Sikorsky pilot Bill Fell and Boeing pilot Ed Henderscheid have a combined 60-plus years of helicopter experience between them and are part of the program to bring the Future Long-Range Assault Aircraft (FLRAA) to the United States Army. In this Q&A, they share what they love about the Lockheed Martin Sikorsky-Boeing SB>1 DEFIANT technology demonstrator and the DEFIANT X, which the companies are proposing for the FLRAA program.
Q: What’s it like to fly the Sikorsky-Boeing SB>1 DEFIANT, the DEFIANT X technology demonstrator based on X2™ technology that the companies are offering for the U.S. Army’s Future Long-Range Assault Aircraft (FLRAA)?
Bill Fell: The DEFIANT is a great helicopter with a long list of accomplishments. The roll rate is crisp and sporty, the acceleration is exceptional, the low-speed manoeuvring is as good as any helicopter and the demonstrated external lift is superb. There are two distinct ways to fly DEFIANT:
You can fly it with the prop (the rotating blade on the back of the aircraft) engaged. In this mode, we still fly it like a helicopter in a low-speed environment. That helps with acceleration or pitch pointing the aircraft. This feature has awesome safety implications. The pilot can provide some reverse prop to keep a nose-low attitude to get a better view of everything in front of them. This is helpful in obstacle-rich environments not only for combat but also for any application.
You can fly DEFIANT with the prop disengaged. This adds amazing survivability as the tail of the aircraft is no longer flight critical like, for example, a tail rotor. If DEFIANT takes significant combat damage to the prop, the pilot can disengage the clutch and fly home at speeds higher than helicopters fly today.
Having the ability to fly DEFIANT with and without the prop engaged also allows us to manage the acoustic footprint based on the environment and greatly increases survivability.
What’s amazing about this aircraft is how quickly pilots take to it in the simulator and in the aircraft. The robust flight controls provided in the full authority system even make it easy for those with no flight experience to fly the aircraft. The flight controls in DEFIANT X will add all the bells and whistles expected of a modern aircraft. It will make flying the aircraft a lower-workload task, so the pilots can focus on the mission.
Q: What has impressed you most about the aircraft so far?
Ed Henderscheid: What has really impressed me is the ability to sustain “g” – which is essentially impossible in a conventional helicopter – as well as the flexibility and responsiveness of the fly-by-wire flight controls. Perhaps most significant to me is the amount of power available at the hover. It takes big engines and a lot of horsepower to go the speeds DEFIANT was required to meet. That translates to carrying a very generous amount of power back to the low-speed regimes, enabling extreme high-hot performance, as well as the capability to safely hover with one engine inoperative, which we demonstrated in the flight test.
Bill: What has impressed me is the capability the prop provides to decelerate and descend. The braking provided by the prop approaching landing is exceptional – one might say eye-watering. It really makes you feel the raw power of the prop as your shoulder straps pull at you to keep you back in your seat.
Q: What makes DEFIANT different from other helicopters you’ve flown?
Bill: It’s the way you size the power requirements of the aircraft. In an X2 technology aircraft, we chose installed power based on airspeed requirement rather than a specific hover condition. This is more powerful than a comparably sized helicopter. As a result, you have more excess power in the hover, which provides snappy manoeuvrability, rapid vertical climbs and amazing single-engine capability. Vertical climb capability is often considered an excellent predictor of helicopter manoeuvrability. In DEFIANT, we hovered at a mission weight with one engine at idle and the other engine peaking below its torque limit. We’ve also climbed vertically, quickly at mission weight. DEFIANT’s manoeuvrability is impressive and sure to provide better survivability and improved safety.
Ed: One of the things that takes a bit of getting used to with a coaxial rotor is not having to worry about or manage a tail rotor. Yaw control is managed by the flight controls using differential main rotor torque. The adverse handling qualities noted in sideward and rearward flight in conventional helicopters – caused by adverse interactions between the main and tail rotors – don’t show up in DEFIANT.
Q: How will DEFIANT X accomplish the long-range assault mission?
Ed: It is hard to imagine any other aircraft or configuration so thoroughly meeting the mission, not to mention choosing DEFIANT X will minimize the training and sustainment burden to capture that capability. Any time the aircraft is operating at speeds more typical of a helicopter, it flies just like one. The aircraft is designed to be able to integrate with all current facilities and ground support equipment.
Q: Tell us about some of the recent mission profile flights you’ve flown to demonstrate the helicopter’s capabilities?
Bill: We have flown DEFIANT into a very tight confined area landing several times. The capability and footprint of the helicopter made this task even easier than doing the same in a BLACK HAWK. Manoeuvring, approaching and departing the landing zone, was better with that crisp aircraft response providing the ability to carve a path through the trees with precision and ease – and problem-free.
We also flew DEFIANT 700 miles to the Army Aviation Association of America annual summit in Nashville. The aircraft performed flawlessly there and back with the plan executed with no deviations. I was proud to be a part of this team effort that involved all elements of leadership, engineering and maintenance to be able to display our aircraft.
Q: Any observations about the Honeywell engines on the demonstrator?
Ed: The T55 series is a known quantity and workhorse in the heavy lift fleet around the world, powering the best cargo helicopters ever put into service. Its ability to make power under duress is legendary among the pilots that have flown aircraft powered by that engine. It seems we are always getting the best out of those engines. It was certainly the best choice for DEFIANT, and I’m looking forward to seeing how Honeywell’s new engine the HTS7500 evolves for DEFIANT X.
Bill: DEFIANT used the T55 Honeywell engines for power. These engines are reliable and powerful. They supported all our flight test needs and helped get us to 247 knots in level flight. It is logical that we would choose this robust engine with a lot of history for DEFIANT X. DEFIANT X has challenging range requirements. After all, the program is called Future Long-Range Assault Aircraft. To meet the Army’s needs, Honeywell will be modernizing the T55 to a next-generation engine called the HTS7500 to provide the efficiency needed and improve on everything we already love about the power and reliability of the T55.
In Their Own Words: About Bill and Ed
Bill: I served in the US Army for 20 years in various pilot roles: Scout & Attack Helicopter Pilot, Instructor Pilot, Fixed Wing Pilot and Experimental Test Pilot. After the Army, I joined Sikorsky where I have been developing several different rotor-craft for the past 15 years. I was fortunate to join the X2 Technology Demonstrator Team in 2009 and from there helped to start the S-97 RAIDER program. I flew all the initial development on the S-97 and remain involved in the program today. I was also around for the start of the Joint Multi-Role Technology Demonstrator (JMR-TD) program and to date have flown on every flight of the program with SB-1 DEFIANT. I consider myself to be exceptionally lucky as a test pilot to have a central role in three once-in-a-career programs: RAH66 Comanche, S-97 RAIDER and SB-1 DEFIANT. I am excited to use my experience from those programs as we design, refine and fly the DEFIANT X and RAIDER X aircraft.
Ed: I grew up in small-town airports as the son of a crop duster. I’ve been flying on my own since high school. I joined the Army when I was 17 years old as a UH-1 Huey mechanic, and went to flight school in 1995. I flew Army helicopters for 25 years. I have over 3,000 hours of AH-64 Apache time and was afforded the opportunity to be rated in every rotorcraft model in the Army inventory before I retired. I spent my last 10 years on active duty as an experimental test pilot working on a number of programs, but primarily weapon and mission systems upgrades to Apache. I’ve been with Boeing for four years, working on the H-47 Chinook Block upgrades and project pilot for JMR/Future Long-Range Assault Aircraft (FLRAA) since 2019. DEFIANT is the first truly new aircraft I’ve been involved with and what an amazing education and opportunity it has turned out to be.
DEFIANT achievements include:
Low-altitude manoeuvrability at speed
Treetop manoeuvrability at speed
Confined Area Operations
Demonstrated Level 1 low-speed agility with fly-by-wire controls
Greater than 60-degree banked turns
Demonstrating mission-relevant cargo capacity by lifting a 5,300-pound Guided Multiple Launcher Rocket Storage Pod external load
Achieved 247 knots
Executed multiple test flights with U.S. Army experimental test pilots at the controls
Based on the Collier Award-winning X2 Technology