Commercial Fixed Wing
Situational Awareness
Ground Event / Encounter Other / Unknown
General Physical Injury / Incapacitation
Equipment / Tooling
I was in the process of pre-departure for [the] flight. I have just completed my walk around the aircraft and proceeded to move the ground power unit out of the envelope. I parked the unit; disconnected the tongue of the unit from the tractor and pushed it up so it would lock. The tongue was locked in the up position and stay in place. As I brought my hands down; the tongue locking mechanism malfunction and disengaged by itself and hit me in the jaw; causing major injury. Supervisor was called and notified. I never expected the tongue of the ground power unit to malfunction.
Ramp employee reported that the tongue locking mechanism on a ground power unit malfunctioned and injured a ramp employee.