On the other hand the bolt must breake as planed early enough when extremely overloaded. Thereby the integrity of those highly loaded components must not be affected by wear and corrosion. To those belong especially dynamic loads.These are apparently not always sufficient known ( Fig. In one respect, the connection bolt must meet the high safety requirements against a failure under the normal long time operation loads. With this feature the design will be a difficult task. "Fracture of the engine connection at the pylon"). This is also required to avoid the fracturing of the wing tanks ( Fig. "Engine mounts specific problems of elements"), certain connection bolts (fuse pins) may only fail in a defined sequence ( Fig. Not to endanger the structure of the wing or the nacelle ( Fig. 10-6): Overload during operation: This develops by unbalances or the failure of a mount element ( Example "Engine mount maintenance deficit"). In this case a catastrophic accident becomes probable.įigure "Engine mounts specific problems of elements" (Ref.
Because if the primary thrust load path fails and also the second it's to reckon with the separation of the engine ( Example "Engine mount maintenance deficit"). The concerned connection bolts must be assembled again with the right torque.Ĭomment: Just because the importance of the concerned component for the fail safe-behaviour tis feature is not second-rank. These are different types of a twin engined aircraft. In an “emergency airworthiness directive” (EAD) more then 200 concerned aircrafts are addressed. This shall guarantee the fail safe-behaviour ('only active upon failure') should the primary thrust load path fail. 23.3.1.1-2) and increases the risk of a fatigue failure.Ĭoncerned are components of the „ secondary thrust load path“. This resulted in a too low initial tension which means a higher dynamic load (German edition, Volume 5 Ill. Thereby a too low torque at the connection bolt of the front engine mount, differing from the instructions, was applied. It goes back to an other airworthiness directive. 10-5): The problem developed within a maintenance task, ordered by the OEM (service bulletin). These are addressed at the operator to check and possibly change the affected parts/components.Įxample "Engine mount maintenance problem" (Ref. In such cases instructions like AD-notes serve the risk minimisation. Usually first signs will be identified in time by maintenance or overhaul before a catastrophic failure may occur ( Example "Connecting bolt failing by corrosion" and Example "Connection rods showing cracks"). "Load transfer from the engine into the wing" and Fig. Problems with engine mounts which even lead to the separation of the engine are seldom ( Fig. stiffness/rigidness, planes of containment/fragment trajectories) of the particular engine type, aircrafts will be only offered in combination with an approved engine type. Because they must be adjusted at special features (e.g. "Engine mounts specific problems of elements"). To come up to the multifaceted demands, mounts of engines can be surprisingly complex ( Fig. Thereby of cause, the naturally special features of the mount at the nacelle have to be considered. "Destroyed engine mount by uncontained fragments".
"Containment with 'nesting' in the fan area" and Fig. At the aircraft regarding safety aspects in case of uncontained fragments: Fig.