Quote:
Originally Posted by Vendor
Has it happened many times.  |
only a couple of instances come to mind, but i believe the first occasion was the result of the failure of a Fan blade and this one is likely to be the same cause.
here is video of a test showing what occurs when a fan blade fails:
the most impressive footage begins around 1:20
as you can see, a single fan blade detachment can cause a chain reaction which damages and separates additional fan blades, and ultimately causes the engine to ingest thousands of bits of jagged metal which further damages turbine components, compressor blades etc
Fan blade failure is probably the most dangerous and catastrophic type of engine failure one can experience in a turbofan engine.
One of the immediate dangers in such an event is that of debris and shrapnel. Yet, there are design elements in place meant to contain the failure and prevent such debris from fragmenting into more critical areas like fuel systems, hydraulic systems, or worse... the passenger cabin. (as was the case with Southwest Airlines recent experience.)
In the 2016 case, the failure occurred in such a way so as to carry debris either up and away from the cabin, or down and away from the cabin. This was sheer luck alone.
this most recent event, unfortunately saw the failure occurring in such a way as to carry the debris into the fuselage and main cabin, and it cost a woman her life.
Preliminary indications are that a hairline crack, not immediately visible to the naked eye, caused the blade to fail. Fan blades are subjected to enormous physical stress during their normal operations. It is not clear whether the stress of normal wear and tear caused the hairline fracture, or if it was a case of manufacturer defect.
another question investigators are surely looking at is - why was the failure in either case of these engines not contained?
it would be impossible to contain 100% of such failures unless the engine cowl itself were made of thick plate steel armor but that would be like going after a house fly with a sub-nuclear bomb. So some fan blade failures will cause this sort of destructive damage, but most will not. and on the whole, it is a fairly rare occurrence. but odd that it would happen to two engines of the same type, on two aircraft of the same type within such a short span of time.
EDIT:
reference the Sioux City crash of United flight 232- shrapnel from a catastrophic fan blade failure knocked out the hydraulic system of the entire aircraft leaving the flight control system inoperable. The skill of the crew alone was the only thing that achieved the outcome of that flight and the fact that there were not 100% fatalities is testament to their capability. The outcome of the flight is also testament however to the potential severity of such a fan blade failure