World’s first fly-by-wire helicopter provides passengers’ comfort
WITH a luxurious 88-square-foot cabin and space to fit 20 passengers in boardroom-style comfort, the Bell 525 Relentless makes some high-flyers happy in the sky.
Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface that provides a level of control previously unseen in a commercial helicopter.
The craft is aimed to be a limo in the sky for offshore oil and operations and also expects to be used for difficult search-and-rescue and firefighting missions due to its huge capacity and improved control in tough conditions.
Depending on the configuration of the interior, the 525 holds 16 or 20 passengers along with the two flight crew with what the builders say is best in class passenger cabin height (137cm) and floor area (8.2 square metres).
The 525 is the first commercial helicopter to incorporate fly-by-wire flight controls, which delivers ‘superior handling qualities and increased level of safety’ with features that, among other things, stabilise the aircraft without the need of input from the pilot.
For the technically savvy, it is also the first commercial craft if its kind to include the Garmin G5000H, a glass touchscreen avionics suite for the flight deck that replaces knobs and switches with what they say are simpler controls and information, such as weather, charts, traffic, terrain and Global connectivity options, for the pilot. For the 525 it’s been rebranded as the ARC Horizon system.
The Senior Vice President of Commercial Programme, Bell 525 Helicopter, Matt Hasik said: “When we started designing the Bell 525, our customer advisory panel really stressed the need for a flying experience that’s safer, easier and more repeatable”.
“We can design a product with class-leading speed, range, and a host of product features, but the real focus of the Bell 525 was to make a step-function improvement in capability for the pilot, enabling him/her to manage every aspect of flight in the cockpit with a new level of awareness and control.”
The Bell 525 Relentless leverages a triply redundant flight control system to maximize safety and control. Pilot inputs are electronically transmitted and processed by the flight control computers. With three flight control computers and triplex electro-hydraulic actuators, the digital FBW control system provides full-authority stability, control and guidance; offering reduced pilot workload in pitch, roll, yaw and lateral and vertical motion.
Fly-by-wire also makes the overall flying experience easier for operators. The open, clutter-free cockpit features two tower-mounted cyclic and collective side sticks and unique trim pedals that greatly improve control throughout the flight envelope. The flight control system and flight director interface can automatically fly the helicopter in a variety of modes. The flight director can also be coupled to an autopilot system to provide hands-off navigation. However, if preferred, the pilot can also choose to decouple the flight director from autopilot and manually fly the Bell 525.
In case of a double engine failure, the controls give the pilot a head start. The autorotation procedure in a conventional helicopter begins with the pilot lowering the collective pitch to keep the rotor turning fast enough. If the pilot fails to do so within a handful of seconds, rotor rpm may drop dangerously to 80 percent. At this point, the pilot may never get the required 100 percent back, meaning the engine failure will translate into a serious accident. The 525’s flight controls automatically lower the collective pitch after a double engine failure. It does so immediately, ensuring rotor rpm will remain at or above 100 percent.
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