VKF test crew, recent hire earn recognition for Tunnel C repair

  • Published
  • By Bradley Hicks
  • AEDC/PA
ARNOLD AIR FORCE, Tenn. --  Thoughts of abandoning ship never entered the minds of the von Kármán Gas Dynamics Facility Test crew and a newcomer to Arnold Air Force Base after a leak was discovered in Wind Tunnel C.

Although they had never run into this issue before, the group quickly completed the research, secured the materials and arranged the work necessary to ensure that testing in Tunnel C could continue as planned.

The test crew and VKF Test Operations/System Engineer Brad Peckinpaugh, who has been on the job for less than one year, were recently recognized with Directorate Spot Bonus awards on behalf of the leadership with the Test Operations and Sustainment (TOS) contractor for their efforts to bring about a favorable resolution.

“The crew worked together, helped each other, overcame obstacles, solved problems, remained flexible and stayed focused on this high-visibility job,” said VKF Test Cell Supervisor Greg Sterling.

Peckinpaugh, who in June 2018 began his career with National Aerospace Solutions, the TOS contractor at Arnold AFB, is credited with coordinating the work needed to complete the timely repair.

“Brad remained calm and focused during this maintenance period and ensured the work was performed safely and with high quality,” Peckinpaugh’s Spot Bonus certificate reads. “His attitude, leadership and professional demeanor exemplified NAS covenants.”

The VKF Test crew encountered the internal water leak in early February after the installation of the Mach 4 Aerotherm Nozzle. This nozzle, installed in preparation for a test, is used for materials testing, primarily to evaluate the performance of thermal protection materials for supersonic flight vehicles.

Due to the high temperatures test articles would be subjected to, the use of cooling water is an important part of the test process. It was during a high-pressure water checkout that the leak was encountered in the Mach 4 Throat, a critical high-pressure water cooled component of the Mach 4 Aerotherm Nozzle assembly.

Prior to its installation, the Mach 4 Nozzle had last been used in Tunnel C in 2009. Because of this, many on the VKF Test crew were unfamiliar with the assembly. This, however, did not inhibit the efforts of the crew to address the situation in the tunnel.

“The VKF crew had little-to-no experience with the Mach 4 Assembly in Tunnel C at all, let alone disassembling and reassembling the various components,” Sterling said. “The crew’s willingness to communicate and learn this system together really made this repair successful.”

The Mach 4 Throat is located in the middle of the Mach 4 Aerotherm Nozzle assembly. It, along with other components such as the stilling chamber and the nozzle itself, had to be taken out of the Tunnel C test circuit to begin repairs. The assembly was removed and the larger components were disconnected.

Special rigging was then used to remove the Mach 4 Throat from the downstream end of the assembly. This component was disassembled into its primary pieces.

Damage to an internal silicon O-ring was discovered on the upstream end of the throat and identified as the source of the leak. Parts of the Mach 4 Throat were sent to the Arnold AFB Model and Machine Shop to be cleaned before reassembly.

“The Model Shop was able to clean up some residue marks and stains (caused) from the water,” Sterling said. “The components were received back in like-new condition.”

New O-rings were made and installed.
Once the work was done, the assembly was reinstalled into the Tunnel C circuit. A subsequent water checkout confirmed the assembly to be free of leaks.

“There was no other significant damage as a result of the leak,” Sterling said.

Peckinpaugh coordinated the repair work with limited inputs from other engineering staff. Throughout the process, he reviewed drawings, followed instructions previously written by VKF Group Manager Shannon Tibbals, went over historic service records, ordered materials and coordinated multiple work crews, using only day shift hours while incurring minimal overtime.

“This was not the first time the Mach 4 assembly has had an internal water leak, so there were some notes of the tear down/rebuild from years ago that Shannon Tibbals originally wrote that I was able to read through while we attempted to fix the same problem,” Peckinpaugh said. “There were many drawings to sort through. The repair itself was a huge group effort.

“David Faucett and Greg Crabtree’s assistance when making crucial decisions helped tremendously. Brad Tucker and Dusty Rogers from the Model Shop were extremely helpful in scheduling cleaning and work on the integral parts of the Mach 4 assembly. While we had everything disassembled, Drew Barnett helped take advantage of a great chance to re-measure the Mach 4 Throat diameter.”

In all, the repair work was completed in around three weeks.

Peckinpaugh further credited the efforts of those who worked with him for the successful fix.

“Without the help of Clarence “Remo” Rogers, Andy Houser, Adam Gilliland, Josh Jernigan, Tim Waggoner, Dan Randall, Aaron Blaser, Wayne Whittington, Russell Tabler, Jim Crawford, and many others I am sure I’m missing, the repairs would not have gone so smoothly,” he said.

With the repairs finished, the first Mach 4 aerothermal test since 2009 was completed in VKF. Additional testing using the Mach 4 Aerotherm Nozzle is scheduled to take place in the coming weeks.