Wings of Tu-154M at the center of Smolensk crash dispute
thicker than anticipated
Published: February 22, 2020
On January 12, 2011, the Russian Federation released the final report (“MAK report”) on the investigation into the crash of the Polish aircraft Tu-154M in Smolensk, Russia, on April 10, 2010 (“Smolensk Crash”). In its final report, the Russian Federation blamed the Polish crew for the crash. In the final conclusions no. 3.1.69-70, the Russians wrote:
“In 4-5 seconds after the first collision with the obstacle, the aircraft collided with the birch with a trunk diameter of 30-40 cm, which led to the left outer wing portion of about 6.5 m ripped off and intensive left bank. In 5-6 seconds, inverted, the aircraft collided with the ground and was destroyed.”
The same conclusions were repeated in the first Polish report released on July 29, 2011 by the government of Donald Tusk (“Miller’s report”). This report stated that an impact with a terrain obstacle resulted in separation of a part of the left wing with aileron and consequently led to the loss of aircraft control and eventual ground impact.
In 2012, a team of researchers from the University of Akron published an academic paper that presented results of the extensive numerical analysis of a Tu-154M aircraft wing impact with a birch tree of 44 cm diameter wide in the impact area.1/ A detailed finite element model of a full scale Tu-154M aircraft was developed on the basis of data available form public sources. The researchers conducted parametric studies to (i) analyze how the thickness of the skin and the spar in the wing structure influences the degree of damage to the wing, and (ii) investigate what is the critical thickness for the spar failure.
In general, the thicknesses of the wing skin may vary from 1.6 mm to 5 mm on the whole wing surface. For this parametric study, the thicknesses of the spar, rib and skin were assumed to be constant along the wing length. The skin thickness was assumed to be between 1 mm and 5 mm, the thickness of the spar was assumed to be between 5 mm and 20 mm, while the thickness of the ribs was assumed to be 3 mm based on knowledge of the aircraft structure. Assumptions were made to keep the geometry of the aircraft simple and parameters conservative. Stringers, joints and bolts were ignored.
The Finite Element simulations successfully reproduced the aircraft's wing impact with a birch tree scenario. The results conclusively ruled out the possibility of a birch tree of 44 cm in diameter cutting off 6.5 m of the Tu-154M wing.
These conclusions were vehemently opposed not only by the Russian investigators but primarily by the Polish supporters of the Miller’s report. Wide-ranging attempts were undertaken in Poland and abroad to discredit the findings of this research. The main arguments used in the attacks focused on the incorrect input data. The supporters of the Miller’s report argued that the elements of internal structure of the wing used in the study were too thick, in other words the wing was made too strong, and therefore the study do not represent the real situation in Smolensk.
In 2016, a new Polish government of Prime Minister Szydło formed a new Polish Commission for Re-Investigation of the Smolensk Crash (“Reinvestigation Commission”).
Between 2017-2019, a detailed measurement of all critical parts of the twin Tu-154M aircraft was conducted by the Reinvestigation Commission in Poland. The painstaking work of technical experts who located, measured and analyzed every element of the structure of the Tu-154M aircraft confirmed that the input data used for the finite element model of Tu-154M wing in the 2012 study was very conservative, meaning that parameters used in 2012 study were much smaller than the real parameters confirmed by the subsequent measurement of the real twin Tu-154M.
To illustrate to what extent the Tu-154M model used in 2012 study aired on a conservative side some comparison is in order. The thickness of the skin for initial 2012 parametric study was assumed to be between 1 and 5 mm. But as we see in the picture above, the real thickness of the lower surface of the wing structure near the fixed leading edge at the place of a hypothetical contact with a birch tree was as high as 15.99 mm. It means that the model of the wing used in the 2012 study used the skin almost three times thinner than the skin in the real wing of Tu-154M.
The above comparison of the parameters used in the 2012 study with the real parameters of the Tu-154M wing are critical in evaluating the credibility of the 2011 Russian MAK and Polish Miller’s reports that incorrectly attribute to the birch tree the ability to cut off 1/3 of the Tu-154M wing that led to the Smolensk Crash.
Click on the thumbnails below to view screen dumps from the detectors used to examine the wreckage and seats from the Polish president's plane crash in Smolensk. An "X" denotes the presence of the detected explosive substance and its type. The underlined Polish word "Probka" or "probka" in the screen dump 1 and 2, means "Sample"
Why did they all fly on the same plane?
Synopsis: January 12, 2013, Toronto, Canada. The wife of the late Deputy-Minister of Culture Tomasz Merta: "What I am about to tell you now, are suspicions - and not even my own - but, rather the [suspicions of the] individuals in the inner-circles of the [Polish] military... I heard a statement that was made - but, I am not taking any responsibility for how credible, or not credible it is. [I heard that] had the generals and journalists' not been re-assigned to different aircraft, it wouldn't have been the Tupolev [Tu-154M], but rather the Casa [transport aircraft] that would have been taken out.
Because the Generals were no longer onboard the Casa, there was no reason for it to get airborne. And for this reason it was the Yak[-40] that flew off to Smolensk. This Casa [transport aircraft] was never examined in any way. It was not subject to any examination. Aside from a single note in the deposition given to the military, no one was interested why this aircraft didn't fly [to Smolensk]. Perhaps, this is someones crazy phantasy, but perhaps it isn't.
Some [Polish] military personnel had suggested, that it [the Casa] had to stay behind at the Okecie military [tarmack], so that the explosives could be removed from it - because they were no longer needed [...] I am only repeating what I was told."
"Disarming" Explosives ...
It is worth for us to retrace the entire process of "disarming" the case of explosive substances at the crash site. It all started with the publication of Cezary Gmyz in "Rzeczpospolita" on October 30, 2012, and information that the detectors, which were used by experts in Smolensk (in late September and October) showed traces of TNT and nitroglycerine.
As it turned out, the journalist was also reporting about the indication of Hexogen. The storm broke. The prosecution denied the publication, and ultimately, the editor-in-chief of "Rzeczpospolita," Cezary Gmyz and two other journalists lost their jobs. The entire editorial staff of one of Poland’s most popular weeklies, "Uważam Rze", was also silenced.
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