# Questions tagged [auto-rotation]

Mode of flight in a rotorcraft where the rotor is not powered by the engine. In helicopters this used in case of an engine failure and it allows for a controlled landing. It is also the working principle behind autogyro's.

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### How does gross weight affect helicopter autorotation?

The factors which affect helicopter autorotational aerodynamics include airspeed, gross weight, rotor RPM, and density altitude. The effects of these factors can be examined during a few phases of the ...
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### The relation between Euler-angle rate and body-axis rates?

A paper about quadcopter dynamics and control shows the relation between Euler-angle rate and body-axis rates as: Q1: why are there $R_{v2}^{b}(\dot{\phi})$, $R_{v1}^{v2}(\dot{\theta})$, and \$R_{v}^{...
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### Is there a way for the helicopter rotor to get its power half by wind, half by engine?

Imagine a gyroplane, if something happen mid-flight (when the plane is basically an autogyro and the engine provides no power to the helicopter rotor) and just the wind generated by forward flight can ...
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### Sub-ideal Autorotation in Rotorcraft

I have another AuRo question for you. When a Helicopter autorotates (ideally) it is in the turbulent wake state and there is virtually no flow through the rotor disk (figure of Leishman attached). Now,...
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### Autorotation: Positive Pitch during descent phase possible?

I was wondering if a rotorcraft, that descends very slowly compared to its nominal rotor rotation rate (for example an RC Helicopter vertically autorotating with 3m/s descent rate and 2200RPM on the ...
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### Is autorotation possible from a 0 rpm start at high altitude?

I am working on an enclosure that is to be ejected from a rocket at apogee (10,000') and fall to a target altitude at a descent rate below 20ft/s before releasing its payload. The idea is to have ...
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### Does shutting down the engine affect the rate of rotation during autorotation?

If a helicopter's tail rotor shears off while flying then the helicopter's fuselage will start rotating in the direction opposite to the main rotor's rotation direction. During autorotation, if I ...
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### What causes a helicopter to autorotate farther?

Which characteristics improve a helicopters ability to glide a farther distance in autorotation? Do these same characteristics reduce minimum decent speed in autorotation or is that affected ...
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### Is autorotation possible in a tandem rotored helicopter?

I just wonder, whether a synchronized autorotation is possible in case of turbine failure (one or both gas turbine engines). All Gearboxes obviously must turn not to desynchronize -> lethal
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### How can you calculate the vertical speed of an helicopter during auto-rotation?

How can I calculate velocity of a helicopter when it falls with autorotation when the engine fails, given all the parameters such as mass , height , wing size etc.
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### Why are autorotations to a full touchdown not practised any more?

What is the history behind a decision to discontinue helicopter autorotations all the way to ground contact? In the 1960s, our Army flight program directed full ground contact for any and all ...
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### What is the autorotative rate of descent for a Bell 47-H?

I would like to estimate the amount of time a pilot would have before a forced landing after suffering engine failure in a Bell 47-H at 1,000ft. This is for purposes of understanding a historical ...
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### Is there a minimum start altitude for autorotation landings?

If a helicopter is flying relatively low, say for sightseeing, can it still land using autorotation if required? What about if there was an issue during a routine landing? Is there any cutoff point ...
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### For a rotor in vertical autorotation, what is the relation between pitch, vertical speed and rpms?

In other words, what happens to vertical speed and rpms in vertical autorotation if I change the pitch of the blades of the gyro I use to fly...?
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### How would a helicopter deal with auto rotation when it transports a hanging payload?

How would a helicopter deal with auto rotation when it has a payload? Will it deploy it's payload and continue with auto rotation as normal? Can't find much online, this research is for my senior ...
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### How does the forward speed of an auto-gyro relate to the rotation speed of the rotor during auto-rotation?

In my other question I was looking for a relation between the forward speed and the thrust (lift) of an auto-gyro. I have come to the conclusion that for an auto-gyro in auto-rotation the forward ...
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### How to calculate the amount of thrust of a autogyro during auto rotation?

When a autogyro/gyrocopter is in a horizontal steady flight the rotor should be able to provide enough thrust using the auto rotation principle if the horizontal speed can be regulated by the vertical ...
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### Why is vortex state impossible in autorotation?

An article at Skybrary states that for a vortex ring state to occur: The aircraft has to be in powered flight. If the engines are not producing power, the aircraft is in autorotation and the upflow ...
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### Why is *vertical* autorotation in a helicopter not recommended?

Helicopters can autorotate back to earth in case of emergency. The FAA recommends a flight profile similar to the following procedure: Notice that in section (2) there is forward speed: vertical ...
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### How do helicopter pilots practice auto rotation?

How do helicopter pilots practice auto rotation, and specifically, the landing phase? Timing the flare as ground is approaching seems critical to a successful auto rotation landing. Yet I can't ...
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### Can a passenger drone perform auto-rotation?

(Source) The Dubai Drone is an Ehang passenger drone planned to start commercial services in July 2017. If there is a failure, can such an electric multi-copter auto-rotate a landing? I'm wondering,...
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### Is it possible to fly a tandem-rotor helicopter after a single rotor failure?

Tandem-rotor helicopters, such as the Boeing CH-46 Sea Knight and CH-47 Chinook, are helicopters with rotors distant by more than 10 m. Photo by Cpl. Ryan Carpenter on SNAFU It seems unlikely a ...
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### With helicopters, is normal landing or auto-rotation landing any different when landing on water?

I noticed something from investigating my other answer to a not-really-related question. A wiki article here says: The "water bird" emergency landing is a technique developed by the Canadian ...
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### Is it ever possible to auto-rotate with a missing rotor blade?

A couple of years ago a UH-60 managed an auto-rotation landing with "badly damaged rotor blades." (Couldn't find further details on that incident.) Is it ever possible to auto-rotate in a helicopter ...
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### Can an Autogyro with wings survive a rotor mechanical failure? Will it be safer?

I'm not an expert but as I understand autogyro sustentation relies on the rotor. If the rotor breaks, the aircraft will fall as a rock to the ground... But If the autogyro was built as a tractor ...
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### What happens if one or more rotors are stopped during autorotation on a quadrotor?

I get the basics of autorotation when it comes to a helicopter in unpowered flight, but it's a bit unclear to me when it comes to quadrotors. My objective is to cover some directed horizontal ...
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### Is the autorotation in San Andreas movie realistic?

San Andreas is an awful movie, but given how helicopter-centric its plot is I'm wondering if they even got the autorotation landing correct? In the middle of the movie the hero is cruising in (I ...
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### Are control inputs different during autorotation?

My understanding is that during power-off autorotation the main rotor is still coupled to the tail rotor, and the flight controls execute the same functions as during power-on flight. Two questions: ...
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### Can the V-22 autorotate?

Can tilt-rotors like the V-22 execute an autorotation landing? If so, are the conditions under which that would be possible (and survivable) different from a helicopter?
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### How is auto-rotation different in coaxial rotor helicopters?

Coaxial Helicopters have two main rotor sets, one on top of the other, spinning in different directions to eliminate the need for a tail rotor. I've heard it said they're also more maneuverable, all ...
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### How does a helicopter pilot execute an auto-rotation landing?

What are the critical steps a pilot follows to perform an auto-rotation landing?
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### Is this a reasonable way of thinking about an auto-rotation?

Related to this question. My instructor described an auto-rotation as: Entry. Lever down, stick back, pedal in. Fly normally, with a little tweaking of RRPM to keep it in the green, until about 50 ...
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### What is auto-rotation? [duplicate]

Inspired by this question. My knowledge concerning helicopters is quite limited: what is auto-rotation? are there other "rotations" possible? in what do they differ?
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### Is it possible to control the direction during auto-rotation?

Is it possible to control the direction during auto-rotation, and how does it work?
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### What happens when a helicopter loses an engine?

It seems like at this point it would be game over, since the spinning rotor is the only thing keeping it in the air. Is there any way to land a helicopter in this condition without crashing?
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