Commercial, Products

Bell Raises 525 Performance Targets as Fly-by-Wire Development Progresses

By By Thierry Dubois, on Twitter: @aerodub | July 17, 2013
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Bell Helicopter is improving the performance of the 525 Relentless medium twin. Although the helicopter has not flown yet, it seems design engineers have refined their calculations or revised their objectives. In addition, development of the fly-by-wire control system is well under way. The eight-metric-ton-class Relentless was unveiled in early 2012 and targets offshore oil and gas operators.

Maximum cruise speed is now said to be 155 knots, instead of 140 knots, and range 500 nm, instead of 400 nm. Mtow increases from 18,000 to 19,300 lbs, while useful load raises from 4,000 to 7,400 lbs. As a result, the Bell 525 will be able to fly six passengers over 500 nm, with PC2e takeoff performance in ISA+20 temperature conditions.

Development of the fly-by-wire control system is ongoing. Despite being poised to be the first on a civil helicopter, the system is not causing any delays, according to Bell officials. The maiden flight is still scheduled for 2014.


“Bell is in charge of the software, including redundancy, built-in tests and emergency situation modes,” Jeffrey Lowinger, Bell’s executive vive president of engineering for XworX and commercial programs, told Rotor & Wing. Meanwhile, BAE Systems has responsibility for the computer hardware and Moog for the actuators.

“We have a certification basis with the FAA,” Lowinger said, referring to the AW609 tiltrotor. Before AgustaWestland took over Bell’s stake in the program in 2011 (then known as the BA609), it was a joint program and Bell still has a role in AW609 fly-by-wire development. The AW609, however, has seen its planned certification date postponed numerous times. The latest update from AgustaWestland indicates a 2017 certification, which would be 14 years after the first flight of the BA609.

Fly-by-wire enables flight envelope protection, which obviously brings more safety into the helicopter’s design. But it has other, less expected benefits. “As you avoid regimes the crew should not enter, you no longer need some margins you usually build into the airframe, so you can take some weight out,” Lowinger emphasized. This is especially beneficial to a large aircraft like the 525, he added.


Bell 525 cockpit with Garmin G5000H at the Paris Air Show. Photo by Thierry Dubois


In the cockpit, sidesticks free up space in front of the pilots, as there is no more central cyclic column. The pilots thus have a better view of the displays and improved situational awareness, Lowinger pointed out. The new architecture also replaces bulky linkage with underfloor wires. Hence the possibility to introduce crew doors, he explained.

Bell Helicopter claims a fly-by-wire control system even makes flying easier, as it get rids of coupling. In other words, a single-axis input does not have to be followed by compensation. The next generation of pilots, which the new cockpit – also featuring Garmin’s G5000H avionics suite – has been designed for, can expect a reduced training time. Bell started manufacturing the 525’s airframe on June 26 in Amarillo, Texas.

Related: Airframe News


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