Originally Posted by
munnst
Be interesting to understand what sort of bird caused the failure. You would think a jet engine could withstand say a Pidgeon impact. Are the engines really that frail?
The engines are not frail, but they are intolerant of taking a mass down the core. Any damage to a blade will cascade downstream, and the blades are running anything up to 20K plus for small N1's, and 30K for the N1. The blades have high radial loads on them, many are running root loads well over 20 tons, with the tip running mach 1.6 or more. Hitting a bird on one of these engines will curl the blade forward normally, and that will twist the blade to a higher AOA, and higher out of plane forces which help the blade tear itself up.
If a bird is a problem on a fan blade or compressor and is considered to be "frail.... ", try catching a piece of 80gm plain paper with a tail rotor blade of a Robbie.