How to change flipbooks

I’m making a 2d game where the main character can transform from one form to another

the “A” and “D” for movement .
i want to know how to change the flipbook from human to car if z is pressed , and from human to helicopter if x is pressed and to human if c is pressed

i made something like that but i have to hold the key to apply the animation here is a pic to it

What i just want to transform when a buttons is pressed and return to idle when “a” or “d” is released and move when pressed

Also i am trying to do this. But i didt not know how it is? If you have any Youtube Tutoirals or other thing. Please Some one help me.