to it a revolution counter in order to have an absolute measurement of the position of the rod of the jack 6 a 6 b the position measuring member therefore returns a value representative of the number of revolutions performed by the drive rod and an angular measurement value these two values make it possible to determine precisely the length of deployment of the rod of the jack 6 a 6 b a diagram showing the steps of a method according to the invention for the calibration of the jacks is depicted in fig3 first of all the calibration procedure is started by a command 100 which comprises applying power to the electronic elements particularly the position sensors that sense the positions of the jacks 6 a 6 b this command can be issued from the airplane cockpit or from a nacelle electronic controller this command is followed by a checking step 101 which checks whether the operator has selected a manual or automatic calibration mode in the case of manual calibration 102 the operator manually closes the reverser during a step 103 in so doing he places the jacks 6 a 6 b in the retracted position the operator then asks the controller to log the position values from the resolvers of each jack 6 a 6 b during a step 104 these values determine an electric retraction stop the operator then manually brings the reverser into the deployed position during a step 105.