EXCERPT from the REPORT dated April 11, 2022
on the CRASH of the Polish Air Force One TU-154M on APRIL 10, 2010
over the SMOLENSK-SEVERNY AERODROME IN RUSSIA
Comparing results of computer simulations
with the factual state of debris on the wreckage field
The American National Institute of Aviation Research (NIAR) and the Polish Military University of Technology (WAT) conducted computer studies aiming to simulate the impact of the Tu154M airplane into the ground according to the initial conditions in the configuration assumed in the Russian MAC and Polish Miller’s final reports released in 2011. These studies were designed to produce simulated debris fields that would be compared to the factual debris field for verification purposes.
The development of a numerical model of the aircraft required a reverse engineering approach. This approach included many geometric measurements of individual structural components of the twin Tu154M airplane, experimental characterization of materials used for those components, building a CAD model of the entire airplane, and converting this model into the Finite Element Model for LsDyna analysis.
The entire FE model consisted of 33 million elements, including a large number of 1D elements, used for connections such as rivets and screws. A close-up of the center wing shows the structural accuracy of this model. The simulation can be considered an accurate computer representation of the crash event. Results can be used to examine the validity of the assumed initial conditions by comparing the simulation results with the real state of destruction.
The initial conditions of the simulation are as follows:
-aircraft is rotated around its axis about approximately -150 degrees
– impacts into the soft and wet soil with a horizontal speed of about 76 m/s and a vertical speed towards the ground of about 18 m/s.
Overlaying the results over the satellite image of the main debris field with a 5-meter grid, the visual representation of the destruction of the 80-ton airplane can be observed in the simulation for the duration of 1 second from the moment of the contact with the ground. NIAR ended the computer simulation at 1075ms. At this time, all parts of the aircraft are still in the process of moving over the surface of the ground with a speed from 20-50m/s decelerating due to friction.
In the next part of the presentation, we focus on large fragments of the aircraft and compare simulation debris to factual debris. In each case, fundamental discrepancies prove that the actual destruction of the airplane was not caused by the impact into the ground of the entire airplane in the configuration and with the initial conditions assumed by MAC and Miller’s reports.
First, we will examine the passenger section of the fuselage. The computer simulation shows the roof collapsing into the interior of the fuselage. However, the factual damage of this section of the airplane shows the roof opened outward. Analysis shows that the roof of the fuselage fractured along the row of rivets that connects the stringer with the skin of the aircraft. This was caused by circumferential principal stress generated by large internal pressure. Furthermore, the fracture of the fuselage roof had to take place in the air prior to impact with the ground so that the ground would not impede the opening of the roof.
Next, we will examine the pressure bulkhead of the airplane. In the computer simulation, the tail part of the plane broke off from the passenger part of the fuselage, but the pressure bulkhead remained connected to the passenger part. We can see that the bulkhead is damaged only near the ground and it moves forward together with the passenger part of the fuselage sliding on the ground.
In reality, the pressure bulkhead remained connected to the tail part. This demonstrates that the internal pressure in the fuselage not only tore apart the roof but also sheared off all rivets with the bulkhead and exerted an aft pointing force on the tail with the engines. In this way, the progressive kinetic energy of the heavy engine mass was reduced by this force.
The tail part and the engines are the heaviest fragments of the Tu154M plane. According to the laws of physics, such a massive part should travel the farthest on the ground in the main field of debris due to the law of momentum. The reality that this large mass stopped at the beginning of the main field of debris is the outcome of a rapid impulse in the aft direction.
Let’s see what happened to the engines in the NIAR simulation. Both engines – right and left – broke away from their pylons, and the middle engine freed itself from the mounts inside the tail and partially slid outwards. In reality, only the right engine was detached completely from the pylon, and the other two engines stayed together with the tail section in the main field of debris. The mounts of the middle engine were not broken so that this engine remained inside the tail part in its normal position.
Now let’s examine the destruction of the vertical and horizontal stabilizers. In a computer simulation, the vertical stabilizer was not separated from the tail section, while the horizontal stabilizer completely broke off from the vertical stabilizer. In reality, a significant part of the vertical stabilizer together with the horizontal stabilizer was separated from the aircraft before the Kutuzov road. This detached T-shaped fragment flew towards the southern border of the main field of debris and hit the ground with the tip of the right section of the horizontal stabilizer at the rotated configuration of about – 210 degrees. This fact can be found in the documentation of the MAK report. Thus, in the simulation, the forces on the stabilizers acted differently than they did in reality.
Let us now discuss the process of destruction of the passenger door from the starboard side. In the simulation, the fuselage together with this door impacted into the ground. As a result of this impact, a large crater in the soft wet soil has been excavated. The door was crushed and twisted due to the interaction with the heavy fuselage sliding on the ground above the door. Due to the rapid sliding movement of the fuselage on the ground, the door has no chance to be driven perpendicularly into the ground. Instead, the fuselage moved faster from the door which eventually was dropped behind, became airborne to land back several dozen meters further away, flat on the ground.
In reality, the door was driven like a razor blade perpendicularly to the surface, one-meter deep into the ground, at the very beginning of the main field of debris. Inside the door structure, the remains of human tissue were found, which had to be squeezed into the door structure cavity before the door was ejected from the airplane. The polymer material from the cabin side door cover had visible signs of high-temperature exposure. The actual deformations of the door structure are also completely different than the deformations obtained in this computer simulation.
Another NIAR study was dedicated to the analysis of driving the passenger door into the ground in such a way that the door is buried the same way as in reality, and the resulting deformation and damage is similar to that observed in reality. The results concluded that the necessary condition to reach this goal is a minimum vertical speed before impact with the ground of about 125m/s while the horizontal speed needs to be smaller than 30m/s.
The only way to obtain the necessary conditions for the door to be injected perpendicularly into the ground is for the door to be violently ejected by high internal pressure within the fuselage while the fuselage is still in the air. The position of the fuselage must be oriented with the left wing pointing into the ground and the cockpit pointing slightly down. In this configuration, the door launch speed vector was directed to the ground and backward, which resulted in an increase of the vertical speed from 18m/s to over 125m/s and a decrease of the horizontal speed from 76m/s to below 30m/s.
To assess the importance of the vertical speed of the crashing airplane into the ground, WAT performed impact simulations for the entire aircraft similar to the NIAR simulation but assuming the initial vertical speed to be 12m/s, according to the vertical speed recorded in the black box just before the loss of power. The vertical initial speed in NIAR simulation was assumed to be almost 18m/s. The comparison of WAT and NIAR simulations has shown that a lower vertical speed increases the survivability rate of passengers, especially those seating in the rear part of the fuselage.
The results of the NIAR simulation of the airplane impacting the ground, even at a very high vertical speed, do not agree with the actual state of the wreckage of the airplane and the scattering of the remains of the victims on the main field of debris. In fact, tens of thousands of fragments of the fuselage debris and human remains were scattered over a width of up to five times the fuselage diameter. In addition, heavy parts of the aircraft, such as the engines and tail part marked with the numbers “62” “55”, stopped at the beginning of the wreckage field, while the lighter parts of the fuselage landed about 100 meters away, as can be seen on the situation map from the MAK report.
If we include visualizations of fragments found underground by Polish archaeologists, we see the actual degree of fragmentation of the airplane. The airplane system must contain enough energy to break off and deform into so many fragments. The impact of the airplane into the ground would not achieve the degree of fragmentation of the aircraft that is observed in Smolensk. Explosions provide the additional source of energy needed to obtain such a degree of fragmentation as we observe on the wreckage site in Smolensk.
The dispersion of all fragments on the ground is presented on a map of the actual state of damage for this airplane in the form of debris, victim fragmentations, and damage to the trees and traces on the ground, which allowed us to discover the true nature of the disintegration of this aircraft.
Conclusions:
- The assumptions adopted in the Russian MAC and Polish Miller’s report used in the NIAR and WAT simulations gave results that do not correspond with the actual state of the evidence found on the field of debris in Smolensk.
- The left wing was torn apart as a result of an explosion about 100 meters before the so-called Bodin’s birch;
- A significant part of the vertical stabilizer together with the horizontal stabilizer was torn off before the Kutuzov road;
- The pressure bulkhead rivets were sheared off from the passenger part when the roof of the fuselage was fractured by high-pressure stresses while still in the air;
- The left passenger door was ejected from the fuselage while the plane was still above the ground by a high internal pressure which was required to generate necessary velocity vector components to embed this door along with fragments of human tissue one meter deep into the ground;
- The ballast fuel tank under the third compartment of the center wing was destroyed by a significant explosion;
- The fuselage along the starboard side was destroyed by a series of small explosions;
- The passengers and crew of the Tupolev were killed as a result of the explosions.
Scientific analyses and results of experiments on several aspects related to the Smolensk crash were published in the peered reviewed international journals.
See the video of this presentation with simulations here: https://www.youtube.com/watch?v=wycYXnJDTKY
