Abstract: On May 20, 1999, Employee #1 was working with a crew of at least eight other mechanics performing routine maintenance on an L1011 airplane. The work included the replacement of parts and various filters. Near the end of the shift, Employee #1 wanted to check a certain filter for leaks while the other members of the team were cleaning up and logging the replaced parts in the aircraft logs. The filter was located above and aft of the port of the Engine Number 1, in the pylon. The filter was accessible through an inspection port. The easiest way to check this filter for leaks would be to wipe it clean and then to start and stop the engine and check for oil in the area. For an unknown reason Employee #1 asked the crew chief to start the engine, which was done, and then it was shut down. This is a low pressure system and Employee #1 wanted to exert maximum pressure, so he then asked the crew chief to run the engine. The crew chief cautioned Employee #1 to keep the engine clear as he went back to the cockpit and Employee #1 said he would do that. At that time Employee #1 set a 10-ft ladder up next to the pylon, so that he could look into the inspection port. The ladder was in new condition and had been modified so that it would not fold. As the engine started, the exhaust blew the ladder toward the rear of the aircraft and Employee #1 fell straight down, striking his head. Employee #1 sustained concussion and was hospitalized.