With each landing, the inner bore of the shock absorber wears out a little bit more. When the maximum is reached, the shock absorber becomes too weak and therefore unreliable. Its life span can be prolonged by inserting a metal tube, a sleeve.

Brute force versus mastered power

To get the sleeve inside the shock absorber used to be a physical test for the mechanics at Fokker Services : The inner bore of the shock absorber measures 0,02 mm less than the sleeve. To expand the metal, the shock absorber was heated (150°C) first. Then, two men with heavy hammers slammed the sleeve in quickly and with brute force. This way, the sleeve could easily get stuck and then it would become totally useless.

Simply using one cylinder was not an option, since the stroke length is insufficient to insert the sleeve in one motion. But then Holmatro presented a solution which does generate sufficient stroke length and pulling force. After heating the shock absorber, three coupled double acting hollow plunger cylinders now pull the sleeve inside the shock absorber in one controlled movement, by means of a tailor made iron bar.