Commercial, Products, Public Service

Bell 525 Progress Continues: Focus on Relentless Systems & Simulators

By By Pat Gray | February 1, 2013
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Bell 525 Relentless in the hangar at the manufacturer’s facility in Amarillo, Texas.

During an update session with Larry Timmesch, vice president of Commercial Programs at Bell Helicopter, along with David King, chief engineer on the Bell 525 Relentless, it became apparent that the company is committed to bringing the Relentless into the “super-medium” twin market. The first helicopter build is set to take place during second quarter 2013 in Amarillo, Texas. The first flight is scheduled for mid-2014. Timmesch states that Bell has a yet-unspecified first delivery date and that orders will be taken after the first flight.

As of June, the 525 is locked into the preliminary design phase for the basic configuration and interfaces. Amarillo was selected as the manufacturing site, with Fort Worth designated as the flight test facility. The manufacturer has assembled modular build teams for defined areas of construction such as rotor systems, control systems, engine selection/installation, landing gear, cabin layout and cockpit configuration. Weight has also been set, though Bell doesn’t plan to release those figures for a while. All major suppliers are on board and some parts are already being built within the supply chain and at the factory.


Relentless will be the first commercial production helicopter that is 100 percent fly-by-wire. The flight control system (FCS) is a real focal point for Bell. In a sense, it will be acting as the “brain” of the helicopter by using its three computer control modules to sense and direct all control inputs, resulting in a highly stabilized flight in all axes. This is referred to as translational rate control (TRC) and is not to be confused with an autopilot. Perhaps a highly refined SAS would more aptly describe it.

David King (left) and Larry Timmesch in front of the Bell 525 display in PHI colors.

Works in Progress

The FCS has completed initial development and is undergoing link up configuration with the 525 input controls.

The avionics suite is the Garmin G5000H that uses touchscreen technology similar to smart phones. The menu selections are accessed through icons that look like Aps. There are three multifunction display (MFD) screens and the Garmin system is already set up in the mockup and in the simulator for testing purposes.

Bell has chosen the General Electric CT7 engine (1800 shp) and there are no plans for substitute engines.

All design and structural plans are digital using 3D virtual screens at every manufacturing and assembly point in the factory. There are no paper drawings. The helicopter is now in the detailed design phase and many of the digital drawings have been approved and released. 

A systems integration lab (SIL) is up and running. This engineering unit integrates all the systems that will be a part of the production aircraft and is now functioning doing preliminary testing of the flight controls, the avionics system and the tail rotor system.

Cyclic in the Bell 525 Relentless along with Garmin display panel.

A simulator cabin (SimCab) is also up and running for control law and math model development. This differs from the SIL. The SimCab reproduces most of the research done in the SIL. This cabin is a cockpit mockup with a 358-degree field of vision that is programmed for several scenarios such as offshore and HEMS and is flown just like any other simulator. At present it is used to validate SIL programs concerned with the fly-by-wire control modules and the Garmin Avionics suite and how they will relate to actual flight through the TRC process. As development progresses, the SimCab will become more sophisticated to the point where the initial test pilots will have considerable experience with flight performance prior to the first test aircraft leaving the ground.

The engineers allowed me to take a brief flight in the simulator and I chose the offshore configuration. It was an interesting experience. One example: while completing an approach to an offshore helideck, the simulator engineer, Nick Walton, said to note when my forward motion stopped over the deck. He then had me release all the controls and the simulator remained motionless over the deck at hover height. Using the collective beep button, I gently lowered the simulator to the deck and by reversing the input, raised it back to hover height. This was an early example of what Bell refers to as translational rate control. The demonstration model is still being refined but it will be an integral part of the production aircraft. The standard cockpit configuration will have a side-mounted cyclic control (as does the simulator) that allows for reduced stress, especially on long flights.

Prior to finalizing the design, Bell solicited input from a cross section of large operators designating them as the customer advisory panel (CAP). They have assisted in the design process by relating to their field experience with legacy helicopters, especially in the areas of easing maintenance access to components, writing of maintenance manuals and procedures and defining the necessary from the unnecessary throughout the design. Engineering groups from Bell have also gone out into the field to monitor some of the problems and solutions the operators deal with every day. Timmesch feels that the two-way feedback should result in a better product and better aftermarket communication.

The Bell 525 Relentless is on schedule and appears to on track toward the Bell Helicopter’s goal to provide a user friendly, safe, comfortable long-range helicopter for the 21st century.

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