V-280 Valor begins ground vibration testing

Bell Helicopter’s V-280 Valor demonstrator aircraft began ground vibration testing in Amarillo, Texas, Feb. 16, as the manufacturer works toward a planned first flight of the third-generation tiltrotor in September 2017.

The V-280 is Bell’s submission for the U.S. Army’s Joint Multi-Role Technology Demonstrator (JMR-TD) program, a precursor to the Future Vertical Lift (FVL) program to identify a replacement for the service’s existing medium-lift helicopter fleet of Sikorsky UH-60 Black Hawks and Boeing AH-64 Apaches.

Powered by two 5,000-horsepower General Electric T64-GE-419 engines, the V-280 is designed to carry two pilots, two crew chiefs, and 11 to 14 passengers at a cruise speed of 280 knots and a combat range of 500 to 800 nautical miles.

The prototype’s electrical systems were powered on for the first time a couple of months ago, and the aircraft is now 95 percent complete, with Bell crediting its rapid progress to lessons learned from the legacy of the V-22 Osprey, and efficiencies gained from its digital design. It’s the third type Bell has developed within a digital environment, following on from the 525 and 505.

As an example of the time savings, Scott Allen, V-280 build manager, said it took about 700 to 800 hours to produce all the engineering drawings for the hydraulics system on the right side of the V-22. “We did the same thing on [the V-280] in less than 40 hours by leveraging the digital data that was out there,” he said.

And it wasn’t just at the design stage that time was saved; 3D scans of all the major structural interfaces allowed the team to attempt to mate the sections together in a digital environment long before the parts ever met, practically eliminating anomalies when the time came to assemble the prototype. Installations of the fixed drive system, propeller rotor gearboxes, and engines took a matter of minutes rather than days.

The fuselage, produced by Spirit AeroSystems, is composed of an aluminum frame with a composite skin. As with the V-22, Bell manufactured the V-280’s wing itself. The wing is almost entirely composite (the exception being a few metallic locating provisions), with a thick outer skin, a thin inner skin, and a large carbon core to give the wing the stiffening it needs to support a maximum gross weight takeoff.

“We’re predicting 20 percent the part count of a V-22 wing, and we’re estimating it’ll be less than half the cost,” said Allen.

Safety is also front of mind in the aircraft’s design, so the V-280 has a triple redundant fly-by-wire flight control system, and a driveshaft that can transfer power between powerplants so seamlessly in the event of an engine failure that it would be practically indiscernible, according to Allen.

The Army’s requirements for the demonstrator call for hot and high hover performance (at 6,000 feet and 95 F), and the ability to self-deploy 2,100 nautical miles at a speed of at least 230 knots.

“If you’re interested in speed, range and payload, tiltrotor makes a lot of sense,” said Allen. “It’s a technology that has proven out over many years now with the V-22, [with] 300,000 flight hours.”

One of the key differences between the two aircraft is the mechanics of how they transition from vertical to horizontal flight; the V-22’s engines rotate with the gearboxes, while in the V-280, the gearbox is the only thing that rotates. The V-280 will also have the ability to rotate its propellers back beyond 90 degrees, although Bell wouldn’t reveal the exact extent of this capability.

According to Allen, one of operational benefits of maintaining the engine’s position is that it avoids directing the hot exhaust onto the ground — which can present a potential fire hazard if landing in an unprepared area with combustibles. It also provides a clearer field of view within a landing area — an obvious benefit for Army purposes if landing in an area while under attack.

And, as the demonstrator is for Army purposes, entry to and exit from the V-280’s 102-square-foot cabin is through two six-foot-wide doors either side of the aircraft — rather than through a ramp at the rear of the aircraft for the Marines with the V-22.

A notable difference in terms of performance between the V-22 and V-280 will be its agility at low speeds, said Allen. “The [V-280] will be very maneuverable at low speed,” he said. “There’s been some changes to the design to facilitate that, and we’re excited to see the results.”

For now, the aircraft is going through ground vibration tests at Bell’s facility in Amarillo. This involves mounting test fixtures onto the aircraft’s rotor masts, which will allow the team to simulate flight conditions on the ground to check for any dynamic frequencies that might be a concern.

“We know what we expect to see; we put it in the GVT fixture to confirm that,” said Allen. “The airframe is basically ready to fly. The ground vibration test is sort of the last [stage] before we go out to start ground testing — it’s the last litmus test to ensure that now that all the systems are installed in the structure, everything is going to essentially perform as expected.”

Like the 525, the V-280 development program includes a systems integration lab in which the fly-by-wire aircraft’s flight controls are continually tested and data points collected as the aircraft’s software evolves.

“What they’re learning there as they continue to develop the software, we load the software here, and then basically run a series of checks to confirm that everything is as it should be,” said Allen. “There’s just a lot of checks and balances that go into it before we actually get air under the tires for the first time. It seems like a lot of time [until the aircraft is scheduled to fly], but we’ve still got a lot of work ahead of us to be ready for first flight in September.”