ARNOLD AIR FORCE BASE, TENN. – A trio of craftsmen at Arnold Air Force Base recently made a more than 2,300-mile trip out west to help the National Full-Scale Aerodynamics Complex expedite its return to service.
In early February, John England, Andy Riis and Tim Taylor traveled to NFAC, located at Moffett Field, in Mountain View, California. There, the three provided fit-up and welding support in NFAC’s 40-foot diameter fan drive section.
NFAC has been offline since June 2017 and is not yet back online. An incident occurred in which debris severely damaged a portion of the NFAC fan drive when it passed through the system during a test.
NFAC is a large low-speed wind tunnel. The facility has two different test sections, one that is 80- by- 120-foot and another that is 40- by- 80-foot. These test sections are the world’s largest and second largest. Various models, from fixed-wing aircraft, helicopters, parachutes wind turbines and trucks, are tested at NFAC, and many of the models are either full-scale or close to full-scale. The facility also has the ability to perform acoustic testing concurrently with aerodynamic testing.
The facility’s fan drive is comprised of six 40-foot diameter fans that push air around the circuit. Behind the fans are stationary blades, known as stators, which help direct the airflow and remove swirl. Between each stator is an airfoil-shaped steel tube called a vibration control strut that helps stiffen the stators and ties them together to act as a single unit.
To prepare NFAC to return to service, these tubes needed to be welded into place. The steel fairings that covered the connections at each end of the stator also needed to be welded into place.
“All the welders onsite here have been busy since October repairing the damage in the tunnel wall,” said NFAC Facility Mechanical Engineer Dan Boyd. “We completed stator repairs and reinstallation and saw an opportunity to get the vibration control struts and the stator fairings installed without taking resources from the tunnel wall welders. This work is a prerequisite for other return to service tasks that are still in queue to be done.”
To keep resources on task, NFAC project engineers reached out to leadership at Arnold to see if the facility had three welders available to assist with the installation of fairing boots and vibration struts on the fixed stator blades in the 40-foot diameter wind tunnel section. A quick response was needed.
“The first I heard about (this request) was at about 8 a.m. on Friday morning, Feb. 2,” said Arnold Technology/Manufacturing Planner and Scheduler Jeff Tate. “Riley Hoge, another planner in my office, laid a stack of pictures on my desk, stated that the folks at NFAC needed help in California starting on Monday morning, and that he thought this would be my planning work.
“I reviewed the pictures, agreed that it would be my job to plan, and got back with Manufacturing management to confirm the need and schedule, which they did. This started the planning wheels in motion of further discussion with NFAC management to gather information, develop scope for the work, develop welding procedures, procure welding consumables, pick the guys going, put tools together, and make arrangement for transporting the craftsmen and equipment to California.”
After all these details were nailed down, Tate and others began work to select the craftsmen who would travel to NFAC. Based on similar work done at Arnold in the past, the decision was made to send two boilermakers and one sheet metal worker, all of whom were to have the proper welding qualifications.
Shop supervisors Crethton Caldwell and Vaughn Wilson started with the senior qualified person in each craft and went down the seniority list asking for volunteers until the three slots were filled.
England, Riis and Taylor, the three men who represented the volunteers, viewed the photos and were provided with the scope of work on Feb. 5. They boarded a plane and flew to California on Feb. 7.
“Basically, we had two days to assemble all of our materials, weld machines, personal protective equipment and, of course, our luggage from home,” England said.
Riis said, “We were shown about four or five pictures of what we were going to do, so we kind of threw everything but the kitchen sink in there so we were prepared for whatever hit us.”
As boilermakers, England and Taylor typically work with thicker metals than those they were responsible for welding at NFAC. Some of the material was .049” in thickness, and England said, “It was very tedious, tight welding.”
The welds on the fairings and struts were done in the field and in all welding positions, making the welds somewhat tricky.
“They had to work on a variety of structures in some atypical positions and do so safely,” Boyd said.
The Arnold craftsmen were originally slated to work at NFAC through Feb. 23. However, England returned to Tennessee on Feb. 11 and Riis and Taylor returned on Feb. 16, thanks to a piece of recently-acquired equipment the crew opted to bring along.
They anticipated having to complete the project using a heliarc welding process, but Riis suggested that the crew bring along a metal inert gas welder acquired by the Sheet Metal Shop just before the trip to NFAC. Riis said the MIG welder is made specifically for welding thin materials, with England adding that its use “greatly expedited the work.”
“It had come in two days before we left, so we threw that in,” Riis said of the MIG welder. “We just lucked up.”
The group from Arnold was originally tasked with installing fairings and struts on one of the NFAC 40-foot fans but, due to their proficiency, England, Riis and Taylor ended up completing work beyond the initial scope including welding other bracings and fixing other stators.
“They gave us more work than what was planned because they had seen we were so efficient,” Riis said. “The job we went out there to do was to do just one of the six fans. Before John left, we were caught up to where they were ready for us to put it on, and I said, ‘What else you got?’”
“When I got there, I told them, ‘We’re here to make you look good,’” England said. “They were pleased with our work and said as much.”
In an email sent to the Arnold craftsmen and their supervisors on Feb. 20, Boyd wrote the work of England, Riis and Taylor was of “tremendous help” to NFAC as the team there prepares works to return to service. Boyd also wrote their work will help NFAC move on to its next phase of work sooner.
“The guys are extremely hard workers that performed difficult work and accomplished it ahead of schedule,” Boyd wrote. “I think that their work here over a week-and-a-half helped us recover more than two weeks of schedule by allowing several processes to be done in parallel instead of in series. We are greatly appreciative of their work and the work of their managers in getting them out here. These guys deserve recognition for the work they did.”
England, Riis and Taylor, along with Tate, received that recognition during an appreciation luncheon Feb. 23 at the Model Shop, when each craftsman received a commemorative coin of appreciation from Technology/Manufacturing Branch Manager Mark Chappell.