Bigger isn't Always Better

I needed to drill eight holes (two visible in picture to left) in the chassis for the primary engine mounts. However, the space was too tight for my right angle drill.

Using a cutoff wheel, I was able to shorten a drill bit so that I could drill the hole with more clearance. However the other hole was a no go. What to do?

You have to love internet search and aircraft tools. In the picture below the drill on left is a Dewalt right angle drill with standard length 5/16" drill bit -- well over 3x too large. The air-powered aircraft drill on right has stubby 5/16" drill bit mounted. The bit between the two drills is a 'short' 5/16". To get to that tight form factor, they do away with the drill chuck by using special bits with 1/4-28 threads as can be seen in the close up picture.