 The first XBTM @-@ 1 made its maiden flight on 26 August 1944 and began flight testing after it reached the Naval Air Test Center ( NATC ) on 11 December . The Navy ordered 750 more aircraft on 15 January 1945 although this was reduced to 99 aircraft after the surrender of Japan in August . The second prototype made its first flight on 20 May . Initial flight tests conducted with the first two prototypes revealed significant problems with the engine , its cowling , the vertical stabilizer and rudder . In response , the cowling was lengthened 6 inches ( 152 mm ) and the engine mount was canted two degrees to the right to offset the engine 's tremendous torque . The length of the carburetor air scoop was extended and the propeller spinner , rudder , and the vertical stabilizer were redesigned . In April 1946 the aircraft designation was changed to AM @-@ 1 when the Navy replaced its Bomber @-@ Torpedo classification with Attack , well before the redesign was completed in early 1947 . 
