Techie drawing? How being able to draw a cone and sphere intersecting in Isometric will help you fly I don't know.
Did it a O grade level and the another year of it at Uni. Might give you a heads up if you looking a a system schematic but once you get your head round one of them the rest are of a similar format.
Maths, Physics, Biology and if there is such a thing these days pratical engineering studies (piston engines, levers and a bit of materials). A language or 2 would be very helpful, I must admit I would have found Spanish very helpful in my travels.
To be honest your best doing what you enjoy. There is nothing worse than slogging your way through a subject you are totally not interested in.
MJ