Complex sentence: At 16:09, the flight crew successfully unjammed the horizontal stabilizer with the primary trim system, however, upon being freed, it quickly moved to an extreme "nose-down" position, forcing the aircraft into an almost vertical nosedive.
Split into simpler sentences: At 16:09, the flight crew successfully unjammed the horizontal stabilizer with the primary trim system. However, upon being freed, it quickly moved to an extreme "nose-down" position, forcing the aircraft into an almost vertical nosedive.