Abstract: An employee was working from an aerial lift, performing a line-clearance tree-trimming operation in a residential area. The aerial lift truck was a Ford F700 chassis with an Altec (Serial No. 0388-S0317) insulated boom and bucket with a maximum height of 14.6 meters. The employee was trimming around a three-phase, 12-kilovolt overhead power line. The outside phase conductors were 12.8 meters above the ground, and the center phase conductor was 13.1 meters above the ground. The employee positioned his bucket about 3 meters below the power line. He took his hydraulic saw, switched on the control lever, which powered the saw and locked the upper and lower bucket controls, and reached out to make a cut. The bucket began rising, and he could not stop it. He yelled for a ground worker to turn the engine off. He was pinned between the center phase conductor and the left side of the bucket, but was able to push the conductor off his face, limiting further injury, just before the ignition was turned off. A supervisor for another crew had difficulty lowering the bucket. The injured employee fractured his jaw in two places and suffered abrasions on the right side of his face and some tooth damage. He required surgery and was hospitalized for his injuries. The cause of the mechanical malfunction was not determined.