(2) While the validation aspects listed above are important for representation of the windmilling loads, the fan blade loss correlation is also pertinent to the windmilling event because the event involves predicting the response of the entire propulsion system under a high level imbalance load. Correlation of the model against the § 33.94 test is a demonstration that the model accurately predicts initial blade release event loads, any rundown resonant response behavior, frequencies, potential structural failure sequences, and general engine movements and displacements. To enable this correlation to be performed, instrumentation of the blade loss engine test is used (e.g. high speed cinema and video cameras, accelerometers, strain gauges, continuity wires, and shaft speed tachometers).
9. HIGH POWER IMBALANCE CONDITION.
a. An imbalance condition equivalent to 50 percent of one blade at cruise rotor speed considered to last for 20 seconds may be assumed. It should be shown that attitude, airspeed, and altimeter indications will withstand the vibratory environment of the high power condition and operate accurately in that environment. Adequate cues should be available to determine which engine is damaged. Strength and structural endurance need not be considered for this condition.
/s/ Vi L. Lipski VI L. LIPSKI Acting Manager, Transport Airplane Directorate Aircraft Certification Service, ANM-100 13