To notapilot15, the silica from sand deposits in the engine, in the hot section it forms what is commonly known as glass, this is not a problem when molten but on engine shut down / cool down, it solidifies and causes the most problem on the T1 blades where it blocks the cooling holes; on engine start when max temperature is critical, the blades have reduced cooling and suffer extra thermal stress, hence life shortening, especially when this occurs on more times on short cycle operation. One has to remember the Operator of short cycle flights has a modified maintenance schedule which should capture this accelerated degredation by more emphasis on cyclic life. As stated earlier ANA are fleet leaders and 1st to experience such unpredicted events.