TerraN_EmpirE
Tyrant King
One of the technologies being used in X2 is vibration dampening. The Main rotors make extensive use of active and passive systems built in to the rotor mast head and the helicopter to counter it.
S97 Raider and JMR/FVL program News + Videos
- Thread starter TerraN_EmpirE
- Start date
TerraN_EmpirE
Tyrant King
and this one is for you Blackshark, Lord Corporation Raider Partner on Vibration control
Black Shark
Junior Member
I think you mist my point. It does not matter how much dumping systems they install a rigid rotor based on same design (co-axial) or (main/tail rotor) will always have more vibrations than a non rigid rotor with same measures of dumping systems. The main benefit with co-axial designs is that the vibration is greatly reduced since it has no tail rotor, which produces about 60%+ of the vibrations, by using of rigid rotor on co-axial the vibrations the fuselage and especially important the pilot experiences are increased, making it less suitable for recon and attack/combat purposes. The problem here is that recon/command/attack helicopters need good accuracy and all vibrations will ultimately effect FLIR,Radar or any other sensors like DIRCM and will worsen their accuracy which is crucial especially for DIRCM's since they have a very narrow dazzling beam and are already aimed at threats over MAW sensors that are dislocated of their own LOS.
Rigid rotors are usually not favored on attack and recon choppers because that makes solutions for Targeting Systems redundant and unnecessary but if a plattform is already decided to have a rigid rotor design than it will be 2nd row solutions that will need to be thrown at them and this is also the main reason why targeting systems and weapon accuracy on Attack Helicopters increases over years, by "simply" reducing the vibration effect on Targeting Systems and Weaponary.
TerraN_EmpirE
Tyrant King
Well as you have said a coaxial design would have reduced vibration compared to a conventional configuration with a tail rotor, even if it has a rigid rotor the vibrations would still be what equal to or less then those of a conventional lay out? And if they are equal to that of a conventional chopper then targeting systems would only need to be stabilized like they already are in attack choppers like the Apache.
In Terms of Turning and Maneuver, Raider is not using the same setup as a conventional helicopter or Kamov coaxial design , The Forward and rearward momentum being from the pusher, at speed the Raider uses Elevator and Rudder controls well. the shrouding around the rotor hub is intended to reduce drag.
In Terms of Turning and Maneuver, Raider is not using the same setup as a conventional helicopter or Kamov coaxial design , The Forward and rearward momentum being from the pusher, at speed the Raider uses Elevator and Rudder controls well. the shrouding around the rotor hub is intended to reduce drag.
Black Shark
Junior Member
And how accurate are the current Attack Helicopters? You can figure that out for yourself by watching videos or reading reports of accuracy tests aswell the reports and research on IHADSS where the main issue of vibrations clearly have worsen the accuracy of weaponary and Targeting Sights.
There was a survey and research for improvement for IHADSS and the common known negative effect on human eye aswell EO sight systems that blur out the objects that are focused, the cause for this is mainly vibrations that are created by the helicopter which the majority comes from tail rotor, gearbox and followed by main rotor.
Page 63,
Design Issues for Helmet-Mounted Display Systems for Rotary-Wing Aviation said:
The Probem addresses mainly the issues for HMDS (IHADDS) as research ground on Apaches for this problem since it was experienced on this helicopter most of times and is an issue addressed quite often on the inaccuracy of the Apaches gun fire which is addressed in the following research by US Army. The vibrations in the cockpit of 3-8 Hz are similiar to the vibrations of EO systems and far higher vibrations on Mast mounted Radars which is another problem and why the Guardian got a new designation since the US worked on the problems with the Longbow since almost two decades and the issues were solved just recently and it now comes up to the advertized performance. However the vibrations that occure at front nose section of the helicopter where most of EO sights on Attack Helicopters are, are effected by those vibrations, the problem here the usual vibrations that occure on the EO sights from rotors,gearbox and structural resonance to rotor vibrations can be and are dumped down to some degree but the rest of the remaining vibrations are handled by the gyrostabilisation system that works over mechanism and electronics to induce same amount of vibrations on the EO sight to counter the choppers vibrations, the problem of course never can be solved with 100% success especially since vibrations are not constant and are not always in same axis not to mention the vibrations that occure on firing gun, launching weapons or the vibrations on the EO sights that occure from the movement of the very same EO sights like TADS.
Black Shark
Junior Member
The targeting sights and systems that are currently on conventional designs would actually need a better plattform with less vibrations, because such developed technology and affordable aswell for Targeting Systems does not exist in military active service. Since you use the Apache as part of a comperision so we can use it as a comperision for further how accurate it as a plattform is. I think that i've addressed the issues with vibrations coming from rotors that will inevitable effect and worsen Targeting Systems from HMD to EO sights and Radar's accuracy. Now we will put this in numbers given by a research of Apaches gun fire accuracy and Hellfire accuracy.
Page 87 (M230) and Page 83 (Hellfire)
In Military there is clear definition on "effeciency" put in numbers that 80% Hit probability, kill probability are the basis to call accuracy or effeciency on hit "Effective" this is not the case for the Apache, but he is not alone, you just need to see the offbore engagements of Tiger helicopters aswell as offbore shooting of any 30mm cannon on Attack Helicopters, the big difference here is that Apaches have not only uneffective (inaccurate) offbore engagement with cannon but also in front sphere, but the WSO in most videos is to blame for that which are usually cowboy behaviors and not sticking to what they have been teached.
Since this post is already far longer then i've expected due the quoting, since i dislike and don't trust quotings that are citing only one or two senteces taking the entire point out of context, i therefore rely on such long quotations, sorry for that.
TerraN_EmpirE
Tyrant King
Shark I am getting your argument
So you state a rigid rotor produces more vibration on a conventional helicopter. I can accept that. but If in a slower turning coaxial configuration would it produce anywhere near greater vibration of a conventional helicopter with tail Rotor? I just can't see how. I mean eliminating the tail rotor left a platform that produced only >40% of the conventional configuration. adding Rigid can't then pile back on way more (<60&) vibrations can it? and if it ends back up at equal vibration to the conventional I still don't see a issue as for military roles the conventional configuration is still the norm including I might add in the Mi24 and Mi28
But here is the thing I just don't see the major issue as major. Why? because compared to a conventional configuration helicopter which has been doing the job for decades the Raider and it's descendants would be no worse the platform. other than Kamov and Boeing Vertec every current combat helicopter whether transport, Attack, Scout or Ambulance use the same configuration pioneered by Igor Sikorsky on his Vought-Sikorsky VS-300 the single main rotor with a tail rotor to counter torque. as you yourself have said.
Now in Raider's case there is a pusher which could be called a tail rotor but it's used differently, can be turned off and is dampened. However your argument is centered on the rigid rotor. but you have said that <60% of the Vibration comes from the tail rotor.
So you state a rigid rotor produces more vibration on a conventional helicopter. I can accept that. but If in a slower turning coaxial configuration would it produce anywhere near greater vibration of a conventional helicopter with tail Rotor? I just can't see how. I mean eliminating the tail rotor left a platform that produced only >40% of the conventional configuration. adding Rigid can't then pile back on way more (<60&) vibrations can it? and if it ends back up at equal vibration to the conventional I still don't see a issue as for military roles the conventional configuration is still the norm including I might add in the Mi24 and Mi28
and yet I point out a number of rated combat choppers under development or in service are looking or use rigid rotors, the HAL Light Combat Helicopter, HAL Rudra, HAL Dhruv, Eurocopter EC635, and Messerschmitt-Bölkow-Blohm Bo 105.
Black Shark
Junior Member
Either i got carried away or you missed the point i was trying to make. The military always tries to optimize everything as much as possible for cost effecient resources. The rigid rotor has its advantages like more responsive, slightly better with speeds and more forgiving due better response, the disadvantages on this part are usually not well suited for co-axial designs for the advertized roles it should fullfil. Rigid rotors combined with this civil purposed rotor blades which are no more than plastic to describe it as best, they will can not meet the standards for combat aircrafts that will be involved in any frontline attack/assault roles.
To fullfil such a role for any low intense battlefield as an assault/attack aircraft it needs certain standards to meet to be well suited for such a job (that does not mean it could not performe such missions physically speaking). A rigid co-axial rotor with civil purposed rotor blades that meet no standards any other rotor blades from OH-6 to AH-1/64 they are not resilient enough. The issue i see here is that a rigid co-axial rotor with such polymere like rigid rotor blades is somewhat a contra measurement to the entire co-axial design for combat involved roles. A rigid rotor translates the vibrations from the main rotor, gearbox to the strucutre and further to cockpit and gun/EO sights. A conventional "loose" rotor will have dumped down some of the vibrations by the freedom some parts have due the looser design, the vibrations of a rigid rotor will not be as worse as a conventional design, but that is not the problem on the whole system, the point is will the vibrations that are translated into the cockpit be similiar and from the videos of the X2 it seemed quite alot considering that it is a co-axial design. For combat roles high maneuverability, basic armor and speed are essential the co-axial design is good for all of those points, it won't have much armor due lift is used for cargo, speed is given but the maneuverability is a confusing and not optimized due the contra design decisions. What i mean is a helicopter during maneuvering has very high stress on rotor blades especially the tip which is quite high Gforce, a rigid rotor is not benefitial for the given higher maneuverability of co-axial designs that comes from the less to non flexible rotor blades and mainly the disc along with those plastic like rotor blades the stress on the rotor blades is reducing its usefullnes for such combat roles.The point i try to make is it is not good design for combat role, not meaning it couldn't performe it, it means there are better solutions for such roles. However it is very well suited and further upgrades will probably make it optimized for CSAR missions where it would rival the Mi-35 as the current king for CSAR missions due the speed, armor and armament it has better than any current CH.
I think i focused to much on rigid rotor and did not explain what i intended to do, lost myself in the long quotation post.
The difference with this helicopters and with S-97 Raider is that those helicopters use composite rotor blades and not polymere rigid rotors that have no elastomeric capabilities which reduces its lifespan, stress load and will also not be comparable resilient to bullets like composite rotor blades. This was the main point i was trying to make and failed.
TerraN_EmpirE
Tyrant King
The Rotor blades of the 6 bladed coaxial main Rotor are manufactured by Eagle Aviation Technologies they also make the blades for the V22 Osprey. It's not a polymer it's a composite. The exact specs have yet to be released so I don't think we can actually judge just how tough they are yet.
When this bird ultimately is inducted...it will be an excellent aircraft for the role intended.
I will say right now, that I expect them to perform, and perform very well in combat, or any other role they are designed for.
As you know, T_E, the people doing this work know what they are about...they have some of the best aerodynamic engineers in the world, and they will take into account and solve any stability, any dynamics, or other issues...or the aircraft will never get to the LRIP stage.