The United States’ FVL Programmes Preparing to Close the Era of Conventional Helicopters / PART 2

Winner of the FLRAA to Take the Throne of Black Hawk

Alper ÇALIK / a.calik@milscint.com

In this part of our series of articles examining the Future Vertical Lift (FVL) programme being carried out under the leadership of the U.S. Army, in which focus is on the development and supply of next-generation rotary wing aircraft, we address the Future Long-Range Assault Aircraft (FLRAA) component of the programme.

New Platform to Change Air Assault Concept

The schedule of the FLRAA programme, being carried out under the leadership of the U.S. Army, closely resembles that of the Future Attack Reconnaissance Aircraft (FARA) programme – the other component of the overarching FVL programme. After the development of a general purpose aircraft in the first stage of the FLRAA programme, plans are in place to develop special versions for the Special Forces and Marine Corps within two years of the U.S. Army taking delivery of the first batch of aircraft. Among these versions is one with an attack role, and while it has not been identified as a priority, the competing companies are considering such a role in their designs.

The FLRAA programme foresees the development of an assault helicopter with a minimum cruising speed of 280 knots to replace the UH-60 Black Hawks in the inventory of the U.S. Army, which have a maximum speed in the range of 140–150 knots, depending on the version. The new aircraft is to be able to carry 12 fully equipped personnel at minimum, equalling the 12-passenger capacity of the UH-60, while among the other requirements are a range of 1,725 nautical miles without refuelling and a vertical climb speed of 500 feet/minute. Furthermore, the dimensions of the new aircraft should not exceed the current dimensions of the UH-60, and they should be able to fit wherever a UH-60 can fit.

The companies that have made it through to the next phase in this programme are the Sikorsky-Boeing consortium and Bell, both of which have completed construction of the first prototypes of their designs and have started conducting flight tests.

V-280 Valor: V-22 Osprey’s Little Cousin

Bell is proposing the V-280 Valor tiltrotor under the FLRAA programme. Considered a little cousin of the V-22 Osprey, which has been serving for years in the inventory of different military units in the United States, Bell’s V-280 has a number of features that distinguish it from the V-22. Briefly, the propulsion systems at the wingtips of the V-280 do not fully rotate, as is the case with the V-22; rather, the engines and nacelles remain fixed, while the rotors rotate with the help of a gearbox.

Unlike the V-22, which has a rear ramp, the V-280 has a door on either side, each measuring approximately 1.8 meters wide, allowing quick ingress and egress. Since there are no nacelles hanging from the wingtips, the doors can be equipped with machine guns for self-defence, which is especially beneficial during take-offs and landings in the battlefield. This enables the V-280 to overcome the self-defence issue, which is a significant deficiency of the V-22.

The name V-280 comes from the cruising speed of 280 knots that the aircraft can easily reach and even exceed, with the maximum cruising speed of the V-280 reported to date being 300 knots. The V-280 has a V-style tail and no rear ramp. The aircraft can accommodate a crew of four and has a passenger capacity of 14 fully equipped personnel. During flight tests, the aircraft has proven its ability to perform several manoeuvres autonomously, without the need for pilot control.

SB>1 DEFIANT: Featuring an Attack Version with Tandem Cockpit

The Sikorsky-Boeing consortium, as the other competitor remaining in the FLRAA programme, is offering the SB>1 DEFIANT compound helicopter. Sikorsky is providing X2 technologies to the programme, while Boeing is working on the mission equipment.

DEFIANT uses such technologies as a coaxial double main rotor and a pusher propeller in the tail, similar to the RAIDER X, with the most significant difference from the RAIDER X being in its dimensions. Aside from a crew of four, the aircraft can accommodate 12 fully equipped personnel. In the flight tests conducted to date, DEFIANT reached a cruising speed of 205 knots, but without making use of the entire power of the engine, but Sikorsky claims that DEFIANT can reach speeds of up to 250 knots.

Although an attack version of the platforms being developed under the FLRAA programme has not been stated as a priority, it is understood from the statements and images released by Sikorsky and Boeing that the consortium is working on a specialised attack version of the platform, with suggestions that the two versions will be 85 percent identical. Some of the components that will be common for both versions are the engine; the rotor, shaft and propeller systems; the complete tail cone; control surfaces; the mission equipment; the fuel system; the hydraulic-like secondary systems; and the training systems. The main differences between two versions will be in the forward airframe, while the attack version will have no passenger cabin and a tandem seating configuration in the cockpit, as in the AH-64 Apache.

Valor vs. DEFIANT

As is the case of the FARA programme, it is too early to comment on which will be the winning design, although a number of conclusions can be drawn from information in the public domain, from company data and from the images published to date:

• Speed: Even though speed is not normally a high priority in assault helicopters, the cruising speed of 280 knots is one of the few requirements defined by the U.S. Army, as in the FARA programme. Valor has already demonstrated its ability to easily meet this requirement, with speeds of around 300 knots reached in tests. DEFIANT has yet to start pushing its limits. It is said that DEFIANT has reached a speed of 205 knots, but has the ability to reach 250 knots. The X2, which is a much smaller vehicle developed previously by Sikorsky, but that used the same technologies, was able to reach speeds of 250 knots. Time will tell what DEFIANT can do.
• Seating Arrangement: The aircraft models competing in the FLRAA programme should be examined in terms of passenger rather than pilot seating, as when it comes to a helicopter that is to land troops in a combat zone, what is important is how quickly the soldiers can egress and ingress the aircraft. Featuring a relatively wider body, DEFIANT’s passenger seats face toward the front and back of the helicopter, like in a bus, which can make ingress and egress difficult in combat situations. In contrast, the passenger seats in Valor are in a row, extending from the front to the back of the aircraft, back to back, with the passengers facing the sides when seated. This means that more than one soldier can ingress and egress at the same time.
• Attack Version: According to the images and statements released by the companies, DEFIANT has a customized attack version for this role. The only difference in the attack version of Valor is that the aircraft is equipped with additional weapons. It is obvious that the guided missile equipped version of an UH-60 Black Hawk helicopter will not be an optimal solution for an attack helicopter, and the same can be said for Bell’s offering. Although further works may improve this situation, it would seem that the large wings required to carry Valor’s engines will prevent any significant narrowing of the fuselage.
• Engines: Similar to the FARA programme, the development of a new engine and the use of this engine during serial production is on the agenda for the FLRAA programme. In this sense, there is little point in comparing the engines of the aircraft prototypes, although it is worth examining this issue. DEFIANT currently features two Honeywell T-55 engines that are used also on CH-47 Chinook helicopters, and which generate 4,800 horsepower. On the other hand, Valor is powered by two GE T64-419 engines, with 4,750 horsepower. In terms of horsepower, engines used in both aircraft have very similar performance. It is fair to say, therefore, that the engines that will be supplied in the mass production stage will be more powerful, and that the performance of the two aircraft will be affected in the same way.

When these parameters are evaluated together, and when considering only the assault helicopter role of the aircraft, the V-280 Valor would seem to be superior, although the user may decide to procure assault and attack versions together, and so may choose the DEFIANT option.

Conclusion

It is too early to tell who will win the FARA and FLRAA components of the FVL programme, but several inferences can be made based on a review of the statements made by the companies and the end users, the published images and the opinions of aviation experts. Whatever the outcome, the U.S. Army seems to be committed to leaving behind the classical helicopter design, which dates back to the 1950s, and to add new-generation aircraft with vertical-take-off technologies to its inventory. Moreover, U.S. authorities have underlined that despite the global COVID-19 outbreak, no concessions can be made in the schedule of the FARA programme. Accordingly, it would seem that works in these programmes will not remain in the prototype phase, as is the case with the RAH-66 Comanche helicopter, strongly indicating the early emergence of a new generation of platforms.

When considered from this point of view, it is obvious that works on the FVL will shape the perception of vertical take-off aircraft around the world, and break down old paradigms, and once this new generation aircraft enters the inventory, the nature of combat will change, as was the case in the Vietnam War when helicopters were used intensively for the first time.

FVL Can Close the Helicopter Era

The work of the United States on the procurement of next-generation aircraft with vertical take-off and landing capabilities is being followed under two separate but parallel programmes. Of these, the Joint Multi-Purpose Technology Demonstrator (JMR-TD) Platform aims, as implied by its name, to showcase the development and feasibility of next-generation technologies. Furthermore, a series of programmes carried out under the FVL framework are focusing on the further development and procurement of platforms after their feasibility has been proven.

Led by the U.S. Army, the FVL covers multiple joint programmes, including the FARA and the FLRAA programmes, aimed at the procurement of various platforms with vertical take-off and landing capabilities. That said, although the programme is being carried out by the Army, different versions of the aircraft that are to be developed under these programmes are being looked at by the Marine Corps and the Special Forces, although it has been stated that these two users will wait at least two years to get their new helicopters after the U.S. Army takes delivery.

Helicopter Fleet Ageing

There are many different types of helicopters in the inventory of the U.S. Armed Forces, being used for various missions, such as in assault roles, or for armed reconnaissance and attack, but this fleet is ageing, and recent operations of the Unites States in Afghanistan and the Middle East have taken their toll. Furthermore, it is thought that the future helicopters to be used by the United States will need to reach higher speeds than at present. That said, the U.S. authorities have stated that although several modernization and R&D studies have been launched to identify ways of improving the performance of helicopters in such areas as the engine, blade and fuselage materials, such efforts have generally hit a stalemate. In short, these helicopters, which were designed in the 1960s and 1970s, have a theoretical limitation on the maximum speed they can achieve due to the phenomenon of Retreating Blade Stall, as detailed in the box called “Theoretical Limits of Helicopters” in the first part of this article.

For this reason, the FVL programme focuses on the development of platforms that fly based on different principles to conventional helicopters. Another important requirement of the FVL is that the completely different platforms to be procured are to have identical critical components, such as the avionics, sensors and engines. It is also requested that the aircraft be designed with an open architecture so that technologies that will be developed, for example, 20 years from now, can be quickly integrated into the platforms as they age. This capability, which can be described as “plug and play”, similar to today’s PCs, is considered to be a critical aspect of the programme by officials, based on the belief that the battlefield and technologies of the future will change much faster than today, and that it must be possible to update platforms quickly to keep up.

The aircraft to be developed under the FVL programme are expected to undertake the tasks currently performed by the OH-58 Kiowa, AH-64 Apache, UH-60 Black Hawk and CH-47 Chinook helicopters, while plans are in place to replace the helicopters in the inventories of the Marine Corps and the Special Forces. The aircraft to be developed under the FVL are expected to be superior to those they replace in terms of:

• Manoeuvrability
• Range
• Speed
• Carrying Capacity
• Survivability
• Reliability
• Logistics requirements