Sofia,
I only got asked 2 questions regarding aircraft. One was where a boeing 737-300 was likely to fly and the other was the cruising speed of an Airbus A319. As I had revised the whole document from cover to cover I could answer the questions but they could ask you anything about aircraft so my advise would be to learn it all. The only annoying thing is if you do learn the whole thing, you kinda feel that they haven't asked you enough!
But if you go prepared, you won't be caught out. It's as simple as that
Good Luck!