the hydraulic fluid contained in the annular chamber 4 is pushed back to the pressurized hydraulic fluid supply of the aircraft since the pneumatic chambers are thus placed beside the main cylinder the shock absorber thus has an extended length l that is particularly compact in a particular aspect of the invention the shock absorber is designed to enable the rocker beam to be retracted in order to limit its aerodynamic drag in flight for this purpose controlled shortening of the shock absorber is organized as follows high pressure hydraulic fluid typically at 206 bars is injected into the annular chamber 4 via the first controlled valve 30 thereby tending to retract the rod 2 into the main cylinder 1 simultaneously a second controlled valve 31 enables the uninterrupted chamber 5 to be put into communication with a flask 40 such that the hydraulic fluid contained in the uninterrupted chamber 5 can be evacuated into said flask 40 the hydraulic fluid received in the flask 40 pushes back a piston 41 slidably mounted in the flask 40 which in turn pushes back the hydraulic fluid present under the piston 41 towards the supply of the aircraft it should thus be observed that the hydraulic fluid from the uninterrupted chamber 5 does.