Keeping aging aircraft flying long past their originally intended retirement dates is a growing challenge for North Atlantic Treaty Organization (NATO) countries concerned with unacceptably low mission-readiness rates – the percentage of time that defense assets are in adequate condition to perform at least one mission.
In the US, for example, only three out of 50 aircraft types met their mission-capability goals of 70% for most of the fiscal 2011-2019 period, the US Government Accountability Office recently reported.
Frequent deployments of decades-old aircraft over the past 20 years have taken a toll, particularly on American, British and French airplanes and helicopters. Heavy demands, combined with aging aircraft, requires more maintenance, upgrades and enhancements – also known as sustainment – for the aircraft to remain operational beyond their expected lifespans.
In contrast, commercial airline operators consider anything less than 98% ready-to-fly performance of their aircraft fleets unacceptable.
Adding to the pressure to extend the life of existing defense assets: NATO-member countries’ static defense budgets, exacerbated by the high cost of new technology. The combination makes it extremely to replace aging equipment with new systems, which can then take 10-15 years or more to develop and put into operation.
One increasingly popular strategy for troubleshooting, repairing or upgrading aircraft? Using virtual twin experiences, which allow crews to visualize issues in interactive 3D and simulate the results of different approaches, to enable quick identification of optimal maintenance strategies.
“We’re building a blueprint for a unique approach to improving mission-readiness of critical defense systems – a blueprint that will become prevalent across the military – while helping the government to develop the requirements needed to standardize what we’re doing,” said Melinda Laubach-Hock, director of sustainment at Wichita State University’s National Institute for Aviation Research (NIAR). “When other contractors follow in our footsteps, government customers will understand the level of fidelity they need in these computer models.”
Boosting mission readiness with virtual twins
NIAR, for example, is spearheading a project to demonstrate how virtual twin experiences can improve the sustainment of legacy airframes.
NIAR’s goal, which it is pursuing in cooperation with industry and government partners, is to help boost mission readiness of certain defense systems, including the B-1B Lancer bomber and the UH-60L Black Hawk helicopter, while reducing maintenance costs.
Both aircraft were designed and manufactured mostly from paper drawings decades ago, but planned retirements for the B-1B and the UH-60L are now 2040 and 2050, respectively. Converting those drawings to interactive virtual twin experiences that enable rapid analysis of various sustainable strategies should greatly accelerate maintenance teams’ ability to identify, simulate, test, verify and implement maintenance strategies and upgrades.
Additional US Army and Air Force equipment will undergo the same process. The F-16 Falcon – more than 2,200 are deployed by air forces around the world – will be the next program targeted for virtualization. No retirement date has been set for the F-16, which entered operational service with the US Air Force in 1980.
A memo from then-US Secretary of Defense James Mattis, establishing a goal of 80% mission capability for certain defense systems, prompted the NIAR initiative. For example, the B-1B’s mission capability was less than 53% in 2017. Congress responded to Mattis’ call to action by authorizing funding to employ technology to improve readiness.
“We’re building a blueprint for a unique approach to improving mission-readiness of critical defense systems.”
Melinda Laubach-Hock, Director of Sustainment, NIAR
While NIAR’s work may not bring the B-1B and UH-60L fleets’ readiness up to Mattis’ 80% target, the institute and its partners are confident of achieving significant improvements, said Laubach-Hock.
NIAR and its government partners strategically selected airframes for the program, targeting those where the addition of virtual twin technology will have the largest impact in extending the platforms’ service life. As a result, “now we’re starting to see military leaders include funding for digital engineering,” Laubach-Hock said.
Forecasting the future
The two current programs involve reverse engineering both aircraft, beginning with disassembling them down to the nuts and bolts and digitally scanning nearly every part to create 3D models. Using the scan data and legacy engineering drawings as a template, the NIAR team will then create manufacturing-quality, 3D computer-aided design (CAD) models. These models will be digitally reassembled to create the airframe’s virtual twin, an exact digital model of the airplane as it exists in the physical world.
In addition to the geometrically correct virtual twin, the team will develop high-fidelity engineering models and validated them, using stress and strain data obtained either through structural tests or airframe operation. Once validated, virtual “loads” can be applied to these models to forecast structural failures, fatigue, corrosion and cracking under different flight conditions over time – a predictive maintenance capability that largely eliminates the age-old approach of only repairing something after it breaks.
As of mid-summer 2021, NIAR is about halfway through the two-year UH-60L program and was digitally reassembling the rotorcraft. In parallel, a NIAR technical team is about 18 months into the six-year B-1B program and preparing to complete the digital modeling of its wing structure.
By producing a physics-based virtual twin, engineers can capture the digital heartbeat of entire defense systems. Each one will serve as a living record. People who service these aircraft will be able to use predictive analytics – the “experience” portion of virtual twin experiences – to devise and validate appropriate maintenance schedules and processes to optimize mission-readiness – including predicting when a specific part should be replaced, based on the mission profile and flight hours.
“We’re using digital technology to look at potential problems that could occur 10 or 15 years from now, so the Army and Air Force can become very proactive when it comes to sustaining their assets instead of having to be reactive,” Laubach-Hock said. “The virtual twin provides a single authoritative source of truth for all the data needed to maintain legacy systems.”
France’s 10-year plan
The concept of coupling virtual twins with the power of big data and analytics to achieve smart sustainment isn’t unique to the US Department of Defense.
In France, a business innovation platform for creating and managing virtual twin experiences is the centerpiece of a 10-year maintenance agreement between airframe manufacturer Dassault Aviation and the Aviation Maintenance Division of the French Ministry of Armed Forces. The project’s goal: to optimize the availability of 152 French Air Force and Navy Rafale fighter aircraft, whose readiness hovers around 70%, a Paris-based defense industry consultant said. The RAVEL (RAfale VEticalLise) contract covers most of the airframe of the multi-role aircraft, which is expected to remain in service beyond 2050, GIFAS, the French aerospace industry trade organization, reports.
Long term, Dassault Aviation expects to improve the availability, or “Maintenance in Operational Condition” (MCO), of the Rafale fleet to at least 76%. In addition, the ministry reports that extended logistics services will enable the fleet to carry out more operational missions. Predictive maintenance is considered the key to achieving this level of mission readiness, so the program’s integrated data environment is built on a common data model covering a defense system’s entire lifecycle, with all data relationships managed by the platform.
The platform collects all Rafale usage across the fleet, which enables monitoring of RAVEL contract-stipulated performances, collects lessons learned and enriches predictive maintenance algorithms. It also can securely process data from the fleet and generate individual aircraft “health records.”
Thus far, France is the only European NATO member that has implemented the virtual twin approach to improving mission readiness. NATO’s other European members understand the concept but are not yet prepared to implement smart sustainment. As one European aerospace and defense consultant with close ties to NATO put it: “They’re still trying to figure out the art of the possible.”
Future uses
In service, every aircraft behaves differently and requires specific maintenance based on its operational history. Therefore, a virtual twin experience may be integrated with individual vehicle health and usage monitoring systems to provide fleet operating insights. On-board sensor data and usage information for each aircraft provides a rich cache of data for analysis, to better understand system performance and reliability.
“A virtual twin allows the development team to perform more detailed analyses earlier, ensures a perfect fit during initial production and allows testing to begin earlier. This reduces risk.”
Dina Halvorsen, Program Director, Sikorsky Aircraft
Beyond sustainment, many defense contractors now employ virtual twins to develop new aircraft.
“The payoff of a virtual twin manifests itself across the entire lifecycle of the product – design, production and sustainment,” said Dina Halvorsen, program director at Sikorsky Aircraft, which manufactures the UH-60L. “It manifests itself in design with lower development costs and reduced time to field the product. A virtual twin allows the development team to perform more detailed analyses earlier, ensures a perfect fit during initial production and allows testing to begin earlier. This reduces risk.”
For NATO in general and the US Department of Defense (DoD) in particular, the use of virtual twins represents a new paradigm for extending the operational life of complex hardware.
“It’s not a matter of whether we’re going to apply this technology to more platforms, including ground vehicles, but rather what are we going to do next, based on the greatest need,” Laubach-Hock said.
Read more about the challenges and opportunities facing the defense industry today.
Tony Velocci is former Editor-in-Chief of Aviation Week & Space Technology (AW&ST) magazine and remains deeply engaged in the aerospace industry. At Aviation Week, he received the distinguished McGraw-Hill Corporate Achievement Award for Editorial Excellence and was named the Royal Aeronautical Society's Aerospace Journalist of the Year (2006 and 2002).