This allowed longitudinal trim in the absence of a separate horizontal stabiliser. Without a horizontal stabiliser the aircraft entered an uncontrollable dive. The tail surfaces were all-moving, without a fixed fin or horizontal stabiliser. The horizontal stabiliser is a spareless carbon sandwich shell. The rear section is called the elevator, and is usually hinged to the horizontal stabiliser. Profiles of the same family were selected for the slender, wide-span horizontal stabiliser. The empennage was a T-tail arrangement to keep the horizontal stabiliser above the central engine. Aft, a long dorsal fin extends to a T tail with rudder and horizontal stabiliser. On a three-surface aircraft, the tailplane acts as a conventional horizontal stabiliser. This addition disturbed the airflow over the horizontal stabiliser, requiring small finlets on either side. This featured a redesigned wing of greater span, and modified horizontal stabiliser and landing gear. The horizontal stabiliser and fin were sharply swept at their leading edges. The tailplane comprises the tail-mounted fixed horizontal stabiliser and movable elevator. The horizontal stabiliser had a straight leading edge but tapered at the rear. The trimmable horizontal stabiliser was also modified to have increased span and more travel.