Aeronautical Engineering/brake noise


I have a RV9-A. The left brake makes a noise each time you use it. It is not a squeal. It is a loud vibrant sound. Put on new brake pads(Rapco) -no different. The brake disk is square. I put on a straight edge and there was no warping. Brakes work fine while using them. What could be the cause? Replce disk?

Certain aircraft are known to exhibit this problem. For example large commercial jet pilots have reported the MD-80 occasionally has bone jarring vibration just before stopping. Small aircraft operators refer to this as "chatter". There have been many scientific papers written on the subject of "Friction Induced Vibration".

There is a wide variety of noise and vibration phenomena in aircraft brake systems that must be accounted for in the design process of such systems. These phenomena include such modes as whirl and squeal, the latter of which can be quite different from its counterpart in automotive systems. Complicating matters is that brake‐induced vibration often involves strong coupling with the aircraft structure, thereby necessitating a system level understanding beyond the brake itself.

I suggest two possible solutions...

1) I have taken a clean cloth and wiped an extremely small amount of silicone lubricant on the rotor - you do not want the pad to absorb any. Then carefully taxi the airplane and make sure there is not uneven grabbing. If you over do it a little bit, you can use carburetor cleaner or brake cleaning fluid as a solvent to get rid of excess silicone. It is always easier to dab a bit more silicone lub than to have to remove it all and start over.

2) Many pilots are unaware that RAPCO, GOODRICH, CLEVELAND, and other manufactures recommend brakes be "broke in". It is a rather counter intuitive violent method! See this link...  

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Jan Zumwalt


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Current president of EAA chapter 837 (Payette, ID)

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