ABS system use impact on braking torque in aviation brake

ABS (Anti-Locking) systems improve performance and safety of the braking systems. Use of ABS is now factory standard in both commercial and military aviation. ABS system in its origin was designed in order to prevent wheels from slipping and locking on the low friction surfaces such as ice. By preventing wheel, locking ABS system helps in not losing control over the vehicle during difficult braking conditions. In Aviation ABS, systems were introduced quite early as mechanical systems but their common usage is connected with computer and electronic systems development in 1970’s. In aircraft, ABS systems are responsible for safety of braking by preventing phenomena described above and for preventing landing with engaged brakes what is common in military and in big commercial aviation. In modern aviation ABS systems use is both safety and economical feature resulting in visible profits during airplane lifetime. Other question is efficiency of the process i.e. braking torque value. Braking torque is the most important parameter of brake from exploitation point of view. It is directly connected with braking distance as well with amount of force needed to achieve assumed braking parameters for the mechanical vehicle. Stability of braking torque is important in order to get optimized characteristics of the braking process itself. Most of the brake characteristics and efficiency calculations were based on assumption that braking torque should be stable during braking process. In this paper author would like to investigate ABS use impact on braking torque, which by definition is not stable in anti-lock equipped systems. Author will base on literature sources as well as on results of laboratory tests made during development of ABS system for 2700 kg take off mass airplane made in Landing Gear Laboratory of Warsaw Institute of Aviation in which author works on daily basis.