Leonardo da Vinci (1453-1519) drew his plans for a helicopter hundreds of years before people were fire able to fly. Helicopters are lifted into the air by their large rotating propellers or rotors. These work like narrow wings, generating lift as they spin rapidly through the air. It climbs by increasing the angle of the rotor blades. It moves forward by increasing the angle of the blade moving back on every rotation so that it pushes against the air.
FACT FILE
The hovercraft is an ingenious machine that rides on a cushion of air. It looks like a flat-bottomed ship and is powered by huge propollers
resources: Tell me Why (Chancellor Press)
image 1: https://www.wired.com/wp-content/uploads/archive/images/slideshow/2007/11/gallery_helicopter/21_Sikorsky_VS300.jpg
image 2: https://ottawow.files.wordpress.com/2016/11/spectra2a.jpg?w=620
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