a suspension system including a front suspension plane located at an intermediate turboshaft engine casing and connecting same to a pylon , a rear suspension plane located at an exhaust casing of the turboshaft engine and connecting same to the pylon , and a failsafe intermediate suspension plane located between the front and rear planes and including at least one connecting rod connecting the turboshaft engine having a structural outer casing to the pylon , the connecting rod mounted on the turboshaft engine with a predetermined clearance that renders the connecting rod inoperable while the suspension system of the rear plane is operating . the connecting rod is advantageously arranged between the outer casing and the pylon , and an element made of a flexible material is combined with the connecting rod to create the predetermined clearance by an elastically deformable nature thereof .