Polish President and wife killed in Tu-154 crash

[Evan]

The only (and remotely) plausible explanation would be that the Russian IL-76 did some damage to the trees through some crazy manouvering during its 2 failed approaches in the fog.

Well, I read somewhere that the IL-76 was originally designed to be used in this way to clear forests in Siberia, so I suppose this is plausible.

...I'm also thinking that this accident hasn't really been investigated on a quantum physical level, and that there may be certain particle physics phenomenon involved that only scientists could understand. For instance, how do we know that the plane did not exist in multiple dimensions both above and below the runway elevation at the same moment? I'm very interested to hear from these scientists...

[Gabriel]

Here we have a tree sawed off in the path of the downed aircraft, and a scientist trying to show that hitting the tree wouldn't have damaged the wing to the extent it is indicated in the report.

That's nothing. It's hard for us, from outside, to "prove" that the brich broke the wing and not the other way around. The brich is broken, the wing is broken, but establishing a causality there is not so easy because the wing cold have broken at any step of the sequence when hitting something else.

But according to Northwester, the report says that the plane missed the tree by at least 14 meters!!! It must have done a lot of wind to brake the brich.

[Northwester]

Give me an opinion, and I'll find you a "scientist" who supports it.

Scientists produce just as much bullshit as anyone, especially when they are politically or financially motivated to produce evidence for a particular point of view.

This Dr. Binienda, whatever else he may be, is another conspiracy nut, judging by the tabloid-like "status report" in which he participated (looking at his "Current Research Activities" in his faculty profile).

He is a Polish American conducting utterly biased "research" in order to find fault in the official reports. People like him give scientists, not to mention Poles, a bad name.

Gabriel's analogy was perfect. A scientist could set out to analyze a skid mark on the road to show that it wasn't caused by the car that veered out of control and hit a post, but that doesn't change the reality of what happened. Here we have a tree sawed off in the path of the downed aircraft, and a scientist trying to show that hitting the tree wouldn't have damaged the wing to the extent it is indicated in the report.

Whose money is funding this research, which is to no one's benefit in terms of improving safety or anything else useful to mankind?

It is really touching to see that you are concerned whether someone else's actions are "useful to mankind". Time is going to show if Binienda is right or wrong. I don't know what his motivation is but he did not create some crazy conspiracy theory. He just took one of the elements of the investigation and examined it using his expertise and experience.

"Whose money is funding this research?" Really?

[Northwester]

If those guys read the TAWS data right and came up with the conclusion that the plane was flying higher than shown in the report then there are 2 most obvious scenarios:
- the plane was in fact flying higher and the damage to the trees was done in some other way
- the plane was flying through the trees and the TAWS data is incorrect

The second scenario is easier to accept but then one has to find out why was TAWS data incorrect.

[Northwester]

Here's a part of the explanation.

[Gabriel]

Here's a part of the explanation.

I can't believe what I read.

I mean, I am not a famous scientific, and yet some of the things written in that very short paragraph are so stupidly wrong that make me cringe.

[Northwester]

I can't believe what I read.

I mean, I am not a famous scientific, and yet some of the things written in that very short paragraph are so stupidly wrong that make me cringe.

Can you be more specific?

[Gabriel]

Ok.

To begin with, the plane could have never hit the brich which still got broken? We covered that part already.

Second, even if the wing had hit the tree, our structural dynamic impact simulation shows that it's impossible that the damage made by the tree on the wing was enough to slice the wing.

And if the wing got sliced, then the motion would have been such that it could have never reached the position that it did reach.

Now, I beg you pardon, but if your simulation shows that the wing tip do not separate from the wing, how do you know the dynamic reaction of the wing tip if it had? To tell anything about the trajectory of the wingtip once separated you need to know things like initial speed, rotation rates, initial trajectory, and initial angular position (with initial I mean immediately when the last little bit of material connecting the wing tip with the rest of the wing fails). If your simulation shows that the wing tip do NOT separate from the wing, how on Earth can you estimate any of the above?

It's like saying "it's impossible that that person (who drowned) could have reached the bottom of the sea alive because our simulation shows that even in the most favorable scenario he could not survive without breathing the time it takes to reach the bottom of the sea, now if he had reached alive he would have had air for not more than 1.37 minutes". Contradiction anyone?

When you study the debris field after an in-flight break-up at altitude, the initial conditions of the body (except the forward speed) are not very important, especially not if the object is unstable (as I expect a mainly flat object such as a portion of the wing to be). You calculate the average ballistic number (drag coefficient divided by mass) and that's all, with the object being unstable you can assume that it will randomly pass through all the ballistic numbers and that the net effect of the lift will be zero, giving you the same trajectory than that of a non-lifting object with a fixed ballistic number equal to said average. If the initial reaction of the object was such that, due to lift, it initially climbed a few dozens of feet, it won't make any difference in a 5000 feet fall. It will make a world of a difference if the initial altitude was one dozen of feet though. More on this later.

But don't stop there. Now comes the best part:

The plane could have not rolled inverted after the impact because it would have dug the remaining of the wing in the ground. The Russians, to fix that, had to "invent" the stupid story that the plane was climbing. Incidentally, that theory would also help explain the wingtip reaching further than expected.

What's the evidence supporting the claim that the plane could have not be climbing after the impact? That the plane could not sustain a climb with 1/3 of one semi-wing broken!!!

This is simply stupidly wrong.

To begin with, if the plane was already climbing at the moment of the impact with the brich, and 100% of both wings separated on impact at that instant, the initial motion of the plane will be a climb. It's called momentum (inertia for the laymen) and it's so basic that I would put an F in an exam of introductory Physics to any student that says the contrary, no matter if the rest of the exam is perfect. Just by chance, the plane being climbing at the moment of impact is perfectly compatible with the field of damage in the trees and wires in the zone. Not only the initial impact was well below the brich breaking point, but also damages to other trees and bushes were well below that point and in terrain that was raising toward the brich.

Then, not only the initial motion could be to keep climbing, but also the motion after that can be to increase the climb even with the missing part of the wing. How do I know that for fact? It's really pretty basic too.

Let's start with this: What fraction of the full wing area (both sides) does the area of the broken tip represents (it's about 1/3 in span of half wing, so it's 1/6 of the span, and in a zone where the wing is narrower). Just of the sake of the argument let's say that it was 1/10 of the area (it won't change much if it was twice or half that much).

If the wing produced an even lift per square feet, that would mean that 1/10 of the lift is instantaneously lost. But the wing tips are not as loaded as the wing roots, and even more in this case where the root was with flaps extended and the tip had no flaps. Again, just for the sake of the argument let's say that the lost tip was bearing 1/15 of the total lift.

Typical approach speeds are in the order of 1.3 times the stall speed. That is enough lift to provide a maximum lift (just before stalling) of 1.7 times the weight. And we know that they were faster than Vref. Again, just for the sake of the argument let's say that the speed was such that the wing could have provided 2 Gs (which is within the structural design loads with the flaps extended). Since there was an abrupt pull-up just before that (which the Russians said the plane would have stalled if it had not crashed), we can think that the plane was at about 1.8Gs at the time of the impact, loosing 1/15 of that immediately after the impact giving about 1.7 Gs.

Now, 1.7 Gs is a vertical inertial acceleration of 0.7 g (0.7 times the acceleration due to gravity: you need 1 G to fly level and the remaining 0.7 is used to accelerate up). That's a gain of vertical speed of 6.8 m/s every second. If we think that the plane was already climbing 2 m/s at the moment of impact, that would put the plane one second after the impact at an altitude of about 5.4 meters above the point of impact, still gaining altitude at a rate of 8.2 meters every second, and probably still increasing that climb rate. If during the next second the vertical acceleration was instantly reduced to zero, the plane will be 13.6 meters above the point of impact after that second second. This is perfectly consistent with the damage found at higher and higher altitudes in the following trees.

Is the above accurate for this specific accident? I don't know, but saying that the plane could have not be climbing after the impact because it could not sustain a climb with the broken wingtip is simply stupidly wrong.

And now the strawberry of the cake.

We've said that the wingtip was making maybe 1/15 of the airplane's lift. What fraction of the wight would you think that this wingtip wighted?

Obviously, most of the weight is carried in the fuselage in the form of fuselage itself, payload, fuel and engines. The itself is relatively light. The idea is that the lift made by the wing bears much more than the weight of the wing itself. And within the wing, the farther you go toward the tip the lighter the structure, because there are less systems, less or no fuel, and the smallest bending moments, shear loads, and torsion loads.

Under no way can the that wingtip weight more than 1/100 of the total airplane wight (and again, if it twice or half that much it won't change things).

Now, do you know what happens if you take a part of the wing that weights 1/100 of the airplane weight and that is making 1/15 of the total lift at 1.8 Gs and suddenly separate it from the rest of the plane? It will be subject to 1.7 * 100 / 15 Gs. That's 11 Gs!!! One to go level and 10 to accelerate up. This means that the wingtip, even if the plane was flying level at the time of impact, will be 50m above the point of impact 1 second later!!! And still climbing like hell!!! Ok, this acceleration won't last long because the wing will unstabilize not too much after it's separated from the rest of the wing. But it's not to crazy for me that an object travelling at 300 km/h (about 80 m/s!!!), starting at 50m and still climbing will reach about 100m from it's point of impact.

Is the above what happened? I don't know, but I really don't understand (not to say that it is ridiculous) how on earth he says that a wingtip that could have never be detached would have never reached more than 20m if detached.

Does all this satisfies your request for specify?

When you want to investigate something you need to find a theory that fits in the evidence. Not the other way around.

[Northwester]

Does all this satisfies your request for specify?

When you want to investigate something you need to find a theory that fits in the evidence. Not the other way around.

This was more than exhaustive.

The fact that he says that the wing tip could not have been separated by the collision with the tree but if it was separated it could not have travelled that far does not bother me that much because he could have modified his experiment and used, let's say, a steel beam instead of the tree to force the separation in order to observe the behavior of the flying part. That would be reasonable and if he factored everything in (weight, speed, angle, rotation, bending forces in the wing itself, etc.) he should have obtained a probable trajectory of the wing part. Hopefully he will explain next week how the experiment was conducted.

What bothers me is his statement that the plane couldn't have gained altitude after loosing the wing part. I don't know how narrow his area of expertise is but as a scientist he should have known better.

What is more important: his main argument now is that the plane was flying higher than what was shown in the reports. He will have to do more than a good job in his presentation to convince anyone.

[Gabriel]

The fact that he says that the wing tip could not have been separated by the collision with the tree but if it was separated it could not have travelled that far does not bother me that much because he could have modified his experiment and used, let's say, a steel beam instead of the tree to force the separation in order to observe the behavior of the flying part. That would be reasonable and if he factored everything in (weight, speed, angle, rotation, bending forces in the wing itself, etc.) he should have obtained a probable trajectory of the wing part. Hopefully he will explain next week how the experiment was conducted.

I disagree. The weight, speed, rotation, etc after the impact are all functions of the pre-imact state and the phisical properties of the objects involved in the impact.

Figure this: "This ball could have never bounced over this surface made of fresh clay, now if it had it would have bounced 4.2 meters high"

[3WE]

Ok.

To begin with.............

[A classic high-volume Gabriel post.]

........ Not the other way around.

Man, I keep hoping that you will render your opinion on my thought that maybe the pilots- under some pressure from their high-profile passengers and high-profile mission- tried to fly below their MDA using instruments- hoping for a random "break" to see the runway and land, but that like one or two other cases in the history of aviation, they ran into stuff on the ground instead? Any possibility that's what happened?

[Northwester]

I disagree. The weight, speed, rotation, etc after the impact are all functions of the pre-imact state and the phisical properties of the objects involved in the impact.

Figure this: "This ball could have never bounced over this surface made of fresh clay, now if it had it would have bounced 4.2 meters high"

I get your point. I agree that if he used a steel post of exactly the same dimensions as the tree, the flying part would have not behaved exactly the same way after separation as if the tree caused it. But the difference would have probably been not be that great. He should have never mentioned what would have happened if the tree caused the breaking off the wing. He should have simply said that, according to his experiment results, the tree did not cause the wing to break, and based on the location and position of the part on the ground the wing part must have separated at such and such point. BTW, he repeated his experiment adding strength to the tree and increasing its diameter beyond the 40 cm and still the wing stayed intact.

[Evan]

Ouch. If it is impossible for the tree to have caused the separation, then how can we determine how the separation would have occurred had the tree caused it?

That's quite easy to determine. You just take it out of the performance data chart: "Optimum Tree Diameters for Wing Removal during Zero Visibility Visual Approach Operations"

BTW, he repeated his experiment adding strength to the tree and increasing its diameter beyond the 40 cm and still the wing stayed intact.

BTW, Gol Airlines conducted a similar experiment colliding a 737 wing with a comparatively fragile Embraer winglet (not made of solid birch) and half their wing went missing. What exactly are these Tupolev wings made of?

Man, I keep hoping that you will render your opinion on my thought that maybe the pilots- under some pressure from their high-profile passengers and high-profile mission- tried to fly below their MDA using instruments- hoping for a random "break" to see the runway and land, but that like one or two other cases in the history of aviation, they ran into stuff on the ground instead? Any possibility that's what happened?

Great. Give away the ending halfway through the thread...

[Peter Kesternich]

(...) BTW, Gol Airlines conducted a similar experiment colliding a 737 wing with a comparatively fragile Embraer winglet (not made of solid birch) and half their wing went missing. What exactly are these Tupolev wings made of? (...)

Baaad, Evan... BAAAAAD...

[Northwester]

BTW, Gol Airlines conducted a similar experiment colliding a 737 wing with a comparatively fragile Embraer winglet (not made of solid birch) and half their wing went missing. What exactly are these Tupolev wings made of?

The last I've heard - titanium with carbon nanofibers. And some diamond dusting along the edges.