Bell will certify the 525 Relentless using four test aircraft, and a senior Bell executive maintains the company retains confidence in the super-medium twin’s original design. The program has stood down flying since the fatal crash of the first prototype, FTV1, registered as N525TA, on July 6.
The NTSB is continuing its investigation as to why the main rotor blades struck both the tailboom and the nose during the in-flight break-up sequence that destroyed the helicopter and killed both test pilots. FTV1 was one of three 525 prototypes in the flight-test program, which at the time was budgeted for five aircraft. FTV1 is believed to have been conducting tests at or near Vne speeds when main rotor rpms dropped off and the main rotors significantly “departed their normal plane of rotation,” according to an NTSB spokesman.
Bell is continuing assembly of the next two flight-test aircraft and beginning the build of the first several customer aircraft, according to Larry Thimmesch, vice president of Bell 525 sales. Thimmesch said FTV4 is heavily kitted with search-and-rescue equipment and more flight-test instrumentation than originally planned. It should be ready to fly early next year. FTV5 will have a lot of the oil and gas kits on it. Between those two aircraft, approximately 50 kits will be certified as part of the initial flight-test program. Aircraft six through nine are in structural subassembly. “We are moving forward. We understand our production configuration,” Thimmesch said.
Thimmesch said Bell has been spending the downtime modifying the test aircraft to the latest production configuration and continuing non-flight testing, including drive, system and structural testing, as well as making continued progress with certification authorities in Canada, the U.S. and Europe. Bell is using its Fort Worth Systems Integration Lab to continue to work software updates into the aircraft’s Garmin G5000H avionics and fly-by-wire control system. “We have more than 40 software packages on this aircraft and [the 525 Relentless Advanced Systems Integration Lab] is a great platform to mature those and validate the latest software drops and to integrate some of those improvements in the system,” Thimmesch said. “The fly-by-wire system was very mature at first flight. The inner control loops were perfect. The only thing we had to change were some of the outer loops because of some of the contour changes we made on some of the overhead cowlings” to improve airflow. He called the 525’s FBW system “rock solid.”
Bell also is continuing design work on add-on kits that will be part of future configurations, Thimmesch said. “Really, the only thing on the program that has not moved forward is actually flying the aircraft. And [before the accident] we really had flown the envelope of the aircraft and we really understood the aircraft.” Thimmesch said Bell and the NTSB are working together “very aggressively” to get the 525 back in the air. “We have a return-to-flight team working with the FAA hand-in-hand. That has been very productive,” he said.
“The confidence in the aircraft within Bell is as strong as it has ever been,” Thimmesch said, adding that when the NTSB concludes its investigation Bell will have “very clear messaging to the industry about the helicopter.”