LHX Program

[quellish]

Frank, you are correct. After a little more research the Testors model is strictly conjecture. I remember various blade concepts under development in the 80's to reduce tip votices and it was such information that Testors used to create the scimitar blade design used in their LHX.

"Testors combined many of the ideas then under development -- including a faceted composite exterior, scimitar-shaped blades and a propeller-less tail -- to create this conjectural design."

http://www.fantastic-plastic.com/STINGBAT%20LHX%20HELICOPTER%20PAGE.htm

Some of the latest on the application of blade vortex generation and noise reduction can be found in an interesting article on the new Blue Edge blade system.

http://www.wired.com/autopia/2010/02/eurocopter-moves-one-step-closer-to-whisper-mode/

A couple of different, exotic blades like these were looked at as means of reducting helicopter RCS in the early 1990s. Part of the problem is the rotor head itself it seems.

 

[Sundog]

Everybody keeps talking about how great the Bell 680 BMR (Bearingless Main Rotor) rotor is without saying why it's so great. So, if any of the rest of you were in the dark like I was, here is a good reference for you.

Bell BMR page 1
Bell BMR page 2
Bell BMR page 3

 

[F-14D]

Everybody keeps talking about how great the Bell 680 BMR (Bearingless Main Rotor) rotor is without saying why it's so great. So, if any of the rest of you were in the dark like I was, here is a good reference for you.

Bell BMR page 1
Bell BMR page 2
Bell BMR page 3

Besides lowered vibration (which offers all kinds of Good Stuff), it also puts out a lot of power. On the AH-1Z, which uses a derivative of the 680 rotor, I believe 44,500 lbs. of thrust is available (should not be directly compared to thrust as out the back end of a jet). My recollection of the actual thrust may be wrong, but I do know it's an enormous amount. Since the AH-1Z got a new tail rotor and didn't just carry over the W's tail rotor (as did the AH-1 4BW) some marine officials early in the program were saying (before they were told to keep quiet) that with the 680, the AH-1Z could meet the LHX's agility.

 

[donnage99]

I actually have a real copy of the Hughes "Fighter" LHX print matted and framed. I got it as a young aviation officer who had visions of Hughes fighters and Bell BATs swirling in my head, thinking I was going to have such a cool flying career. Boy did I get jipped! Here I am thirty years later chugging around in a souped up Model T (as in tweeked single rotor helo's that don't go much further or faster than their predessors).

Hopefully you can get to ride this in a not so distant future:

 

[amsci99]

yasotay,

Would definitely like to take a look at the Hughes LHX print, could I trouble you to post a scan of it on the forum. My thanks and appreciation.

 

[Sundog]

Besides lowered vibration (which offers all kinds of Good Stuff), it also puts out a lot of power. On the AH-1Z, which uses a derivative of the 680 rotor, I believe 44,500 lbs. of thrust is available (should not be directly compared to thrust as out the back end of a jet). My recollection of the actual thrust may be wrong, but I do know it's an enormous amount. Since the AH-1Z got a new tail rotor and didn't just carry over the W's tail rotor (as did the AH-1 4BW) some marine officials early in the program were saying (before they were told to keep quiet) that with the 680, the AH-1Z could meet the LHX's agility.

Yeah, everything I've heard or read about the AH-1Z was good. I hadn't realized that this was the technology it used, although I realized it, obviously, had a new rotor system. I take it the thrust you are referring to is that of the rotor at SL static? As helo power is usually measured in SHP from the engines and I assume that isn't what you're talking about. Also, I assume the new tail rotor is to allow it to handle the higher torque generated by the power of the new rotor? It's been a long time since I've had to mess with rotor aerodynamics. I just remember being in the computer room at night in college and falling asleep face first into the keyboard while trying to get a rotor downwash program I had written for one of my classes to compile. Oh, the fun days, lol.

 

[yasotay]

donnage99 - when I was flying OH-58A/C it was not much more than that, but they wouldn't give me hand grenades :'(

amsci99 - the picture is the same one flateric posted at the top of this page and it is in a sealed matted frame. Would be hard to pull apart.

 

[F-14D]

Besides lowered vibration (which offers all kinds of Good Stuff), it also puts out a lot of power. On the AH-1Z, which uses a derivative of the 680 rotor, I believe 44,500 lbs. of thrust is available (should not be directly compared to thrust as out the back end of a jet). My recollection of the actual thrust may be wrong, but I do know it's an enormous amount. Since the AH-1Z got a new tail rotor and didn't just carry over the W's tail rotor (as did the AH-1 4BW) some marine officials early in the program were saying (before they were told to keep quiet) that with the 680, the AH-1Z could meet the LHX's agility.

Yeah, everything I've heard or read about the AH-1Z was good. I hadn't realized that this was the technology it used, although I realized it, obviously, had a new rotor system. I take it the thrust you are referring to is that of the rotor at SL static? As helo power is usually measured in SHP from the engines and I assume that isn't what you're talking about. Also, I assume the new tail rotor is to allow it to handle the higher torque generated by the power of the new rotor? It's been a long time since I've had to mess with rotor aerodynamics. I just remember being in the computer room at night in college and falling asleep face first into the keyboard while trying to get a rotor downwash program I had written for one of my classes to compile. Oh, the fun days, lol.

Someone who is more knowledgeable about rotor dynamics (I wish Ray Prouty was here!) could probably explain this better than me. You are correct in that helo power is usually measured (or at least described) in terms of engine shp. It's a convenient way to compare theoretical power available (discounting friction, efficiencyand accessory losses), and doesn't depend or rotor design. But remember, that power is delivered to the rotorhead. It is not what lifts or propels the helicopter. As that power is delivered, it turns the rotor. That rotor, and the air it moves, is what produces the thrust, and it is that which lifts and propels the helicopter. Couple of ways to visualize it would be to take a Bell 206 and put the blades in totally flat pitch ( or even remove them, as long as you had some drag mechanism to keep the gearbox from running away). The engine would still produce its rated shp, but there'd be zero thrust. Conversely, when a JetRanger is autorotating down after an engine failure , it's storing energy in the freewheeling rotor. When the collective is pulled just before the flare, the rotor expends that energy to arrest the 'copter's descent. Here, the rotor is briefly producing a lot of thrust even though there is no engine power at all.

An autogyro works on a similar principle. The forward motion of the vehicle sends air through the center section of the rotor and spins it up. The center portion is powered by that air, and essentially procues no thrust. But the inner portion is connected to the outer portion, and the outer spins faster, because it has to travel a larger arc in the same amount of time as the inner, and so it produces thrust. In fact, all the thrust (= lift in this case) comes from the outer ~ 1/3 of the rotor in an autogyro, so the aircraft gets thrust and flies with a rotor that is receiving no power at all from the engine. That's why an autogyro can't hover, has a staling speed and doesn't take off vertically unless there is an auxiliary power system to spin up the rotor for a "jump" takeoff.

As for the new tail rotor, it allows more of the engine power to be used at the rotorhead, allowing the new rotor to generate its greater thrust. This also allows faster sideways flight into the wind because it can counteract not only the higher torque from the greater amount of engine power being used to power the rotor, but the weathervane effect of the aircraft wanting to turn into the wind.

 

[Sundog]

Someone who is more knowledgeable about rotor dynamics (I wish Ray Prouty was here!) could probably explain this better than me. You are correct in that helo power is usually measured (or at least described) in terms of engine shp. It's a convenient way to compare theoretical power available (discounting friction, efficiencyand accessory losses), and doesn't depend or rotor design. But remember, that power is delivered to the rotorhead. It is not what lifts or propels the helicopter. As that power is delivered, it turns the rotor. That rotor, and the air it moves, is what produces the thrust, and it is that which lifts and propels the helicopter. Couple of ways to visualize it would be to take a Bell 206 and put the blades in totally flat pitch ( or even remove them, as long as you had some drag mechanism to keep the gearbox from running away). The engine would still produce its rated shp, but there'd be zero thrust. Conversely, when a JetRanger is autorotating down after an engine failure , it's storing energy in the freewheeling rotor. When the collective is pulled just before the flare, the rotor expends that energy to arrest the 'copter's descent. Here, the rotor is briefly producing a lot of thrust even though there is no engine power at all.

An autogyro works on a similar principle. The forward motion of the vehicle sends air through the center section of the rotor and spins it up. The center portion is powered by that air, and essentially procues no thrust. But the inner portion is connected to the outer portion, and the outer spins faster, because it has to travel a larger arc in the same amount of time as the inner, and so it produces thrust. In fact, all the thrust (= lift in this case) comes from the outer ~ 1/3 of the rotor in an autogyro, so the aircraft gets thrust and flies with a rotor that is receiving no power at all from the engine. That's why an autogyro can't hover, has a staling speed and doesn't take off vertically unless there is an auxiliary power system to spin up the rotor for a "jump" takeoff.

As for the new tail rotor, it allows more of the engine power to be used at the rotorhead, allowing the new rotor to generate its greater thrust. This also allows faster sideways flight into the wind because it can counteract not only the higher torque from the greater amount of engine power being used to power the rotor, but the ruddervane effect of the aircraft wanting to turn into the wind.

Yeah, I understand the physics, I was just making sure I was on the same page as you. Although, your last paragraph I hadn't considered in the sense that the more efficient and less power the tail rotor uses, the more is available for the main rotor; I mean I've known that, but I didn't think about it. I also hadn't considered the "sideward" flying part of the envelope.

I develop aircraft for flight simulator and work on mainly the flight dynamics, although I haven't worked on a helo. But I definitely get the relationship between the engine and how the thrust is actually generated as a lot of people get that wrong in FS. That's why I am always looking for good engine decks, which are damn near impossible to find. Because, it doesn't matter how much you know about the aircraft's flight dynamics/aerodynamics if the engine/propulsive modeling is incorrect. In that sense, I've worked a lot with trying to get propeller aero/thrust correct. It would be the same with a helo model, I would start with the engine and then the rotor aero/thrust, because if you don't get that right, you'll never get the right combo of performance for the given lift/drag, etc. Although, the FS standard Helo flight modeling isn't the best, my understanding is that the Dodo Sim 206 is very realistic, because of how well they were able to model the flight dynamics and systems.

 

[F-14D]

Someone who is more knowledgeable about rotor dynamics (I wish Ray Prouty was here!) could probably explain this better than me. You are correct in that helo power is usually measured (or at least described) in terms of engine shp. It's a convenient way to compare theoretical power available (discounting friction, efficiencyand accessory losses), and doesn't depend or rotor design. But remember, that power is delivered to the rotorhead. It is not what lifts or propels the helicopter. As that power is delivered, it turns the rotor. That rotor, and the air it moves, is what produces the thrust, and it is that which lifts and propels the helicopter. Couple of ways to visualize it would be to take a Bell 206 and put the blades in totally flat pitch ( or even remove them, as long as you had some drag mechanism to keep the gearbox from running away). The engine would still produce its rated shp, but there'd be zero thrust. Conversely, when a JetRanger is autorotating down after an engine failure , it's storing energy in the freewheeling rotor. When the collective is pulled just before the flare, the rotor expends that energy to arrest the 'copter's descent. Here, the rotor is briefly producing a lot of thrust even though there is no engine power at all.

An autogyro works on a similar principle. The forward motion of the vehicle sends air through the center section of the rotor and spins it up. The center portion is powered by that air, and essentially procues no thrust. But the inner portion is connected to the outer portion, and the outer spins faster, because it has to travel a larger arc in the same amount of time as the inner, and so it produces thrust. In fact, all the thrust (= lift in this case) comes from the outer ~ 1/3 of the rotor in an autogyro, so the aircraft gets thrust and flies with a rotor that is receiving no power at all from the engine. That's why an autogyro can't hover, has a staling speed and doesn't take off vertically unless there is an auxiliary power system to spin up the rotor for a "jump" takeoff.

As for the new tail rotor, it allows more of the engine power to be used at the rotorhead, allowing the new rotor to generate its greater thrust. This also allows faster sideways flight into the wind because it can counteract not only the higher torque from the greater amount of engine power being used to power the rotor, but the ruddervane effect of the aircraft wanting to turn into the wind.

Yeah, I understand the physics, I was just making sure I was on the same page as you. Although, your last paragraph I hadn't considered in the sense that the more efficient and less power the tail rotor uses, the more is available for the main rotor; I mean I've known that, but I didn't think about it. I also hadn't considered the "sideward" flying part of the envelope.

I develop aircraft for flight simulator and work on mainly the flight dynamics, although I haven't worked on a helo. But I definitely get the relationship between the engine and how the thrust is actually generated as a lot of people get that wrong in FS. That's why I am always looking for good engine decks, which are damn near impossible to find. Because, it doesn't matter how much you know about the aircraft's flight dynamics/aerodynamics if the engine/propulsive modeling is incorrect. In that sense, I've worked a lot with trying to get propeller aero/thrust correct. It would be the same with a helo model, I would start with the engine and then the rotor aero/thrust, because if you don't get that right, you'll never get the right combo of performance for the given lift/drag, etc. Although, the FS standard Helo flight modeling isn't the best, my understanding is that the Dodo Sim 206 is very realistic, because of how well they were able to model the flight dynamics and systems.

Remember I said there were others who explain this better than me? What I was getting at was that rotor thrust wasn't the same as engine power and is not rigidly related. The torque was generated by the engines, not the rotor thrust. What the AH-1Z's new rotor/transmission does is along with its better design, allow the aircraft to absorb more power from the engines and in turn translate that into more thrust. By absorbing more power you get more torque.

The more efficient (higher thrust) a tail rotor, the less power the engines need to supply to it, which allows the use of smaller engines or the availability of greater power to the transmission if it can absorb it. It also allows for more agility in military scenarios. In the case of the 4BW, they ran those tests with the original Whiskey tail rotor, and found they were running out of tail rotor authority before the engine/rotor was running out of power. It was decided that the extra cost of a new tail rotor was worth the cost by allowing the upgrade to use the full capabilities that it was delivering.

 

[Sundog]

Well, the torque is generated by the engines and transferred to the rotor, and the torque due to the rotor inertia is what has to be counteracted by the tail rotor. Of course, that will be a function of the mass properties of the main rotor and it's RPM's. Of course, something I never considered is where the main flight loads are transferred from the main rotor shaft to the airframe. I would assume it's at the main bearings, since you would definitely not want those forces transmitted to the transmission itself. I was just thinking about that, due to the increased performance of the AH-1Z when compared to earlier Cobras.

So why isn't the Army looking at AH-1Z's as a basis for advanced Scouts? Are they too afraid of what it would it would do to the Apache? ;D

 

[F-14D]

Well, the torque is generated by the engines and transferred to the rotor, and the torque due to the rotor inertia is what has to be counteracted by the tail rotor. Of course, that will be a function of the mass properties of the main rotor and it's RPM's. Of course, something I never considered is where the main flight loads are transferred from the main rotor shaft to the airframe. I would assume it's at the main bearings, since you would definitely not want those forces transmitted to the transmission itself. I was just thinking about that, due to the increased performance of the AH-1Z when compared to earlier Cobras.

So why isn't the Army looking at AH-1Z's as a basis for advanced Scouts? Are they too afraid of what it would it would do to the Apache? ;D

The performance increase comes mainly from the new rotor's dynamics and its and the transmission's ability to absorb and use more of the power the engines can put out and its thrust and dynamics. The 4BW testbed was a straight -1W and it realized a big performance gain. In fact, originally the Zulu was to use the same T700 as the -1W because it provided enough power. Now it looks like they'll use the slightly more powerful engine in the UH-1Y primarily for logistics and commonality reasons.

As far as your question, although there were some people talking about putting Comanche avionics in an AH-1Z for the Army, it really didn't go anywhere. It would be hard to justify having both the Apache and the Cobra (which the Army just got rid of) in the inventory. For one thing, why would a -1Z scout for an AH-64? Since the -1Z was already faster, more agile and carried a heavier load, just do it all themselves. Also, supposedly the Army needed a smaller helo for the role envisioned for LHX. Problem there is Comanche never was required to do all the things originally envisioned for LHX.

Not to be discounted, of course is the famous "Not Invented Here". It's outside the scope of this topic, but I'll give you a related classic example of this going on right now: USAF is starting another big competition to select a helicopter to replace its UH-1Ns (a requirement that has been criminally neglected for too many years). Instead of doing that, why not just look to how the Marines' idea for replacing their old UH-1Ns: convert them into UH-1Ys? Yes, I know the Marines later decided to go new build with their -1Ys, but that's because -1N operations abroad have worn out many Ns to where the conversion costs as much as new build, and also operational temp abroad precluded Hueys airframes being out of service for the conversion. USAF probably wouldn't have that problem, but even if they did I'll wager new-build -1Ys would be the better way to go. Oops! Can't do that: N. I. H.

 

[yasotay]

So why isn't the Army looking at AH-1Z's as a basis for advanced Scouts? Are they too afraid of what it would it would do to the Apache? ;D

Certainly not any fear of what it would do to the Apache, better performance or not. The Army is well satisfied with the performance of the Apache both from a weapons platform and as a survivable combat helicopter perspective. Both AH-1Z and AH-64D are larger aircraft (in many aspects) than what the US Army wants for a LIGHT reconnaissance platform. Logistically both are much more thirsty than OH-58D and parts are $$$ in comparison. As has been discussed above LHX was to be a light weight inexpensive scout (because historically they got... shot down more) that was relatively easy to make and operate from the farmers fields of Central Europe. Today that is still the case... other than Central Europe. There is even less necessity for the protections that caused LHX/RAH to grow in protective measures to be more of an attack helicopter. While it must still deal with the traditional threats to rotorcraft, light to medium caliber guns and MANPADS, they are not in the density that LHX expected to try and survive in.

On top of the logistics cost I mentioned, I also suspect that AH-1Z and AH-64D are both likely about twice the acquistion cost the Army would want to pay for a scout helicopter.

 

[Sundog]

So why not new build OH-58's with new engines, avionics, and rotors? I mean, they like the platform, they just need something newer, right?

 

[F-14D]

So why not new build OH-58's with new engines, avionics, and rotors? I mean, they like the platform, they just need something newer, right?

They did. It was called the ARH-70 Arapaho. That was canceled in 2008. As to liking the OH-58 platform, that's a subject for a topic elsewhere.

 

[F-14D]

So why isn't the Army looking at AH-1Z's as a basis for advanced Scouts? Are they too afraid of what it would it would do to the Apache? ;D

Certainly not any fear of what it would do to the Apache, better performance or not. The Army is well satisfied with the performance of the Apache both from a weapons platform and as a survivable combat helicopter perspective. Both AH-1Z and AH-64D are larger aircraft (in many aspects) than what the US Army wants for a LIGHT reconnaissance platform. Logistically both are much more thirsty than OH-58D and parts are $$$ in comparison. As has been discussed above LHX was to be a light weight inexpensive scout (because historically they got... shot down more) that was relatively easy to make and operate from the farmers fields of Central Europe. Today that is still the case... other than Central Europe. There is even less necessity for the protections that caused LHX/RAH to grow in protective measures to be more of an attack helicopter. While it must still deal with the traditional threats to rotorcraft, light to medium caliber guns and MANPADS, they are not in the density that LHX expected to try and survive in.

On top of the logistics cost I mentioned, I also suspect that AH-1Z and AH-64D are both likely about twice the acquisition cost the Army would want to pay for a scout helicopter.

REmeember: The original purpose for LHX was to be more than just a scout helicopter. In fact, even the dumbed down requirement for RAH-66 said it was to replace both the OH-58 and the AH-1. I wonder if, by the time they canceled it, whether the acquisition and logistics costs really were going to be less than, say, an AH-1Z or AH-64--which would be a good reason why they killed it.

 

[yasotay]

So why isn't the Army looking at AH-1Z's as a basis for advanced Scouts? Are they too afraid of what it would it would do to the Apache? ;D

Certainly not any fear of what it would do to the Apache, better performance or not. The Army is well satisfied with the performance of the Apache both from a weapons platform and as a survivable combat helicopter perspective. Both AH-1Z and AH-64D are larger aircraft (in many aspects) than what the US Army wants for a LIGHT reconnaissance platform. Logistically both are much more thirsty than OH-58D and parts are $$$ in comparison. As has been discussed above LHX was to be a light weight inexpensive scout (because historically they got... shot down more) that was relatively easy to make and operate from the farmers fields of Central Europe. Today that is still the case... other than Central Europe. There is even less necessity for the protections that caused LHX/RAH to grow in protective measures to be more of an attack helicopter. While it must still deal with the traditional threats to rotorcraft, light to medium caliber guns and MANPADS, they are not in the density that LHX expected to try and survive in.

On top of the logistics cost I mentioned, I also suspect that AH-1Z and AH-64D are both likely about twice the acquisition cost the Army would want to pay for a scout helicopter.

REmeember: The original purpose for LHX was to be more than just a scout helicopter. In fact, even the dumbed down requirement for RAH-66 said it was to replace both the OH-58 and the AH-1. I wonder if, by the time they canceled it, whether the acquisition and logistics costs really were going to be less than, say, an AH-1XcZ--which would be a good reason why they killed it.

Comanche was cancelled because it was consuming a huge part of the Army Aviation budget and the Army was in combat operations. With the same money the Army got the entire UH-72 program, UH-60M program, CH-47F program, AH-64D Block 3, functioning ASE, MTADS and a slew of ground support equipment. Gives you an idea of the size of the investment. To be clear some of the programs got funding boost that accelerated their acquisition vice being entirely new efforts. Some had been waiting in the wings for more funding (a.k.a. a miracle).

As to to refit of the OH-58D, it is getting refit... again. The ARH program demonstrated that trying to modify civil platforms (Bell 407) can be as difficult as coming up with a purpose built military aircraft. You have to change out fuel tanks, add armor, strengthen structures, build a new transmission, etc. These can be as expensive in redesign as new start.

 

[Sundog]

So, what is it you guys are recommending, based on your understanding of what is needed? Is it something similar to the Comanche, but without the low RCS requirements? A militarized, slightly scaled up X2 (Assuming the tech works)? Or do you guys see the LHX/Light Scout mission as just not required anymore?

 

[F-14D]

So why isn't the Army looking at AH-1Z's as a basis for advanced Scouts? Are they too afraid of what it would it would do to the Apache? ;D

Certainly not any fear of what it would do to the Apache, better performance or not. The Army is well satisfied with the performance of the Apache both from a weapons platform and as a survivable combat helicopter perspective. Both AH-1Z and AH-64D are larger aircraft (in many aspects) than what the US Army wants for a LIGHT reconnaissance platform. Logistically both are much more thirsty than OH-58D and parts are $$$ in comparison. As has been discussed above LHX was to be a light weight inexpensive scout (because historically they got... shot down more) that was relatively easy to make and operate from the farmers fields of Central Europe. Today that is still the case... other than Central Europe. There is even less necessity for the protections that caused LHX/RAH to grow in protective measures to be more of an attack helicopter. While it must still deal with the traditional threats to rotorcraft, light to medium caliber guns and MANPADS, they are not in the density that LHX expected to try and survive in.

On top of the logistics cost I mentioned, I also suspect that AH-1Z and AH-64D are both likely about twice the acquisition cost the Army would want to pay for a scout helicopter.

REmeember: The original purpose for LHX was to be more than just a scout helicopter. In fact, even the dumbed down requirement for RAH-66 said it was to replace both the OH-58 and the AH-1. I wonder if, by the time they canceled it, whether the acquisition and logistics costs really were going to be less than, say, an AH-1XcZ--which would be a good reason why they killed it.

Comanche was cancelled because it was consuming a huge part of the Army Aviation budget and the Army was in combat operations. With the same money the Army got the entire UH-72 program, UH-60M program, CH-47F program, AH-64D Block 3, functioning ASE, MTADS and a slew of ground support equipment. Gives you an idea of the size of the investment. To be clear some of the programs got funding boost that accelerated their acquisition vice being entirely new efforts. Some had been waiting in the wings for more funding (a.k.a. a miracle).

As to to refit of the OH-58D, it is getting refit... again. The ARH program demonstrated that trying to modify civil platforms (Bell 407) can be as difficult as coming up with a purpose built military aircraft. You have to change out fuel tanks, add armor, strengthen structures, build a new transmission, etc. These can be as expensive in redesign as new start.

The ARH-70 selection was also quite controversial (and surprising). Story is that almost all the operational interst wanted the H-6 based entry.

 

[F-14D]

So, what is it you guys are recommending, based on your understanding of what is needed? Is it something similar to the Comanche, but without the low RCS requirements? A militarized, slightly scaled up X2 (Assuming the tech works)? Or do you guys see the LHX/Light Scout mission as just not required anymore?

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this. Personally, and this represents only me, I'd either go back to the original LHX specification before the dumb down, or do nothing. Something like UCARS for the scout role, if we really need such a scout (and what happened to the AH-1 replacement requirement?), and buy more attack helos. Of course I doubt if the interest, and therefore budget, is there to deal with the situation at all.

 

[Stargazer]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

Maybe. But I believe one way of shortening that timespan would be to find applications in unmanned vehicles. Once the technology is proven in unmanned configuration, it will be easier to "sell" the manned version of it to the armed forces.

 

[F-14D]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

Maybe. But I believe one way of shortening that timespan would be to find applications in unmanned vehicles. Once the technology is proven in unmanned configuration, it will be easier to "sell" the manned version of it to the armed forces.

Personally, I don't think manned or unmanned will make much difference. If it proves itself practical and economical, and it's still a long way from doing that, then it'll be a viable candidate for roles requiring that level of performance, manned or unmanned. I don't see there being a worry about man-rating it, as we do with rockets. It either works or it doesn't

What we need is some program that benefits from advanced rotorcraft technology, like next generation powered lift attack vehicle, Osprey escort, etc. The Marines' low-key VMAO program or the original "pre-dumbing" LHX requirements would be ideal.

 

[sferrin]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

X2 "technology" is not exactly revolutiuonary. Better than what there is now but it's not like you're jumping to anything fundamentally different.

 

[F-14D]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

X2 "technology" is not exactly revolutiuonary. Better than what there is now but it's not like you're jumping to anything fundamentally different.

I really hope it works. If it wasn't fundamentally different, we'd have seen it from someone years ago. Thing is, the last time we tried it, it was a disappointment at best. So far this time it's years behind schedule, is moving at a glacial pace and as yet hasn't demonstrated anything beyond what we could get from a conventional helo.

Giving credit where credit is due I'd say the technology, should it prove successful, is revolutionary, in the same sense Tilt Rotor was. It's going to have its trials and tribulations as any advance does. But even if everything from here on goes swimmingly, you're not going to see a large scale military production ABC in the next few years.

 

[yasotay]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

X2 "technology" is not exactly revolutionary. Better than what there is now but it's not like you're jumping to anything fundamentally different.

Plus there is an actual aircraft in flight test. If TR is so great where is the Bell XWORKS TR prototype for continuing to explore the only rotorcraft technology that the United States has a clear lead in? Where is the Byzantine BA-609? Yes the MV and CV-22 are in operations these days but saying a large medium transport demonstrates viability in scout and attack roles is a stretch. The V-22 at Pax River is not exploring new rotor components, drive trains or reconfigured anything. To my knowledge, other than a glossy picture of a "semi-TR" there has not been anything from Central Texas or Philly on the TR front. Maybe they are being quiet...

On the H-6 series. It does great things for the SOF community, but I think for the aero-scout role its probably a bit short legged, especially when you put the weapons the Army probably wants on board (Hellfire, rockets, gun). Interestingly RUMINT had it that everyone thought the H-6 was a shoe in because the Army's Vice Chief of Staff, at the time, was a former Special Ops type who knew the aircraft. It is also rumored that a number of the operational types (i.e. warrant officers who actually fly the aircraft in combat) were not as keen on the aircraft as others were. ARH-70 was probably thought to be a "quick turn", "off the shelf" that turned into a fiasco.

... this is starting to get seriously away from the old LHX program, perhaps we should move the discussion elsewhere.

 

[sferrin]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

X2 "technology" is not exactly revolutiuonary. Better than what there is now but it's not like you're jumping to anything fundamentally different.

I really hope it works. If it wasn't fundamentally different, we'd have seen it from someone years ago.

We did, three and a half decades ago, it was called the XH-59 ABC. And don't mistake "haven't seen it before" for new necessarily. Sometimes there's just not a compelling reason to give up the same-old, same-old. Consider the propulsion system RASCAL was going to use. To many it would have seemed revolutionary but to others it would be no more than "isn't that the same thing they threw on the F-4 for Skyburner?"

(As an interesting bit of trivia, apparently in a bit of dark humor, Sikorsky workers referred to the ABC concept as "Already Been Crashed" ;D )

 

[F-14D]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

X2 "technology" is not exactly revolutionary. Better than what there is now but it's not like you're jumping to anything fundamentally different.

Plus there is an actual aircraft in flight test. If TR is so great where is the Bell XWORKS TR prototype for continuing to explore the only rotorcraft technology that the United States has a clear lead in? Where is the Byzantine BA-609? Yes the MV and CV-22 are in operations these days but saying a large medium transport demonstrates viability in scout and attack roles is a stretch. The V-22 at Pax River is not exploring new rotor components, drive trains or reconfigured anything. To my knowledge, other than a glossy picture of a "semi-TR" there has not been anything from Central Texas or Philly on the TR front. Maybe they are being quiet...

On the H-6 series. It does great things for the SOF community, but I think for the aero-scout role its probably a bit short legged, especially when you put the weapons the Army probably wants on board (Hellfire, rockets, gun). Interestingly RUMINT had it that everyone thought the H-6 was a shoe in because the Army's Vice Chief of Staff, at the time, was a former Special Ops type who knew the aircraft. It is also rumored that a number of the operational types (i.e. warrant officers who actually fly the aircraft in combat) were not as keen on the aircraft as others were. ARH-70 was probably thought to be a "quick turn", "off the shelf" that turned into a fiasco.

... this is starting to get seriously away from the old LHX program, perhaps we should move the discussion elsewhere.

To briefly answer your points: TR is no longer an experimental technology For further development of TR, there has to be another funded program-- right now there isn't. There is some rotor blade technology investigations on V-22 but that is an operational, not developmental aircraft. That's like saying why isn't the 777 being used to develop advanced propulsion technology. Go back a year or so ago, and note what was generally looked on as the most promising technology for JLH. However, smaller vehicles are probably easier to do than larger. Again, the key is the technology, not so much the vehicle and that's the opportunity lost when LHX requirements were scaled back.

Regarding the BA-609, lead for that was passed to Augusta some time back. With the world business aircraft environment what it is right now, it's been slowed and is looking for 2012-13 in service dates. Everything new is slow right now, Cessna even decided to cancel their world beating Columbus. BTW, FAA has already published proposed airworthiness standards for it

H-6 was not a good choice or preferred or even considered for the LHX or even Comanche role. Those programs wanted a lot more. What it was preferred for by those who would have to use it was the role to be filled by ARH-70 or even the original OH-58. No one expected those to carry Hellfires and the like. Why those H-6s didn't happen is way outside the scope of this topic, as you say. We are getting a bit far afield.

 

[F-14D]

It'll be quite some time before X2 technology would be trusted enough to be considered for an operational role such as this.

X2 "technology" is not exactly revolutiuonary. Better than what there is now but it's not like you're jumping to anything fundamentally different.

I really hope it works. If it wasn't fundamentally different, we'd have seen it from someone years ago.

We did, three and a half decades ago, it was called the XH-59 ABC. And don't mistake "haven't seen it before" for new necessarily. Sometimes there's just not a compelling reason to give up the same-old, same-old. Consider the propulsion system RASCAL was going to use. To many it would have seemed revolutionary but to others it would be no more than "isn't that the same thing they threw on the F-4 for Skyburner?"

(As an interesting bit of trivia, apparently in a bit of dark humor, Sikorsky workers referred to the ABC concept as "Already Been Crashed" ;D )

The XH-59 was what I was referring to when I said, "Thing is, the last time we tried it, it was a disappointment at best". The point I was making was that just because someone builds something that looks like a concept, it doesn't really advance the state of the art until you can have a successful execution of the concept that is a basis for going forward. I mean, they built an X-Wing demonstrator but thank goodness it never flew. The XV-3 flew in 1955, but a vehicle that could make the Tilt Rotor concept successful didn't lift off until 22 years later with the wildly successful XV-15, which involved a major evolution of the concept. The XH-59 was much the same. ABC as involved in it, but it didn't really validate it and wasn't really a basis to go forward, and that's why no one else pursued it and Sikorsky didn't have enough confidence to use it as a demonstrator to advance the concept. Maybe the X2, which Sikorsky says involves fundamental advances over XH-59 will, but so far it's too early to tell.

 

[Sundog]

Completely OT: Wow, I had no idea Cessna had canceled the Columbus. No wonder I haven't heard anything about it recently.

Back OT: Why haven't we seen more NOTAR designs? Is it because the concept is patented, or that it just isn't as effective as, say, a Fenestron or tail rotor? Just because, to me, the design makes sense from a safety standpoint. I also realize they have the fan driven at the base of the tail, but does it reduce vibration, or is it negligible, as most of the vibration comes from the main rotor?

BTW, the NOTAR design for LHX, the Bell/MDD proposal, has anyone ever seen good blueprints of it? I would love to have some good drawings of the single seat version. I realize the production/proposal was the two seat design. I just prefer the look of the single seat variant.

 

[AeroFranz]

IIRC, there was an article on Rotor & Wing describing how one of the NOTAR helos used by the police had lousy hot and high performance compared to the conventional, rotor-ed version. Does anyone know whether power demands for NOTAR are higher than for a conventional rotor? It does seem like a rotor is a pretty efficient way of generating side thrust...

 

[yasotay]

IIRC, there was an article on Rotor & Wing describing how one of the NOTAR helos used by the police had lousy hot and high performance compared to the conventional, rotor-ed version. Does anyone know whether power demands for NOTAR are higher than for a conventional rotor? It does seem like a rotor is a pretty efficient way of generating side thrust...

I do know that the Special Operations Aviation guys looked at NOTAR and elected not to go down that path.

FYI I started a thread in the Aerospace for us to haggle over the best means of VTOL for scout and light attack rotorcraft: so as to return the LHX thread to its normal program....

 

[F-14D]

IIRC, there was an article on Rotor & Wing describing how one of the NOTAR helos used by the police had lousy hot and high performance compared to the conventional, rotor-ed version. Does anyone know whether power demands for NOTAR are higher than for a conventional rotor? It does seem like a rotor is a pretty efficient way of generating side thrust...

I do know that the Special Operations Aviation guys looked at NOTAR and elected not to go down that path.

FYI I started a thread in the Aerospace for us to haggle over the best means of VTOL for scout and light attack rotorcraft: so as to return the LHX thread to its normal program....

An excellent idea. Thank you. Clearly, the original discussion of decisions made as to the what and hows of the original LHX program have gone way off topic and I'm as guilty of that as anyone.

 

[flateric]

late Boeing/Sikorsky LHX configuration - almost RAH-66 as we know it
Microwest desktop model

 

[quellish]

I do know that the Special Operations Aviation guys looked at NOTAR and elected not to go down that path.

The issues that lead to 160th SOAR not adopting NOTAR were specific to the A/MH-6, and specific to 160th SOAR's needs. They actually did want it, and worked with the vendor to try to resolve these issues.

 

[yasotay]

I do know that the Special Operations Aviation guys looked at NOTAR and elected not to go down that path.

The issues that lead to 160th SOAR not adopting NOTAR were specific to the A/MH-6, and specific to 160th SOAR's needs. They actually did want it, and worked with the vendor to try to resolve these issues.

I had heard that 160th had worked to make NOTAR meet its requirements, wanting to get away from tail rotors which are risky in small places like roofs and streets where many of the missions are likely to be performed. I was led to believe that the two main sticking points for them were the slower yaw rates and that the NOTAR tail was not good for some of the mission parameters.

I have to think that the Army, so bent on a conventional helicopter, would not even entertain a new fangled tail authority system that might have helped deal with one of the most delicate components of the combat helicopter. Does anyone know if there was work done to see how much damage a NOTAR system could take before becoming ineffective?

 

[Triton]

Artist's impression of Boeing Vertol LHX concept.

Source: "LHX 'first team' promotes" Flight International November 30, 1985
http://www.flightglobal.com/pdfarchive/view/1985/1985%20-%203126.html

 

[flateric]

mine's much better

 

[Colonial-Marine]

Regarding NOTAR, what I have read was trials with versions of the MH-6 revealed reduced speed as well as shorter range due to higher fuel consumption.

 

[Triton]

Artist's impression of Sikorsky LHX concept with ABC rotor.

Artist's impression of early version of the Boeing/Sikorsky proposal.


Source:
http://www.arcforums.com/forums/air/lofiversion/index.php?t202161.html

 

[Triton]

Bell BAT (Bell Advanced Tiltrotor) LHX concept.

Source:
http://www.arcforums.com/forums/air/lofiversion/index.php?t202161.html