Turbine Discs and Blades:
The inspection for cracks is of the utmost importance, most inspections are visual, the dye penetrant method of inspection being too impractical. Cracks on discs however small will necessitate removal of the module or engine for overhaul. Blade cracking also will invariably require removal of the module or engine. Some manufacturers limitation allowance will permit repairs to be effected to damaged turbine blades. Figure refers. Cracks however are not acceptable and will require blade replacement. In extreme cases part or whole blades may be missing due to severe overheating causing the blade to melt, on some engines this does not always show up on the vibration indicating system.