Here are two correct ways to write the sentence. Both are OK — choose the one you like:
A powerful rotor lets a helicopter lift straight into the air, hover, and fly in any direction.
Or keeping your word "mighty":
A mighty rotor lets a helicopter lift straight into the air, hover, or fly in any direction.
Why these are correct (simple steps):
- Subject: "A mighty/powerful rotor" — this tells who or what.
- Verb: "lets" — this tells what the rotor makes happen.
- Object and actions: "a helicopter lift..., hover, (and/or) fly..." — these are the things the rotor helps the helicopter do.
- Comma and word choice: Use commas to separate the actions. Use "and" if you mean the helicopter can do all three, or "or" if you mean it can do one of them.
Nice work noticing the sentence — you're doing great at checking grammar!