Adequate Protection Systems for Reduction of Wear on Tornado Aircraft

The use in service life of the Tornado aircraft showed several areas subjected to wear. Due to its design some of them include, for example, the attachment for the variable wings, the related components and the flap tracks; some concern the taileron and the air intake ducts. According to this, the affected interfaces of different materials and the structural components have been protected with appropriate coatings to maintain the operability of the aircraft. Depending on the function of the moveable joints on the structure coatings with adequate hardness and wear resistance have been adopted. The range of applied anti wear coatings comprises both organic and inorganic compounds, such as polymers, composites, oxides, carbides, etc.. Sometimes the adopted protection methods showed good results; in other cases, alternative systems to improve the wear protection have been investigated. This paper describes protection systems proposed and introduced on components in the Tornado aircraft structure subjected to adhesive and erosive wear. Particular attention will be addressed to the flap tracks and to the leading edges of both taileron and air intake ducts. 1.0 INTRODUCTION The Tornado is a multirole fighter – bomber aircraft with a variable sweep wings. In relation to its characteristic, several structural groups, in addiction to the engines, are subjected to different kind of wear that include, for example, the wing attachment, the nib an the fairing. In particular, the related components of the wing attachment, such as the pivot pin, the bearing and the shear bearing device, are affected by sliding and fretting, as well as the roller and the bearing pin of the nib are exposed to friction. Other structural parts, such as the leading edge, are exposed to damage caused by the impingement of raindrops of high speed or owing to the missile firing. In an effort to find a solution, IAF, GAF, RAF and the related Industries have been concerned to introduce adequate protection systems to maintain the operability of the aircraft. Therefore, investigations with several materials were performed by tests simulating the realistic service conditions, in terms of loads, speed, temperature and environmental exposition. The wear resistant coatings comprise composite materials [1, 2], ceramics [3], and both organic [4] and inorganic [5] compounds. The minimum cost and the best performance in terms of wear resistance, high temperature strength and chemical stability made in the last years more attractive the use of ceramics and composites. Most of the adopted systems showed good results in terms of FH, so that they have been introduced on Tornado aircraft structure. Table 1 shows some structural parts subjected to wear and the specific materials applied. Nevertheless, in some cases, the achieved results were not satisfactory and further investigations are still ongoing. Paper presented at the RTO AVT Specialists’ Meeting on “The Control and Reduction of Wear in Military Platforms”, held in Williamsburg, USA, 7-9 June 2003, and published in RTO-MP-AVT-109.