At the U.S. Marine Corps Air Station in Cherry Point, North Carolina, USA, officials with the Fleet Readiness Center East (FRCE) recently hosted the first-ever U.S. trials for a new cold spray technology application. Program officials say the results were promising.1
With annual revenue exceeding $835 million, FRCE is North Carolina's largest maintenance, repair, overhaul, and technical services provider, with more than 4,000 civilian, military, and contract workers. The depot generates combat air power for America’s Marines and naval forces while serving as an integral part of the greater U.S. Navy; Naval Air Systems Command (NAVAIR); and Commander, Fleet Readiness Centers.
If approved, the new cold spray technology would help reduce turnaround times and decrease costs for repairs that were not possible when using previously approved cold spray systems.
First Field Demonstration
In late 2019, NAVAIR materials engineers with the FRCE’s advanced technology team, along with representatives of VRC Metal Systems (Box Elder, South Dakota, USA), completed the first U.S. field demonstration of an on-aircraft structural repair using a mobile, autonomous cold spray metallization system.
Over the course of two days, the team completed an on-aircraft repair to the windowsill of a V-22 Osprey, as well as an off-aircraft repair to a surplus H-1 skid tube.
“The system operated better than predicted,” says Frederick Lancaster, lead for the cold spray metallization integrated product team at NAVAIR. “[It] worked as planned at five sites, in five different climates, at five different times of the year. Once it was programmed, the system worked without human intervention, on aircraft, and worked faster and more precisely than a human.”
The cold spray process bonds metal to metal in a relatively low-heat environment in order to deposit a coating onto a surface, or substrate. Solid metal powders are accelerated through a heated gas and directed toward a metallic substrate. From there, the moving particles impact the surface and embed in the substrate, forming a strong bond.
The repairs completed during the pilot trial were consistent with those made using a stationary cold spray system, Lancaster says. Once approved, the new, mobile system will support the on-site repair of aircraft materials and increase mission readiness through rapid turnarounds.
Saving Time and Money
“With this program, we’re looking to bring structural repair capabilities closer to the aircraft, so you don’t have to take an aircraft apart to repair it,” says Jessica Templeton, a NAVAIR materials engineer at FRCE. “The end goal is to take the most cost-effective way of making these repairs, and make them available at the lowest level possible.”
The team has targeted parts like aircraft skins—the outer surface covering much of the wings and fuselage—and windowsills, as well as areas on the tail as ideal candidates for repair without removal from the aircraft. Being able to repair parts to standard without major disassembly can lead to cost savings that are “pretty tremendous,” Templeton says. The autonomous aspect of the unit means that the work is done by a robotic arm which, after programming, requires minimal input from the workforce.
“Turnaround time is important, too,” Templeton explains. “Once you start routing these parts through the shops, that adds a lot of lead time to your repairs. With this technology, we would be able to repair existing parts to standards of airworthiness, rather than waiting for new parts.”
“It was realized early on in the deployment of cold spray technology that it would be more economical to perform repairs on-aircraft, in place, without any major disassembly,” Lancaster adds. “[With this program], we are testing the capability of the system to perform precision work autonomously.”
In determining which components to target for initial testing, the advanced technology team reached out to the depot’s many aircraft lines and asked for their “head-hurters.”
“Whenever we reached out to a platform, we asked them for their biggest item cost-wise or lead time-wise—the components they aren’t able to get that they need—and we tried to see if we could solve that issue,” Templeton says. “When we reached out to V-22, they came back with a list. Not every repair is feasible, because not every component is easily accessible on the aircraft, or easily removable.”
For example, one item on the V-22 wish list was a fitting that is impossible to repair with the depot’s existing cold-spray system without major disassembly of the aircraft.
“To remove it from the aircraft, spray it with cold spray, and put it back on is just not cost effective. If we could spray it in place, that would be the golden ticket,” Templeton says. “They wouldn’t have to take off all these different panels, and an entire wing piece, and disassemble these individually to allow us to cold spray in a booth—if we could spray it on the aircraft, or on a wing, that would be great.”
Challenges like these are the driving force behind development of the mobile, autonomous cold spray unit, but the system was also used earlier in 2019 to demonstrate repair of small-scale components during a Navy-wide cold spray event at the Marine Corps Base Hawaii. The Navy has employed cold spray technology for years, but this mobile, autonomous system could make that existing technology available in new and different ways.
Most cold spray systems currently used by the Navy are located in booths, which creates size limitations, Templeton explains. There are finite limits to the size of the components that can be treated in the booths, which means that parts often have to be removed from aircraft before spraying, or the components cannot be sprayed at all due to their size. Because this system is mobile, it can be fielded in locations that don’t have permanent cold-spray booths, lending itself to the possibility of on-aircraft repairs.
Another difference: The new system utilized a high-pressure cold spray, rather than the low-pressure systems currently in use at FRCE. Templeton says the high-pressure system is necessary for structural repairs, “to get the velocity, and get those particles moving at a fast enough pace to really impact and get that bond.”
The Path Forward
While the pilot testing was not conducted on an operable aircraft, and the repairs made are not-yet-approved procedures, the trials do give program leadership an idea of the system’s potential future capabilities for on-aircraft repair, Templeton explains.
“It’s definitely where we want to go with the cold spray, and where we see the technology needing to go,” Templeton says. “We’re trying to take this cold spray one step further and go toward structural repairs.”
The demonstrations took place as an initial evaluation of the program, which is a joint effort between NAVAIR and the U.S. Office of the Secretary of Defense’s Foreign Comparative Testing (FCT) program. By using the FCT and technology already developed and qualified by the Australian Defence Science and Technology Organisation, NAVAIR was able to shepherd the program to an advanced Phase III transition status in less than three years for under $1 million. That represents a cost avoidance estimated at $6 million over eight years of development, had the project started with the traditional Small Business Innovation Research program, Lancaster notes.
This testing represents the first in a series of demonstrations and assessments that will allow authorities to determine the airworthiness of these repairs, Templeton says. The next steps include fatigue testing, to gauge the strength of the materials and the bond; finite element analysis, which predicts how a product reacts to real-world force and physical effects; and many other evaluations. This first trial was a way to determine whether the on-aircraft structural repairs were logistically possible using a cold-spray unit.
“In the near term, the next step is taking proven and qualified cold spray repair processes for dimensional or for applying a metallic corrosion preventative coating and transitioning them to on-aircraft application,” Lancaster says. “The future is with structural repair on aircraft, now that NAVAIR has a proven system that can perform precise, automated, high-pressure cold spray repairs.”
If that process can be achieved, he adds, the system can be used to perform more on-aircraft corrosion damage repairs, along with dimensional and wear issues.
Source: U.S. Defense Video Imagery Distribution System, www.dvidshub.net.
1 “FRCE Pilots New Application for Cold Spray Tech,” Defense Visual Information Distribution Service News, Jan. 17, 2020, https://www.dvidshub.net/news/359608/frce-pilots-new-application-cold-spray-tech (Feb. 24, 2020).