TINKER AIR FORCE BASE, Okla. -- While it takes a coordinated nationwide enterprise of depot maintenance to keep the Air Force operating at its highest capability, a single shop at Tinker Air Force Base is responsible for powering every aircraft in the entire Air Force.
Operating with a crew of 73, Tinker’s Constant Speed Drive Shop is one of the few locations in the Air Force responsible for the overhaul and maintenance of an aircraft’s vital constant speed drive.
“Our mechanics have a sense of pride in their work supporting the warfighter because of the significant work our shop does here at Tinker,” said CSD Flight Chief John Marinko, 552nd Commodities Maintenance Squadron
An accessory that mounts to the aircraft engine, a CSD turns the aircraft’s generator similar to how a car’s transmission functions, according to Ira Hinkle, lead process engineer for the CSD Shop.
Because generators are required to maintain a constant 400 hertz, Hinkle said the generator’s shaft speed needs to be kept at a consistent rate. He added that the number of generators varies according to plane size, with larger planes utilizing around four generators and smaller fighters only a single generator.
“As the engine’s [revolutions per minute] go up and down, the CSD is a device that, with a varying input speed, maintains a constant output speed,” Hinkle said. “The generator provides electrical power to the plane, so if the CSDs are not working the plane would get no power and you would want to be landing as soon as possible.”
The shop overhauls a total of 13 different CSDs supporting fighter, tanker, surveillance and bomber aircraft. Parts support consists of Defense Logistics Agency and Air Force-managed parts, as well as parts locally produced in Air Force organic manufacture shops.
Outputting approximately 100 CSDs a month, the shop has two distinct processes that govern what maintenance process a CSD undergoes: a full overhaul or an evaluated overhaul.
Evaluated overhauls take an average of three-to-four days and are now the most common procedure in the shop. Under this process, the shop evaluates the device and pinpoints the exact problem so it can be repaired up to an operational level.
Full overhauls are completed when it is determined that the CSD is unable to perform without the replacement of one of several key parts. If a CSD fails several test points in the evaluation process, the shop will completely tear down the device and replace any of the bad parts before putting it back together in a process that can last from eight days to several weeks, depending on parts availability and other factors.
“One good thing is that all the processes fall under this one flight,” Marinko said. “If there is a constraint that’s not a parts constraint, it falls within our flight so we are not relying on outside shops. That way if there are any problems, I don’t need to go to a flight chief in another organization in order to resolve a problem in a timely manner.”
With such a vital component, ensuring that it spends as little time as possible in the overhaul process is an objective that the shop is continually working on – whether by working to reduce obstacles in the parts procurement process or by making innovative changes to how the shop approaches overhaul.
Changes to the overhaul procedure over the last several years have provided the shop with the most improvement in expediting the CSD maintenance process, specifically the implementation of the evaluative overhaul procedure.
“When I first got here, the shop was overhauling pretty much every [CSD] that came in,” Hinkle said. “We might get a few that looked pristine that we might try maintenance on to see what we could do, but if it did not pass testing it went to tear down. There wasn’t anything in between, like a partial overhaul.”
By bringing in more evaluations at the front end of the overhaul process, Hinkle said that it would determine whether a full overhaul was necessary. When the CSDs failed tests, they would also work to pinpoint the exact problem and then repair that specific part if possible rather than overhauling the full device, which said dramatically reduced the amount of full overhauls the shop was doing.
Between February 2018 and February 2019, Marinko said that the shop had managed to reduce backorders by more than 224 devices thanks to these measures. The overall reduction in necessary parts and maintenance provided the shop with an overall cost avoidance of $8.5 million in material cost avoidance.
“Improving our position to better support the warfighter is not something that happened overnight, and it’s been thanks to a lot of hard work from our folks,” Marinko said.