Why don the wings of a airplane have to flap like the wings of birds?
There are some aircraft whose wings flap like the wings of birds. They’re called ‘ornithopters’. They are, however, experimental aircraft, for the very simple reason that when designing something to fly through the air, humans don’t have the same limitations as evolution does. In other words, we can play with different ideas on paper and with models before we commit to the real world. I agree with some parts of various answers above. To really understand how birds gain lift and propel themselves forwards, you need a sound knowledge of aerodynamics. But if you want the short version, it’s like the idea of sculling or paddling in water. A bird’s wings generates lift as well as thrust through a quite complicated sequence of motions. Look closely at a bird next time one flies past you, or better still, seek out some nature show that features a flying bird in slow motion. It’s not just a simple up-and-down action; at different times when the wing is moving forwards, downwards, towards the r
