Why is piloting a helicopter considered more challenging, despite not requiring much space to take off and land and being able to stabilize in the air and stand still?
In: Engineering
One of the most terrifying things about a helicopter is [this diagram](https://en.m.wikipedia.org/wiki/File:Hvcurve-en.png).
When your engine fails in a helicopter, you start falling. While you’re falling, if you angle the helicopter *just* right, you can make air flow through the rotor blades and slow your descent. Do that enough, and you can softly land on the ground rather than completely being smashed to bits. Angling the helicopter just right requires a bunch of forward momentum as well as downwards.
See that red segment on the left? That represents “the forward momentum you have now plus the forward momentum you can gain on the way down isn’t enough to stop your downwards momentum”. Close to the ground, you need less forward momentum because you will pick up less downwards momentum. Further up, you can gain a bunch of forward momentum on the way down, so you need less now. In the middle? Well, you’re in trouble. The red segment on the bottom right represents “you don’t have enough time to react to stuff on the ground if something unexpected happens”.
You almost always start in the bottom left, so taking off requires this somewhat perilous trajectory – gain a little height, pick up a bunch of speed, maintain your speed and move upwards as much as you can. Yes, a helicopter doesn’t need a long runway, but it *does* need a clear space for a safe takeoff. You can head into the red region, but there’s an inherent risk if your engine fails.
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