144. The only hand tools that should be used on gas turbine engines are chrome plated, nickel plated, or which of the following?

Unplated tools, like chrome and nickel-plated tools, minimize foreign object damage (FOD) risk by preventing plating flakes from entering the engine. Other platings, such as bronze, silver, and cadmium, are prone to chipping and contamination, which can damage compressor or turbine blades. Always consult the manufacturer's maintenance manual for specific tool restrictions.