The pilot reported that, the day before the accident flight, he had flown the airplane, and wanted to become more comfortable with the new instruments which had been installed. So, after the flight, while in a hangar, he and a friend turned the airplane's electrical power on to familiarize the pilot with the autopilot system, and specifically how it would follow heading bug settings. During the familiarization, they "ran the [pitch] trim all the way up". The pilot added that, during the accident flight, before takeoff, he did not check the pitch trim setting because he believed it would be the same as his previous flight, instead of the pitch trim setting after his autopilot ground familiarization. He added that, during takeoff, the nose pitched up severely. He lowered the nose, entered a negative G condition, discovered that he "did not latch the seat belt very good" and observed his seat belt had disconnected, and he was no longer in his seat and could not regain airplane control. The airplane struck the runway, porpoised, and on the third cycle, the nose landing gear collapsed. The airplane skidded and struck a taxiway light. Postaccident examination of the airplane revealed that the vertical trim tab was in the "full down position," indicating that full nose-up trim was applied. The airplane sustained substantial damage to the both engines and fuselage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot operating handbook checklist titled "Before Takeoff" stated: 1. Seat Belts and Shoulder Harnesses – CHECK It continued: 15. Trim – AS REQUIRED FOR TAKE-OFF