case. It did not have any contact with the core.

I accept that correction and have acknowledged it in my more recent posts.

Plus, the engine in WTC2 did not exit the building in the simulations, but it did not damage the core either. It was nowhere near it. By the end of the simulation it had slowed to under 100mph as it destroyed workstations.

I'll grant you the engine did not appear to be on a trajectory path to impact any columns in WTC 2.

How does a credible Model simulation account for a high speed, 5 ton, titanium steel bullet being stopped inside WTC2 by impacting unanchored work stations? An engine identical to the ones NIST shows removing and seriously deforming heavy steel core columns before being stopped?

MM

 

[R.Mackey]

Turns out I'm leaving a little bit later than I thought. Here's one last reply before next week.

My reason for noting the above items, is that they directly call into question the accuracy of the 2 NIST figures and thus could account for misalignments which would easily explain why the 2 sets of landing gear would have passed through WTC 1 without impacting the core columns.

That is my answer!

I'm sorry, but that doesn't answer my question, and isn't helpful to me.

Again, what I asked you was to explain your theory. You claimed in your Part 2 post, as highlighted in my last reply, that you believed the heavy pieces which exited, opposite the impacts, passed through without doing any damage to the core. I asked you to explain how you think this is possible. You haven't answered this. Nobody except you can answer this question, which has nothing to do with NIST.

I need to understand your position before we can continue. But before I rephrase the question, let me address an additional error you made about the NIST contents:

Okay, just to be clear, we are discussing WTC 1. ...

The first NIST figure creates a line-up of the engines and landing gear with the core columns which would indicate a full stop expectation.

The second NIST figure shows the vertical and lateral approach angles, but both figures appear to make the assumption of perpendicular entry.

For all 3 scenarios, for the WTC 1 impact, NIST used zero degrees for aircraft Trajectory - yaw and Orientation - yaw.

(Color added for emphasis)

This is completely incorrect, and should be immediately clear from my figure.

In the case of WTC 1, the NIST report absolutely does not specify a perpendicular trajectory. There are two angles at work, not one. The aircraft has angles of yaw, which would be perceived as turning left or right by the pilot, and pitch, perceived as the nose pulling up or down. The third angle is roll or rotation around the ordinary direction of travel, and this angle isn't a factor in terms of perpendicularity. You identified the yaw, but you ignored the pitch angle.

In table 6-3 on page 158 of NIST NCSTAR1-2, NIST declares its initial conditions. Among them, the horizontal angle of incidence (roughly equivalent to "yaw") is given as 180.3^o +/- 3, which as you noted above is by itself effectively perpendicular, and understandable given that the terrorists were trying to hit the building square. But the vertical angle of incidence is 10.6^o +/- 4, and that isn't anywhere near perpendicular. Ten degrees of pitch is actually quite a lot for a commercial aircraft.

The figure I posted before shows, quite clearly, that the aircraft did not impact perpendicularly. My figure is consistent with the table above. I don't understand how you reached your conclusion here, either.

-----

Now, let me rephrase my question. You apparently refused to answer this time because you don't accept NIST's estimate of the aircraft trajectory. As you correctly point out and NIST makes no effort to hide, the trajectory estimate does have some uncertainties. But that's fine. I don't need you to accept NIST's estimate. You can use any trajectory estimate you wish, perpendicular or not, although if you cannot justify your estimate, I will challenge you on it.

I only require two boundary conditions: The entry point of the landing gear, and the exit point. Unlike the trajectory of the aircraft prior to impact, these left visible holes in the structure that were photographed and carefully analyzed. Since below you agreed that these observations were substantiated, I trust that you will accept these boundary conditions.

Below I present my figure again, as before copied from NIST NCSTAR1-2, E-25(a) and E-26(a), except this time I don't include trajectory guidelines. Instead, the initial position of the aircraft is as in the figure, and the exit point of the landing gear is portrayed by the red rectangles. These rectangles reflect damage "postulated*" to columns 329 through 331 on floors 94 through 96, as described in NIST NCSTAR1-2, pg. 269. Here's the figure:



Now let me restate my question, thus: The landing gear started in the body of the aircraft at left; this is "Point A." The landing gear exited at or very near the red rectangle at right; this is "Point B." You have claimed that the landing gear got from "Point A" to "Point B" without damaging the core. How do you think this happened?

OK, now I'm really gone. I look forward to reading your carefully considered and thorough reply when I return on Monday. Thanks again.

*: I am quite comfortable with the word "postulate," as I have a degree in mathematics. The NIST report accepts that it could not inspect the landing gear or perimeter section itself given the time differential, and the secondary effects of the horrific collapses. Rather than dive into a thorough evaluation of the fragment, NIST simply observes that the fragment could not pass through a window due to its size, and that no other significant breaches of the perimiter on that side were evident. This is its "postulate." While there is also uncertainty about the fragment and its trajectory, given the clarity of photographs and the WTC structure, it is inconceivable for its exit point to be more than one "waffle section" away from the NIST estimate.

 

[beachnut]

None of the simulated debris impacting the south wall happened to contain landing gear fragments. 340 NIST NCSTAR 1-2B, WTC Investigation

So we need to calculate what this means to the overall energy impacting the WTC structure.

It is believed that a portion of the main landing gear of AA 11 exited WTC 1 at the 94th or 95th floor and landed at the corner of Rector and West Streets. This debris is believed to be a tire, wheel, brake assembly, and hub of a main landing gear, as shown in Figure 9–122. Based on the final position of the landing gear and assuming the landing gear to be a projectile with a horizontal initial velocity, the exit speed of the landing gear from the south wall of WTC 1 can be estimated to be about 105 mph.
344 NIST NCSTAR 1-2B, WTC Investigation

That energy would be 0.004 percent of the energy that is now missing. The part of the landing gear. It was less than 1/8 of all the main landing gear, there is a nose gear two, brining the total tires to 10. We take the weight of the landing gear, and the velocity at impact vs the velocity at leaving the building and the total energy that escapes is 0.004 percent of the total energy of impact. That is what we call insignificant. This point is insignificant and therefore the petition is insignificant.

Another piece of landing gear debris, shown in Figure 9–123, was found embedded in what is postulated to be the panel containing columns 329, 330, 331, running from the 93rd to the 96th floors. This panel was dislodged from the building and found at Cedar Street near its intersection with West Street. As little other damage had been documented on the south face of WTC 1, it is postulated that the landing gear debris that landed at the corner of Rector St. and West St. also exited through this panel location. NIST NCSTAR 1-2B, WTC Investigation 345

This is a piece of the building that fell off with some landing gear in it and thus the energy of the landing gear was all used up I will have to give this a big ZERO energy lost and proof that part of the building structure holding the façade was totally destroyed as this piece used up all of its energy destroying the building. Zero percent lost here!

A portion of the landing gear of UAL 175 exited WTC 2 and landed on the roof of 45 Park Place. No photographic evidence was available to document the size of the fragment and whether this was a nose or main landing gear. 352 NIST NCSTAR 1-2B, WTC Investigation

Another aircraft, darn, lets say it is similar and I will run some number and we get 0.006 percent lost energy. That is bigger, but only due to the fact 175 was over all at a lower energy state at impact. Once again you take the mass of the landing gear ejected and the speed of impact vs. the speed of ejection to get the total percent of energy lost by the impact ejecting a piece of landing gear as 0.006 percent. Insignificant.

A portion of the port main landing gear was seen to exit the building at approximately 230 mph in the more severe impact analysis,
as shown in Figure 9–131(b). No landing gear debris exited the building in either the base case or less severe simulations. At the conclusion of the simulation, the base case analysis had a substantial piece of the starboard main landing gear still at approximately 130 mph that was expected to impact the northeast corner. NIST NCSTAR 1-2B, WTC Investigation 353

I am not sure why you question where the landing gear ended up in the model? I was at the corner, at 130 mph, that is very slow and with only 5 percent of its energy left as it stops at the corner with not enough energy to break through the shell. And if it had escaped like in real life this would still only represent 0.006 percent of all the impact energy. Showing the model is very close to real life in a very complicated model.

Observed trajectories of specific aircraft components, such as the landing gear and engines, were considered to be of lower importance in validating the simulated damage to the tower. A fairly precise knowledge of the internal configuration of the building would be needed in order to simulate the trajectory of specific aircraft debris. Damage to the opposite side of each tower from the point of impact was also of lower importance. These parts of the tower were modeled with lower resolution and as a result, the models were not sufficient to capture the detailed damage.

Darn, they are explaining why the model may not be like real. Wish the truthers would explain the whole story instead of just telling lies it would be so much easier to see what they left out if they would tell us. NIST tells you about the model. Your truth movement lies and leaves out the rest of the story. Good job showing me NIST is telling the truth and giving out the information on the model.

Table 9–13. Comparison with observables from WTC 1.
Landing gear trajectory was deemed by NIST to be slightly significant and in poor agreement.NIST NCSTAR 1-2B, WTC Investigation 363

Observable-s? Goodness can Dr Jones read NIST, not a thing he has in the petition makes sense after seeing what NIST did. The more I learn about this the more the petition becomes insignificant.

Table 9–14. Comparison with observables from WTC 2.
Landing gear trajectory was deemed by NIST to be not significant and in fair agreement.NIST NCSTAR 1-2B, WTC Investigation 363

I have shown the same, the landing gear was 0.004 percent of the energy flight 11 had to give the WTC. NOT SIGNIFICANT.
0.004 percent ----

There you have the specifics on the landing gear!

Now, here you have the real specifics on the landing gear!

0.004 percent. NOT Significant. Debate is won because 0.004 percent of the total energy is insignificant. In a football game this means you have one point, I have 24,999. The petition is down by 24,998 points.

What about the engine? Did you know if you calculate the energy the engine. I did, and even the ejected engine would only be 0.16 percent of lost energy when it was ejected. That is insignificant too.

Thus the petition is insignificant. I have used numbers to show this and unless you can refute the numbers, the petition is faulty and insignificant.

 

[Mancman]

The reference made to "other heavy debris hit the south wall" needs to be sourced and clarified for me to better understand and respond. I refer to the core stopping major aircraft components and landing gear exiting through the opposite perimeter wall.

I'm sure lots of 'heavy' debris hit the south wall but without explanation the statement has no meaning. If you're saying these are offsetting losses, it's necessary to prove that simulated exiting debris had the same core-destructive potential as the additional aircraft components stopped by the core in the simulation. Since NIST tagged the debris and knew in all 3 simulation scenarios for WTC 1, that no landing gear or engines exited and that they determined they were all stopped by the core, I don't know what simulated debris remained at the south wall that had the destructive potential to make your argument work?

Ok, fair request. I postulate that the south wall was hit by something substantial based on this:

Because of model size constraints, the panels on the south face of WTC 1 were modeled with a very coarse resolution. Neither the spandrel splice joints nor exterior column butt joints were modeled.
Column ends and spandrel edges were merged together. The model, therefore, underestimates the damage to the tower on this face. The calculated damage produced by the more severe impact is shown in Figure 9–121. Columns 329–331 on floors 94 through 96 had sustained substantial damage. Had a fine
mesh been used on these columns, it is likely that they would have failed on floor 95, and possibly on 94 and 96. Based on the failure modes observed on the north face and on the speed and mass of the debris, the panel would potentially be knocked free by failing at the connections.
NIST NCSTAR 1-2B, Pg342.

I won't begin to speculate precisely what debris did this because I have no idea. But clearly, it had the potential to sever columns and it was not spent in the core. In reality, it may have been spent in the core. That's all I was saying.

I'll grant you the engine did not appear to be on a trajectory path to impact any columns in WTC 2.

How does a credible Model simulation account for a high speed, 5 ton, titanium steel bullet being stopped inside WTC2 by impacting unanchored work stations? An engine identical to the ones NIST shows removing and seriously deforming heavy steel core columns before being stopped?

MM

Because, in the model, the engine struck a floorslab and was slowed by 200mph upon impact, and split in half. It then had 200ft of office between it and the northeast corner.

The engine debris then continued through the tenant space of the 81st floor, plowing through the workstations and contents. Whether or not the fragment passes over these contents, or if other debris and fuel remove the contents from the engine’s path, affects the deceleration of the fragment.
At the end of the simulation, the speed of the aft portion of the engine was below 80 mph, and it was more than 60 ft from the northeast corner of the building. For these calculations, it was estimated that the building contents would likely stop the engine fragment prior to impacting the northeast corner of the exterior wall.
NIST NCSTAR 1-2B, Pg 351.

This is of course the same engine that NIST claims would exit the building with 'minor modifications'.

 

[Belz...]

In WTC 1, In reality the core stopped 2 engines and 1 complete set of landing gear while the other 2 sets of landing gear exited through the opposite perimeter wall partially intact. Possibly some landing gear debris remained behind or exited as smaller debris. Regardless, in the simulation, the core stopped it all, 2 engines and all 3 sets of landing gear.

Really ? Did they really model the engines and landing gears separately in the simulation ?

The fact is, reality found away for this to happen and it's a shortcoming of the model that it can't reproduce an important observable.

Well, unfortunately, our simulators aren't Holodecks, and we can't get everything 100% right like Data. Sorry about that.

 

[R.Mackey]

Well, it's Monday, and I'm back as promised

I'm sorry to have to guess that Miragememories won't be returning, seeing as he has posted five times since last week, but still hasn't replied in this thread, leaving my questions still unanswered.

That's fine. To Miragememories, in case you merely forgot about thsi thread, you are welcome to rejoin the conversation at any time.

I'd like to press on, however, since this thread gathered more interest and went quite a bit longer than I expected it to. I think it needs some closure. Let me then revisit my last question:

Now let me restate my question, thus: The landing gear started in the body of the aircraft at left; this is "Point A." The landing gear exited at or very near the red rectangle at right; this is "Point B." You have claimed that the landing gear got from "Point A" to "Point B" without damaging the core. How do you think this happened?

To answer this question, I propose the answer is that it is impossible.

My reasoning is as follows: Consider my figure in the post quoted above. We have a pretty solid estimate of where the landing gear entered the building and where it exited. So what happened in between?

We know the landing gear came in contact with structural elements at some point. There is just no way for it to get from one side to the other without doing so. The core is a mesh of cross members and columns spaced about 15 feet side to side, and 12 feet high. If the aircraft had hit it flat and level, lucky objects as big as perhaps ten feet square could have made it through, if they were perfectly aligned -- but the incoming aircraft is looking at this at a ten degree angle. This means that anything that enters the core will exit on a different floor than it arrived, as seen in the diagram.

Using these estimates, the widest "slot" of daylight that any piece will see is a mere 2.6 feet high from its perspective. Or at least it would, if there wasn't a substantial floor present in the core. But the floors make no difference for purposes of this argument, since the landing gear, entering sideways, is almost four feet across. It simply won't fit.

Ever play one of those carnival games, where you try to throw a baseball through a just-barely-bigger-than-a-baseball hole? Ever win anything? Me either. This situation is far worse.

Since we know the landing gear contacted the core, we also know that it damaged the core. The landing gear passed essentially straight through the structure, indicating little elasticity in its collisions. Furthermore, it has sufficient momentum to exceed the column P-I limits as expressed in NIST NCSTAR 1-2B, chapter 10. It is likely that the landing gear was itself heavily damaged after the initial contact with the core, so perhaps it inflicted only minor damage later in its path -- but at some point it had to hit the core, and hit it hard.

There are two other clues. The pieces that exited all showed extreme damage. We do not expect main gear, buried deeply in the back of the aircraft, to be destroyed by the perimeter columns, since the nose and fuselage of the plane should have cleared that out. We also do not expect the building interior to have had much effect, since its trajectory was hardly deviated by anything, including the much stronger structural elements. However, if the landing gear had inflicted no damage on the core, we would expect it to hit the far perimeter more or less intact. It did not. Only one wheel and part of the carriage made it through, not even a quarter of the landing gear's original structure. Also, we would have expected the landing gear to exit with much more speed, had it not experienced major impacts inside the structure. Its exit speed was estimated at about a quarter of its entry speed.

If you crash a thousand planes into a thousand WTC towers, you probably would see a landing gear set make it through the core more or less intact a few times. High-speed collisions are complicated and difficult to predict. So are simulations. Done right, they accurately capture the "deterministic chaos" effect where minute changes to the initial conditions have significant downstream effects to a particular trajectory. Weird things can happen. This is why any model will have some inaccuracies, and we need to accept that. A point I've made here before is that we cannot accurately simulate what a single thrown die will do, and likely never will. The large scale behavior is much more important than fussing over every individual piece of debris.

Nonetheless, had this event been one of those lucky trials, we would have been able to tell by the condition of the exiting debris. It didn't happen on these flights. We know the landing gear was badly damaged, and we know the core did some if not all of it, and suffered in the process.

----

This argument shows that landing gear debris passing through the core means damage was inflicted on the core. This is the first step in a logical chain, that goes as follows:

1. The exit of landing gear opposite the impact, through the core, signifies damage inflicted on the core.

2. This is true for all debris, not just landing gear.

Rationale: Material strength and discrete impacts are minor effects in computing impact damage. Collisions inside the building are largely inelastic, as evinced by the near straight-line trajectory of the debris path, thus energy transfer is governed by momentum and not by hardness or ultimate strength of materials in the aircraft or in the tower.​

3. More debris exiting the other side of the core means more damage inflicted on the core, in the real-world scenario.

Rationale: Since any individual piece exiting opposite the core is understood to have inflicted some damage according to 2. above, we can reason inductively to prove 3. rigorously -- for any impact scenario, adding a new piece of debris exiting means adding more damage, therefore the amount of damage in the new scenario is higher than that in the old scenario, for any arbitrary amount of debris pass-through.​

4. More debris exiting the other side of the core means more damage inflicted on the core, in the simulation.

Rationale: This is empirically observable, repeatable and testable. The NIST report shows that severity of impact is correlated with the amount of debris pass-through. There can be no doubt on this point, though this is actually the crucial observation.​

5. Combining 3. and 4., an observation of more debris pass-through in the real world is best fit by a simulation of more severe impact.

Rationale: Both real-world and simulation show a increase in core damage when debris pass-through is increased. Therefore, an increase in observed debris pass-through is never better fit by a simulation with lesser impact severity.​

6. The best fit to the real-world observations in WTC 1 and WTC 2, out of the three cases NIST studied for each, is the most severe case.

Rationale: The baseline and less severe cases show virtually no debris pass-through. There are no cases with less pass-through than zero. Since both WTC 1 and 2, real-world, experiences some pass-through, 5. above guarantees that the baseline case underestimates the impact. Since the simulation shows the correct correlation between core damage and debris pass-through, we infer that the baseline case (and thus the less severe case as well) underestimate core damage.​

QED.

On the basis of this logical chain, the petition "demanding corrections" is therefore proven to be in error. Steven Jones and his friends are either willfully attempting to confuse readers, or unable to comprehend the contents of the NIST report. Their motive is not central to this discussion -- we reject their conclusions regardless of the source of their error.

Thank you again for your participation. I'll return again to clean up a few remaining details, as I promised to do last week.

 

[R.Mackey]

Loose ends, Part 1

Welcome back.

As we've now finally disposed of the petition that started this whole thing, as promised I'm going back to clear up remaining points of confusion.

I understand what you are saying. The problem is we share different levels of faith in the acceptability of the model and the validity of the allowances it permits.

The key problem with this statement is the word faith. Faith has no place in a scientific discussion. The uncertainties in the NIST model are not an issue of faith; they are declared, quantified, and tested for sensitivity. What NIST discovered, and demonstrates in the report, is that the ejection or not of the pieces you're talking about has only a minor effect on damage to the core, which is understandable given that we're talking about a relatively small amount of the aircraft being ejected. What's more important is whether or not they could be ejected, i.e. whether they made it through the core, not whether or not they were ejected.

As beachnut has explained, we're talking about less than 1% of the impact energy. The pre-impact velocity uncertainty of the aircraft alone introduces over 40% uncertainty in the total energy. The fact that the tower response over such a wide range is mostly similar speaks to the model's tolerance to these kinds of errors. And this is borne out by reality -- WTC 1 and 2 were hit very differently with even more variance in total energy, yet the phenomenology of the collapses were similar. The NIST model predicts this result nicely.

This is why NIST isn't so concerned about this effect. It has nothing to do with faith, but is based on calculation and careful experiments.

Yes I've adopted energy transfer explanations, though I continue to disagree with how energy transfer should be expressed and applied to the simulation. You agree with NIST that the "less severe case" should be ignored because it is the "worst fit of the three cases" as it fails to plausibly match the actual event as well as the baseline and more extreme case simulations.
You support this by pointing to the TOTAL AMOUNT OF DEBRIS PASS-THROUGH as it matched the "actual event".
My problem with that argument continues to be the generalization of how debris is handled.

As before, your basis of energy transfer is an argument from a karate book. The situation in the WTC towers is quite a bit more complicated.

The material strength and even size of any particular piece of debris has little effect on its contribution to damage, because of the situation we're dealing with. I'll treat that in further detail below. Because of this, generalizing debris is entirely valid. The NIST experiment proves this by showing their results are not strongly affected by the ductility of the aircraft, which they varied by +/- 25%.

Since NIST was unable to make direct observations, and have no records of the actual internal damage for each tower, following the aircraft impacts and prior to collapses, there is no mechanism to validate that the simulation got it right other than it generates a successful collapse initiation.

Absolutely wrong. At this stage of the calculation, there should be no tower collapse. We cannot apply this test without running the fire model and then applying the fire results to the structure, and we haven't even started those steps yet. NIST actually uses the opposite criterion -- any simulation that results in an instant collapse has obviously overestimated the damage, and is therefore too severe. This is one of the factors that convinced them to attentuate the "more severe" case in WTC 2.

Treating similar sized pieces of debris as equals ignores the significances that are characteristic of different types of debris.

As above, there isn't that much difference. Momentum is key, not material strength. Collisions are not elastic enough to matter.

I was unable to resolve what you meant by 155-156 of the part 2PDF?

NIST NCSTAR1-2B is broken up into Chap 1-8 and 9-11. I was referring to the second half, and within that half, pp. 155-156 as shown by the PDF browser itself. The true page numbers I referred to will be accurate.

I noted that there is a significant uncertainty in this estimate associated with the exit trajectory, aerodynamic effects, landing position rather than final resting position of debris, etc. pg352 NIST NCSTAR 1-2B, WTC Investigation.

They're all related. And part of the problem is that landing gear fragments tend to bounce or even roll...

Back to your point though about, "there was no exit of landing gear in the baseline or less severe cases" BUT, in reality; "a portion of the landing gear of UAL 175 exited WTC 2 and landed on the roof of 45 Park Place.

This is the landing gear that you refer to in your 102 mph example above. Very ODDLY, "No photographic evidence was available to document the size of the fragment and whether this was a nose or main landing gear." pg352 NIST NCSTAR 1-2B, WTC Investigation. It seems very strange that NIST would not have a photograph, or any documented description of this landing gear debris, yet they were able to clearly identify it and document it's discovery in their Report?

Why is that odd? Their investigation didn't even start until over a year after. And any photos would have had to been taken in the brief period between the impact and the collapse. You expect someone to climb up on the (damaged) roof of 45 Park Place just to get a photo? There were more important things to deal with. I'm guessing a news or police helicopter spotted and mentioned it. And it's a nitpicky detail.

We also have a complete engine that exited WTC 2.
The residual velocity and mass of the engine after penetration of the exterior wall was sufficient to fail a core column in a direct impact condition. liv NIST NCSTAR 1-2B, WTC Investigation.

Irrelevant, since the engine you're talking about missed the core entirely. WTC 2 was hit at an angle, and the starboard engine passed outside the core.

Note that each engine weighs 5 tons!

Another interesting statement from NIST;

"Eyewitness accounts of damage to stairwells and visible floor damage were also significant as they were the only available data on the damage to the tower interiors. That these observables were in good agreement adds greater credibility to the predicted damage to the tower interiors."NIST NCSTAR 1-2B, WTC Investigation pg363

This calls into question how loosely they use the assessment of "good agreement!", since a few survivor eye witness observations regarding "stairwells and visible floor damage" hardly constitutes a broad base of observation made by structural experts. It suggests that NIST finds "good agreement" in observations that suit their needs.

One does not need a "broad base of structural experts" to tell you whether stairwell walls were standing or knocked down. This is actually a fairly important point, since the three stairwells were widely distributed, and yet all three (in WTC 1) were blocked after the impact. This is a pretty complicated phenomenon that the model should be required to match. It does.

No, I don't think that's established merely because you have roughly simulated a landing gear debris exit for WTC 2 for just the extreme case. The complete engine exit is still ignored. “None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower.” (NCSTAR 1-2B, p.353)

The complete engine exit is irrelevant for purposes of core damage estimation, because it missed the core. While the model for WTC 2 may have underestimated the perimeter column damage, that information was observable from the outside, so the model result isn't as critical.

Again, notice this is an underestimate of damage. In all cases, the phenomenology you're complaining about means the Towers were even more damaged that NIST predicted. This is why we are biased towards the "more severe" scenarios.

It's important because particles or groups of particles would not be as significant as a large object known to definitely come from the aircraft. As we know, the only aircraft components capable of remaining relatively intact were the heavy steel components like the titanium engine and landing gear. The rest of the aircraft and it's contents, due to lack of material strength would have become part of the debris cloud.

"Relatively" intact. Not intact. The landing gear stayed "relatively" intact because of its placement towards the rear of the aircraft. The WTC 2 engine stayed "relatively" intact because it missed the core. Again, material strength is really not the issue. I don't know why you think it matters.

You are again ignoring the virtually complete engine or "large engine fragment" as NIST likes to call it, that exited WTC2.
NIST NCSTAR 1-2B, WTC Investigation pg359

I'm ignoring it because it missed the core.

Calling this a fragment calls anyone's objective credibility into question?
“None of the three WTC 2 global impact simulations resulted in a large engine fragment exiting the tower.” (NCSTAR 1-2B, p.353)..looking at what they term as a fragment, calls again NIST's supposed unbiased judgment into question when evaluating evidence.

Calling it a "fragment" is scientifically accurate. Nothing that exited the buildings was anything other than heavily damaged.

Three pieces of landing gear!

Regarding the landing gear that was embedded in the exterior columns of WTC 1 and then 'fell free' as you put it. This piece of landing gear debris, (from WTC 1) shown in Figure 9–123, was found embedded in what NIST postulated to be the panel containing columns 329, 330, 331, running from the 93rd to the 96th floors. pg346 NIST NCSTAR 1-2B, WTC Investigation
As you can see by the photo, it remained embedded, it took the panel with it during it's high velocity exit (otherwise the MIST postulation below would make no sense (supposedly, it cleared a path for the 105 mph landing gear behind it to exit). That would suggest it had to be the nose gear.

I don't see any reason why this would have to be nose gear. The evidence and pictures suggest it was main gear. We also expect the nose gear to have suffered more damage at the perimeter, since it hit first, whereas the main gear entered the building through the hole created by the nose of the aircraft.

NOTE: postulate = suggest or assume the existence, fact, or truth of

Postulate means "state without proof." Not every detail in the NIST report was deemed important enough to investigate thoroughly. As remarked before, the specific disposition of landing gear is not particularly significant in terms of the overall scenario. The salient point is that an estimable amount of debris penetrated the core with enough velocity to exit the perimeter. Nobody really cares what pieces they were, or exactly where they landed.

As little other damage had been documented on the south face of WTC 1, NIST postulated that the landing gear debris that landed at the corner of Rector St. and West St. also exited through this panel location (as above, Figure 9–123). pg344-45 NIST NCSTAR 1-2B, WTC Investigation. Partial main landing gear (tire, wheel, brake assembly and hub) exited WTC 1 at an estimated speed of 105 mph exiting through the opposite perimeter wall. pg344 NIST NCSTAR 1-2B, WTC Investigation.

The obvious conclusion is; NIST is saying we are dealing here with 2 separate pieces of landing gear debris exiting with significant velocity from the WTC 1.

They are postulating that the piece shown in the photograph of Figure 9-123, removed the perimeter panel containing columns 329, 330, and 331.
Based on limited damage documentation for the south face of WTC 1, they are then postulating that the partial main landing gear (tire, wheel, brake assembly and hub) noted first, exited through the opening created by that panel removal.

Correct. I'd just like to add that the pieces of main gear that exited total much less than half of a single main gear, and show extremely heavy damage to that landing gear.

A portion of the landing gear of UAL 175 exited WTC 2 and landed on the roof of 45 Park Place. No photographic evidence was available to document the size of the fragment and whether this was a nose or main landing gear. 352 NIST NCSTAR 1-2B, WTC Investigation

Addressed above.

Regarding the impact potential of the fuel;
The analysis of the impact response of the aircraft fuel cloud had several limitations. Smooth Particle Hydrodynamics (SPH) was used to model the fuel in the impacting aircraft, and approximately 60,000 SPH particles were used for the approximately 60,000 lb of fuel in each aircraft. Therefore, the particle size in the fuel cloud was approximately one pound. The air in and around the towers was not modeled, so the deceleration of the fuel particles in the cloud by aerodynamic resistance was not included. The contact algorithm for the fuel particles and tower did not include a sticking or “wetting” behavior so the fuel particles bounce off of components in the tower. The results of these limitations would spread the fuel cloud over a larger region in the simulation. Finally, the deflagration of the fuel was not modeled, and the resulting dynamic over-pressures in the tower from the combustion process were not included in the analysis.
pg.196 NIST NCSTAR 1-2B, WTC Investigation.

Also note the simulation ran for less than one second. "Wetting" on those timescales is postulated to be negligible. As for air resistance, you cannot model it without trying to estimate what the airflow looked like inside the building -- an aircraft impact would naturally introduce an enormous "gust" of wind, at speeds comparable to the impact velocity. It's reasonable to say that, in that one second, the fuel travelled in locally stagnant air, accelerated to its own speed by pieces of aircraft, and thus aerodynamic deceleration is negligible as well. It certainly has a minor effect compared to the solid contents and structure of the Tower itself.

The aircraft fuel SPH particles tended to bounce off of internal structures.The physics of fuel impact and dispersion in this type of impact event is complex and no appropriate validation data could be found. The fuel starts as a continuous fluid within the tanks and ends up distributed both on the tower structures and as small droplets that interact with the atmosphere surrounding the impact zone. No single analysis technique is currently available that can analyze this full range of fuel dispersion without significant uncertainties.
NIST NCSTAR 1-2B, WTC Investigation pg.219

Correct. I've remarked before that this simulation is at the cutting edge of computer modeling. This is one area where our desires exceed our abilities.

What NIST essentially did with the fuel load was to model it as an incompressible solid with zero mechanical strength, finite density, and minimum granularity of one pound. It's actually not too unreasonable given that we only require three quarters of a second of kinematic evolution. Fluid effects will be small over those timescales, except for the one-pound parcels breaking apart, and since we have 60,000 of them in a confined space this doesn't make much difference either.

The fuel impact loads used in the above example were an upper bound on the damage that could be produced by the fuel at the core since the fuel was still assumed to be in a solid rectangular section at full density. In reality, the impact with the exterior wall broke up the wing structures, and the fuel cloud spreads out to some extent prior to reaching the core columns. The impact with the internal building contents also reduced the severity of the fuel impact at the core. pg.376-77 NIST NCSTAR 1-2B, WTC Investigation

Fuel damage due to the added momentum it gives the wing, would do most of it's damage to the perimeter. After passing through the perimeter wall, the wing would be shredded and the rapidly unconfined fuel would disperse in a cloud that would tend to bounce off of most solid structural components.

That is correct. Except "disperse" is misleading. Each individual bit of fuel would disperse, but there are so many of them, spread over such a wide area, that the impact floors are pretty well saturated. This only becomes significant at the edges.

Nonetheless, nobody is claiming that fuel alone destroyed core columns. NIST reports that accounting for dispersion, by itself the fuel was unable to provide sufficient pressure-impulse. However, the P-I is added to that from the aircraft fragments, and in combination there is enough to fail several core columns.

I'll tackle Part 2 and 3 later on.

 

[gumboot]

You seem to have this well covered, and it's way over my head... but one thing that I'm curious about...

The impact studies done at The Pentagon determined that a significant proportion of the column damage was actually caused by the aircraft's Jet Fuel, rather than solid aircraft debris.

I'm wondering... wouldn't one expect a similar occurrence at the WTC? Or are the situations too dissimilar for this sort of comparison?

-Gumboot

 

[R.Mackey]

Not at all. In fact, I've invoked the Pentagon example to explain why the solid debris isn't so important.

One minor correction, as I explained here at the behest of Russell Pickering, the Pentagon BPR states that interior column damage showed conclusive evidence of failure due to "distributed loads," i.e. they failed because of pressure over the entire face of the columns rather than being hit by a single solid object. They cannot distinguish whether the distributed load was all fuel, all small bits of airplane, or actually a pressure wave from igniting fuel. In reality, it's probably all of the above.

What we expect from the Pentagon experience is that after impact, the shredding aircraft, unburned fuel, and early stages of ignition combine to create a heterogenous cloud of flying bits and pieces, basically a fluid. We can treat this as a pressure load. There are probably a few large bits of debris inside the cloud, but for the most part, the Pentagon observed failure due to this cloud rather than engines and landing gear smashing everything in their path.

We likewise expect the WTC cases to behave similarly. At the perimeter, the aircraft is still intact and blunt impact is the order of the day, but immediately afterwards, we should see this distributed effect. This is why the trajectory of any single piece of debris isn't that significant, nor is the material strength of any debris significant.

The Pentagon is a useful example because, unlike the WTC towers, it didn't totally collapse, destroying all physical evidence of what transpired at the point of impact. It was only 77 feet high and only partially collapsed. The actual columns that were hit survived in good enough condition to evaluate their performance. Not so in the WTC cases, where we have to infer the status of the impact floors from modeling and other observable criteria.

 

[Lisa Simpson]

As this thread has calmed down, I have taken off the moderation. Should it get even a little "noisy" again, back it goes. I ask that everyone keep in mind the Membership Agreement when posting.

Replying to this modbox in thread will be off topic  Posted By: Lisa Simpson

 

[gumboot]

Not at all. In fact, I've invoked the Pentagon example to explain why the solid debris isn't so important.

One minor correction, as I explained here at the behest of Russell Pickering, the Pentagon BPR states that interior column damage showed conclusive evidence of failure due to "distributed loads," i.e. they failed because of pressure over the entire face of the columns rather than being hit by a single solid object. They cannot distinguish whether the distributed load was all fuel, all small bits of airplane, or actually a pressure wave from igniting fuel. In reality, it's probably all of the above.

What we expect from the Pentagon experience is that after impact, the shredding aircraft, unburned fuel, and early stages of ignition combine to create a heterogenous cloud of flying bits and pieces, basically a fluid. We can treat this as a pressure load. There are probably a few large bits of debris inside the cloud, but for the most part, the Pentagon observed failure due to this cloud rather than engines and landing gear smashing everything in their path.

We likewise expect the WTC cases to behave similarly. At the perimeter, the aircraft is still intact and blunt impact is the order of the day, but immediately afterwards, we should see this distributed effect. This is why the trajectory of any single piece of debris isn't that significant, nor is the material strength of any debris significant.

The Pentagon is a useful example because, unlike the WTC towers, it didn't totally collapse, destroying all physical evidence of what transpired at the point of impact. It was only 77 feet high and only partially collapsed. The actual columns that were hit survived in good enough condition to evaluate their performance. Not so in the WTC cases, where we have to infer the status of the impact floors from modeling and other observable criteria.

Thanks for the clarification. This is along the lines of what I thought.

It seems to me, in some ways, that this process of "fluid-isation" of the aircraft would actually cause more severe damage than if it remained intact. I seem to recall somewhere that the impact force contained enough kinetic energy to severe every single column on a single floor (purely from an energy point of view).

A hypothetical fully intact aircraft would focus all of this force through a relatively small part of the building (the fuselage of a 767 is only 5m across and the critical mass width (engine to engine) is only 19m) with significantly excessive force than necessary to severe all of the columns in its way. Thus a great part of the impact force would be wasted.

In contrast, the "fluid-isation" of the aircraft spreads this force over a very large area of the building, thus causing more widespread damage, and thus more severly threatening the building's structural integrity.

I think of it akin to an armour-piercing round versus a hollow-point.

-Gumboot