Design and Safety Assumptions - continued

The following design and safety assumptions are relevant to this accident:

1. There were no harmful interacting vibratory modes existing within the engine operating range.
2. Engine design and certification standards require the engine structure to contain damage resulting from a single rotor blade failure at the outermost retention groove. The National Airlines engine failure resulted in a number of complete fan blades being released from the fan disk at high speed and the engine structure (fan containment case) separating from the engine which reduced its effectiveness in containing the fan blades and minimizing the hazard to the aircraft. This failure mode exceeded design and certification standards for the engine and aircraft safety relied upon aircraft design considerations for minimizing hazards caused by uncontained engine debris.

Now let's take a look at the precursors that have been identified for this incident. Select Next to continue.