Sikorsky’s X2 advancing blade helicopter has sustained a cruise at 181 kts, and has done so at very low vibration levels, the show stopper for Sikorsky’s XH-59A ABC helo in the 1970s, are a good sign.
This is about 40 kts faster than most conventional helicopters, and faster than almost any other helicopter out there.
They hope to make it to 250 kts, and they have yet to install the center hub fairing, which should further reduce drag, and the transmission is really not optimized for the mission, which implies that with some minor changes, performance could be improved:
The prototype is designed with no clutch between the main rotors and propulsor, which requires the pilot to increase forward speed through the variable pitch control on the six-bladed rear propeller. Once in the 180kt realm, the X2’s computer will automatically slow the main rotors and increase collective pitch to prevent tip speeds from entering high-drag transonic region, with Bredenbeck correspondingly increasing propulsor pitch to increase the X2’s speed as the propulsor also slows.
One of the things that blows my mind here is this vehicle has tested so well, so far, without any wind tunnel testing:
Weiner credits configuration maturity to Sikorsky’s advanced analytical tools given that the company did not perform windtunnel tests of the design before flight-testing. He says windtunnel tests would likely precede the design for a production model, the first of which could be a systems development and demonstration vehicle for the US Army’s potential competition to replace the Bell OH-58D Kiowa Warrior later this decade.
The first flight of the U.S. Marine Corps’ heavy lifter CH-53K helicopter has slipped two years to 2013, while its initial operational capability (IOC) has slid three years to 2018, officials have confirmed to AVIATION WEEK.
The date slips come as no surprise to the Marines and the CH-53K program office at Naval Air Systems Command (Navair). In January 2009, program manager Capt. Rick Muldoon submitted a Program Deviation Report for the aircraft’s critical design review (CDR) to the Pentagon acquisition headquarters. The CDR is now slated for September, representing a year’s delay.
There is no indication of technical problems or of development issues that would justify this.
Why slow the program? When delivered, the new fly-by-wire CH-53K will, in theory, transport 27,000 pounds of external cargo out to a range of 110 nautical miles, nearly tripling the thirty-year old CH-53E’s lift capability under similar environmental conditions–all while fitting under the same shipboard footprint.
The CH-53K will also provide unparalleled lift under high and hot conditions while maintainability and reliability enhancements to the CH-53K will decrease recurring operating costs over the current CH-53E (the CH-53K aims at a more reasonable $10,000 dollars per flight hour while the CH-53E costs twice that). Survivability and force protection enhancements will also increase protection dramatically, for both aircrew and passengers. What’s not to like?
The CH-53K was an unsung showpiece for those preaching the virtues of incremental development, and, as a result, appetite for the platform has grown by about 30 percent, with the program of record expected to increase from156 aircraft to 200.
But, in the process, the CH-53K has become something of a MV-22-killer. Is this the problem?
Ummm ……… Yes?
The CH-53K is steadily eating away at the V-22 Osprey market. In late 2009, the Marine Corps decided to go with the CH-53Ks to replace their 40-year old CH-53D fleet (MV-22 Ospreys were originally slated to replace the CH-53D). At about the same time, Israel decided to forego the Osprey for the CH-53K, killing the Osprey’s best hope of snaring an international buyer. And with the Osprey 65% availability and the MV-22s high operating costs of about $11,000 dollars an hour, the CH-53K posed a serious threat to the MV-22 program.
Even worse, studies from the Pentagon demonstrated that a CH-53K-equipped big-deck amphib provided a lot more logistical support for embarked Marines than the MV-22, suggesting the mix of embarked MV-22s and CH-53Ks needed tweaking (and possibly fewer MV-22s).
(emphasis mine)
Much in the same way that the USAF is scrambling to retire legacy F-16s and F-15s so as to make the F-35 JSF a dire need, the Marine Corps is slow walking the CH-53K in an attempt to protect their orders, and possibly encourage foreign orders, for the ruinously expensive Osprey.
The program is being delayed because it is too successful.
This is what is wrong with defense procurement in the US Military in a nutshell.
Startup company American Dynamics Flight Systems has been developing a UAV to address the needs of the various services for high speed cargo UAVS most notably the Marine Corps VTOL Group IV Program and Medium Programs, the USAF Unmanned Cargo VTOL UAV Program, and the US Coast Guard’s VTOL UAV Program.
All of these programs are requiring fairly high speeds, a cruise at least 250 kts, which pretty much rules out a conventional helicopters which tend to cruise at less than 175 kts.
The solution that was adopted on the V-22 is a tilt rotor, where the propellers are pivoted from horizontal to vertical in the transition from horizontal flight to vertical takeoffs and landings.
The issue with a tilt rotor system is that, even more than in a conventional helicopter, managing the transition from horizontal to vertical flight can become difficult and complex.
In the V-22, this is handled with a cyclic type control system that mirrors the swash plate type setups that exist on helicopters.
While this is obviously a known quantity in vertical lift mode, issues in transition to wing-borne flight had to be resolved before the tilt-rotor could become viable, there is a cost in complexity, cost, and reliability in using a complex prop assembly for such a system.
ADF Concept
Moves in pitch and yaw
The solution for the AD-1 is different. A ducted fan which is controllable in pitch and yaw, but where the pitch of the fan is fixed is used, the High Torque Aerial Lift (HTAL).
Pitch is obviously a given in any tilt rotor, which theoretically makes the addition of yaw actuators for the propulsors less complex, and hence lighter, cheaper, and more reliable than going with a full up cyclic control system.
Fixed Aluminum Prop
This sort of control system has been used in the past, at the dawn of the development of helicopters, where the use of tilting rotor hub, rather than a swash plate style cyclic was, for example, used by Raúl Pateras Pescara used this on his early helicopters in the 1920s, where he pitched the hub forward to allow for forward flight without the need for a separate propeller to provide lateral thrust.
The application to a tilt-rotor aircraft, and the use of rotor hub in yaw, appear to be unique, and a patent is pending.
Propulsor shroud panel
Additionally, the use of a shrouded propulsor provides for greater thrust/lift for a given disk area, by acting as a nozzle to accelerate flow.
The shrouds themselves have composite skins. The panel shown is well under 10 pounds.
The use of a shrouded prop should also simplify deck handling, since it mitigates against the possibility of someone walking into a moving prop, and there are added efficiencies because the down wash in vertical lift mode does not impinge on the wing.
All moving ruddervators
It should be noted that the aircraft has been designed from the outset to be low cost, and so notwithstanding its appearance, it is not designed to be a low-observable (“stealth”) airframe.
The top mounted inlet is intended to minimize the possibility of FOD damage to the engine, the all moving ruddervators were developed after it was determined that a rear moving flap on a conventional rudder fin would not provide sufficient control authority, and the wing configuration is designed to minimize pitch changes during transition from vertical to horizontal flight.
Wind tunnel model
AD1 Development
ADF is relying heavily on computational fluid dynamics (CFD) to determine the characteristics of the, and according to Paul Vasilescu, VP of Engineering, their experiences at the Paul Vasilescu Glen L. Martin wind tunnel at the University of Maryland have been closer to the calculated predictions than any prior systems tested at the facility.
The simulations are run on 64 bit Linux rack mount systems, with some of the more complex simulations, which are being modeled in 6 degrees of freedom.
Instrumented Test Rig
The propulsors have been modeled, both in full size, and at the reduced size in which they will be tested in the wind tunnel, which should serve to further validate the mathematical modeling.
It is anticipated that the propulsors will be tested in full scale on an “iron bird” instrumented test rig at Aberdeen Proving Ground, where ADFS hopes to, “Confirm CFD performance data for hover in ground effect (HIGE) and hover out of ground effect (HOGE),” later this year, using a T53 turboshaft, used on the original UH-1 models, but flight models will use the T700, which is currently in use on the AH-64 and UH-60.
The mechanical design is done in SolidWorks®, which I’ve used extensively, and should be more than capable of generated the required geometries, though it’s associated FEA package, Cosmos®, is intended for less intensive analysis.
AD-1 Manufacturing Capabilities
Applied Dynamics Flight Systems has a 14,700 square foot manufacturing facility at the Jessup headquarters with 3 & 4 axis CNC mills, and anticipates being able to assemble 12 units a year upon receipt of a contract.
Manufacturing workshare
Paths not taken
At this point, the company does not believe that there is a reasonable market for civilian applications for UAVS, the FAA has not yet come up with a coherent regulatory environment, and the technology to allow UAVs to operate in civilian airspace, so called “sense and avoid” technology, is immature.
They believe the situation to be rather similar in terms of ambulance applications on the battle field, an area where the Israeli firm Urban Aeronautics’ similarly sized Air Mule is attempting to carve out a niche, there are serious issues with landing aircraft into unprepared areas, as many of the cues that a pilot has in a cockpit are lost on a remote display, and so additional technology needs to be developed in terms of automated imaging and auto-landing systems before one can expect a UAV
Sikorsky expects to exceed 250 kt. with its X2 Technology coaxial-rotor compound helicopter demonstrator early in the year, resetting speed expectations for rotorcraft that have been stuck at around 150 kt. for decades.
A modern reinterpretation of Sikorsky’s XH-59A Advancing Blade Concept (ABC) testbed, which reached 238 kt. in the 1970s, the X2 combines fly-by-wire control, integrated engine/rotor/propulsor system, variable-speed rotor, high-lift/drag rigid blades and active vibration control to realize the speed potential of a coaxial rotor while retaining the hover agility of a helicopter.
The ability to auto-rotate in an emergency is a big plus too.
It works by offloading the retreating blade, and so preventing retreating blade stall, which occurs when the relative speed of the blade versus the air at higher speeds falls.
The issue has always been the complexity of the flight controls, the X59A required two pilots, and vibrations, which appear to be satisfactorily addressed through active digital flight control system on the X2.
I’ve always favored it over the tilt rotor concept, it appears to be both simpler and more redundant, and the rotors are not a compromise between lift and propulsion that they are in something like the V-22.
The Russians make the largest production helicopter in the world, the Mi-26 “Halo”, and they have been considering an updated helo in the same (humongous) size range for some time.
Seeing as how the helicopter originally flew in 1977, and has been in service since 1983, there is a lot of room for improvement.
Just updating the transmission to modern aluminum alloys in the transmission and going with a more modern rotor system would probably add about 10% to payload and range performance, but that would be an upgrade rather than a completely new design.
A completely new variant might be based on the canceled Mi-46, though that was about a 12 tonne class machine.
I think that the reason for a joint venture has more to do with a potential market, they want to sell to the Chinese, than it does to any real technical or development advantage that they might gain.
It makes sense, really. Israel is the size of New Jersey, and the CH-53 is much more flexible, and the difference in speed does not make much of a difference.
Let’s roll the numbers
V-22
Ch-53K
Speed
450 km/h
315 km/h
Payload
6,800 kg
15,900 kg
Range
1,627 km
841 km
Cabin Size (lxwxh)
7.3m x 1.8m x 1.8m
9.1m x 2.7m x 2.0m
Since going from one corner of Israel to the other is on the order of 400 km, the CH-53 K can cover the entire country, carrying more, and carrying more internally.
Additionally, the V-22 costs about $70 million as versus about $30 million for the CH-53K.
With a reduced payload and supplemental tanks, something like a special forces insertion is going to have similar range, and the larger internal payload allows the on an offloading of larger vehicles more quickly.
Finally, in a “hot” landing zone, the V-22, with its heavily loaded props/rotors, is more susceptible to vortex ring state (basically a stall in a rotary winged aircraft), and has to descend more slowly, increasing vulnerability to ground fire.
It’s a no brainer for Israel not to buy the V-22.
Come to think of it, it may be a no brainer for everyone not to buy the V-22.
DARPA Concept: Potential Settings for Active Rotor
One of the differences between rotor blades and modern aircraft wings is the relative lack of sophistication of the rotor blades. While wings have had flaps and/or slats for years, and have actively changed the shape of the wing with the benefit of fly-by-wire controls since the 1970s, the F-16 being a prime example, rotor blades have remained a single fixed airfoil with no leading or trailing edge devices.
Sikorsky is testing a control system with individual blade control, a departure from the current swash plate setup used in helicopters (middle picture) in addition to testing a system with actively blade flaps, and Boeing is testing a rotor with piezoelectrically driven flaps. (top picture)
Additionally, Sikorsky is looking at some more involved, and potentially fieldable concepts:
As part of the 30-month active rotor program with AATD, Sikorsky will also study active blade slats, adaptive flight controls and a dual-frequency rotor head-mounted vibration suppression system. The study will produce the conceptual design for an H-60 [Blackhawk & Seahawk] size active rotor.
DARPA is in on this too, with its Mission Adaptive Rotor program. (the mission adaptive wing program of the early 1970s led to much of what we have now on fixed wing aircraft).
They anticipate increases in payload and range of 30-40%, reducing noise by 50%, and reducing vibration by 90%.
Well, it’s beginning to look the army is going to take another look at a guided 2.75-inch rocket after the congress took the money from their advanced precision kill weapon system program, and transferred it to the Marine Corps, who were apparently much further along on the task of integrating guided rockets into combat units that the Army.
The original concept was to have a guided weapon to hang from the OH-58 and similar helicopters, but given the hot and (very!) high operating conditions in Afghanistan, and the nature of the targets, a Hellfire is overkill for a truck or an ox cart.
As the picture shows, you can carry 7 rockets (right of picture store) for each Hellfire:
A market survey released on 28 August by the army’s joint attack munition systems office says that high-altitude conditions require the army to trade the number of “stowed kills” on board an aircraft in favour of adding extra fuel.
“This undesirable trade is believed to be unnecessary given recent developments by industry on lightweight precision munitions,” it adds. “Industry efforts have resulted in a number of semi-active laser (SAL) munitions that may have the potential to satisfy army aviation’s need for a lightweight, precision munition.”
Market survey? I know what they mean, but the juxtaposition of the phrase “Market Survey,” and US Army is a bit odd.
The cost for the 2nd seat and radar that were added in the upgrade from the Ka-50 is that a lot of the armor has been removed to keep weight below 10 metric tonnes.
Mostly I’m posting this for the picture, because I’ve always found the coaxial helicopters to look “cool”
In a way, it’s a microcosm of problems in military contracting. Had the specifications remained as they were at the start of the program, the helos would now be in service for less than was spent not buying them.
Unfortunately, Bush and His Evil Minions™ decided to gold plate it, adding plush carpeting, a bathroom, a kitchen (!), videoconferencing gear, for a helo that would take the president on short (less than one hour) hops to a secure location or Air Force 1.
Said the president’s former Republican rival, “Well, thank you, Mr. President. And thank you for doing this…Just one area that I wanted to mention that I think consumed a lot of our conversation on procurement, it was the issue of cost overruns in the Defense Department. We all know how large the defense budget is.”
And, McCain noted, “your helicopter is now going to cost as much as Air Force One. I don’t think that there’s any more graphic demonstration of how good ideas have — have cost taxpayers an enormous amount of money.”
Meow…..That’s a slam, right?
Not so much:
Said Obama, “I’ve already talked to (Defense Secretary Robert) Gates about a thorough review of the helicopter situation.”
Added the president, to laughter, “the helicopter I have now seems perfectly adequate to me. Of course, I’ve never had a helicopter before. So, you know, maybe — maybe I’ve been deprived and I didn’t know it.But I think it is a — it is an — an example of the procurement process gone amuck, and — and we’re going to have to fix it.”
I think that he was expecting this from someone, and had just the response to make the accuser look small and petty.
They are currently installing a 3rd engine to power the propulsor, and expand the envelope to 193 kts (223 mph).
In the meantime, Sikorsky is looking toward taking its X-2 advancing blade helicopter to about 250 kts (288 mph). It’s already powered up the propulsor on the ground, and they look to open the envelope slowly, as this is a privately funded project.
Interestingly enough, it appears that they may exceed 250 kts in test at some point, as the manager of advanced programs notes, “We are comfortable getting to a 250-kt. cruise. The dash speed will be higher.”
I can see one or both of these technologies as a replacement for the A-10, which is a fine aircraft, but the US Air Force has wanted it dead for 30 years, and they only grudgingly address the close air support needs of ground troops.
The plan is to put drag-reducing fairings on the rotor, and then slowly transition to higher speeds, which would put more and more power toward the tail thruster, with the retreating blade stall being handled by offloading the blade as it moves aft.
The Mi-28 “Havoc” was intended to replace the Mi-24 “Hind” in the 1980s, and the Ka-52, a derivative of the single seat Ka-50 attack helo, which was the winner, and then the loser, against the Mi-28 over the past few decades looks to serve as a scout attack helo.
It looks like both will eventually, the radar is still in development, be equipped with millimeter radar guided missiles, much link the longbow.
After the Army canceled the Bell proposal because of delays and cost overruns and put out proposals for new bids, we are now seeing Eurocopter enter the fray.
As they are already delivering the UH-72A Lakota (EC145) to the US army, they may have a leg up on competitor Boeing.
Bell could reenter the competition too, but seeing as how their helo was canceled following a 4 year day and a threefold increase in development costs, I don’t think that they will.
Photo: Sikorsky, By Way of Ares
In this case, it’s the Marine Corps, which is 
Well, it’s beginning to look the army is going to 
The Russians are starting trials with a 
Piasecki helicopter is looking to 
As you can clearly see, after a few months of testing with the aircraft powering just the coaxial rotors, they 
With development beginning in the 1970s, the Mi-28N and the Kamov Ka-52 attackers, and the more recent Ansat-U training helicopter, are