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Discussion in 'World Armed Forces' started by TerraN_EmpirE, Feb 4, 2015.
The First Bladed Ground Test of the S97 Raider compound Helicopter Prototype.
This is going to be a great helo...and will lead to an entire family of US built counter-rotating aircraft.
Of course, the Russians have been using this technology on many of their helicopters for a long time.
true Kamov has been around for decades but the really unique bit is that pusher prop. That's the part that will leave Kamov's existing designs in the dust until they build the KA92 in the mid 2020's
Agreed...in addition to the sensor suite and other goodies these babies will get as various configurations are developed.
Best opener would be US Army 160 SOAR (A) Who already operate a aircraft types not considered in "Regular Army" service, particularly I believe would be phase in as replacements for the 51 MH/AH-6M Little Birds, Raiders 6 man passenger configuration and armed mission capabilities would do well there. And potentially the Army then could absorb them force wide as scouts with allies then picking them up for similar missions. particularly South Korea who has been looking for a new scout chopper.
Raider would also be a stepping stone to the Defiant for JMR M and JMR M-Attack
If you look at Russian coaxial helicopters (Kamov), you will see the blades are very far apart to avoid collision as the blades flap and pivot. The key to the Sikorsky design is the use of tightly coupled rigid rotors. I am not sure if the rigid rotor is necessary to the "retreating blade stall" problem that limits high speed flight on helicopters in general. I suspect they are since an upper stalling blade would fall into the spin plane of the lower blades unless you spaced the blades so far apart that the rotor mast would become ungainly and heavy. The coaxial layout balances the blade stall by having the two sets 180 out of phase. It still stalls but lift symmetry is maintained.
the X2 configuration also boosts speed by having the rotor focus solely on lift in forward and reverse flight with the pusher acting to propel, where conventional and even Kamov choppers have the Rotors serving as lift and propeller.
lets take a refresher on the JMR/FVL program.
There are four intended weight classes for JMR Light, Medium, Heavy and Ultra
Table form Flight Global..
This was intended to serve as a scout and Trainer as well as Special ops Bird was slated for the late 2030's but at least in Theory could be introduced earlier.
this platform could also serve as a basis for future Fire scout type UAV. currently Sikorsky's Raider would fit this role nicely alternatively Bell who has been partnered with Agusta could in theory try and offer a Scout based off the AW609 or wait and develop a derivative of there Vallor, How this one plays out is up in the Air.
FVL is the Demonstrator for a Medium lift class rotary wing platform that will eventually be the basis of JMR-M the design used to replace the H60 BlackHawk potentially UH1Y Venom series helicopters and a Attack version to replace the AH64E Apache Guardian and AH1Z Viper. If successful This will likely be the most Widely seen platform in all 5 Us services, The Army, who has the largest rotary wing fleet, The Marines and Navy as well as the USAF and USCG.
JMR Heavy is intended to replace the Army's Chinook series and has also been pushed to replace the Osprey. First Why not Osprey?
The US Army is not the USMC, Or the USN or the USAF it has different needs and Critically It's top Chopper is the CH47 It never adopted the Seaknight seeing it as to small, Well the Marines operate the CH53 and will soon pick up the CH53K for heavy lift. the Army cut back to a smaller Heavy lifter in the Form of the Chinook.
The Osprey was designed as a replacement for the Ch46 Seaknight a smaller Helicopter this places some special restrictions on Osprey. for example Well a Chinook could carry a Unarmored Humvees internally a Osprey cannot as the ramp and interior of the Osprey has a clearance of 64 inches well a Humvee has a width of 85 Inches. Well a US Army Chinook or Marine CH53 can carry such internally with a 90 inch wide door on Chinook. This means that Osprey has to be partnered with specialized Vehicles such as the Growler or Flyer 60 or Phantom badger. Farther more the Army's JMR aims to be even bigger then the platforms it intends to replace. if you looks at the stated weight class of the JMR-H 13,608Kg at it's max thats 908 kg over the max of Chinook and equal or greater then the capacity of C27J with a speed of half the C27 but twice the Ch47. now End game wise. I think If it goes through What I suspect is that Osprey would be upgraded with tech from the JMR-H well the Army pushes for it's own heavy lift chopper.
The Final JMR and the Largest of the JMR's aimed for a payload range of 18,144 Kg to 32,625 kg for comparison sake a C130J-30 the largest of the C130J's has a payload of 19,958 kg and Ch53K of 15,900 kg. the A400M from Airbus has a Payload of 37,000 kg this would make a lifter potentially larger then a KC390 but smaller then A400M
It may however just be a push to get the Air Force to develop a new tactical lifter.
Looking at all this, I actually feel that the "light" should be the one being pursued and inducted first.
In the form of an aereal scout I think it's the most needed VL requirement of the army at least. They're trying to find a new one for almost decades now, and all the efforts have led nowhere. The Koiwas will retire and the role will be filled by guard Apaches. The Apaches being heavy attack helos, that will make the scout element logistics heavy as well and in my opinion put restrictions on deployability. Sure there's now only one type to be supported, but still ...
Additionally, in a rather simple / light airframe environment, it might actually be cheaper to test new VL technologies, that can later be potentially upscaled to the other JMR-types.
The passenger space can be used for additionl fuel and / or sensor equipment in the armed scout role, or be indeed usefull for quick small combat element insertions.
I also think such a Raider type would be a more proper replacement for the Venom, a light utility / fire support helo for the Marines.
I have some small doubts, however, that a tilt rotor type alla "Bell", might be right for the role. Considerng how widespread the use of that future JMR-L will be, such a small Osprey cousin might be a bit too complex to be used so widely. Although there would certainly be some niche application were it would fit almost perfectly.
In the medium and heavy category with the latest Blackhawk, Chinnok F and the upcoming -53K variants, the need for a replacement appears not pressing to me. Although JMR-M should be next after light.
I'm also not so sure about a V-22 replacement already. I think for the Marines and AF they are finding their role quiet nicely. To make up the large fleet of the army again something a little less complex / more conventional might be the smarter move.
Russians don't use rigid rotors because rigid rotors have disadvantages that for most jobs are not suitable or toleratable especially for helicopters operating anywhere near combat zones.
The advantages of rigid rotor design is that the design is more forgiveable in situations where pilots could make some errors, meaning it is little bit more responsive the other point is that a rigid rotor also translates positive in speeds but there are also merits and disadvantages like higher vibrations pilots have to bear with in the cockpit like we can see from X2 videos. The big disadvantage however with a rigid rotor for co-axial designs is that it must be compact meaning it can not have bullet resistent heavy rotor blades, which from its design will bend inevitable when reaching more than 4 meter radius. Sikorsky has to use stiff, light weight rotor blades that are very thick near the rotor chord if you pay attention to that and than thin out to the tips. This design gives stiffness but is also very unfavorable for maneuverability which is very important for frontline combat involved helicopters and that it must have some standards for survivability of helicopter and crew meaning bullet resilient rotor blades which Sikrosky with such polymere like rotor blades can not offer at least not to anti aircraft relevent calibres. This is the reason you won't find a single helicopter with such rotor blades be it light weight OH-6, Bo-105 or be it AH-64,Mi-28 or whatever Attack Helicopter you may choose for comperisions, on the military issue.
However the Helicopter offers quite promising future for CSAR missions.
PS: Retreating blade stall has nothing to do with rigid or non rigid rotor. The distance between rotor discs is merely an issue of G-force that is applied to the rotor disc tip when maneuvering the helicopter at higher Gforces and not during straight flight. Like the last part of you rightly explained that the co-axial design advantage for higher speeds is it balances its lifting out and makes it more symetrical.