In military aircraft maintenance, repair and overhaul operations at Fleet Readiness Center East (FRCE), the workforce is accustomed to seeing oversized dimensions: the 79-foot span of an H-53 main rotor, for example, or the 84-foot spread of a fully expanded V-22 Osprey. But smaller measurements are common, too – and for those, the depot relies on the team at its Precision Measurement Center (PMC), which routinely works in increments as small as a ten-thousandth of an inch.
Recent equipment acquisitions in the PMC – a component of the Advanced Measurement Services and Reverse Engineering Labs (AMSREL) Division of the Maintenance, Repair and Overhaul Engineering Department at FRCE – will allow the program to perform these precise measurements more efficiently. A new optical comparator and laser trackers allow mechanical engineering technicians to more easily assess items small and large, including aircraft components, support fixtures and more – improvements that will help FRCE continue to improve product quality and drive down turnaround times.
An optical comparator allows technicians to inspect the geometry and measure the dimensions of small manufactured parts and assess whether those dimensions are within tolerance to required specifications. The tool uses lights, mirrors and lenses to magnify the parts and cast a two-dimensional image to a screen, allowing for non-contact measurement and evaluation, which prevents potential damage to the parts. At FRCE, the optical comparator is primarily used in first article inspections, a process that involves measuring prototype parts created by defense contractors before the companies begin full production of the items, said mechanical engineering technician James Gray.
“When the contractors start making parts, they’ll send us a run of them to inspect, so that we’re confident the item is being produced to specification,” Gray explained. “The shipment typically comes with criteria, with a drawing and a checklist. And we’ll examine the parts, record the actual value and then certify our findings.”
Thanks to technological advances, the new machine provides the ability to obtain more detailed measurements with higher precision than the version it replaced, Gray said, which improves overall accuracy. The new optical comparator is accurate to within five ten-thousandths of an inch, he explained, which is about one-fifth the width of a human hair. It also offers innovative features including the ability to write a program to automatically measure certain characteristics of a specific part, and the addition of new digital tools that allow for the export of data.
“It gives us more flexibility and detail than the older technology,” Gray said. “And it’s much faster when you’re measuring the same type of part with the same criteria multiple times – you can save a routine for that part and then basically click ‘go.’ You run the program, and the machine will measure everything for you and report back whether it’s within tolerance or out of tolerance.”
The ability to write an automated program for individual parts measurements will likely have the biggest influence in allowing FRCE to complete first article inspections more efficiently, which helps move the needle on eventual turnaround time and readiness impact, Gray said. That impact will only increase as more routines for more parts are added to the programming inventory.
“We’re saving time on the front end, and improving the quality and quantity of what we can do for the warfighter,” he added. “We measure parts here all the time, and the more you use it for, the more time you’re saving … and the better it gets.”
The new optical comparator is already producing results in the PMC, said Michael Wagoner, Metrology Engineering and Precision Measurement Center branch head at FRCE.
“The new equipment has already made a difference in our output; we have reduced our overall turnaround time on first article inspections by 10 percent,” Wagoner said. “The team really came together to ensure we were able to obtain this new equipment. The results have been worth the effort.”
Laser tracker systems offer accurate three-dimensional measurements by projecting laser beams to reflectors mounted on the object to be measured. The machines calculate dimensions by measuring two angles plus distance. These multifunctional tools are used at FRCE for a number of roles, from calibrating support equipment fixtures to aligning weapon systems to ensuring precision placement of critical aircraft components. The laser tracker system has a wide variety of applications in a range of locations, but is a specialized piece of equipment used by technicians who are highly trained in its usage, said James Liesse, laser tracker management operations lead at the PMC.
“We do a lot of support of the aircraft lines, for the V-22 and H-53 lines. Our workload is such that we take the trackers out to the aircraft – that’s where we normally go with them,” he said. “All we do is tracker work, and we get called up to measure a lot of different things.”
Properly-calibrated laser trackers are accurate within approximately 30 ten-thousandths of an inch at distances up to 260 feet. This accuracy makes the laser tracker an ideal candidate for measuring precision placement of items like the K-fitting on the MV-22 Osprey, a joint that combines panels on the aircraft’s wings. When conducting a replacement, artisans must place the new fitting within 30 one-thousandths of an inch of the original fitting’s location, Liesse explained.
In addition to improved accuracy, the new systems offer a distinct advantage over legacy versions: They can be operated by one person, rather than requiring a team of two.
“With the handheld devices that come with the new trackers, taking a lot of these measurements can be a one-man show,” Liesse explained. “We have two new trackers, so we can send two people out in different directions and cover twice as much ground.”
This means reduced wait times for equipment and fixture calibration, large item measurements and other services the laser tracker team provides, which translates to time saved in returning aircraft to the fleet, Wagoner said.
“These trackers replace aging equipment and provide state-of-the art capability to reduce laser tracker inspection turnaround times,” Wagoner said.
FRCE is North Carolina’s largest maintenance, repair, overhaul and technical services provider, with more than 4,000 civilian, military and contract workers. Its annual revenue exceeds $1 billion. The depot provides service to the fleet while functioning as an integral part of the greater U.S. Navy; Naval Air Systems Command; and Commander, Fleet Readiness Centers.
Mechanical engineering technician Clement Morris, right, with the Fleet Readiness Center East Precision Measurement Center, tests the lab’s new laser tracking system with measurements on an UH-1N medium fuselage repair fixture at FRCE’s facility in the North Carolina Global TransPark in Kinston while James Moffitt, also a mechanical engineering technician, observes the data collected by the tracker.
The new optical comparator at Fleet Readiness Center East Precision Measurement Center uses lights, mirrors and lenses to magnify the parts and cast a two-dimensional image to a screen, allowing for non-contact measurement and evaluation, which prevents potential damage to the parts. The new version of the equipment provides the ability to obtain more detailed measurements with higher precision than the version it replaced, which improves overall accuracy.
Anthony Haddock, a mechanical engineering technician with Fleet Readiness Center East Precision Measurement Center, uses the lab’s new optical comparator to inspect the geometry and measure the dimensions of a prototype part sent to FRCE by a defense contractor. Using the optical comparator helps technicians assess whether the part’s dimensions are within tolerance to required specifications.
For more information: www.navair.navy.mil