Bell’s (Booth No. N1816C) 525 “Relentless” super-medium-twin helicopter continues its march toward FAA certification, now likely sometime next year. Currently, four test ships are flying with a fifth slated to join the program soon. Overall, test aircraft have accumulated 1,300 flight hours through the middle of September. Approximately six production aircraft are already in work at Bell’s Amarillo, Texas assembly facility.
Josh O’Neil, 525 program flight test manager, told AIN that load level survey testing was completed in the first half of this year. “We’ve completed nearly all of the development testing needed for certification and are beginning the transition to certification flight testing,” he said. “We’re looking toward the finish line and getting the FAA in here to fly the data with us and then beginning the report generation required for certification.”
He said that there has been some confusion in the industry around the special certification conditions Bell has applied for that have shown up in public documents. He said the majority of those were related to Bell’s fly-by-wire (FBW) system for the 525 and are merely a way to find common ground with regulators inherent with a “next-generation vehicle” when “[existing] regulation didn’t foresee some of this [FBW] technology. I wouldn’t characterize any of those as deviations or exceptions. It is all positive and we’ve gotten to common ground on a lot of [them].”
According to O’Neil, approximately 700 more flight test hours need to be logged before certification, with most of that flying to be done by the program’s two newest aircraft—ships #14 and #15. Ship #15 is the first production-representative aircraft, fitted with an oil-and-gas interior. The helicopter was recently completed in Amarillo and will join the other test ships at Bell’s Arlington, Texas flight-test facility in the coming days.
O’Neil said flight testing “has gone very well and yielded very little in the way of surprising results. In any program, you sometimes find things that aren’t quite what you expected. In our case, we have been very fortunate that it has come in as predicted.” He said the 525 is faster than originally predicted and likely will have a maximum cruise speed of 160 knots. The aircraft’s fly-by-wire system is also “set,” said O’Neil.
“The little bit of development we have ahead of us is really not related to technical issues. It’s a little bit of tuning and that kind of thing," he added. "We are very confident in the product.” O’Neil said customers who have flown the aircraft have given “very positive” feedback.
“We have entered a phase [in the program] where customer pilots have flown the aircraft and non-pilots have ridden in the aircraft,” he said, adding that Bell recently hosted a customer delegation from the North Sea region. During that visit, customers had the opportunity to review 525 training materials, maintenance processes, and tour the production line in Amarillo.
He said these customers were “extremely delighted” with Bell’s digital maintenance materials that use the same 3D engineering models to construct the aircraft. “You can click down in 3D and go from system to component to individual maintenance procedures with simple step-by-step instructions using the engineering data.”
O’Neil also said that development of the 525’s level-D full-motion simulator is well underway and that the target is to have it ready at aircraft certification. It will be located at the Bell Academy in Fort Worth, Texas. Other simulators will be placed globally as needed.
Digital Definition
O’Neil said Bell’s decision to design the clean-sheet 525 in the “digital thread environment”—a process that connects traditionally siloed elements in a company to provide an integrated and real-time view throughout a program product’s lifecycle—demonstrated its worth during this year’s cold-weather testing in Yellowknife, NWT, Canada, where two test aircraft were routinely cold-soaked to -40 degrees F, but nevertheless performed well over the course of a 2.5-month campaign.
“Digital definition allowed us to take into account the different impacts of thermal stresses at the component level and throughout the aircraft’s design in a design model that adds all interfaces and parts. It’s not a cheap way to go, but the value proposition is to design all of that in before you make a part, put it together, and try and make it work.” O’Neil said this year’s cold weather test data will be used to pursue flight-into-known-ice (FIKI) certification for the aircraft, which he estimates will occur within “a few seasons” after primary certification is received.
He said digital definition also will allow Bell to produce mission-kitted aircraft more efficiently. “There is a significant amount of kitting that has been part of the design of the aircraft from the outset. Quite a few offshore and SAR kits are designed into the aircraft now and have been brought along with the aircraft. The wire routing and the provisions for all the relevant kits have already been designed and will be tested as part of certification. The ones that haven’t will require pretty minimum changes in configuration and installation.”
O’Neil said that fielding a military variant of the 525 “is being discussed” but for now will take a backburner as Bell concentrates on gaining certification for the civil design. (In October, Bell announced its entrant to the Pentagon’s future attack reconnaissance aircraft competition—the model 360 “Invictus”—would have a main rotor system and FBW borrowed from the 525.) “We don’t have a [military] demonstration aircraft in plan.” However, he said discussion of a militarized 525 is “almost inevitable” due to its rugged airframe that meets all the latest amendments to FAA Part 29 certification requirements and its FBW flight controls.
The 525 has a projected mtow of 20,500 pounds, a maximum range of 580 nm (no reserve), and passenger seating for 16 to 19 (commuter/high-density). The aircraft is powered by two 1,800-shp GE CT7-2F1 engines driving an all-composite five-blade main rotor system and a four-blade tail rotor. GE Aviation received FAA type certification for the CT7-2F1 earlier this year.
Bell's 525 will incorporate a triple-redundant fly-by-wire flight control system with a BAE flight computer and the Garmin G5000H touchscreen-controlled glass panel integrated avionics suite with four main displays and Telligence voice-command capabilities. The company has not officially disclosed the number of orders or the price of the aircraft. The program’s schedule has slipped in recent years following the fatal crash of its initial flight test aircraft in 2016 and a general deterioration of a major market segment for the aircraft—the offshore energy industry.