mounting a propulsive system on an aircraft airframe 12 by means of an external strut 4 which connects the engine 1 with the airframe 12 said strut 4 comprising a plurality of spars 8 intruding into the airframe 12 and means 7 9 11 for attaching said spars 8 to the internal airframe structure 10 the cited means 7 9 11 being dampers shock absorbers or active actuators with characteristics chosen so that the said means 7 9 11 are particularly suited for the efficient reduction of attachment and internal dynamic loads arising mainly but not only from hard landing events and aircraft flight manoeuvres and for damping sustained vibrations of the propulsive system airframe 12 assembly the said arrangement allowing the easy removal of the strut 4 from the rest of the said airframe 12 and the interchangeability of the said strut 4 between different aircrafts being also the cited arrangement tolerant to damage or complete failure of at least one of the said spars 8 application_number US 99899107 A description the installation of modern high by pass engines cowled or uncowled on aircraft requires consideration of the large loads introduced in the airframe due to the dynamic response of the engine pylon airframe assembly to normal and emergency flight conditions consideration must also be given to the level of sustained vibration in the cabin during normal flight and also in such conditions as those produced in and after the event of losing one or more rotor blades in flight the problems caused by the dynamic response can be particularly severe in the case of high by pass engines due to the large centrifugal forces generated by the unbalanced rotation of the relatively heavy rotor blades at high speed the rotor unbalance may be caused.