字幕列表 影片播放 列印英文字幕 Helicopters kinda look like fat bugs lying on their backs flailing their legs around… so how exactly can they fly with more precision than an airplane? Airplanes fly because their wings are curved on the top and flat on the bottom, allowing them to harness the Bernoulli Principle. With speed, the air passing over the wing is less dense than the air under it, creating lift. Helicopters have rotor blades that also create lift. As the blades spin they move the air. Less dense air passes over the blades with denser air passing underneath it. Put that way it sounds simple, but it's far more complicated, because while airplanes get lift naturally by moving through the air helicopters have to constantly generate it themselves. This is how they can takeoff and land vertically, and also fly backwards, sideways, and hover in place. But they can't glide if something goes wrong; they aren't aerodynamic like planes. Helicopters fly by sheer brute force, which is really incredible, but gives them some limits. Planes can fly upside-down — the fixed wing means that as long as air is moving over the wing, usually by tilting the nose upwards slightly, it still has lift. As a helicopter's rotor spins, the generated thrust moves upwards with the direction of lift, so flying upside-down would demand redirecting the blades so the thrust is the opposite way, supporting an upside-down vehicle. That said, a helicopter could fly a barrel roll if it was moving fast enough, but that's a stunt you're more likely to see at an airshow than from a news helicopter over a city. Speaking of helicopters over cities, you always know when one is out there. Because they're loud. They're loud not because of the engine, but because the blades are running into turbulence from each other, properly called the blade–vortex interaction: the tips of the rotor blades vibrate against the air as they whip around. Airplane wings have changed overtime to have flaps and malleable shapes that react to flight conditions. Helicopters have done this too; different blade shapes, tip shapes, and even materials have shown to decrease the noise of a helicopter. One kind of blade has flaps on edge of that move 15 to 40 times a second to reduce the noisey blade-vortex interaction. Even NASA is looking into developing better blades for a quieter helicopter, looking to a future where larger, versions can carry a sizable passenger load between cities. Without runways, commuter chopper flights could limit air traffic congestion. But helicopters with one rotor can only lift so much. Which is why bigger choppers like the Chinook have two. More blades can provide more lift, but it also adds weight and complexity. For a heavier helicopter the extra lift from the added blades is sometimes vital. Not only do those look cool, but they're useful. Just like a helicopter should be. For more epic stories of innovation that shaped our future, check out TheAgeOfAerospace.com Speaking of flying, every wonder why we get airsick? We've got the answer in this video right here. Do you still have questions about helicopters? Let us know in the comments, be sure to like this video, and subscribe for more Seeker.