Complex sentence: The engines were set to the takeoff thrust and the aircraft climbed to an altitude of, where the crew pushed the yoke causing the horizontal stabilizer of the aircraft to be deflected to a 5 degree nose-down position.
Split into simpler sentences: The engines were set to the takeoff thrust and the aircraft began to climb. When it reached the altitude of, the crew pushed the yoke and simultaneously the horizontal stabilizer of the aircraft deflected to a 5 degree nose-down position.