Aircraft brake springs requiring testing in excess of 200lbs can be physically and technically demanding. Hydro pneumatics solved the first problem but in its application, consistency was not easily achieved, due to the inherent out of square condition of all spring's end faces. This problem was accommodated by the mechanical referencing of the end faces and by averaging the multiple test procedure. A test reading can be taken every five seconds.
To change from testing one spring type to another with different test loading, is just ten seconds.
Hanley Smith - Solving aircraft maintenance issues.
