By Kris Osborn - Warrior Maven

(Washington, D.C.) When facing hostile fire and closing with an enemy amid a massive mechanized armor attack, air delivery of infantry and high-speed MEDEVAC could prove decisive, especially in mountainous terrain less navigable by ground vehicles.

Once an initial breach is achieved, either through long range fires, armored attack or air support, advancing forces need to be quickly reinforced quickly by large numbers of infantry on the ground to maintain position within an offensive. This can be done on the ground with infantry carriers or even tactical trucks should terrain be passable, or it could be done by air with a C-130 cargo transport planes and helicopters.

However, in a hostile environment wherein arriving forces are confronting enemy ground fire or some kind of heavy resistance, a cargo plane or large utility helicopter might not be survivable enough to enter what Army forces call a “hot LZ” or actively contested Landing Zone.

This potential scenario, wherein terrain or enemy resistance take away tactical options, is likely a huge part of the Army’s concept of operation intended for its new Future Long Range Assault Aircraft, or FLRAA. The program, intended to fly alongside and augment the Army’s upgraded Black Hawk helicopter, is now airborne with unprecedented speed, agility and AI-enabled mission systems and computing. The FLRAA, now being developed by Bell Helicopter and Lockheed’s Sikorsky-Boeing, is now being engineered to travel twice as fast and twice as far as the existing BlackHawk and call upon breakthrough levels of weapons applications, avionics and radar-signature reducing attributes.

Lockheed Sikorsky-Boeing’s DEFIANT X

DEFIANT X Future Long Range Assault Aircraft

“This medium lift, tactical assault and medical evacuation capability will augment the Army’s H-60 Black Hawk utility helicopter fleet to provide Combat Aviation Brigades with long-range, high-speed options that are survivable in contested environments... It will provide power projection from relative sanctuary with significantly increased range, speed, mobility, and payload capabilities over current Army and U.S. Special Operations Command (SOCOM) aircraft,” an Army report says.DE

DEFIANT X from Lockheed Sikorsky-Boeing 

One of the vendors is architecting its platform with a specific mind to target high speed attack and reconnaissance, while also ensuring a crucial ability to operate in large, multi-aircraft formations needed in major warfare. Lockheed Sikorsky-Boeing’s DEFIANT X is engineered with a BlackHawk like size configuration to ensure large airfleets of utility and attack helicopters could approach in close proximity if need be. In a major warfare scenario, large numbers of condensed, armed and low-observable FLRAA aircraft might need to swarm a hot-LZ with high-speed, maneuverability, quick MEDEVAC and fast-paced infantry delivery to support and sustain a fast-advancing attack.

FLRAA Developed by Bell Helicopter and Lockheed’s Sikorsky-Boeing

DEFIANT X in Formation 

Just how fast is “high-speed?” Well, the specifics of the DEFIANT X are not available for security reasons, yet is it known to come close to if not reach speeds twice as fast as the 150mph speed of a Blackhawk, an attribute which of course enables commanders with large-scale attack options far more survivable that cargo planes or tactical trucks. In major power future warfare, there are anticipated scenarios wherein high-speed, less detectable and more survivable helicopters will be needed to quickly deliver large numbers of infantry or add crucially needed close-air support to advancing armored forces.

The Army envisions its Future Longe Range Assault Aircraft to “augment” or fly alongside its upgraded Black Hawk helicopter, yet massively increase “combat power build,” speed, agility and close-in maneuverability under hostile fire. Despite these differences, there are some fundamental dynamics in terms of mission connecting the FLRAA and Blackhawk moving into the future.

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Mission alignment and expansion is likely one reason why Lockheed-Sikorsky-Boeing built its DEFIANT X FLRAA at roughly the same size as a Blackhawk. The overall width of a BlackHawk is 53.7’, something similar to the DEFIANT’s width of 56.6. Interestingly, there is a specific aerodynamic reason for this, enabling multiple aircraft to successfully operate in close proximity to one another. A technical phenomenon known as “rotor downwash” happens when aircraft of a certain size generate turbulence or unstable air in the vicinity around them, making it impossible for other aircraft to operate nearby. The larger an aircraft is, the more “rotorwash” it generates, potentially making nearby aircraft vulnerable to unstable flight and even crash.

A related phenomenon, of particular concern with tiltrotors, is known as “Vortex Ring State,” an aerodynamic condition in which upward flow can generate turbulence, resulting in a loss of lift. According to a 2012 FAA Helicopter Flying Handbook, Chapter 11 “Helicopter Emergencies and Hazards,” Vortex ring is described as a “state, in which airflow is upward on the inner blade section, producing a secondary vortex in addition to the normal wingtip vortices. Turbulent airflow results and loss of rotor efficiency. If allowed to continue, uncommanded pitch and roll oscillations may occur, with a large descent rate.”

The DEFIANT X is specifically engineered at a certain size, configuration to address and mitigate these risks and optimize aerodynamic performance. Essentially, downward rotor wash and Vortex Ring state concerns are not an impediment for the DEFIANTX, as it is being built with those concerns in mind. The DEFIANT X is designed to operate in larger, potentially more consolidated attack formations in closer proximity to one another, providing attacking forces with a survivable, high-speed delivery mechanism for large amounts of infantry, firepower or time-sensitive medical support. The DEFIANT X is intended to leverage and optimize “combat power build” for land attack by landing and dispatching coordinated groups of fast-advancing soldiers. The problem of rotor downwash or “vortex ring state”, however, could be significant with much larger platforms, requiring much greater separation between aircraft.

DEFIANT X in Flight

DEFIANT X in Flight

An interesting 2007 U.S. Army paper called “The Fundamentals of Flight” further explains the “downwash” phenomenon, an aerodynamic circumstance which can generate unstable, turbulent air components in the surrounding vicinity of an aircraft when rotorblades generate a “downward flow of air.” Naturally, the heavier and larger the aircraft, the more substantial and destablizing this downward air flow becomes. It is one of several key scientific reasons why engineers built the DEFIANT X in its current configuration, a clear effort to enable faster, smoother, more condensed large scale attack when and if necessary in warfare.

“As blade pitch angle is increased, the rotor system induces a downward flow of air through the rotor blades creating a downward component of air that is added to the rotational relative wind. Because the blades are moving horizontally, some of the air is displaced downward. The blades travel along the same path and pass a given point in rapid succession. Rotor blade action changes the still air to a column of descending air. This downward flow of air is called induced flow (downwash). It is most pronounced at a hover under no-wind conditions,” the essay writes.

The issue of needed separation is given specifics in an interesting essay in Breaking Defense by Scott Trail, a former V-22 Osprey developmental test pilot and CH-46E helicopter pilot.

“According to the 101st Airborne, H-60 helicopters can land safely with just 30 meters (98 feet) of separation. By comparison, the V-22 requires 76m (250ft) separation, two-and-a-half times more than the H-60,” Trail writes in the essay.

There are additional tactical reasons why an ultra high-speed aircraft the size of a BlackHawk could prove advantageous, as a DEFIANT X is built with a measure of agility such that is can fly very close to the ground, thus below the radar, so to speak, and be less susceptible to enemy detection. The DEFIANT X is built with the aerodynamic configuration sufficient to fly at high speeds close to the terrain as low as 200ft, making it much less vulnerable to enemy fire by reducing any angle of attack and of course minimizing radar signature.

“If you think of what a Black Hawk does when inbound to an LZ, then picture a 2030 contested operational environment. We will be flying twice as far and twice as fast but they still have to be very maneuverable in and around the objective area,” Jay Macklin, Sikorsky business development director, Future Vertical Lift, told Warrior in an interview earlier this year.

- Kris Osborn is the Managing Editor of Warrior Maven and The Defense Editor of The National Interest --

Kris Osborn is the Defense Editor for the National Interest. Osborn previously served at the Pentagon as a Highly Qualified Expert with the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Master's Degree in Comparative Literature from Columbia University.