by-pass valve
 

Hi all

What is the function of the bypass valve in steering system in landing gear systems?

I don't know what kind of machine your talking about, but basically, its to release hydraulic pressure from the nose steering system during push back, so the hydraulics don't blow things apart when the tug operator turns the nose gear with the tow bar.

Bypass in the steering system normally means that both sides of the steering cylinder are connected to each other. So you have no counteracting force when the tow truck is doing his work.