Expert: Marc Ebelini - 12/7/2008

Question
Dear Marc,

I was wondering how it can be that pedals in an airplane are used both for braking and for controlling the rudder.

First, how does a pilot use the pedal for one or the other, and second, how is this double function implemented technically?
Do pedals in all planes work the same way?

Thank you very much in advance,
Dennis  

Answer
First of all not all aircraft use the rudder pedals as the brake pedal.
Neither are all aircraft steered on the ground with the pedals. The nose gear on larger aircrcraft use a little steering wheel for this function that is noramlly hydrylically controlled. While it would take hours to go throught the different aircraft models to discribe them all I will try to keep it simple. First with the dual pedals. The shaft that is pivoted on the bottom will have the pedal mounted with another pivot in the center of the pedal. Pushing the pedal uniformally controls the rudder but on the ground the pressure is applied at the top using his toes for force rather than his whole foot. The force on the top pushes down on the hyd clylinder behind the pedal. On the old Piper cubs it was a straight functioning pedal and the heel was applied to a pedal on the floor that controlled each wheel cylinder. This was needed to lock a wheel so that the tail would swivel to turn the aircraft on the ground. Piper used these same brake cylinders in their Piper Tripacer where they were pulled by a cable attached to a lever to brake the aircraft. That was because they steered the plane by the pedals on the round. One more scenerio. Beechcraft Bonanza's copilots pedals retracted into the floor. when retrieved for use they only functioed as rudder pedal and the pilot was responsible for braking with his toe brakes. Hope this satisfies your curiousity?