International Journal of Crashworthiness and ASCE Journal Smolensk Crash Articles
Smolensk Crash Scientific Research Articles by Dr. Wieslaw Binienda, PhD, Menglong Ding & Dr. Andrzej Krzysiak, PhD
Published: March 16, 2020
"Numerical approach to a reverse problem using LS-DYNA3D analysis: collision of an aeroplane door with the ground"
by Wieslaw K. Binienda PhD & Menglong Ding
Nonlinear finite element analysis (FEA) with LS-DYNA3D is used to determine the initial conditions needed for aircraft components to become damaged as observed after impact with the ground. Determining initial conditions of aircraft or components—impact velocity, orientation with respect to the ground before impact, and average soil properties—could reproduce the damage observed at the final state and reveal the condition of the structures immediately prior to collision with the ground. Predictive methods using FEA require detailed reverse engineering modelling of components, highly accurate material model characteristics and multiple numerical simulations for unknown parameters in order to identify average soil properties and initial conditions of components such that the numerically generated final results will agree with the condition observed following impact. A case study is presented in which various scenarios are considered for the impact of the door of a large passenger aircraft with soil at the crash site.
Often at aircraft crash sites, some fragments of an aircraft are found buried in the ground, while others create visible grooves or craters in the soil at the site. One of the tools available to crash investigators is a reconstruction of the physically possible conditions of the aircraft and its components immediately before impact with the ground that can reproduce the final damaged state of the component and the ground at the impact area. Since the nonlinear finite element analysis (FEA) code LS-DYNA3D can be used to compute large models using a parallel computer cluster, it has become possible to determine the unique initial conditions needed to reproduce the final damage state of the aircraft components or the entire aircraft [1–3]. Hence, the inverse problem can be solved to determine the initial state based on information about the final state.
Recently, Zinzuwadia and Olivares  described such an inverse problem solving (or ‘reverse engineering’) effort conducted by the U.S. National Institute for Aviation Research (NIAR) for simulation of the crash of Turkish Airlines Flight 1951, a Boeing 737 aircraft that crashed during its approach to Amsterdam Schiphol Airport, Netherlands, on 25 February 2009. The results of this study were used to validate a predictive methodology developed by NIAR that can help to simulate other collisions or can be used to evaluate designs from the point of view of structural crashworthiness when, for example, new materials such as fibre-reinforced composites are incorporated. The Federal Aviation Administration of the United States (FAA) now requires that applications of composite materials into an aeroplane structure must produce a design at least as safe as the best understood aircraft materials that are composed of metals and metal alloys, and the NIAR methodology may prove useful in validating new designs.
In the study presented in this paper, the same NIAR methodology used to simulate the crash of Turkish Airlines Flight 1951 has been applied to identify the initial conditions for the passenger door found buried in the ground following the crash of a Tupolev Tu-154M aircraft in Smolensk, Russian Federation, on 10 April 2010. Based on the investigation of this door, the final damage condition and configuration of the door in the ground was established: the door was embedded in the ground to a depth about 1 m and found in a position that was nearly perpendicular to the ground. After the door was excavated, the level of damage was documented in a photograph and was also represented by a schematic, as shown in Figure 1. The ground was penetrated by the door plate, starting with the long edge originally positioned forward (toward the front of the aircraft), which is defined here based on its final orientation as the bottom leading edge, since it was the edge that had penetrated most deeply into the ground. Hence, at the moment immediately prior to impact with the ground, the door was positioned in such a way that the inner side (concave face) of the door pointed in the direction of motion of the aircraft, the door was rotated 90 sideways (with the long edges of the door at the top and bottom), and the door shell was in a nearly upright position (i.e. was perpendicular to the ground) with the long forward edge making first contact with the surface of the ground. The damage to the door, as observed on the inner face, is shown in Figure 1.
"Wind Tunnel Tests of Damage to the Tu-154M Aircraft Wing"
by Dr. Andrzej Krzysiak, PhD
Wind tunnel experimental tests were performed to investigate the influence of the damage to the Tu-154M aircraft wing on its aerodynamic performance. The wing damage concerned the detachment of one-third of the aircraft left wing and the loss of the left slat and flap and the loss of the left outer wing. The presented research referred to the Polish government aircraft Tu-154M disaster near the Smolensk airdrome on October 4, 2010, and one of the hypotheses about its causes. The experimental investigation was carried out in the Institute of Aviation low speed wind tunnel T-1 with a 1.5 m diameter test section at the V∞=40m/s . The Tu-154M aircraft model at the 1∶40 scale was used. Aircraft aerodynamic characteristics were obtained by balance measurements. Wind tunnel tests showed that the damage of the aircraft left wing results in the appearance of the aircraft rolling moment of a significant value. The investigation proved that in the case of one-third wingtip loss there were opportunities to balance the aircraft flight by simultaneous aileron (at 20°) and spoiler deflection (at 45°) on the right wing or by putting the aircraft into a sideslip.
The history of aviation knows many air accidents when, as a result of a collision with other objects (flying or ground), a part of an aircraft was lost. In particular, a loss of a part of control surfaces or lift surfaces was very dangerous and often led to a crash. It was usually due to the lack of the aircraft flight control possibility or the lack of airplane crew skills to react properly in such a situation.
There were also some other accidents when despite the loss or serious damage of some parts of an aircraft lift surfaces or control surfaces, the crew of the aircraft managed to continue their flight and landed safely. Probably, the most spectacular air accident, after which the crew managed to land safely despite the loss of a significant part of the wing and outer aileron, took place in 1965. This accident occurred shortly after takeoff of the Boeing 707-321B (with 143 passengers and 10 crewmembers aboard) from the San Francisco airport, at an altitude of about 240 m above the ground. After the explosion of the outer underwing engine, the aircraft lost about 7.5 m of its outer wing (the aircraft wing span–44.4 m) including outer aileron.
Another well-known incident occurred in 1983 in Israel during a mock aerial combat between two F-15D Eagles and four A-4N Skyhawks, when one of the F-15Ds collided with the A-4N (Grant 2013; Leone 2014). As a result, the Eagle lost almost the entire right wing. Furthermore, considerable fuel leaked from this wing, and the aircraft fell into a spin. The pilot realized the fact that the aircraft had been seriously damaged, but he regained control of the aircraft and landed safely. A similar incident took place in 2014 when during a mock aerial combat two F-16Cs collided. As a result, one of the F-16C lost almost half of the right wing. Despite this damage, the pilot landed safely at the airport.
The history of air accidents, including the above-mentioned events, indicates that even serious damage to the wing does not necessarily lead to a plane crash. Much depends on the flight conditions during accident, on the skills of the pilots, and their proper reaction in such a situation.
An aircraft control capability in situations of a loss of part of the aircraft, and the possibility of maintaining controlled flight to a safe landing became the subject of scientific research. This subject was taken among others by the NASA within the Integrated Resilient Aircraft Control Project IRAC (Guo and Litt 2007). This project aimed to develop technologies to prevent or recover from aircraft loss of control and ensure safe flight under flight upset and hazardous conditions. One of the investigated issues was the loss of part of the aircraft. To determine the flight dynamics after the aircraft damage during the flight it was necessary to obtain aerodynamic characteristics of the aircraft in damage configuration. To accomplish this, wind tunnel tests were conducted to measure the aerodynamic effects of damage to lifting and stability/control surfaces of a commercial transport aircraft (Shah 2008, 2012).
Wind tunnel tests described in this paper relate to the crash of the Tupolev TU—154M aircraft of the Polish Air Force near the city of Smolensk, Russia. All 96 people on board were killed. Among the victims were the President of Poland Lech Kaczyński and his wife. The causes of the disaster are still being investigated. Experimental investigation relates to the conclusion presented by Russian and Polish special commissions for the investigation of the accident that the direct cause of the crash was a collision with a birch tree resulting in the loss of about 6.5 m of the left wing tip including the left aileron (Interstate Aviation Committee “MAK” 2010; State Commission on Aircraft Accidents Investigation 2011). The resulting asymmetrical lift caused an uncontrolled aircraft roll to the left, and then the plane turned upside down.
The main purpose of the presented research was to provide the aerodynamics data of the Tu-154M aircraft after its wing damage which would help in the final determination of the disaster process. In the paper, the wind tunnel test results of the Tu-154M aircraft model at 1∶40 scale are presented. To determine the influence of the wing damage on the basic aerodynamic characteristics of the Tu-154M aircraft, the model was tested both in configuration with an undamaged wing and in several configurations with the damaged wing.
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.
Disclaimer: The views and opinions expressed herein are those of the author and do not necessarily reflect the views the SmolenskCrashNews.com. All information is provided on an as-is basis, and all data and information provided on this site is for informational purposes only. The Smolensk Crash News DOT COM makes no representations as to accuracy, completeness, currentness, suitability, or validity of any information on this site and will not be liable for any errors, omissions, or delays in this information or any losses, injuries, or damages arising from its display or use.