It takes 2600lbs to kill a hangar, not 3000.
Also, I'm not sure that kinetic energy means squat against ground objects, especially when considering HE shells. Really, the shells were "15 lb" shells. How much equivelant ord that is, I don't know.
I suspect they're a bit overmodeled, what with being a super tank killer that everyone has shown.
There's an easy solution to your kinetic energy problem: Land the plane! It's got tricycle gear! Just taxi around (at a safe distance) and try it when not moving!