Expert: Paul Soderman - 4/24/2009

Question
I'm trying to understand some brake aicraft noise after landing. The problem only occur during taxiing after landing if the brake is hot. I notice more occurence during winter than summer season.
Do you think carbon brake can produce noise?
Is de-ice fluid or runway contamination during winter could impact in the noise problem?
thank you
Wilfried

Answer
Wilfried
I know little about aircraft brakes, but I would be surprised if they did not make noise.  They are comprised of multiple discs in the main wheel hubs (some fixed, some rotating) that are squeezed together by a piston on landing.  The huge kinetic energy of the aircraft is turned into heat in those discs, not counting the aerodynamic braking and engine reverse thrust.  That brake friction makes a lot of noise.  And even with the brakes released they are still hot.  I assume the components will have expanded and may rub in such a way to continue to make noise.  When they are cool, the components will have separated a bit to make much less noise.  I also assume a fluid in the brakes would change the noise, but I am making too many assumptions.  A brake expert could be more informative.
Paul