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- - Sikorsky X2 coaxial heli developments. (https://www.pprune.org/rotorheads/245168-sikorsky-x2-coaxial-heli-developments.html)

This pilot is "007"???

C'mon, EVERYBODY knows it should say "Bart" :ok:

Gee, thought it would be much bigger!

Video of odometer during speed trials.

IFMU, that video is excellent! Looks like the CX2 was done by someone within Sikorsky. A lot of knowledge about the fuselage details. I wonder whether it was done while X2 funding was a little tight - i know the frustration that can cause. Any inside info CEFOSKEY?

This is the talk given at Heli Expo on X2:

http://www.youtube.com/watch?v=ILI_v...eature=related

The thing i find amazing is that X2 disc loading is similar to S-76! Hence has a similar autorotation ROD! This for a helicopter which could leave most ground vehicles (including an F1) behind is awesome. Also you can see the rudder hinge lines on the outboard vertical stabilisers for good yaw authority in autorotation. Flight safety has not been compromised for the additional performance.

The horns imply that there is a mechanical connection to the rudder control at least. I have been trying to work out whether the FBW head is hydraulic or brushless DC. I assume the central shafts hold a concentric spider arrangement for the coaxial rotors. This means there would be good access to both swash plates for either actuator. What was Comanche?

I can't wait to see the YouTube video of the real thing. :ok:

Graviman,

Quote:

The horns imply that there is a mechanical connection to the rudder control at least.

:confused:
Please elaborate.

Thanks.

Quote:

I have been trying to work out whether the FBW head is hydraulic or brushless DC.

Graviman,

You lost me here. Are you implying they are using IBC? I haven't seen that in any of the propoganda, surely if they were that far ahead they would drum their chest about it.

-- IFMU

ifmu, when you say propaganda, it means that you dont believe what they are saying - a pox on you! Those guys who are working on the X2 are just like you and me (except they know what they are doing, mostly.)

Grav, the FBW control systems are hydraulic, the FBW works a dual valve on the servos.

To my knowledge, the full electric servos that have been propagandized on other aircraft have some real problems, and those programs are a bit behind, due to that. jamming and wear on the jackscrews is reported thru the grapevine.

Quote:

To my knowledge, the full electric servos that have been propagandized on other aircraft have some real problems, and those programs are a bit behind, due to that

Does that include the B787?

A month or few ago, Jeffery Pino said that electric servos are to be Sikorsky's next R & D project.

The accuracy of the above recollection is subject to an Alzheimer's and a dementia test.

Heli Expo unveiling of X2 (FastForward to 29 sec):
http://www.youtube.com/watch?v=FlrqYowMgNI
Although Rotorheads got a sneak preview, including that beautifully engineered bearingless rotor hub. :ok:

Dave, what i mean is the rudder horns visible at the lower tips on the outboard vertical stabilisers. These increase the aerodynamic loading ahead of the hinge line. They are a mechanically simpler method of fitting trim servos to keep the control forces down.

Nick, that's interesting about full electric servos being difficult to implement in helicopters. I imagine the duty cycle must be far more extreme than even a manouvreable fixed wing, since there will be 1P load variation from aerofoil moment changes. With the upper rotor causing various additional pitch link loads on the lower rotor, from spanwise variations in AOA at least, X2 designers sensibly opted for a hydraulic solution proven on Comanche.

212man, check out the 5th story on this link:
http://www.vtol.org/news/issues106.html

Quote:

Agusta Westland Starts Fly-By-Wire EH101

Agusta Westland has launched the Helicopter Electro Actuation Technology (HEAT) program for the Royal Navy EH101 Merlin HM Mk.1. The HEAT system introduces an all-electric primary flight control system with electro-mechanical actuators. DC brushless motors, high speed motor controls, and quadruplex fly-by-wire primary flight controls will eliminate hydraulics, accessory gearboxes, and most mechanical flight controls. HEAT promises to enhance EH101 reliability and reduce crew workload, aircraft weight, and aircraft maintenance costs. The system will introduce Advanced Control Technology, including active side-stick controllers and is expected to open ship operating limits in adverse weather and improve tactical handling in low-altitude flight. Agusta Westland previously projected first flight in late 2006.

The third-generation fly-by-wire development effort follows the award of the Merlin Capability Sustainment Plus (MCSP) contract announced by the UK Ministry of Defense (MoD). The contract upgrades 30 Royal Navy Merlins with an option for a further eight aircraft to address systems obsolescence and introduce an Open Systems Architecture (OSA). The Royal Navy Merlin bought 44 Merlin HM Mk. 1s. The aircraft became operational in 1999 and is expected in service past 2030. Lockheed Martin UK Ltd was named preferred contractor in 2003 to assess Merlin upgrades and remains responsible for mission system improvements. Work at Yeovil starts in 2010, and the first modernized Merlin is expected in service in 2013.

The HEAT consortium teams Agusta Westland, BAE Systems, and Claverham Ltd with the UK MoD Merlin Integrated Project Team. BAE Systems provides the fly-by-wire system while the Claverham division of Hamilton Sundstrand supplies the actuators. Agusta Westland has had a HEAT integration rig working at Yeovil in the UK since November 2005 and will integrate the technology into the helicopter.

Graviman,

The reduction of control forces by locating the pitch axis of an airfoil at approximately 25% of plan-view area (25% of chord) is understood.

You said;

Quote:

The horns imply that there is a mechanical connection to the rudder control at least.

:confused: Why must it be mechanical? Or, do you mean a mechanical connection without any power assist?

______________________

For comparative purposes; here is a picture and a drawing of the of the S-69 (XH-59) rotor hub.

http://www.unicopter.com/0891_Enlarged.jpg

http://www.unicopter.com/ABC_Rotor_Sleeve.gif

Quote:

Nick,

I would guess that the guys working on the X2 are not the same ones that dish out the propoganda, or marketing if you prefer. Personally I'm a fan of the concept, it will be interesting to see how many of the spin-off aircraft from the marketing become real, or not.

-- IFMU

I thought I read somewhere that if you are down to 1 channel of the HEAT actuator, that you can't react all flight loads. That's a lot different story than hydraulics. Am I remembering that right?

-- IFMU

IFMU,
It really depends on the design constraints, you can make it do anything.

Grav, you hit the nail on the head. The typical helo servo is working like a dog in the 5% region around its cruise setting, and it can really take a beating there. A FW application is more routine, IMHO.

That being said, I diid not know that the 787 was going pure electric. Dave got a reference?
Thanks

Nick

Yes: good old MOOG supplying the actuators!

Nick,

Sorry. I know very little about the Boeing 787.
Perhaps 212man does.

Dave

Quote:

Originally Posted by Graviman

I imagine the duty cycle must be far more extreme than even a manouvreable fixed wing, since there will be 1P load variation from aerofoil moment changes.

I would think that each time a blade passes over the spot on the swashplate where a servo is, it would give it a whack. That would make it an NP phenomenon.

-- IFMU

CEFOSKEY, don't forget to post pics when your project looks the part. :ok:

Dave, that S-69 bearing arrangement is interesting - reminds me of the axle installation i am currently doing. I can see why X2 opted to go the bearingless rotor route of Comanche though - less parts to life.
PS: Regardless of Sky's need for X2 to be a marketing success, the project alone deserves credit for the foresight shown. :rolleyes:

IFMU, agreed duty cycle would be nP, but one of the X2 suite of technologies is active vibration control. There will be an accelerometer somewhere in the hub which alters the input signal to the hydraulic servo dual valves. Although movements will be more, this should actually help reduce the pitch link forces. Rotor figure of merit will benefit too, along with increased frame life.

Nick, i meant to ask whether the dual valves were for failsafe? I'm still reading your Heli Expo presentation for safer heli design.

Quote:

Originally Posted by Graviman

IFMU, agreed duty cycle would be nP, but one of the X2 suite of technologies is active vibration control. There will be an accelerometer somewhere in the hub which alters the input signal to the hydraulic servo dual valves.

Mart,
Don't forget back in post 24 you asked:

Quote:

I'd be interested to know more about the Moog active vibration control though. I could have a reasonable guess at how it might work, but will dig up some papers.

And Nick replied in post 25:

Quote:

Originally Posted by NickLappos

Grav,
The Moog system is the same as that in the S-92, and it works like a charm. I understand the EC225 has a similar system.

The Moog vibration absorber is a electronic motor is digitally controlled to have very precise rpm capability. The digitally controlled motor spins counter rotating weights which are driven eccentrically in and out by separate jackscrews to produce higher or lower vibration amplitudes. Because the rpm of the motor is precisely controlled, the phase of the counterrotating weights can be adjusted, where the phase is the precise direction of the maximum amplitude of the weights. As a result the vibration absorber is capable of being adjusted to precise RPMs and to precise vibration absorbtion direction (lateral, vertical, horizontal). It can also be adjusted automatically by a computer as the aircraft flies. A vibration pickup is located near the place where you want to quell a vibration the most. Using that pickup the computer determines the best way to tune the weights to drive the rpm to its lowest. The computer uses precise logic that learns as the flight conditions change and so the computer becomes specific for the aircraft it is installed in. You can use up to six absorbers with the computers so that it's quite possible to quell the vibration across a very large area. Each of the absorbers weighs around 40 pounds and the amplifier maybe 10 pounds.
Try this patent number: 6,869,375

IFMU, thanks for reminding me about that discussion...

I'm not sure whether the long term intention of "active vibration control" in X2 is simply the Moog eccentric weight type (as fitted to S-92), or the type that is generally known as Higher Harmonic Control. Higher harmonic control would be suited to a fast reacting FBW system, and offers the advantages mentioned. It may be that the Moog eccentric weight system will be fitted with the soon-to-fly hydraulic FBW, but i would be suprised if development stopped here. Part of the long term objective of fully electric FBW might be to fit direct blade vibration control, such as this system being developed at ONERA:

http://www.onera.fr/zoominthelab/17-helicopters.php
http://www.onera.fr/zoominthelab/ima...tif-rpa-s3.gif http://www.onera.fr/zoominthelab/ima...actif-rpa1.jpg

Quote:

To make further progress in developing a silent and comfotable helicopter, "active" solutions need to be found, solutions where the angle of incidence of the blades can be modified. In effect, during rotation, the blades do not experience the same effects when they move in the same direction as the helicopter (advancing blade) as when their movement is in the other direction (retreating blade). Transonic flows may appear at the end of an advancing blade, whereas separated flows appear on a retreating blade and may cause the rotor to stall. In an active governor rotor, it is possible to vary local lift optimally with the help of trailing edge flaps etc. The objective is that the vortices are less intense and pass further away from the following blade. The increase in lift plays a critical role: when the lift is stronger as the vortices get closer then they are pushed further down and make less noise. This effect has been confirmed by calculations and in the wind-tunnel. Other parts of the helicopter may be made active, like the horizontal tail wing (ensuring the stability of the machine and controlling its attitude) or the vertical fin. But work on these aspects is less well advanced.

Development status given here:
http://www.dlr.de/fa/Portaldata/17/R...nschneider.pdf