Investigation of aviation factors in the Tehran- Yasuj plane crash on 18 February 2018

Accidents and accidents in the aviation industry are mainly affected by meteorological and aviation factors. Research has indicated that weather conditions have a powerful impact on military and civilian aviation operations. The goal of this study is to investigate the impact of aviation parameters on flight safety using a well-known numerical model in meteorology, namely the mid-scale research and weather forecasting (WRF) model. This research identifies and analyzes the influential factors in the crash of the Tehran passenger plane to Yasuj near the Dena Mountain range. For this purpose, by calculating the load factor, angle of attack, and stall speed for the desired aircraft, the effect of each factor has been investigated. Considering the sub-zero temperature prevailing in the region, which was obtained by checking the temperature at different altitudes and times for the flight path, the phenomenon of freezing can occur on the body and wings of the plane if the plane is not equipped with a de-icing system. With the formation of ice, the smooth surface necessary for air flow is lost and the drag force increases, and the ability to produce power decreases, which leads to a decrease in height. To compensate for this additional drag, the propulsion force of the aircraft must also be increased. The nose of the aircraft must be raised to produce more thrust and prevent altitude loss, which means the angle of attack must be increased. But as the angle of attack increases, the amount of ice on the wings and fuselage increases. By calculating and checking the angle of attack on the flight path of the plane and the place where the plane hit the mountain, it is shown that the angle of attack first decreases and then increases as it approaches the place of impact. The angle of attack has a direct relationship with the drag coefficient, and with the decrease of the angle of attack, the drag coefficient also decreases, and as a result, the drag force also decreases, and the plane faces a decrease in altitude. At the point of impact, the angle of attack increases, and the plane tries to increase the height, but unfortunately, it hits the mountain. Stall speed is the minimum speed at which the aircraft must fly to maintain proper flight altitude. According to the minimum values of stall speed along the flight path and at altitudes close to the flight height, the plane flies at a speed lower than the minimum stall speed at an altitude of 4467 meters. This causes a loss of height in the flight path. By calculating and checking the load factor in the flight range for different altitudes and times with different coefficients, we reached a negative load factor in the range of the plane hitting the mountain, which indicates a decrease in altitude for the plane and an increase in drag force.