Reduction of aircraft tyre wear by pre - rotating wheel using

Heavy aircraft main landing gear tyres skid immediately after touchdown as result of the high slip ratio between the tyres and runway, which lead to tyre wear and smoke. In this paper, the tyre wear is modelled on the Archard theory using ANSYS mechanical transient, to reveal the wheel’s dynamic and the tyre tread wear. The wheel’s dynamic and the amount of wear are calculated for initially static and for pre-spun wheels in order to find the effectiveness of the technique of pre-spinning the wheel, as suggested by many patents since the early days of airplane use, in order to eliminate aircraft landing wear and smoke. Introduction The heavy aircraft typical landing requires a high approach speed relative to its weight limitation to avoid a high sink rate [1]. This leads to a high slip ratio between the main landing gears wheels and runway as the tyres touchdown with zero rotational speed. At landing impact, tyre sliding occurs and then it spins-up to reach aircraft forward speed. High tyre slip generates heat, which is enough to melt a layer of the tread rubber. Melted rubber became weak as its material bonds linkage is broken when the critical temperature is exceeded [2]. One-third of the eroded rubber burnt off under the skidding tyre vaporizes in the form of smoke, while the remaining eroded rubber adheres to the runway [3]. However, the tyre temperature rises up as slip increases. Therefore, the skidding wheel distance and time are major factors of tyre wear and smoke [4]. However, wear is a complex phenomenon; and it is difficult to get the exact value [5]. The Archard wear theory is a simple and common model used to calculate sliding wear between two bodies and it is chosen by ANSYS [6, 7]. The Archard formula considers the main parameters: the reaction force acting on the tyre contact patch, slip distance, contact surface, and environmental conditions such as temperature, hygrometry, and atmospheric composition [8]. Bennett, M., et al., (2011) studied the smoke generated by aircraft landing using optical and condensation particle counters plus a scanning Lidar system [3]. The researchers showed the total rubber lost from Boeing 747 main landing gear tyres per landing to be up to 1 kg. Multiple studies were found to have simulated aircraft wheel dynamics at landing impact. A Boeing 747-400 main landing gear “shimmy” oscillation has been modeled by Besselink (2000) [9]. The wheel spun-up from zero rotation to free rolling within 0.1 seconds, which agreed with Khapane (2006), who modeled the aircraft wheel dynamic at touchdown [10]. Padovan, Kazempour and Kim (1991) modeled the energy balance of a single wheel of the spaceshuttle. In this study, interfacial friction between the tyre and runway work rate was computed and the spin-up time was estimated to be in a range of 0.1 to 0.24 depending on the constant friction coefficient of 0.7 and 0.3 respectively. After various simulations, they concluded that the tyre wear increased in line with an increase of surface friction coefficients, the horizontal landing speed and the sink rate [11]. In this paper, a case study of a Boeing 747-400 single main landing gear wheel is modeled using ANSYS to estimate the amount of tyre wear immediately after touchdown for static and prespinning wheels; and is based on the Archard wear theory. The model provides results for tyre tread wear, skidding distance and time for a typical aircraft landing, and for wheels already rotated before touchdown, to check how much reduction of tyre wear can be achieved by pre-spinning the wheel, as suggested by many patents [12-14]. The results are expected to be highly accurate as ANSYS provides results which are very close to those in real operating conditions. Moreover, the input data includes assumptions that are used for all simulations are similar in order to get a fair comparison of results. Modeling and Simulation The technique used in a typical aircraft approach is to maintain a constant speed until about 15m above the runway threshold and then flare to reduce the sink rate for a smooth landing. This manoeuvre increases the aircraft pitch angle to induce drag, which will reduce the landing speed by approximately 10 knots (5.14 m/s) to lessen the landing distance [15]. Fig. 1 shows the aircraft landing process; approach, flare, fully locked and spin-up wheels and deceleration. This model simulates the skidding phase after landing impact. Constant horizontal speed is used, because the pilot will not apply the brake immediately after touchdown to avoid more wheel skidding that leads to increased tyre and brake pad wear [16].