Finite Element Analysis Simulation of a Fireproof Test for an Aircraft Propulsion Engine Mount Structure Made of Titanium 2015-01-2621

Aviation regulations requires that engine mounts, and other flight structures located in designated fire zones must be constructed of fireproof material so that they are capable of withstanding the effects of fire. Historically, steel is defined as being inherently fireproof, however, titanium was not. Therefore, a fireproof test was conducted using 6AL-4V titanium structure for the attachment of the propulsion system on a mid-size business jet to satisfy FAA Federal Aviation Requirement 25.865. To determine if the titanium structure would be able to support normal operating loads during the fire event, finite element analysis was performed on the titanium structure simulating the fire test. The fire test simulates a fire on the aircraft from the propulsion system by using a burner with jet fuel exposing the component to a 2000 °F (1093°C) flame. The 2000 °F (1093°C) Flame is calibrated based on FAA Advisory Circular AC20-135. The 2000 °F (1093°C) flame is modeled as a series of convection coefficients across the entire surface of the component. The conductive and convective thermal properties are used for the finite element analysis (FEA) model to simulate the heat transfer effects of the flame. A thermal transient analysis was performed to determine the component temperatures and correlation to the fire test showed excellent agreement. The peak temperatures in the vicinity of the flame on the titanium structure was about 1500 °F (816°C) but much lower at locations that were shielded by the structure. The transient thermal analysis also showed that after about 10 minutes the temperatures appeared to be at steady state conditions.