AEDC Wind Tunnel upgrade improves flexible nozzle accuracy and reliability

  • Published
  • By Raquel March
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  AEDC's aerodynamic customers will have added assurance of smooth Mach number transitions due to recent upgrades underway in the Propulsion Wind Tunnel's (PWT) four foot transonic wind tunnel called 4T.

An AEDC operations and maintenance team recently completed the mechanical installation of new flexible nozzle actuators in a series of scheduled upgrades for 4T, a continuous-flow, mid-size test facility used for conducting small-scale aerodynamic and store separation tests.

The new 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.

"There are 15 actuators on both the top and bottom plates providing a 'mirror image' movement," said Doug Ratliff, an ATA PWT 4T modernization project manager. "These actuators are similar to the ones that were recently installed in VKF (von Kármán Gas Dynamics Facility.)"

Another upgrade to 4T's flow capability includes a new flexible nozzle actuator control system (NCS) like the system utilized in the complex's VKF wind tunnel A which is also equipped with a flexible nozzle.

The NCS is currently being installed and has an operator interface that will allow the operator to position the nozzle plates, monitor the system status and diagnose control system problems.

The NCS also has a positioning program which provides closed-loop control for the nozzle actuators. The protection system in the NCS continuously monitors the hardware and software performance health and plate stress to protect the nozzle plates from damage.

The 4T modernization team was able to rely on in-house expertise for developing the NCS. AEDC's ATA support contractor's Manufacturing Services section fabricated and installed the NCS cabinets and hardware. The ATA Instrumentation and Controls Systems Design section developed the NCS software while the Facilities & Test Techniques section created simulation software. The Flight Systems Operations & Maintenance section is installing the field wiring.

"Due to the unique test facilities and support systems found at AEDC, having the ability to do in-house design and fabrication allows AEDC to quickly respond to any repairs or modifications which may be needed to address unique requirements or changing demands of our test customers," said Ricky Mead, an ATA PWT 4T modernization project manager. "It also means that, should a customer determine during testing that their model requires a modification(s) in order to continue, they do not necessarily have to send the model back to their home office for the modifications, but can get those modifications done right here at AEDC minimizing both the cost and the impact to their testing schedule."

A new 4T roll mechanism, designed and fabricated by AEDC's Model and Machine Shop, has been checked out and is being prepped for installation.

The roll mechanism which supports the sting, or test support arm, and the test article, provides the ability to roll the test article during a test. It will handle higher loads required when operating the 4T Captive Trajectory Support (CTS) system used to conduct staging or store separation testing.

"The nozzle upgrades, along with upgrades to the 4T Data Acquisition System (DAS) and the Captive Trajectory System (CTS), will provide commonality between 4T and the A, B and C tunnels for AEDC customers who wish to test their model in both 4T and tunnels A, B or C," Mead said. "It will also provide a similar look and feel for AEDC test crews who conduct testing in both 4T and A, B and C tunnels."

The 4T tunnel is scheduled for return to service at the end of July 2014.