Mark 13 defects persisted beyond the TBD's service

The cited Bureau of Ordnance history acknowledges that the Mark 13 was inadequate for modern war until extensive alteration. Its weak propellers, leftward deflection, depth-control faults, premature arming, and unstable water entry created overlapping causes of failure. In a 1943 test of 105 torpedoes dropped above 150 knots, only 31 percent produced a satisfactory run, and the categories of failure exceeded 100 percent because some weapons displayed several defects. Lower-speed drops improved results only by forcing aircrews into a tactically dangerous release envelope. The eventual response funded both urgent Mark 13 modifications and a new Mark 25 designed for much faster launch, but neither effort could help the Devastator at Midway. The official figures turn weapon reliability from an excuse into a measurable part of the aircraft's combat story.