Imagine the opposite: someone from the future were to time travel back to our present time. Certain knowledge the they bring would be useful. But a lot probably won't be until necessary technology becomes available.
Just knowing it's possible, with gross engineering parameters, can be half the battle.
They can say that you need 2 wings on the side, and you need to go really fast in a straight line before you can take off. Sometimes you can see the little flaps on the edge of the wing move up and down. Though you can also do it with little planes. And if you want rotating blades then it has to be smaller than planes (helicopters).
This should help a clever person (e.g. Leonardo da Vinci) figure out how to fly.