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Army Scout after LHX...RAH...ARH

yasotay

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Since the debate on capabilities and such was begining to overcome the LHX thread I thought I would attempt to move it here. To start the conversation I found this little bit over at AW&ST ( http://www.aviationweek.com/aw/photos/photopage.jsp?plckPhotoID=6cd19bfa-0fe2-4616-9403-e9e29b3db7ce&plckGalleryID=b1746a72-fce6-489c-9afe-50a1413a668b )

It certainly is a different idea. Kamov rotor type (proven) and ducted fans (proven). Reuse of airframe without that nasty aged tailboom. What more could you want.
 

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Stargazer2006

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Very interesting. But why two fans at the rear instead of two one? Is there a proven gain in this configuration, over the single fan option of a X-49 Speedhawk?
 

Sundog

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Stargazer2006 said:
But why two fans at the rear instead of two?
I believe you meant two/one, not two/two. ;)

If I had to guess, and I do, I'm thinking the two smaller fans get cleaner airflow for pushing the vehicle, since with the double coax rotor, you don't need all of the tail control power for yaw. Also, as I've sort of already stated, the ducted fan on the Speedhawk is used for yaw control at low speed, and these might as well, but they aren't necessary for it, as witnessed by the many Kamov designs. That's why I assumed they are mostly for providing thrust in forward flight, but by putting them outboard, they act like "vertical stabs" with the ducts and you can vector their thrust to act like rudders, because I'm guessing it gives you more control power in some situations and possibly a faster yaw response then the coax rotors would generate. And they are in clean airflow. ;D I know I'm rambling and this paragraph is a mess. No time to edit right now.
 

Stargazer2006

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Sundog said:
I know I'm rambling and this paragraph is a mess. No time to edit right now.
No problem, I get the point. Thanks for your analysis! And yes, I meant two/one...
 

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This is a proposal by Fort Worth-based start-up AVX Aircraft, called the OH-58D AVX, to meet the US Army's Armed Aerial Scout (AAS) requirement (aka Armed Reconnaissance Helicopter Take 2) at lower cost by upgrading its existing Kiowa Warriors. It is being unveiled this week at the Quad-A show.

The proposal is to remove the OH-58D's four-blade main rotor, main transmission and complete tailboom and tailrotor and replace it with two three-blade coaxial rotors, a new transmission and a shorter tailboom mounting the ducted fans. The OH-58D's R-R 250 engine would be retained.

Coaxial rotors do not require a tailrotor to counter torque, so the variable-pitch fans would provide directional control and forward thrust. In the hover, moving the rudder pedals would command forward thrust on one fan and reverse thrust on the other. In forward flight, collective fan pitch (and therefore thrust) would be controlled by a twistgrip on the collective lever.

According to AVX, in an OH-58D hovering at heavy weight the rotors would require 500shp and the fans just 20shp. In the cruise at 120kt the rotors would be "almost idling", taking around 200shp while the fans take 300shp.

The Army is already planning to remove the OH-58D's old McDonnell Douglas mast-mounted sight and fit a new Raytheon sensor under the nose - AVX says this would offset most of the weight increase from the AVX modification.
 

Lauge

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Abraham Gubler said:
Urban Aero X-Hawk tandem, enclosed, ducted fan rotors.
According to the Urban Aeronautics website the AirMule UAV version is making progress on it's flight testing (http://www.urbanaero.com/whatsnew.htm).

Or you could just ask Mr. Cameron for one of the below ;)

Regards & all,

Thomas L. Nielsen
Luxembourg
 

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John21

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What I always wondered is why they plan to move the sight back under the nose? I figured that keeping the older style but in an improved package with new capabilities would improve survivability with the ability to track/designate and lase targets from under-cover. Wasn't that the whole idea originally?
 

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Different types of targets, and different types of terrain.

A mast mounted sight can see very well over trees and terrain, but it cant see anything masked by the fuselage of the aircraft. This is important in close environments and urban terrain especially. SO for a helicopter operating low, trying to seek targets below it, a mast mounted sight is at a disadvantage. OH-58D pilots in Iraq spent a lot of time looking out of their side windows and not through the top sight.

A mast mount also makes less sense if the helicopter is going to operate at medium altitudes to keep it out of range of ground fire, which is the preferred method in the current set of conflicts which don't have a defined front line to hide around.
 

CammNut

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I ommitted to say the point of AVX's proposed mod is to improve the OH-58D's hot-and-high performance, as the coaxial rotors and ducted fans require less power than the single main rotor and tailrotor, according to AVX.

Performance estimates:

Hover out of ground effect at 5,500lb - ie full fuel and full weapons - at 6,000ft/95degF
120kt cruise (vs 95kt hot-and-high for OH-58D, says AVX)
445km range at 6,000ft/95degF
3.1hr endurance at 6,000ft/95degF

Their website - avxaircraft.com - should go active today.

More OH-58D AVX artwork:
 

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yasotay

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Thanks Camm,

Look forward to seeing what they have. Although I will be interested to see how maneuverable it is with the ducted fans to assist the coaxial system (which are usually slow to develop yaw rates).

Hope you will spread the goodness here from the Army Aviation meeting.
 

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Thanks Camm, after reading your first post about it cruising at 120kts, I was thinking, OK, don't we have helos that can fly near that speed now. But as soon as you pointed out the design was geared toward the hot and high environment, it all made sense. Are they going to build a demonstrator, or are they trying to get funding for it atm?

Of course, upon seeing this, I realized a screwed up back in the LHX thread, because when I was asking about why not upgrade the OH-58, I was actually thinking of the OH-6. But F-14D and Yasotay answered all of those questions quite well. Anyway, I must have just confused the hell out of them, since I was well aware of the ARH-70, lol. Doh!
 

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AVX has so far spent $4 million in private funding since 2006 on the design - and says it needs $30 million to build a "bare bones" concept demonstrator, preferably based on an OH-58D or C, but possibly on a commercial 206B or 206L. It would take 18 months to build and fly.
 

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yasotay

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At the risk of sound irreverant, I wonder how much a Ka-226 is going for these days. Small, no tail rotor to worry about and with enough space to give it some good multi-role capability.

Any one want to venture a guess how many zero's behind the decimal point on the probability that the US would buy a Russian helo... for their own use? ;D

It will be interesting to see what goes on at the Aviaiton Association meeting. I suspect Sikorsky X-2, Boeing AH-6i and EADS LUH (recon version) will be the big shows with the new scout program floating around out their.

Lauge - where did you find that picture? Bet there are some who are wondering if that could make that happen. Would be great for urban ops.
 

Abraham Gubler

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yasotay said:
At the risk of sound irreverant, I wonder how much a Ka-226 is going for these days. Small, no tail rotor to worry about and with enough space to give it some good multi-role capability.

Any one want to venture a guess how many zero's behind the decimal point on the probability that the US would buy a Russian helo... for their own use? ;D
Probably very low. But the huge advantage of the AVX concept is not so much the end result air vehicle system but that you can do it to the OH-58D that is already in service. So you don't need to go through all the trouble of building or approving a new helicopter engine, fuel system, communications, armour, etc. All you are doing is taking an exsisting bird and replacing its rotor system with something that offers better performance. And replacing the old 1980s sensor ball with something much better.
 

Sundog

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Abraham Gubler said:
yasotay said:
At the risk of sound irreverant, I wonder how much a Ka-226 is going for these days. Small, no tail rotor to worry about and with enough space to give it some good multi-role capability.

Any one want to venture a guess how many zero's behind the decimal point on the probability that the US would buy a Russian helo... for their own use? ;D
Probably very low. But the huge advantage of the AVX concept is not so much the end result air vehicle system but that you can do it to the OH-58D that is already in service. So you don't need to go through all the trouble of building or approving a new helicopter engine, fuel system, communications, armour, etc. All you are doing is taking an exsisting bird and replacing its rotor system with something that offers better performance. And replacing the old 1980s sensor ball with something much better.
To a certain extent I agree with you, but wasn't that the same argument for the ARH-70? Or was the ARH-70 too modified to be considered in the same context?
 

Abraham Gubler

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Sundog said:
To a certain extent I agree with you, but wasn't that the same argument for the ARH-70? Or was the ARH-70 too modified to be considered in the same context?
The ARH-70 was never a rebuilt aircraft. It was a new build of a modified civil design (the latest Jetranger). While it may look the same on the outside the Jetranger is very different to the OH-58, especially in the area it counts - survivability.

The AVX "Bell-ov" or "Kam-ell" takes a OH-58D out of the air cav with everything already in it that is needed to operate in a war zone (except presumably the aircrew) and pulls out the two things that aren't up to standard - the rotor system and the sensor ball - and replaces them with new that are. Obviously it needs to be flight tested to make sure it can work but if it can it is a far easier and effective way of achieving the end result (a hot and high Kiowa Warrior with a 21st century sensor) than trying to new build again.
 

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The Voljet was designed in the 1980's and is superior to ANY helicopter in terms of safety, simplicity, stability and performance. Not to mention extremely QUIET...
Too bad the design isnt reflected in a 21at century update for LHX. I'm sure that the patents were bought for a large amount of money and an advanced version is flying at some Black operations test range. The capabilities were too superior for it to not have been used by the military.

State that fuel consumption was a problem, But that was so the black projects could get it.

(Tip Jet)-

http://www.youtube.com/watch?v=3h6Q4hTveCo&feature=related
 

Abraham Gubler

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kcran567 said:
The Voljet was designed in the 1980's and is superior to ANY helicopter in terms of safety, simplicity, stability and performance. Not to mention extremely QUIET...
I think the good people at Fairey and Sud would disagree as to a rotor powered by tip exhaust of pressure jets was invented in the 1980s... As to the rest you said about this kind of capability that was pretty wrong as well.

http://www.secretprojects.co.uk/forum/index.php/topic,1084.0

http://www.secretprojects.co.uk/forum/index.php/topic,6365.0
 

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kcran567 said:
I'm sure that the patents were bought for a large amount of money and an advanced version is flying at some Black operations test range.
Good for you ;)

Now, is there any actual evidence to support this notion?

Regards & all,

Thomas L. Nielsen
Luxembourg
 

Sundog

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Abraham Gubler said:
Sundog said:
To a certain extent I agree with you, but wasn't that the same argument for the ARH-70? Or was the ARH-70 too modified to be considered in the same context?
The ARH-70 was never a rebuilt aircraft. It was a new build of a modified civil design (the latest Jetranger). While it may look the same on the outside the Jetranger is very different to the OH-58, especially in the area it counts - survivability.

The AVX "Bell-ov" or "Kam-ell" takes a OH-58D out of the air cav with everything already in it that is needed to operate in a war zone (except presumably the aircrew) and pulls out the two things that aren't up to standard - the rotor system and the sensor ball - and replaces them with new that are. Obviously it needs to be flight tested to make sure it can work but if it can it is a far easier and effective way of achieving the end result (a hot and high Kiowa Warrior with a 21st century sensor) than trying to new build again.
OK, that's kind of what I thought, but wasn't sure. It would be nice to have a helo that could operate Hot & High besides the Chinook. Not that there is anything wrong with a Chinook, I'm just sure for many missions they would prefer something smaller, as in a smaller target if they don't need to carry large loads. ;) Although, didn't the X-22 hover at 8000ft? OK, I'm getting back on my ducted fan horse again. ;D
 

yasotay

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Abraham Gubler said:
yasotay said:
At the risk of sound irreverent, I wonder how much a Ka-226 is going for these days. Small, no tail rotor to worry about and with enough space to give it some good multi-role capability.

Any one want to venture a guess how many zero's behind the decimal point on the probability that the US would buy a Russian helo... for their own use? ;D
Probably very low. But the huge advantage of the AVX concept is not so much the end result air vehicle system but that you can do it to the OH-58D that is already in service. So you don't need to go through all the trouble of building or approving a new helicopter engine, fuel system, communications, armour, etc. All you are doing is taking an existing bird and replacing its rotor system with something that offers better performance. And replacing the old 1980s sensor ball with something much better.
I don't disagree that there might be some utility to the reuse, however these are already very old airframes that have seen better days. They are buying new UH-60M instead of retrofit because the expense of rebuilding the airframes increases dramatically over time. Rotorcraft have to deal with a lot more vibration over a lifetime than do most fixed wing. They tend to get more holes in them over an active lifetime as well.

I have to wonder though if we don't EVER design a new combat rotorcraft we will eventually get to the point that we cannot design one. One might argue that the US is already there considering RAH, ARH, VH-71; and only RAH was a complete new start. Rotorcraft is a very specialized version of aerospace engineering and it does take a while to develop a properly trained rotorcraft engineer. I have been told that it is very hard to attract young talent to the industry when all that is happening is trying to squeeze a few percentages out of an aircraft. Would you as a new aerospace engineer like to cut your teeth on a 7X7, X-45, etc. or figure out how to make a plastic rotorblade for a 50 year old helicopter? From a business perspective why would I want to pay for expensive engineers who spend precious funds on projects that have a low probability of paying off given the customer has not asked for anything new in 30 years?

Indeed it might very well be that AVX which, according to Cammnut's input (and article/blog) are former Bell engineers, might be a practical demonstration that the industry is continuing to cut loose expertise in rotorcraft.

On topic AVX certainly on paper meets what I think a scout ought to be: small, crew o' two, lots of visibility, carries bullets. Only question is how nimble is it?

By the way ducted fan works very well in urban enviroments and has nice accoustic and radar reduction qualities.
 

Abraham Gubler

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yasotay said:
I don't disagree that there might be some utility to the reuse, however these are already very old airframes that have seen better days.
Too true. But because of RAH/ARH it would appear that on scout helos the US Army is behind the eight ball and needs a quick fix before they can move to the long fix.

Perhaps the AVX Hot 'n High Kiowa could be approached in the same way as Chinook Foxtrot; being built in a mix of rebuilds and new builds? This could allow Bell to upgrade the airframe and maybe engine as well? So you get a OH-58E with the AVX fix and then later on a OH-58F with AVX fix on a new build lighter airframe and better engine, better survivability, etc.

yasotay said:
Indeed it might very well be that AVX which, according to Cammnut's input (and article/blog) are former Bell engineers, might be a practical demonstration that the industry is continuing to cut loose expertise in rotorcraft.
Or they had a really good idea to upgrade the OH-58D and it was turned down by Bell’s corporate managers who saw there was a lot more money in making the sucker/customer pay to militarise the Jetranger again (ARH-70).

yasotay said:
On topic AVX certainly on paper meets what I think a scout ought to be: small, crew o' two, lots of visibility, carries bullets. Only question is how nimble is it?
AVX were describing their thrust fans as very similar to the Cheyenne’s thrust propeller in that use of these fans for more than just thrust can strongly affect the aircraft’s attitude. So you can nose up and nose down while flying level, rapidly accelerate and decelerate using the fans in a way that just a rotor couldn’t do. Since there are two of them you could imagine they would be pretty good for yaw as well.

They also said the new rotor system was weight neutral when you replace the old sensor ball. One could also assume that any extra drag from the two extra rotors could be offset by the removal of that big ole ball. But need to get it in the air and see what it can do but all signs point to good.
 

yasotay

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Looking at Camm's blog ( http://www.aviationweek.com/aw/blogs/defense/index.jsp?plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=27ec4a53-dcc8-42d0-bd3a-01329aef79a7&plckPostId=Blog%3a27ec4a53-dcc8-42d0-bd3a-01329aef79a7Post%3a74dbcd32-3ee8-43b4-82ff-d3278ab8b639&plckScript=blogScript&plckElementId=blogDest ) looks like the AAS is getting lots of visibility at the Army Aviation Meeting. I note someone mentions that there is a OH-58D with new kit and engine. Anyone got any info?
 

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yasotay

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Why no Fenestron copter for the military? They're more silent. Is it not sand resistant enough?
 

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mz said:
Why no Fenestron copter for the military? They're more silent. Is it not sand resistant enough?
No one has proposed one for a US requirement beyond the HH-65 Dolphin of years ago.
 

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F-14D said:
mz said:
Why no Fenestron copter for the military? They're more silent. Is it not sand resistant enough?
No one has proposed one for a US requirement beyond the HH-65 Dolphin of years ago.
Doesn't the Boeing-Sikorsky RAH-66 Comanche have a fenestron?
 

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Triton said:
F-14D said:
mz said:
Why no Fenestron copter for the military? They're more silent. Is it not sand resistant enough?
No one has proposed one for a US requirement beyond the HH-65 Dolphin of years ago.
Doesn't the Boeing-Sikorsky RAH-66 Comanche have a fenestron?
Technically speaking, Boeing and Sikorsky said it wasn't it embodied different principles or desgin features. But you're right; I never was sure of the difference
 

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Eurocopter Germany is meanwhile testing a EC-145 with a fenestron.
I presume, that this is only an upgrade for the civil market.

Picture: http://www.flugrevue.de/fm/3/EC145-Fenestron.jpg
 

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Isn't the fenestron kind of a Eurocopter-patented technology? Isn't the NOTAR technology Boeing-owned? I think this accounts for the absence of cross-use of these technologies across the pond, the companies prefer to use technology that is not proprietary of their competitors.
 

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Stargazer2006 said:
Isn't the fenestron kind of a Eurocopter-patented technology? Isn't the NOTAR technology Boeing-owned? I think this accounts for the absence of cross-use of these technologies across the pond, the companies prefer to use technology that is not proprietary of their competitors.
Actually, NOTAR is owned by MD helicopters. I don't know if part of the original agreement that broke up Hughes helicopters allow Boeing to use it for military projects for free. In any case, that size helo seems to be a market Boeing is not actively pursuing.
 

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F-14D said:
Actually, NOTAR is owned by MD helicopters.
MD Helicopters says Boeing retained the rights to NOTAR, but seems to imply that only MD Helicopters can use it. It looks to be a complicated situation.

http://www.mdhelicopters.com/v2/company.php
 

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Fenestron was an Aerospatiale thing. Coupled with the ex-MBB German semi-rigid rotor copters, seems like quite modern helos were born. What's still missing from the palette? How much does noise matter in the Super Puma class missions?
Where to go, what to pursue next if you've Fenestronized everything? There's been some talk of fancy main blade shapes (esp at tip) to reduce noise and vibration further.
 
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