Various engine mounting systems are used to mount gas turbine engines to aircraft. Typically, gas turbine engines are mounted to the wing, fuselage, or tail of an aircraft and may be mounted at various positions between its forward and aft ends. The engine mounts carry various loads to the aircraft such as vertical loads from the engine weight, axial loads due to the thrust generated by the engine, lateral loads from wind buffeting, and roll loads caused from rotary operation of the engine. In addition to carrying these loads, the engine mounts must also withstand both the axial and radial thermal expansion and contraction of the engine during operation.
For example, a front engine mount having a pair of circumferentially spaced apart primary links is one type of mount utilized in conventional engine mounting systems. Each primary link is joined at one end to the aircraft and at the other end to an engine casing, such as the fan case. The front engine mount, as well as aft mounts and other mounts within the engine mounting system, typically incorporates a waiting fail safe system to provide a redundant load path in case the primary load path fails. The waiting fail safe load path does not engage under the normal or limit maneuver load condition.
In the case of these types of front engine mounts, the waiting fail safe system is positioned in between the two primary links. In the event that either primary link fails, the waiting fail safe system is engaged. While effective, the waiting fail safe system of previous designs does not, when engaged, prevent the engine from upward or downward movement due to subsequent vertical loads. The kinetic energy associated with the upward or downward movement will result in an impact force that is higher than the design load, which is determined by the equilibrium under the assumption of static determination. Typically, to account for this potential impact force, a dynamic amplification factor is applied to the static load, as well as fatigue spectrum, to ensure the waiting fail safe system has adequate capability. However, incorporating the dynamic amplification factor into the design results in a higher design load for the waiting fail safe system, and hence contributes to added weight.
There is a need for improved waiting fail safe systems.