Bell could finally gain certification for the 525 Relentless this year, ending a 10-year development effort for the super-medium-twin helicopter.
Speaking on a company video, 525 programme manager Byron Ward says that “great progress” was made towards certification in 2020, completing evaluation of the drive system, plus bird-strike, lightning and fatigue tests. The “primary focus” is now on “flight testing with the FAA in the cockpit”, he says.
“At mid-year 2021 we plan to provide all certification artefacts to the FAA to ultimately achieve type certification,” he says.
Bell is working “in parallel” with other regulators, such as the European Union Aviation Safety Agency, to “provide [non-US] validation just as soon as we can”, says Ward.
The date provided by Ward chimes with a recent proposed special condition published by the US Federal Aviation Administration (FAA) relating to certification of the helicopter’s fly-by-wire controls.
In that notice, published in the Federal Register at the end of January, the FAA said that Bell was targeting a “type certificate issuance date of December 31, 2021”.
Bell initially applied for the 525’s type certificate in December 2011, says the FAA, but this process has been subject to multiple extension requests, with the most recent of these coming on 12 November 2020.
No service-entry date has been given, but this milestone will likely take place in 2022, providing Bell hits its certification targets.
While undoubtedly a hugely impressive helicopter, Bell has struggled to bring the 525 to market. Its development was scarred by the fatal 2016 crash of a flight-test aircraft, in which two pilots were killed, plus the evaporation of a key market with the crisis in the oil and gas industry.
Nonetheless, Bell is persisting with its ambitions in the offshore transportation sector. During the same video presentation, Brendan Lanigan, senior aircraft performance specialist, said that preliminary certification data showed the 525 to be “3dB quieter than the [Sikorsky] S-92 in most flight conditions”.
Internal noise was also “4dB less than at cruise speed than a competitor aircraft that we measured”, he adds.
The 12t Sikorsky heavy-twin is the mainstay of long-distance oil and gas operations, particularly in the North Sea region. While the 9t 525 can accommodate only 16 passengers in a typical offshore layout, three fewer than the S-92, Bell claims the Relentless will burn 30% less fuel per hour “than a typical large offshore helicopter”.
Bell is additionally working to add ice protection to the 525, says Christos Bais, manager for avionics and safety. The design of the system is “well under way and will be part of a follow-on certification”.
The 525 is powered by twin GE Aviation CT7-2F1 engines, each providing 1,980shp (1,480kW) at take-off power. Using a pair of reduction gearboxes, the speed of the driveshaft is cut to under 6,000rpm before it enters the main rotor gearbox.
Bell says this, plus several other improvements to the transmission, will increase safety; tests have shown a run-dry capability of over an hour for all the primary gearboxes, and over 5h for the accessory gearboxes.