# Questions tagged [rotorcraft]

A rotorcraft is a heavier-than-air flying machine that uses lift generated by rotor blades revolving around one or more masts.

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### Are there equations to match power required to mass for rotorcraft?

Is there an equation (or table or whatever) to determine what power is required to fly certain mass? Probably there will be a bunch of nuances, but at least some sort of rule of thumb probably exists.
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### Rotor system Weight of a Helicopter

I was wondering whether there is a "rule of thumb" or some kind of estimate (ideally with a source) that states how heavy a rotor system (blades, swash disk, actuators) typically is as a ...
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### Longitudinal/Lateral CG envelope for hoist operations

Does a Rotorcraft hoisting CG chart show what the CG will be as the load is hoisted from top to bottom or vice versa?
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### Does the CH-47 Chinook generate differential yaw as a side effect of generating differential lift?

I have been reading up on the controls of the CH-47 Chinook. I understand how yaw movement is created not by counter torque but by opposite cyclic on the front and back rotors. What I'm wondering ...
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### How much power and lift margin do helicopters have for hover?

Suppose you are designing a helicopter and trying to size the rotor system for hover and flight. Your helicopter has a certain gross weight at sea level, standard atmosphere. How much additional lift ...
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### How many coaxial rotors could you theoretically stack on top of a helicopter before the design becomes infeasible?

All coaxial-rotor helicopters in existence today have only 2 counter rotating rotor blades. An example of such a helicopter is the Kamov Ka-50. Coaxial-rotor helicopters have one big advantage ...
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### Does a cyclic in a helicopter essentially control rotor attitude?

So the basics of helicopter control as I understand it, at least, in terms of roll and pitch, are as follows: A helicopter is caused to move through space by means of tilting the main rotor disc, ...
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### How is the planform geometry of a helicoptor rotor designed?

Rotor planform specially the tip is designed differently for different helicopter rotor. How the shapes are determined? For example I added 2 photos. How the dimensions of the tip or root of these ...
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### Is there any existing engine which can be converted to turbofan from turboshaft in mid flight?

I read about convertible engines. I want to know if there is any engine existing to meet up hover and cruise together.
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### What is the main rotor speed (RPM) of Sikorsky CH-53E Super Stallion?

In order to calculate the tip speed ($V_{tip} = ω×R$) of Sikorsky CH-53E Super Stallion, I need to find the rotation speed of the main rotor for the forward flight case. Can someone provide an answer ...
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I am trying to create a simplified model of a heavy-lift drone payload at different altitude during hover mode. I tried to derive it simply by considering that the thrust, $T$ is equal to the weight ...
176 views

### Have any helicopter or gyro copter rotors driven by tip propellers been built

I remember the 4 bladed X wing and a two bladed tip jet rotors that were driven by compressed air, in the 1990s. I believe there was a early 1900 rotor that was driven by propellers at the tips. And,...
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### Does the rotation direction of intermeshing rotors have any noticeable effect?

Consider the Kaman K-Max, which has intermeshing (side-by-side) rotors that rotate as indicated below (when viewed from above, the rotor on the right (green) rotates clockwise, the left one (red) ...
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### Would a Tip Jet be more efficient or practical the bigger/longer it gets?

In summary, a tip jet is a jet nozzle at the tip of some helicopter rotor blades, used to spin the rotor without much torque. Source of the picture (it is an article) One of the types of Tip Jet is ...
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### Why can the rear rotors of helicopters move freely in this direction?

As you can see in the video in the imgur link below i recorded a video of the Alouette 2 rear tail rotor and as you can see it moves freely in that direction. Why does it freely move in that ...
315 views

### How does a helicopter phasing unit work?

I'm currently distance studying to become a B1.3 technician and the course material mentions a phasing unit in the control system, but the descriptions and images are very abstract and I'm having ...
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### What is the name of the unequal lift distribution across a helicopter rotor blade?

A helicopter rotor blade will generate more lift at the fast-moving tip than at the slow-moving root, unless it is twisted or tapered. Wikipedia calls this "asymmetry of lift", however I ...
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### Replacing cyclical control with tilt-able rotor using EV motors and servos

I understand the traditional reasons for cyclical control (with swash plates) on helicopters; ie, avoid gyro effect, shaft can be fixed. However, if the power plant was a modern EV motor, and ...
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### Can we bring a rotorcraft like Ingenuity to an altitude of the same pressure as the one on Mars?

At Perseverance's and Ingenuity's location the atmospheric pressure is about 750 Pa (0.11 psi). On Earth, we find that pressure about 110,000 ft high. If we built a copy of Ingenuity, could we bring ...
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### Helicopter mast bumping in low g condition

The helicopter shown in the concrete pouring video seems to taking off from a hill and descending down in a way which can be classified as low G with low rotor loading. Although, the helicopter is ...
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### Can anyone identify this Autogyro?

I've found similar autogyros on the internet, but not this one. Most autogyros appear to have 2 cockpits and this autogyro only has one. Although I have matched its angle-tipped wings with other ...
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### Is engine shp directly correlated with its payload capacity?

For a turboshaft engine, does increasing its shp also increase its payload capacity? What are the other factors determining the payload capacity of a helicopter?
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### Can coaxial rotors be mounted on a piston engine like the Lycoming O-320?

What are the drawbacks of this compared to coaxial configuration with a turboshaft engine?
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### For a coaxial rotorcraft, Do horizontal and vertical stabilizers in the tail really make much of a difference?

Can we design a coaxial rotorcraft without tail and tail boom completely? What might be the consequences?
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### Is it hard to hover a coaxial rotor helicopter?

Convetional rotorcrafts are hard to hover as when we increase collective, even tail rotor pitch needs to be compensated. But in coaxial design, will just increasing the collective do the job as torque ...
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### How to do blade element momentum theory analysis for different geometries of airfoil, e.g. NACA airfoils?

I want to analyse NACA airfoils using BEMT. I have only yet done it for basic symmetric airfoils. I would like to know what all assumptions remain same in NACA airfoil analysis and to what degree it ...
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### What is rotor damping and how does it affect helicopter stability?

What do we mean by rotor damping (in terms of helicopters)? How is it affected by air density? How does helicopter stability depend on rotor damping?
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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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### What forward airspeed produces maximum rate-of-climb in helicopters?

Lift in a helicopter increases with airspeed (from zero IAS up to some Vmax). But in contrast to fixed-wing aircraft a helicopter can generate lift at zero airspeed. Is there a formula for the ...
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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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### What are the applications, advantages and limitations of Gyrodyne rotorcraft?

Gyrodyne is a VTOL rotorcraft. It has ability to power both rotors and propellers for generating lift and thrust. What makes it of lesser popularity than helicopters. Are there any applications of ...
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### Helicopter Basics: How does lead-lag of blades actually help in compensating for increase/decrease in speed due to flapping?

I understand the following - Due to dissymmetry of lift, flapping up and down occurs. Since angular momentum has to be conserved, the speed of blade increases/decreases during flapping up/down ...
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### What design characteristics influence helicopter wind gust spread tolerance during takeoff and landing

Not considering pilot reaction time, what factors influence a helicopter's ability to survive high wind gust spreads (from any direction) during takeoff and landing? I have considered: Swash plate ...
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### Why does disk loading mean anything when rotors/propellers are not disks?

"The helicopter rotor is modeled as an infinitely thin disc with an infinite number of blades that induce a constant pressure jump over the disk area and along the axis of rotation." This is ...
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### What methods are used for calculating maximum takeoff windspeed of a helicopter?

I would like to calculate the maximum windspeed in which a helicopter may safely take off and safely land, assuming a theoretical wind environment with constant wind direction and no gusts. I ...
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### Does a dual-rotor helicoptor like the Chinook transition from hover to forward flight differently than a single rotor helicopter?

I watched this video of an RAF Chinook taking off vertically and transitioning to forward flight. I'm curious if the method for increasing lift to move forward, controlled by the cyclic in a single ...
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### Are a gyrodyne and a compound helicopter the same thing?

Both the gyrodyne and the compound helicopter are typically rotorcraft with driven rotor, additional stub wings and thrust provision. Are they two terms for the same thing or do they differ in some ...
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### What angle of deflection / pitch on the rotor blades can the controls generate?

I was wondering, if a pilot uses full input on cyclic and collective, what pitch angle can be achieved for the rotor blades? Is there a mechanical stop to prevent extreme angles of attack? And how ...
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### Can a tiltrotor fly safely with one engine?

I am curious about tilt-rotor feasibility (such as AW609) against fixed-wing and rotor-blade aircraft (conventional helicopters). One important issue that immediately arises in my mind is that both ...
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### How do a helicopter's cyclic and collective transfer commands to the swash plate?

I understand the function of the cyclic and collective, and I am specifically wondering if anyone has a good image/video showing the mechanism of how the flight control "mixer" works! I can't seem to ...
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### Why does a turbine helicopter need to spin a tail rotor?

Should not the exhaust of the turbine supply enough byproduct to deflect and maintain yaw with a simple deflector (i.e. rudder/stabs)?
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### How does a Delta-3 hinge on a helicopter tail rotor work?

I am trying to understand how adding offset hinges would provide a self-feathering force. Does anyone have more information on Delta hinges on helicopters? I am a bit confused with the information I ...
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### How are performance classes for helicopters/rotorcraft defined?

In helicopter/rotocraft literature, such as ICAO Annex 14 Volume II (how to design heliports), there's constant references to performance classes. How can I tell what performance class a helicopter is ...
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### What angle are front rotors of tandem helicopters tilted and why this value?

I've read that the front rotor of tandem helicopters are tilted forward so that you can get a forward velocity with no nose-down pitching of the fuselage, but what angle is used for this tilt and why ...
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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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### Why are Western helicopters more expensive, yet smaller in size, but Russian helicopters are way less expensive, and larger in size?

So, I was looking around for prices of the Bell 412, Blackhawk and Mil Mi 8/17 prices, and the Bell 412, despite being a lot smaller than the Mi8, was US\$2mil more than the Mi8.
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### Why are aerial taxis multirotored, instead of a single rotor?

source -- image shows Volocopter's design I find that in the designs of aerial taxis, particularly in Volocopter's design, the design consists of a system of multirotors. What is the main reason for ...
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### How Helicopters Change Attitude (Gyroscopic Precession or Thrust Vector Tilt)

I am trying to determine how helicopters pitch and roll (i.e. change attitude). I have heard two explanations. 1) Pitch/roll change is achieved by tilting the tip path plane and therefor tilting the ...
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### Does ATC clear IFR helicopters for a visual approach if landing at a helipad on a high-rise?

I'm guessing that most helipads on downtown high rises don't have any instrument approaches. If a helicopter is on an IFR to a helipad without any instrument approaches, does ATC just clear them for ...
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