Lockheed Tackles Test Data Complexity

Data management software helps accelerate test data analysis on F-35 program.

The F-35 Lightning II Joint Strike Fighter is shown during a test flight. Images courtesy of Lockheed Martin.

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By Brian Albright

December 1, 2014

The F-35 Lightning II Joint Strike Fighter is shown during a test flight. Images courtesy of Lockheed Martin.

Managing design test data can be a complex and arduous process. Managing test data for a massive, multi-billion-dollar, multi-national aerospace project is an even more monumental task, but one that is manageable with the right tools.

Lockheed Martin’s F-35 Lightning II Joint Strike Fighter (JSF) program is tackling just such a massive data challenge as it performs full-scale testing on aircraft airframes to ensure they meet life design requirements. With specialized software tools, the company has been able to provide deliverables ahead of schedule—an important achievement, particularly in a program that is almost as well known for its delays as its technological innovation.

In fact, the F-35 static and durability testing program is bigger than any program in the history of Lockheed, and is being performed faster rate than historical programs thanks to the use of nCode Automation and Glyphworks software. The tools have helped Lockheed manage the complexity involved with accessing, sharing and acting upon test data to improve and modify designs.

“These large scale tests generate tremendous amounts of data that must be monitored and stored for assessment,” says Marguerite Christian, senior manager, F-35 SD Structures Test IPT at Lockheed. “In support of this testing, nCode Glyphworks is used in association with nCode Automation to store and process static and durability test data. These tests are a key element of the structural certification of the airframe design.”

According to Chris Gray, applications engineer at nCode, the tests at Lockheed generate too much data to be managed manually. “In typical, non-aerospace implementations, tests might generate 200 channels or parameters,” Gray says. “Lockheed is generating anywhere from 1,800 to 3,000 channels.”

The nCode software is used to analyze and manage data from static tests that apply worst case loading conditions, and durability tests that repeat the loading of thousands of load steps to replicate several lifetimes of the aircraft in service.

Since 2006, Lockheed has used nCode Automation to help engineers manage, search for, access and examine key F-35 test data. Engineers can download data sets on demand and report back results. Engineers are also able to share data with other project partners, and perform automated time, frequency, statistical and fatigue analyses.

The company uses Glyphworks, a test data analysis system for durability and fatigue analysis, to evaluate how behavior of the structures have changed over time, which could indicate cracks or other system issues.

Monitoring Thousands of Channels

Lockheed uses the nCode software to help manage data from two types of tests: static and durability. In the static tests, the aircraft are exposed to certain loads to simulate the types of loads experienced if a pilot would bank left, for example. The load is applied for a period of time while measurements are taken. In the durability tests, the load conditions change at a faster rate.

In the F-35 program, Lockheed Martin uses nCode software to store, analyze and manage data.

New Model Aids Machining of Composite Components for F-35

Among the design innovations featured in the F-35 Joint Strike Fighter aircraft are components made of composite materials. Last year, Third Wave Systems was awarded a contract by the United States Air Force Life Cycle Management Center to expand its machining modeling technology to composite materials used on the airplane.

Under the $3 million contract, the company will develop a physics-based machining model of the Cycom 5250-4 bismaleimide (BMI) material used on a fan inlet case from GKN Aerospace. Third Wave will also work with airframe builders Triumph Group and Northrop Grumman, along with machining supplier Janicki Industries, to perform similar activities for the Cycom 977-3 and AFR-PE-4 resin systems.

“The machining operations are the last operations in production,” says Troy Marusich, chief technical officer at Third Wave. “The composites are abrasive and the tools wear out quickly, and when you have tool wear the composite can splinter, fray and delaminate. These are expensive parts and difficult to repair and to make conforming once you introduce defects at the machining stage.”

Third Wave is modeling the machining process to better understand how cutters can be redesigned. “We can evaluate the new designs digitally and modify them based on our predictive models, so when we make a prototype we have a higher degree of confidence that they can see improvements through the cutter design,” Marusich says. “We’re also predicting the amount of wear that the design would experience, and then improving it so the tools don’t wear out as quickly.”

Third Wave received a $2.1 million Phase II SBIR (Small Business Innovation Research) project in 2008 through the U.S. Naval Air Systems Command to implement high-performance machining technologies in the V-22 and F-35 programs. For the V-22 program, Third Wave partnered with Bell Helicopter and NAVAIR suppliers to improve the production of titanium-based structures through analysis of cycle times and cutting forces. For the F-35, the company analyzed existing machining practices to reduce distortion seen when machining forged aluminum bulkhead components.

Having a full-scale composite machining modeling software helps reduce costs and manufacturing times, and improve component quality. Third Wave estimates that the solution could reduce composite machining times by 20 to 35% and tooling costs by 20%.Once completed, the model could be used for a variety of composite materials across the Department of Defense supply base.

“There are also ceramic matrix composites that could benefit as well, and that would be for high-temperature applications like in a jet engine,” he adds. “That would enable new components for jet engines, which could reduce costs and make the engine more efficient.”

According to Christian, the static test articles utilized nCode Automation to store a combined 70GB of data for all three F-35 variants: F-35B (Short Take-Off and Vertical Landing), F-35A (Conventional Take-Off and Landing) and F-35C (Carrier Variant). Stress engineers in Texas, Georgia, California and the United Kingdom used HBM MD Client software to remotely monitor strain data in near real time throughout the test program.

“Using the processed data from MD Client the engineers monitored each test and when warranted, issued a pause or abort command to help safeguard the test,” Christian says. “Each static test simulated a different load case such as the air pressure and inertia loads encountered in flight during high-g pull-ups, negative-g push-overs, and roll maneuvers.”

A series of approximately 150 test conditions applied loads at different levels: 60% design limit load, 115% design limit load and 150% design limit load (ultimate load). Each full-scale static test article had more than 3,000 channels of data monitored and recorded. nCode Automation served as a data warehouse during the F-35 static testing and is the software product used for the F-35 durability tests currently in progress.

The durability test articles use nCode Automation and nCode Glyphworks to store and process data for all three F-35 variants. Each test article includes 1,800 to 2,000 channels of strain gage data. Depending on the type of spectrum applied, a series of nine to 15 Glyphworks flows are processed daily to translate raw data and collate lists of channels to assess against pre-defined criteria.

The Glyphworks flows capture maximum and minimum strain levels and compute average values, standard deviation and slope for load cases that repeat throughout the load spectrum.

“Any drift or step change in the strain data is flagged by Glyphworks, which compares the most recent data to historical data collected as the test is running,” Christian says. “Test data for lists of flagged channels are reviewed visually using Glyphworks to identify areas of concern that require further evaluation and inspection.”

The output and plots generated by Glyphworks flows are then compiled at the end of each test block and presented in reviews with engineering and customer personnel.

The software has allowed the company to perform the post processing of more than 4,000 channels of test data much faster than under legacy programs, the company says. The full airframe and HT component test for F-35A and F-35B variants were completed five months ahead of baseline schedules thanks to this faster processing capability. The schedule savings allowed incorporation of expanded capability tests without impacting flight clearance support.

The solution has also provided a common format for partner teams in other geographies to assist with mitigation and resolution of any test anomalies, which reduces down time and saves costs.

“It’s also completely repeatable,” Gray says. “There’s no human element in the statistical analysis.”

Lockheed is effectively managing the analysis of test data that would otherwise be impossible without an army of full-time engineers. In fact, it’s doing so with a degree of speed and accuracy that would be unattainable using manual analysis.

“The nCode software products have proven to be essential enablers to efficiently execute these critical large scale F-35 structural tests,” Christian says.