Bell’s New 525 Super-Medium Twin Takes Shape As Manufacturing Begins

Farnborough Air Show » 2012
July 8, 2012, 3:00 AM

Bell Helicopters is pressing ahead with the secondary design phase for the development of the new 525 Relentless helicopter that it launched in February. Here at the Farnborough International Airshow, the U.S. airframer is displaying a mockup of the super-medium twin, which is on track to make a first flight around the turn of 2013/14 and then enter service in 2015.

“We’re now getting into the detailed design in a secondary level that includes [plans for] on-condition monitoring, ergonomics and maintenance access, and ensuring that the aircraft is corrosion averse,” Larry Thimmesch, Bell’s vice president of new programs, told AIN. Engineers are building a series of mockups aimed at “validating the intersections between the customer and the product.”

Also at Bell’s headquarters in Texas a simulation cabin has been built to serve as a full aircraft simulator for ground testing. It is being used to develop the mathematical models and control laws that will determine how the aircraft is handled and how it maneuvers. The unit also is being used to validate ergonomic design within the cockpit. A systems integration lab is also being used to validate all aircraft systems ahead of any flight testing.

With work continuing with the Relentless customer advisory panel, some digital design models have already been released to the production department. This means that work on the flying prototypes can get under way.

“Nothing has changed in our intent,” said Thimmesch when asked whether certification and service entry goals are on track. “But our biggest focus now is getting it right from a customer perspective. [Certification] will be quicker than we have done it in the past.”

Bell, which has yet to confirm a list price for the 525, is not yet taking firm orders from prospective customers as it continues to consider different aircraft configurations and applications. The customer advisory panel will continue giving input right up to the 525’s entry into service.

The Relentless is the largest civil helicopter in Bell’s history. The program is a major departure for a company that, since the Vietnam War, has counted on military sales for a large share of itsrevenue.

The new rotorcraft is an 18,000-pound-“plus” ship with an expected range of more than 400 nm, a speed near 150 knots and a ceiling of 20,000 feet, aiming it squarely at the oil-and-gas market. U.S. offshore operator PHI is the nominated launch customer and also heavily participated in the customer advisory panel that shaped the 525’sdesign. It and other operators told Bell that they wanted an affordable new aircraft that delivers improved payload range capability, a spacious cabin, more cargo volume and improved situational awareness.

The helicopter’s value proposition is to offer medium helicopter economics while delivering large helicopter comfort and capabilities. It will be powered by a pair of General Electric CT7-2F1 engines (1,800 shp each) driving an all-composite five-blade main rotor system and a four-blade tailrotor.

The rotor system and transmission have been optimized for the engines. The aircraft will incorporate a triple-redundant fly-by-wire flight control system with a BAE Systems flight computer that borrows lessons learned on the Bell/Boeing V-22 and AW609 tiltrotors.

The big helicopter also will feature the new Garmin G5000H touchscreen-controlled, glass-panel integrated avionics suite with four main displays and Telligence voice-command capabilities, two key components of Bell’s new ARC (awareness, react and control) cockpit. The ergonomic cockpit features pilot seats that J-track, pushing back and swiveling outward, for ease of egress. Right-hand, fly-by-wire side sticks replace the conventional cyclics. The ARC cockpit promises flight crews a higher level of comfort and awareness, including the ability to see over the helicopter’snose.

ARC is intuitive and can sense, for example, when system failures require an autorotation and it automatically sets up the helicopter to enter one. “In critical situations the system identifies the problem and does something about it,” said Thimmesch.

While chock-full of new technology, Thimmesch said that the 525’s cockpit will not be so complicated as to befuddle pilots. “This is the first touchscreen interface in a Part 29 helicopter, but we are not overdesigning this thing so it is the Starship Enterprise. This technology makes sense to the operator,” he said. That includes “unparalleled” real-time health usage and monitoring systems data transmitted via uplink with trend monitoring and diagnosticcapabilities.

The 525’s composite and metal airframe also features an emphasis on ease of maintenance and durability. “Our design goal is to be able to remove and replace any [line replaceable unit (LRU)] aircraft component in ten minutes, and that includes access,” said Thimmesch. “To do that we used quarter-turn fasteners for nonstructural aircraft panels and standard link fasteners to get around structural panels. Also, you don’t have to remove one LRU to get at another,” hesaid.

Thimmesch said Bell evaluated more than 20 years of data to identify maintenance-cost drivers for the offshore industry in designing the 525 and found that 32 percent of maintenance is related to fighting corrosion. The manufacturer is using monolithic composites in places susceptible to corrosion, such as the lower airframe structures, and also designing in floordrainage.

The 525’s tailboom has been designed to provide less resistance and more lift that translates into higher hover-out-of-ground-effect altitude than conventional designs. The boom’s aerodynamic shape will allow 88 more horsepower to be directed to the main rotors compared with conventional designs. It directs downwash to provide counter-torque.

Entry to the 525’s 4.5-foot-tall cabin is through a pair of hinged doors located between the cockpit and the first row of four seating areas or through a pair of large aft sliding doors. Each seating area offers comfortable four-abreast seating, for a total of 16 passengers; the company also has a higher density version in mind.

The new helicopter will be built at the Bell’s Amarillo, Texas plant, currently home of the Bell/Boeing V-22 final assembly line. That program has been a cash cow for the company, but is widely seen as winding down in the face of anticipated Pentagon budget cuts. It is likely that Bell will offer a military variant of the 525 in thefuture. Program costs are estimated near $500 million and are part of a $1 billion facility, research-and-development and inventory investment program the company announced earlier thisyear.

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