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, 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 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). 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 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]
Engine model validation for aviation safety requires accurate simulation of blade loss events. Models must incorporate component failure, aerodynamic effects, and speed variations. Validation uses vibration and blade loss tests, predicting transient loads and structural responses. Collaboration between airframe and engine manufacturers ensures model accuracy through testing and experience.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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