AMC E 520(c)(2) Engine Model Validation

• ED Decision 2009/018/R found in: CS-E Amdt 5 - Engines (Dec 2018)

AMC E 520(c)(2) Engine Model Validation ED Decision 2009/018/R (1) Validated data specifically for blade loss analysis typically include: — Finite element model — Out-of-balance, — component failure, — rubs (blade-to-casing, and intershaft), — resulting stiffness changes, — aerodynamic effects, such as thrust loss and engine surge, and — variations with time of the rotational speed(s) of the Engine’s main rotating system(s) after failure. (2) Manufacturers whose engines fail the rotor support structure by design during the blade loss event should also evaluate the effect of the loss of support on engine structural response. (3) The model should be validated based on vibration tests and results of the blade loss test required for compliance with [CS-E 810](#_DxCrossRefBm1371447727), giving due allowance for the effects of the test mount structure. The model should be capable of accurately predicting the transient loads from blade release through run-down to steady state. In cases where compliance with [CS-E 810](#_DxCrossRefBm1371447727) is granted by similarity instead of test, the model should be correlated to prior experience. (4) Validation of the engine model static structure is achieved by a combination of engine and component tests, which include structural tests on major load path components, or by analysis, or both. The adequacy of the engine model to predict rotor critical speeds and forced response behaviour is verified by measuring engine vibratory response when imbalances are added to the fan and other rotors (See [CS-E 650](#_DxCrossRefBm1371447570)). Vibration data is routinely monitored on a number of engines during the engine development cycle, thereby providing a solid basis for model correlation. (5) Correlation of the model against the [CS-E 810](#_DxCrossRefBm1371447727) blade loss engine test is a demonstration that the model accurately represents: — initial blade release event loads, — any rundown resonant response behaviour, — frequencies, — failure sequences, and — general engine movements and displacements. (6) To enable this correlation to be performed, instrumentation of the blade loss engine test should be used (e.g., use of high-speed cinema and video cameras, accelerometers, strain gauges, continuity wires, and shaft speed tachometers). This instrumentation should be capable of measuring loads on the engine attachment structure. (7) The airframe and engine manufacturers should mutually agree upon the definition of the model, based on test and experience. [Amdt No: E/2]