Fan Blade Containment Testing
Fan blade containment testing is important on all jet engines, regardless of size. It is one of several tests that are required to assure the basic design is acceptable. Containment testing serves two purposes:
1. It demonstrates the engine's capability to keep a broken off or ruptured fan blade inside the fan casing, not permitting it to penetrate the aircraft fuselage, or wing.
2. It also demonstrates the engine's capability to continue to generate power, albeit reduced power, for a period of time permitting the flight crew to make corrections in flight settings and to shut the engine down once control is established with an engine out situation.
Other testing is also done to simulate bird strikes, ice ingestion, hail ingestion and high volume of water (rain) ingestion.
Containment is mainly achieved by a kevlar wrapper around the outside of the fan casing, think bullet proof.
Turbine blade out testing is also done to demonstrate containment. It is desirable to have a broken turbine blade or blades exit out the turbine exhaust and not the turbine casing.
Fan, compressor and turbine discs are a much different situation. Given rotational speeds and mass, containment in a general sense is not possible. This is where engineering design and life management comes into play. Discs are designed with substantial safety margins based on their material (alloy) capability/properties. They are subjected to overspeed testing to assure they do not burst short of the design point plus an additional margin. They are critical components and are treated as such in service with a restricted cyclic life limitation and planned NDT inspections. The worst possible situation is to have a disc break loose and overspeed beyond capability (QF32). To prevent that from happening, a break away disc should slide back so that its blades contact the nozzle vanes behind it to slow or stop rotational speed short of burst overspeed rotation. For whatever reason, that didn't happen on QF32.
As a matter of interest, the AA 767 incident at LAX should never have happened. The pilot on a previous flight reported unusual engine vibration at speed but not idle in their write up after landing. The vibration is a key indicator something is not right in an engine. The engine should have been taken off wing and disassembled for inspection. Had they of done that they would have discovered a crack had developed off of one of the disc posts where the HP turbine blades are inserted. Instead, the plane was taken to a remote location and the engine run up in speed causing the crack to quickly run to the center bore and the disk exited. The result, loss of both engines and the aircraft was written off as a complete loss. It didn't have to happen.
Hope this helps your understanding.