Tag: Helicopters

Sikorsky-Boeing Takes Wraps Off Defiant X Design For U.S. Army’s FLRAA | Aviation Week Network

Much Smaller Footprint than a Tilt Rotor

After putting out a representative demonstrator, Sikorsky has revealed off of its Defiant-X helicopter for the Future Long-Range Assault Aircraft (FLRAA) program.

It does not achieve the same speeds as the tilt-rotor competitor V-280 Valor from Bell, 280 kt (520 km/h) from the Bell offering as versus and 250 kt (465 km/h) for the coaxial compound helicopter, but its footprint on the ground and on takeoff and landing, and its agility during takeoff and landing should be significantly greater than the V-280.

Also, the helicopter should be significantly more agile during takeoff, landing, and autorotation, because of lower disk loading.

One lingering uncertainty surrounding the U.S. Army’s Future Long-Range Assault Aircraft has centered on the service’s ultimate requirements for the advanced rotorcraft that will replace its Sikorsky UH-60 Black Hawk utility helicopters.

When the Army launched the precursor Joint Multi-Role Technology Demonstration (JMR TD) program in 2013, it provided industry with a “model performance specification”—placeholder requirements that would allow them to begin designing an aircraft.

The result was a pair of 30,000-lb. gross-weight-class demonstrators—the 280-kt. Bell V-280 Valor tiltrotor and 250-kt. Sikorsky-Boeing SB-1 Defiant, a coaxial rigid-rotor compound helicopter—both substantially larger and faster than the 22,000-lb. gross-weight UH-60M they are designed to replace.

Now, almost halfway through the CDRR phase, the answer to that lingering question about the Army’s requirements may be becoming clearer. The Sikorsky-Boeing team has taken the wraps off its Defiant X offering for FLRAA, and the design differs only in detail externally from the SB-1 now in flight test.

In terms of overall size, the Defiant X has the same operational footprint as the demonstrator, says Jay Macklin, Sikorsky’s director of Future Vertical Lift business development. The Defiant X also fits within the operational footprint of the Black Hawk, which the FLRAA is intended to replace beginning in 2030.

The Defiant X design has been optimized to meet Army requirements for survivability, maneuverability and agility in the objective area, or “at the X,” says Macklin, so that troops can be landed and offloaded quickly and safely during an air assault.

I favor the coaxial helicopter over the tilt rotor.

It seems simpler and safer.

The Return of the AH-56 Apache

Proposed Apache Update

AH-56 Apache

Boeing is proposing a major update to its Apache attack helicopter, that the similarities between it and the 1960s vintage AH-56 apache are striking:

U.S. aerospace manufacturer Boeing has shown footage of high-speed version of Apache attack helicopter during the Vertical Flight Society’s 75th Annual Forum & Technology Display.

Graham Warwick posted images of the Apache gunship concept and photo of a scale model of a new helicopter that was unveiled by the Boeing on social media.

The concept, called the Advanced AH-64 Block 2 Compound, is developing to serve as a gap filler in a U.S. Army Future Vertical Lift (FVL) program.

Jane’s Defense Weekly early reported that the new gunship will feature an enlarged main wing, revised engine exhaust arrangement, large vertical tail fin, and a rear-mounted pusher propeller. The design may also feature a new, rigid rotor system, which is a standard feature on other compound helicopter designs.

Also the Rotor & Wing International said that Boeing already has conducted wind tunnel testing of a scale model of a high-speed Apache gunship.

The similarities between the two helicopters, both in appearance and concept, are striking.

This is Trippy

One sees a number of proposals for using distributed electric propulsion for vertical takeoff and landing systems, but this is without a doubt the oddest concept that I’ve seen yet:

A vertical-takeoff-and-landing (VTOL) design with wings that both tilt and fold, providing stable hover and efficient flight, is under development by Boston-area startup PteroDynamics. The company is targeting the military unmanned-aircraft market initially, but has ambitions to develop an air taxi.

In PteroDynamics’ Transwing concept, the wings tilt and fold back along the fuselage, and the aircraft acts like a multicopter in vertical flight. To transition to forward flight, the wings rotate into horizontal position, allowing the Transwing to fly like a conventional aeroplane.

“Our vehicle is completely unique,” says CEO Matthew Graczyk. “It’s 100% fixed wing in horizontal flight and 100% rotary wing in vertical flight, with no compromises.” Unlike a tiltwing, the Transwing can transition between vertical and forward flight with no stall range, he says. The aircraft can have a long wing for cruise efficiency, but folds into a compact size for VTOL.


PteroDynamics has flown a 12-ft.-span model, but has not yet attempted transition between vertical and horizontal flight and does not know how well the design scales. “We did get lucky with the prototype,” says Petrov. “What will happen at 40-ft. or 400-ft. span we don’t know, but as we understand how it works we see no fundamental reason it will not scale.”

As the wing rotates aft it has more dihedral and sweep and the angle of attack never exceeds 20 deg., while propeller wash helps prevent flow separation. “A tiltwing goes past 45 deg. into wing stall and the wing becomes an obstacle to forward flight,” Petrov says. Transwing “can stall, but mildly. We tufted the wing and video shows the airflow does separate, but not badly. Mostly the flow stays attached.”

Petrov describes the tilt/fold articulation as similar to the wing-fold mechanism on Grumman carrier-based aircraft such as the Avenger and Hellcat, except that Transwing folds leading edge up. The hinge mechanism will carry high loads, but reinforcement of the wing at the fold “should not penalize the aircraft too much, perhaps 5% of maximum takeoff weight,” he says.

I can’t wait for a full size test.

Kamov Advanced Helo

Looks a lot like the S-79

Sikorsky S-79

Kamov, which has been the leading producer of coaxial rotor helicopters for decades, is proposing an advanced helicopter that bears a strong similarity to the Sikorski advancing blade helicopter.

What is notable is that the two rotors are further apart than those of the S-79, it has wings, (and canards) and the propulsor is a turbofan rather than a propeller.

First, it’s pretty clear from this that the rotors are probably not as stiff,  and that the controls are less sophisticated, requiring more space between the two rotor disks to avoid the blades striking each other.

The wings, and the turbofan propulsion, imply that it is designed for a much higher speed, probably at the expense of range, noise, and low speed accelleration

That being said, I am profoundly dubious of their claim of a top speed of 700 km/h (440 mph/370 kts) for any rotorcraft:

Pictures of a Kamov design for an advanced attack helicopter have appeared on a Russian website.

The images appear to have been leaked amid competition between the Kamov and Mil Moscow Helicopter design bureaus within Russian Helicopters to develop the country’s future high-speed combat helicopter, called SBV.

Russian Helicopters announced at the Army 2017 forum in Moscow last September that it had signed a two-year contract with the Russian defense ministry to refine concepts for a high-speed attack helicopter, with both Kamov and Mil working on designs.


The leaked photographs show Kamov General Designer Sergei Mikheyev presenting the bureau’s concept, a winged coaxial-rotor, twin-turbofan compound helicopter reportedly capable of up to 700 kph (380 kt.) This compares with a speed of more than 400 kph claimed for Mil’s single-main-rotor design.


Propulsion is provided by what appear to be a pair of turbofans mounted in the aft fuselage and driving the rotor gearbox via a pair of shafts that project forward from the engines—an arrangement reminiscent of the shaft-driven lift fan in the Lockheed Martin F-35B.

The engines likely direct most of their power forward to shaft-drive the rotors for takeoff, hover and low-speed maneuvers, then shift more of the power to thrust as forward speed increases. The rotor system has a pair of contra-rotating three-blade rotors with swept tips.

Your Military Industrial Complex in a Nutshell

As a part of supporting the Afghan military, the Pentagon is upgrading Kabul’s helicopters.

There are a few small problems though: In addition to the Afgan military not being able to maintain its new Black Hawk helicopters, the Russian Helos that it is replacing outperform the Black Hawk by almost every metric:

A report from a top U.S. military watchdog has finally acknowledged that the UH-60A+ Black Hawks that the United States is supplying to the Afghan Air Force are less capable and harder to maintain than the Russian-made Mi-17 Hip helicopters they have now. The review raises concerns that this could limit Afghanistan’s ability to conduct operations across the country unless steps are taking to mitigate the loss of capability, something we at The War Zone have long warned could easily be the case.


“The transition [from Mi-17s to UH-60s] presents several challenges that have yet to be fully addressed,” the report says in a section dedicated to the issue. “Black Hawks do not have the lift capacity of Mi-17s.”

“They are unable to accommodate some of the larger cargo items the Mi-17s can carry, and in general, it takes almost two Black Hawks to carry the load of a single Mi-17,” the review continues. “Furthermore, unlike Mi-17s, Black Hawks cannot fly at high elevations and, as such, cannot operate in remote regions of Afghanistan where Mi-17s operate.”


“The Mi-17 is ‘much more conducive to the education level available in the general Afghan population than the UH-60As’ when it comes to maintenance,” the 9th Air Expeditionary Task Force-Afghanistan (AETF-A), the U.S. Air Force’s top command for operations in Afghanistan, which also oversees advising the Afghan Air Force, said, according to the Pentagon Inspector General’s review. “The expectation is that the AAF will be almost entirely reliant on contractors for Black Hawk maintenance in the near- to mid-term.”

That reliance on contractors is a feature not a bug:  This is more of the deferred compensation for general officers program that appears to be the raison d’être of the Pentagon these days.

Whoever made this decision will secure a well remunerated post military retirement sinecure with Sikorsky, one of its suppliers, or the contractors that the Afghans (actually us) are paying very well for support services.

Israel Has 2Nd Thoughts about V-22 Acquisition

V-22s Range Advantage has a Cost

Israel seemed poised to purchase the tilt-rotor V-22 Osprey, and now they have put this on hold.

I am not particularly surprised.

The V-22 is a maintenance hog, and cost a fair amount to operate.

While the Osprey is about 100 kts faster, has a longer range, it can only carry about 1/3 of the payload, even though it has 2/3 of the installed power.

Additionally, unlike a conventional helicopter, the V-22 does not have a meaningful auto-rotation capability, and its performance with external loads is pathetic.

Israel simply does not have the need for the additional capabilities offered by the tilt-rotor:

The Israeli air force has frozen its evaluation of the Bell Boeing V-22 Osprey, with a senior defence source indicating that the tiltrotor is unable to perform some missions currently conducted using its Sikorsky CH-53 transport helicopters.

In January 2014, the US Department of Defense notified Congress about its intention to sell six V-22s to Israel. This followed an evaluation conducted by air force personnel, which led to the service seeking a rapid acquisition to support special operations. The proposed purchase met with opposition from elsewhere within Israel’s defence ministry, however.

Other potential candidates to replace the Israeli air force’s aged CH-53s by around 2025 include Sikorsky’s new CH-53K and the Boeing CH-47 Chinook.

Simply put, the IDF does not have the requirements, such as amphibious landings from extreme distance, that have driven the V-22, and as such, it does not make sense.