ARNOLD AIR FORCE BASE, Tenn. – On Jan. 21, 2021, the multi-year efforts of many, yielded the desired results with a successful air-on test run in the Arnold Engineering Development Complex 16-foot supersonic wind tunnel, or 16S, and return to service of the test facility.
“Wind Tunnel 16S will provide the nation a significant capability to rapidly develop weapon systems critical to the National Defense Strategy,” said Lt. Col. John McShane, Aerodynamics Test Branch Materiel leader. “We can now assess weapon system performance in a controlled environment at parts of the envelope that were previously unattainable.”
Later this fiscal year, the tunnel is expected to host customer models for air-on tests for the first time since 1997. Recently, the tunnel was used to conduct a mass flow assembly calibration using only the Plenum Evacuation System, or PES.
The test in January used an AGARD-B standard model to validate operational capability of 16S. The data gathered will serve as a baseline for monitoring of the tunnel and data systems quality.
AGARD models are scalable, generic aerodynamic models that allow for data comparison across different wind tunnels.
“The AGARD model that was tested in Tunnel 16S is also intended for testing in Tunnel 16T (16-foot transonic),” said Jennifer Daugherty, an AEDC project manager. “Being a generic model, we can more widely publish the data and share with any interested customer without compromising proprietary or security interests.”
Return-to-service efforts began in 2013 by assessing the tunnel system. The assessment concluded in 2015 with a successful air-on operation of 16S, providing the Air Force with confidence to invest in restoring the facility and informing the work that followed.
The work completed in order to achieve this current test run involved inspecting and repairing 890 systems and subsystems, ranging from minor repairs to complete overhauls.
The nozzle alone required new motors, repairs of nozzle jacks and a calibration. The control room, which is late-1950s vintage, had 50 percent of the controls updated. Also, a new electronic manometer was installed in parallel to the original mercury manometer board. The manometer shows operators where the shock wave is and is critical to their ability to make sure the tunnel is at the desired conditions.
“The effort has been nothing but teamwork, and the team is very proud of their accomplishments,” said David Reep, a craft supervisor with National Aerospace Solutions LLC, the Test Operations and Support contractor for AEDC. “It is as if we are building something brand new; however, it has been much more challenging since we are using equipment that was put into service in the late 1950s. The team make-up has varied in numbers throughout the project. Most all that have been involved actually hate to leave as we all want to see it back into a testing mode. These team members, former and current, have a lot of pride in what they have accomplished and completing upcoming test projects is that final approval of accomplishment.”
This successful test does not signal the end of the 16S return-to-service efforts. Currently, the tunnel can be operated at Mach 2.2. Plans are to restore the full main compressor capability to run up to Mach 3.4, then operate the facility compressor and PES in a series configuration to demonstrate operation up to Mach 4.75. Additional planned investments include extending the Mach number capability into the hypersonic regime.
The Air Force has also programmed an investment to restore the propulsion test capability to enable the testing of engine-installed systems in conditions that simulate supersonic Mach numbers at altitude. This capability utilizes a suction scoop to remove exhaust and requires the tunnel to be operated at temperatures many times that of standard operations.
Ed Tucker, AEDC senior technical advisor, emphasized the significance of reactivating 16S and praised the team’s commitment and expertise.
“AEDC’s 16S test cell is a world-unique capability,” he said. “The unmatched ability to achieve high-quality, high-productivity testing of large-scale test articles at supersonic speeds is a necessary capability for the development of future aerospace systems.
“The outstanding efforts of AEDC’s test facility experts and wind tunnel test operations team to successfully reactivate 16S represents a key milestone in our continuing effort toward ensuring that AEDC is well-positioned to fulfill its role in developing effective weapon systems that support the national defense strategy.”