 In the case of the B-24, the Liberator's tricycle landing gear design mandated that its A-13 model Sperry ball turret have a fully retractable mount, so that the ball turret would always be retracted upwards into the lower fuselage while the aircraft was on the ground, providing ground clearance with it in the stowed position.The conventional landing gear of the B-17 meant that the ball turret did not need to be retracted for clearance on the ground, but if the plane was required to do a belly landing (such as in the case of landing gear system failure), the ball turret would likely be destroyed due to the lack of clearance, meaning anyone occupying the turret would be in a precarious position if unable to escape.After testing in mid-1943, the ERCO ball turret became the preferred bow installation in the Navy's Consolidated PB4Y-1 Liberator and PB4Y-2 Privateer patrol bombers although other types continued to be installed.