Two points:
Someone I know was a SSgt and wanted to go for a commission. Obstacles were put in his way so he decided to switch to the RAF. They told him he couldn't as . . .
He applied, got accepted, got commissioned and 11 years later is a Lt Col equivalent. Sweeter he has even been in command of ruperts that were his previous bosses.
Secondly brush up on your mental arithmetic. Do as many time/distance problems as you can. Car and helicopter speeds are not too different so do them as you drive around.