Digitizing the F100 Engine and Researching Parts for Additive Manufacturing

The CTMA Program is collaborating to improve the maintenance and sustainment of aircraft engines through a partnership with the National Institute for Aviation Research (NIAR) and the Air Force Life Cycle Management Center by creating a digital twin engine along with the Workbench for Additive Materials.

“The Air Force’s Propulsion Directorate is a recognized leader in the implementation of innovative technologies. Our partnership with the NIAR on the F100 Digital Twin and the Workbench for Additive Materials (WAM) [database] will accelerate the adoption of 3D metal printing and foster competition. Both are instrumental for resolving pervasive material shortages impacting legacy propulsion readiness,” said Beth Dittmer, USAF Propulsion Integration and Innovation Division Chief.

This initiative—Digitization of Jet Engines to Improve Maintenance—is using the F100 engine as a testbed, utilizing digital twin technology to improve engine sustainment across the DOD. The project’s research into additive manufacturing is also expected to benefit the commercial aircraft industry.

The F100 engine is a mainstay for the US Air Force, logging more than 30 million engine flight hours since it powered its first F-15 in 1972. The F100 series remains in use, with more than 3,800 in service, and it will continue to be an important engine far into the 21st century.

To advance F100 engine repair, the team is creating a digital twin of the F100 engine. A digital twin is a digital replica of the physical engine that links the virtual and physical environments. Both operational and maintenance data associated with the physical engine system are supplied to the virtual environment to update the virtual model in the digital twin. The digital twin becomes a precise and up-to-date representation of the physical system that also reflects the operational context of the physical twin, making it possible to track the performance and maintenance history of each physical twin over time, detect and report anomalous behavior, and recommend maintenance.

To create the digital twin, the team is using digital engineering principles, including a model-based systems engineering (MBSE) road map and strategy. MBSE is the formalized application of modeling to support system requirements, design, analysis, verification, and validation activities beginning in the conceptual design phase and continuing throughout development and later life cycle phases.

The team is creating a level 1 digital twin of the F100 engine (modules, components, and parts) from government-furnished technical documents and physical assets. Digital twin maturity models typically delineate five levels, with level 1 being a 2D map/system or a 3D model, object-based, with no metadata. The highest level, Level 5, enables automatic asset control, operation, and maintenance.

Along with creating a digital twin of the F100 engine, the initiative is concurrently creating the WAM database that will be a repository for material specifications, material allowables, and the associated pedigree information for additively producing parts, which is imperative to improving asset readiness and is a high priority across the DOD.

Currently, data on additive materials is still in an early stage and is not easily accessible. This project will change that by producing a database that will contain material data to help engineers design parts using the same or different materials used on the legacy part. The idea is to be able to create parts additively to help speed up production, expand the vendor base with approved suppliers, and to build a comprehensive material specification repository for government use.

“Right now, we’re in a situation where we have to reinvent the wheel every time we want to use a new machine or a new vendor,” said Dr. Mark Benedict, Air Force Research Laboratory Additive Manufacturing Director and America Makes Chief Technology Advisor (CTA). “The hoped-for expectations are that we will reduce the generation of duplicative data and really understand the data generation needs, so we don’t keep doing the same experiments again and again. Long term, this project will help us understand what is unique about a particular manufacturer or material process.”

The WAM project is proceeding in three phases. First, the team is reviewing data sets, security requirements, servers, and software to decide on the optimal structure for the database. Next, they will release a beta version of the database to a small, select group that works with design engineers, including engineers from the Air Force and Army, and use their feedback to improve the database. In the final phase, the team will launch the working database government-wide. Access to the database will initially be for DOD agencies and other interested government agencies. In future phases, access will also be granted to specific supporting contractors who work in the field.

“If somebody wants to additively manufacture a part, this database will provide the material data to start the design work. This could include minimum allowables, machine parameters, material specifications, and pedigree information to understand which machines were used to create the data,” said Polly Kipfer, USAF Program Manager for the WAM project.

“We’re generating data for three different metals: aluminum F357, nickel alloy 718, and a cobalt material,” said Dr. Benedict. He added that titanium data will also be included.

“The datasets include the information created by building coupons with the metals that we then run through tests such as tensile strength, porosity, hardness, etc. Having these specifications in the database will allow engineers with access to run their own analytics to see if a material will work for the part they want to build. By recording the data in the datasets, we build on work already accomplished and stop duplicating builds and tests that are both costly and time-consuming. The engineer can download the information for the material he wants to use and start analyzing and designing for his purpose,” said Kipfer.

The database will do more than report data from mechanical testing.

“There’s the somewhat misguided notion that we just create a database and throw in all the data and we’re good,” said Dr. Benedict. “The reality that we’ve seen and documented is that if you don’t understand the specifics of how data was generated, you will not be able to draw a one-to-one comparison. These specifics are referred to as pedigree data. For example, I may have an additive printer that was working with titanium at 30-micron layers, and a different printer working with titanium at 65-microns. Each will yield different mechanical performances. If I didn’t know that those two had those differences, and I just compare the outcomes, it might lead me to some very inappropriate design decisions or to take more risks than I should. So, it’s really not just sharing the numbers, but sharing how those numbers were achieved, that is needed to promote confidence in the material across the whole of government.”

“For additive, there’s definitely an emphasis on pedigree and fidelity of data that is required to make the right decisions on designs that meet the military’s criteria for airworthiness,” added Angel Rivera, Senior Materials Engineer for the USAF Propulsion Additive Manufacturing Team. “This database will be a location that government engineers, who are responsible for the safe flight of their systems, can easily access and become familiar with these materials and these processes.”

The project is slated to wrap up in November 2025.

“This database is not solely for the Air Force,” said Dr. Benedict. “This is meant to be an across-government activity—primarily, of course, for the DOD, but also for NASA, potentially the Federal Aviation Administration (FAA), the National Institute of Standards and Technology (NIST), or other parties interested in this type of data.”