A bird flaps its wings to move itself forward through the air, and to climb higher in the air. This is, of course, where planes are different. To a bird, flapping its wings is no harder than you flapping your arms. Planes, on the other hand, are (usually) made of metal. Metal doesn’t flap very well. Since we can’t make flappy metal wings, we need something else to keep the plane moving, don’t we?
The solution is to make another, smaller pair of wings that can be moving all the time. A pair of wings to help move the plane through the air. The main wings stay steady, keeping the plane in the air. The smaller wings, on the other hand, just spin, moving the plane along. We call these smaller wings, of course, “Propellers”
Yes, propeller blades are wings. They aren’t “like” wings. They are *exactly* wings, and they do the exact same job, which is moving air. The main wing moves air down to push the plane up, and the little propeller wing moves air backwards to push the plane forwards.
Now, if your daughter has trouble grasping the idea of a bird (or anything else) flying without flapping wings, you can demonstrate by simply making a paper airplane. It flies, but slightly downwards. An engine and propeller (or flapping wings) would keep it flying for longer.
If she asks about jets not having propellers, I think that’s a bit harder to explain. A modern “jet” (technically “turbofan”) engine actually has a propeller… it’s just inside a tube, and has a whole bunch of blades (and they’re all wings, truthfully speaking).
Well, I hope this helps. I’m trying to imagine explaining this to my 6 year old niece without it all going over her head. Not an easy task. Good luck!
Judging by some of the comments, I may not have made my point clear. To clarify, I’m just trying to explain why airplanes don’t have to flap their wings. To do this, you must separate the concept of “lift” from the concept of “thrust.” Birds use their wings for both. Airplanes cannot.
I’m not trying to describe lift, that’s a whole other subject.
I’d like to thank all the people who have upvoted this answer; I’m quite shocked, actually. Thanks for reading, and if you have an inquisitive six-year old, good luck, and have fun teaching the science
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