AEDC wind tunnel modernization benefits from 'in-house' fabrication capabilities

  • Published
  • By Raquel March
  • AEDC/PA
ARNOLD AIR FORCE BASE, TENN. --  The four-foot transonic (4T) wind tunnel in the Arnold Engineering Development Complex (AEDC) Propulsion Wind Tunnel (PWT) facility is benefitting from modern, state-of-the-art instrumentation partly due to the manufacturing capabilities of the Model Shop personnel at the Complex.

Known for aerodynamic and weapons integration testing of U.S. fighter aircraft, 4T is now equipped with a new roll mechanism and a new Captive Trajectory Support (CTS) system used to conduct staging or store separation testing that will handle higher loads needed to test today's modern aircraft and weapons systems.

New flexible nozzle actuators were also installed. The actuators are electro-mechanically driven ball-screw jacks which move the flexible top and bottom plates in the 4T tunnel providing variable Mach numbers or wind speeds.  They will provide precision movement of the flexible plates and the ability to better handle the bending stresses and aerodynamic loads generated while testing.

Another upgrade to 4T's flow capability includes a new flexible nozzle actuator control system (NCS) like the system utilized in the complex's von Kármán Gas Dynamics Facility wind tunnel A which is equipped with a flexible nozzle as well.

The NCS also has a positioning program which provides closed-loop control for the nozzle actuators.

The Model Shop personnel were involved with each of these projects from field measurement work on some to fabrication and installation of the new CTS mechanism.

Lead project personnel involved in the modernization emphasized the importance of having the capabilities to fabricate and machine parts "in-house."

"We did the majority of it [the modernization project] in-house," said Jeff Harvey, machine planner for the AEDC Model Shop. "We do a lot of specific and specialty items that go into the test cells. Many of the craftsmen have 30 or more years of experience and not only experience machining but experience in making things that work."

Due to the synergy between the AEDC craft personnel, designers and engineers, the project progressed at a quick pace.

"We used what you call concurrent engineering on this, and that's working closely with design and engineering departments," Harvey said. "Because this [project] was made up of several assemblies...to go in a high tolerance assembly, that [project] couldn't be achieved as quickly as we did it without having help from the machinists, the design department and engineering department all working together to keep the job working - to keep it going."

The craft personnel worked closely with the designers, and that provided insight and more capabilities for the machine shop where maintenance may be needed later.

"We were able to use people's experiences to make ours [capabilities] better," said John Wright, project manager for the 4T Captive Trajectory System upgrade. "By using AEDC craft in the design, fabrication and installation process, they gained experience that will aid them in future maintenance and repair efforts."

Wright said the fabrication process "was definitely faster" due to the communication between craft personnel and design personnel who were closely located.

Greg Fox, the section manager of the PWT Operations Group, also emphasized the importance of an "in-house" fabrication for the project.

"Since the equipment is all one-of-a-kind and it's designed specifically for our use, it helps us tremendously to have our engineers and our craft, our people here at AEDC involved in the installation, checkout and fabrication," Fox said. "Because when it comes time to troubleshoot problems, to improve it next time, to work on it, to use it, we really understand what we have more so than if somebody were to just drop a turnkey system on us and we would have to start, at that point, learning."

The high quality of each project was due to design changes throughout the process.

Jeff Tate, a mechanical planner in the M&M, called the project unique because, "you didn't have to have the finished design" or "you didn't have to have everything completed to get started" on the fabrication.

"It's a design-build kind of process that makes AEDC unique," Tate said. "Also, the engineering folks are right here on base so they can work with us during the process. We can call and they can be here in 10 minutes to look at something, to discuss items."