# 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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### 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, ...
1 vote
3k views

### 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 ...
266 views

### 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 ...
76 views

### 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.
104 views

### 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 ...
95 views

### 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?
255 views

### 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 ...
78 views

### 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 ...
205 views

### 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 ...
584 views

### Relationship between flapping and lagging frequency

In my rotorcraft module at university, we were told that blades leading/lagging is as a result of blade flapping. To conserve angular momentum, an upward flapped blade (CG moves toward rotor hub) will ...
140 views

### 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?
1 vote
2k views

### 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?
255 views

### 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 ...
190 views

### 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.
1 vote
488 views

### 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 ...
5k views

### 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 ...
5k views

### Can a helicopter really fly with rotors going this slow?

I was watching this youtube video and I noticed that at 3:17 seconds they show a coast guard helicopter rescuing a man from a ship. Whats shocking about this is that the main rotor of the helicopter ...
173 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,...
104 views

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 ...
5k views

### Would it be more effective to increase the length or chord of a rotor blade for better performance?

Would it be more effective to increase the length or chord of a helicopter rotor blade for better performance? (Say, 10%?)
22k views

### Do helicopters use more fuel when hovering?

This answer says A helicopter uses a LOT more fuel hovering than it does in forward flight. Is this correct? Why?
265 views

### 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) ...
406 views

### 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 ...
170 views

### 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 ...
203 views

### 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 ...
813 views

### What is the reasoning behind Kamov twin-rudder design?

Several helicopters, namely the Ka-226, the Ka-25, and the Ka-27, have twin vertical stabilizers that are canted inwards at an angle of about 15 degrees, similar to the feathers on a shuttlecock. The ...
328 views

### 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 ...
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 ...
2k views

### Why do helicopter rotors have constant section and angle of attack?

As I understand it helicopter rotor blades keep a constant aerofoil section along their length, and are not twisted. Other rotating aerodynamic devices such as propellors, turbofan fans and wind ...
178 views

### 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 ...
3k views

### How do the Kaman K-225 rotor "planes" work?

I had the opportunity to go to one of the Smithsonian Air and Space museums today and they had a Kaman K-225 on display. For those who don't know, the K-225 is a dual side-by-side helicopter design ...
1 vote
191 views

### 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 ...
733 views

### Do you know the exact model and use of this rotorcraft?

I've tried to identify this. Someone suggested it is a Bell 206, possibly a Jet or Long Ranger. I disagree. I think it is a US Coast Guard helicopter. It flew over my house in Mobile, Alabama. It's ...
274 views

### 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,...
1 vote
1k views

### 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 ...
3k views

### 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 ...
231 views

### 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 ...
367 views

### 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 ...
60 views

### 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?
64 views

### 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?
588 views

### 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.
420 views

### 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 ...
557 views

### 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 ...
2k views

### 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 ...
604 views

### What are the helicopter frequencies on the LA heli charts used for?

The LA heli charts list frequencies for the different heli routes in LA: Are the frequencies used as a "CTAF" for helicopters, or is there an air traffic controller on that frequency telling ...
178k views

### Why haven't quadcopters been scaled up yet?

Why are quadcopters not flown by human pilots yet? Wouldn't they be more stable and easier to control than helicopters?
69 views

### 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 ...
1 vote
772 views

### 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 ...
1 vote