fig1 shows a gyrocopter 10 according to the invention , which comprises a rotor 12 that is fixed onto a rotor head 14 . the rotor head 14 is driven by a motor not shown in fig1 which is also intended to drive a propeller . fig2 shows the motor 18 in the form of a cylinder motor which is fixed to a support structure 22 of a fuselage 23 by two mountings 20 . 1 , 20 . 2 . the motor 18 comprises a crank shaft 24 which is connected to the input shaft 26 of a pneumatic coupling 28 . an output shaft 30 of the pneumatic coupling 28 is connected to an angular gearbox 32 . the angular gearbox 32 comprises an second output shaft 34 which is connected to a mast shaft 38 by means of a universal joint 36 . the angle between second output shaft 34 and output shaft 30 is between 80 ° and 100 °. in the present case the angle is 90 °. the mast shaft 38 ends with a pinion 40 which works in combination with a sprocket wheel 42 of the rotor head 14 . the propeller 16 has a propeller pivot d and the universal joint 36 is at the height of the propeller pivot d . it is also possible to arrange the universal joint d underneath or slightly above the propeller pivot d . fig3 shows an exploded view of the coupling 28 . the pneumatic coupling 28 comprises a mounting device 44 which should be mounted on the fuselage 23 ( fig2 ). the mounting device 44 comprises four connecting components 46 . 1 , 46 . 2 , 46 . 3 , 46 . 4 which are mounted on a base plate 48 and are connected with a front plate 50 . inside the connecting components 46 a driver 52 is arranged radially which meshes with the crank shaft 24 ( fig2 ) in the mounting position . the driver 52 comprises an anchor plate 54 which acts as a friction partner of a friction connection whereby the other friction partner is made up of a friction lining 56 . the friction lining 56 is mounted on a friction lining support plate 58 . if the motor 18 ( fig2 ) is in operation , the driver 52 rotates and thus also the anchor plate 54 . an axis centering device 60 is mounted on the driver 52 by means of a ball bearing 59 ( cf . fig5 ) into which the output shaft 30 runs and is thus embedded . a cylinder housing 62 ( fig5 ) is fixed onto the front plate 50 with a cylinder 64 . a torus - shaped piston 66 ( fig3 ) runs through the cylinder 64 which has a circular disc - shaped cross - section . the cylinder housing 62 and the piston 66 are part of the pneumatic cylinder 68 . a thrust bearing 70 is mounted on a piston 66 which comprises a primary bearing ring 72 ( fig5 ) and a secondary bearing ring 74 . the primary bearing ring 72 is connected with the piston 66 so that it is torsionally rigid , whereas the secondary bearing ring is attached to the friction lining support plate 58 so that it is torsionally rigid . a release spring 76 is fixed onto the axis centering device 60 which has arms 78 . 1 , 78 . 2 , 78 . 3 ( fig3 ). the release spring 76 is fixed , for example with screws , onto the friction lining support plate 58 at the end of the arms 78 . the holes for the screw connections for the arms 78 . 2 and 78 . 3 in the friction lining support plate 58 can be seen in fig3 . in a disengaged state the motor drives the driver 52 and thus the anchor plate 54 . all remaining elements of the coupling do not rotate . the piston 66 is arranged with its front end 80 ( fig3 ), which has a circular groove , in the cylinder 64 , to the left in fig5 . should the pressure in the cylinder 64 increase , the piston 66 will move from this neutral position against the force of the release spring 76 in fig5 to the right , along a stroke h , i . e . a distance h . in this way the thrust bearing 70 and the friction lining support plate 58 will also move on the anchor plate 54 until a frictional connection occurs between the friction lining 56 and the anchor plate 54 . the frictional connection makes the friction lining support plate 58 rotate together with the secondary bearing ring 74 of the thrust bearing 60 . however , the piston 66 does not rotate . since the arms 78 . 1 , 78 . 2 , 78 . 3 are fixed onto the friction lining support plate 58 , the axis centering device 60 also rotates , and thus the output shaft 30 which is connected to be torsionally rigid with the axis centering device 60 . should the pressure in the cylinder 64 decrease , the release spring 76 pushes the piston 66 back into its neutral position and the friction lining 56 is separated from the anchor plate . the fig3 , 4 and 5 could give the impression that the connecting components 46 are in contact with one of the rotating components . however , they are only connected to the front plate 50 and the friction lining support plate 58 and the anchor plate 54 , for example , freely rotate radially inside the connecting components 46 . the friction lining 54 has a number of grooves 82 . 1 , 82 . 2 , . . . . the grooves 82 run radially outwards and run through the entire friction lining 54 . in this way , during engagement of the coupling the friction lining 54 is cooled by an air stream , which is produced by the centrifugal force . the anchor plate 54 is perforated which improves the cooling of the anchor plate 54 . the pneumatic cylinder 68 is connected to a compressed air supply — not shown in the diagrams — of , for example , 8 bars by means of a schematically drawn throttle entry valve 84 and a compressed air connection 86 . the throttle entry valve 84 is used by means of an electric or mechanic operating device from the cockpit of the gyrocopter . fig7 shows an exploded view of a pneumatic coupling for a gyrocopter according to the invention . it should be recognized that the coupling 28 has a correcting component 88 which is arranged in the torque flow behind the motor and in front of the anchor plate 54 in the present case . the correcting component 88 is designed for the absorption of axial forces which are the result of a thermal expansion of the input shaft . in this way , it is possible to avoid an excessive burden on the input shaft bearings . in the preferred model according to fig7 the correcting device 88 comprises a correcting component 90 made from a rubbery - elastic material , for example rubber . fundamentally , every suitable shape is possible for the correcting component , but it is especially beneficial if the correcting component 90 has protrusions 92 . 1 , 92 . 2 , as in the present case , which work in combination with primary coupling protrusions 94 . 1 , 94 . 2 , . . . of a primary coupling component 98 , and secondary coupling protrusions 96 . 1 , . . . , 96 . 4 of a secondary coupling component 100 . the coupling component 98 , 100 and the correcting component 90 are designed in such a way that a protrusion 92 of the correcting component 90 is arranged between a primary protrusion 94 and a secondary protrusion 96 . the torque flow passes from a primary protrusion 94 through a sprocket 92 of the correcting component 90 and into a secondary protrusion 96 . this evens out the varying torque due to the ignition of the cylinder motor . furthermore , the correcting component 90 is arranged between a primary coupling component 98 , upon which the primary protrusions 94 are formed , and a secondary coupling component 100 , upon which the secondary protrusions 96 are formed . it is arranged in such a way that an axial force acting in the axial direction r compresses the correcting component 90 , so that the axial force which acts upon a bearing of the input shaft — not shown in the diagrams — is also limited to a value of less than a maximum permitted axial force during a thermal expansion of the input shaft . fig8 shows the coupling from fig7 in a cross - sectional exploded view .