What happens when a helicopter experiences engine failure midair?
In: Engineering
In the 17th century, Isaac Newton discovered that objects with mass experienced a force of attraction equal to a ratio of the product of the two masses over the square of the distance between them multiplied by a constant, G. Helicopters use their engines to resist this attraction to the 6 is very large and therefore has significant pull on the objects near it. When a helicopter engine fails, it falls down.
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If it is just the engine that fails, helicopters do a manoeuvre called an “auto rotation”.
It’s the equivalent of “gliding” for aeroplanes.
The energy stored in the spinning rotor blades is conserved and then gradually used up to lower the helicopter to the ground at a survivable speed.
The pilot has to be really quick at getting the rotor blades into the right setting to descend safely without engine power, but it is a skill that they practice a lot when learning to fly.
The pilot will rely on autorotation to try to land safely. Basically the engine has failed and is no longer supplying power to the rotors. The pilot will allow the craft to fall. As air is passing over the rotors it’s making them spin. The pilot will use the momentum of the spinning rotors to create lift as they near the ground to soften the landing.
It’s actually very interesting and worth a deeper dive if you’re interested.
Don’t worry, they are designed for this.
If the engine fails, the first thing that happens is the propeller on top is disconnected from the engine and is now spinning freely. So it doesn’t just come to a stop along with the engine.
What’s next is cool. With the fact that the blades have an angle to them, the fact that air is rushing between them if the helicoptor tries to fall will actually cause the propellers to spin on their own. Furthermore, since they never actually stopped spinning when the engine died, the pilot still maintains a decent amount of control the whole time. Like a plane with no engines, it still has a sort of “glider” effect, slowly descending but still allowing the pilot a lot of control and keeping it in the air. Trying to climb isn’t going to be practical, but a controlled, safe landing is absolutely doable. Of course, like a plane with no engines, you only get one try.
The process is called auto-rotation, if you want to google more about it. It even exists in nature. Check out the seeds of a maple tree, which actually grow themselves little wings and fall to the ground slowly and safely when they fall out of the branches of a huge tree. That’s the same idea as a helicoptor with a dead engine – a safe, slow descent.
They can land using autorotation, kind of like how a plane turns into a glider when the engine fails. In this case the wings of the glider would be the helicopter blades. It’s actually a bit safer than the engines all failing in a plane because you don’t need as much space to land. Helicopters are still more dangerous overall.
If the rotor blades haven’t fallen off, the rotor can be set to autogyro (keep spinning as it falls), and land in a controlled manner. Pilots practice this maneuver.
The rotating mass of metal fatigue surrounded by an oil leak finds its zipcode in which to have an NTSB investigation.
OK, serious answer: [Autorotation](https://en.wikipedia.org/wiki/Autorotation) is the maneuver and principle by which a helicopter that has had an engine failure can glide to a *mostly controlled* landing.
Short of a failure catastrophic enough to seize the rotor (preventing the blades from rotating and robbing the helicopter of its mechanism for developing lift) a helicopter that has had an engine failure can usually be landed relatively safely as long as there’s adequate clear ground in the autorotation glide path.
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