Reducing brake squeal

Engineers at BFGooddrich Aerospace focus on enhancing brake rod bending-mode damping.

In multi-brake aircraft landing gear systems, it is common for brake rod bending to participate in brake squeal vibration modes. Experiments have proven that damping the bending mode of the rod can reduce vibration. BFGoodrich Aerospace has developed such a method using a simple, lightweight, split-tube insert for tubular brake rods.

Brake squeal is well known as one of the dominant causes of aircraft braking system vibration. It can be excited, aggravated, or destabilized by system characteristics such as a negative friction-speed coefficient or structural feedback. The dominant motion is pitch-plane torsional oscillation of the nonrotating brake structure at frequencies near 200 Hz in large brakes. There are several squeal modes of a multi-brake landing gear system, differentiated by the phase of one brake with respect to others, but all are system modes characterized by the participation of nonbrake structural components and motions and include some amount of brake rod bending. The amplitude of vibration can be reduced by introducing damping to any component in the path.