Before I start I just want to say I'm a pretty paranoid guy in general, so bear with me.
Recently I just saw a bunch of engine and gun designs made by planes of old. One of the engines I saw I really liked and I learned how to make it. I am put this engine in my trench run plane for the tournament. Is this copying?
Ok thanks guys @jsaret
agreed
RyneKuczy is correct. I personally prefer to be tagged when someone uses a bit off my design, but otherwise it's OK. Of course, if someone uses my designs to make something offensive (someone once took my B-Moth Y and made a "hitlers plane" out of it – the description was even worse) it's absolutely not OK.
I don't think so unless it was the whole plane you copied.
I would give him credit for it in the description, just say something like 'Special thanks to PlanesOfOld for the engine design'. However if they are your own design then you don't need to give credit