The U.S. Army ordered seven improved XB-7s as Y1B-7 for service testing. The new aircraft were fitted with improved Curtiss Conqueror engines with 75 more hp each. These engines were fitted with three-blade propellers also. Additionally, the corrugated fuselage skin of the XB-7 was replaced with smooth skin for the service test aircraft. These features combined to give the Y1B-7 a top speed of 182 mph, 13 mph faster than the XB-7.
The Y1B-7 was evaluated, but never entered quantity production. This was mainly due to the small bomb load and the better aircraft already being designed (i.e. Martin B-10).
Service test XB-7
TECHNICAL NOTES: Armament: Two Browning .30-cal. machine guns and 1,200 lbs. of bombs Engines: Two Curtiss V-1570-27 Conquerors of 675 hp each Top speed: 182 mph at sea level Cruising speed: 158 mph Service ceiling: 20,400 ft. Range: Approx. 600 miles (400 with full bomb load) Span: 65 ft. 3 in. Length: 45 ft. 7 in. Height: 12 ft. 1 in. Weight: 11,177 lbs. gross Crew: Four Serial numbers: 32-308 to 32-314