Bell Helicopter responded this week to the NTSB’s recent report on the crash of a Bell 525 during a test flight in 2016. “In the time since the accident, a small team of Bell flight technology engineers, pilots and flight-test specialists have worked with the NTSB through the course of the investigation,” company spokesperson Blakeley Thress told AVweb in an email. “Several changes to the aircraft have been implemented and a carefully planned test approach is in place to complete the envelope expansion and certification testing.” The company remains committed to the 525 program, Thress added. “The continued work of the program team will result in a reliable, innovative helicopter with advanced rotorcraft safety features when it comes to market.”
Company officials also told the Fort Worth Star-Telegram last week that Bell technicians had “carefully studied the cause of the vibration, which had never been encountered before.” The vibration was caused by “an unanticipated combination of very high airspeed with a sustained low rotor RPM condition,” according to the statement. After the crash, Bell enhanced its filtering system on the side-stick controller, so its vibrations are not passed on to the rotor system. Also, filtering was added to the control system to stabilize the aircraft during gusts and maneuvers, the Star-Telegram reported. The two pilots were conducting tests that included shutting off one of the aircraft’s two engines to see how the helicopter would perform if one engine failed. Both pilots died in the crash.
