I think it's safe to say that the tailplane on that aircraft was generating a downforce!
That was the US trial of the "Highball" bouncing bomb desined for use against ships. It was smaller and more spherical than the "Upkeep" weapon used against the dams. Designed to be carried by the Mosquito -or similar size it was being trialled for use in the Pacific war. Some were sent out to the Pacific, but the war ended before they were used.