With five prototype flight test CH-53K helicopters in assembly at Sikorsky Aircraft Corp.’s manufacturing facility in West Palm Beach, Fla., along with another two non-flying airframes ready for structural tests at the company’s main plant in Stratford, Conn., the development of the United States Marine Corps’ (USMC) next generation heavy-lift helicopter is at an exciting stage.
But while the aircraft itself incorporates cutting edge technology, its very creation has broken new ground within the industry, too, with the latest in 3D virtual reality (VR) technology used in the CH-53K’s design and manufacture. Indeed, the state-of-the-art process has already received two major industry awards: The American Helicopter Society’s 2012 Robert L. Pinckney Award (for notable achievement in manufacturing research and development for vertical flight aircraft or components), and a 2011 Department of Defense Top 5 Systems Engineering Award. The digital design process has also saved the company money, time and greatly reduced waste in the development process.
A replacement for the USMC’s ageing CH-53E Super Stallion, the CH-53K is a completely redesigned aircraft that only aesthetically resembles the older model. The new variant features three General Electric GE38-1B 7,500 horsepower engines, composite fuselage and components, a new split-torque main gearbox that improves power distribution efficiency, an elastomeric rotorhead, new anhedral swept tip rotor blades, digital avionics and a fly-by-wire flight control system. With virtually the same flight deck footprint of the “Echo” model, the “Kilo” will offer a 40 percent increase in power, meaning it can haul nearly three times the payload — or 13.5 tons of cargo over 110 nautical miles (204 kilometers) at 3,000 feet in 91.5 F (33 C) temperatures.
A Digital Design
Jim Andrews, deputy chief engineer on the CH-53K program, told Vertical 911 that Sikorsky has been using software to design and build aircraft for more than 20 years, but rarely has the rotorcraft industry seen digital technology used to this level. The CH-53K is believed to be one of the world’s first all-digitally designed and manufactured helicopters, with the aircraft first assembled in a VR 3D digital environment.
Interestingly, Sikorsky hadn’t originally set out to complete an all-digital design for the CH-53K, but, following the award of the $3.4 billion US system development and demonstration contract for the aircraft in 2006, the company realized that new digital technologies existed to improve the design and manufacturing process. This involved coupling VR to features of the latest version of computer aided three-dimensional interactive application (CATIA) software.
Sikorsky configured a VR “lab” to improve all facets of the design, systems integration and manufacturing process. It used a model-based design approach from the beginning to incorporate feedback from Marine Corps logistics and maintenance personnel, to make the aircraft as simple as possible to build, maintain, and operate. Andrews said the aircraft was designed to be “put together simply and maintained easily.”
The VR lab allowed Sikorsky engineers to “get inside” the aircraft before any parts of the airframe were physically built. This was done by surrounding the VR lab with cameras that detect sensors on specialized gloves and/or a helmet worn by the engineer, and then translate the engineer’s movements into a 3D animation on a large computer screen. “[It] brings you into the digital environment,” said Andrews.
Sensors can also be added to hand tools to simulate using the actual tool on the aircraft, and a force-feedback device actually provides a tactile input when a user “hits” an object, component, or bulkhead in the virtual world.
In the lab, parts were virtually installed and removed from anywhere on the aircraft, showing how components would fit, and how routine maintenance could be performed simply and easily in the operational world.
Component Integration
Subcontractors fabricate more than 70 percent of the CH-53K’s structure and components. To avoid potential pitfalls in outsourcing major components, Sikorsky leveraged VR technology to keep all of the subcontractors, and the customer (represented by Naval Air Systems Command), on the same page.
Four major suppliers are involved in the fuselage assembly. Aurora Flight Sciences (main rotor pylon), Spirit AeroSystems (cockpit and cabin), GKN Aerospace (transition section -— the rear of the fuselage containing the ramp and sloping upper deck to the tail), and ITT Corp. (tail rotor pylon and sponsons) were all embedded into Sikorsky’s digital environment.
During the design phase, weekly meetings were held with design teams and suppliers where all parties could walk “inch by inch” through the integration of various components in a digital mockup of the aircraft. Manufacturing and design engineers, mechanics, electricians, and inspectors were able to digitally create aircraft assembly plans and validate them on screen in the 3D VR world.
This integration and 3D VR technology allowed Sikorsky engineers to work “inside” the helicopter and, as they say it, “build before you build.” Prior to final assembly, the aircraft was put together from scratch in the virtual world. During the digital manufacture, engineers realized that there were accessibility issues in the tail and transition sections regarding hydraulics and wiring. The team was able to conduct two full redesigns of that section in the digital world to ensure proper fitment and functionality when the actual manufacturing began.
In another example of the benefits of the digital system, engineers, wearing VR goggles, studied over 100 sections of fuel line in the virtual aircraft, and discovered 20 areas that required redesign or alterations to the fittings. Fixing this in the virtual world, before manufacture, saved an estimated month in assembly delays valued at millions of dollars.
From Virtual to Reality
Once the design was finalized, components for the aircraft began manufacture and the Sikorsky team in Florida went to work assembling the first CH-53K, the ground test vehicle.
In place of assembly instructions on paper, the assembly team refers to instructions on laptop computers. The main landing gear, for example, will feature digital animation showing precisely how the assembly is to be completed.
Andrews said this approach “takes all interpretation away,” and that once assembly began, there were “almost zero questions from the guys on the floor,” who gave the system glowing reviews.
Andrews said that physical assembly had revealed no “major” design issues missed in the virtual world, and the only apparent weakness of the system was its inability to accurately model flexible components. He said that droop and sag of various wiring harnesses could not be accurately predicted in the CATIA software, so minor adjustments were made to wire bundles to prevent excessive droop or chafing.
The payoff for the digital integration was immediate and measurable. The team reported that parts were going together relatively quickly and large components did not have the fitment issues that have plagued past designs. A team member assembling the main rotor pylon said that, because the assembly was so seamless, the largest delay he was facing during assembly was the time it took him to get some of the 300 fasteners out of his pockets.
Assembly of the very first CH-53K was completed in half of the time it took to assemble Sikorsky’s previous development medium-lift helicopter. And Andrews predicts that the second prototype CH-53K aircraft, destined for flight test in 2014, will be assembled in 20 percent less time than the ground test vehicle. With such leaps in development time and costs, it should come as no surprise that Sikorsky plans to “build before you build” in all its future aircraft projects.