VERY IMPORTANT CLUE!!! A common problem after hitting the ground hard is that the force of the impact sends the clunk to the front of the tank, bending the pickup line in half, and just about stopping fuel flow. Point the plane nose up and shake it a little. Normally, you should hear the clunk rattle a bit. If you can't hear the clunk, shake it alot. Often, this will cause the clunk to drop back to the correct position. If this doesn't work, remove the tank and shake it outside the plane.