Faute de remplaçant l'USAF les remettent à neuf pour en doubler la durée de vie
A-10 Upgrades Double Operational Lifespan
(Source: US Air Force; issued June 30, 2004)
DAVIS-MONTHAN AIR FORCE BASE, Ariz. --- The first production A-10 Thunderbolt II was delivered here in October 1975. Fifteen years later, the A-10 was called the most formidable weapon system of its type while flying combat missions during Operation Desert Storm.
Today, more than 30 years after beginning service, many of the Air Force’s A-10s are reaching the end of their predicted 8,000-hour service life.
Because there is no replacement for the A-10, aircraft technicians working on a service-life extension program at the Aerospace Maintenance and Regeneration Center here are trying to double the aircraft’s operational lifespan.
Although the aircraft are undergoing countless upgrades, center specialists are discovering new ways to enhance aircraft repairs and encountering unexpected problems along the way.
Recently, mechanics discovered a crack in one of the mounts that connect the center assembly to the outboard wing. The crack was hardly noticeable to the naked eye.
“There had never been any inspection criteria established because this was an unpredictable problem,” said Sam Smith, A-10 wing production branch chief.
The mount was designed to prevent landing-related stress from transferring to the wing. It did the job, but not knowing how much more stress a cracked mount could take was a major concern to the A-10 team.
“There is no way to really know if a cracked (mount) could lead to failure in the aircraft, but our job is to make sure every A-10 is returned to the warfighters in perfect condition,” Mr. Smith said. “Every A-10 wing in the inventory is now inspected for cracks in the (mount). As a result of this unexpected finding a special team of technicians (here) has developed inspection and repair procedures to address the problem.”
Even with the new technology and procedures used to replace the wing mounts, each replacement takes two technicians more than 120 hours.
The team creates a template for each mount that meets tolerances within three-thousandths of an inch -- a degree of error that is about equal to the diameter of a human hair.
“Once the first crack was discovered, we began the search for technical guidance on what to do,” said Mark Perrodin, a wing structural mechanic. “There were no technical orders to address the (mount), and there was no history to show that the problem had been discovered before. It appeared that the mount was supposed to last the life of the airframe. But since our goal is to double its lifespan, we had to find a way to replace (them).”
Technicians found that new mounts were available, but each one had to be custom-milled to fit each wing set.
To solve this problem, the team turned to structural mechanic and expert machinist Tommy Rollins. Starting with a 3-foot-long block of aluminum, he went to work, inventing a tool that could be used to customize each wing mount.
“We needed a way to make each new mount match the old one exactly,” Mr. Rollins said. “We were able to design and manufacture a specialized tool to accomplish the task.”
Mr. Rollins and the mount team not only developed the tool to repair the wing mounts, they also wrote the procedures for other A-10 teams to follow when repairing these cracks.
At the A-10 systems manager’s request, the tool was shipped to Ogden Air Logistics Center A-10 Depot at Hill Air Force Base, Utah. It is currently being used to repair similar anomalies there. Within a week, Mr. Rollins was in the machine shop making another tool for regeneration center workers here.
Once the new mount is milled to exact specifications, mechanics begin installing it.
First, a template is made to match the exact location and angle for each of the original 14 mounting holes.
With surgical-like skill, a technician installs the old mount, marks the location for one hole, replaces the old mount with the new one and transfers that mark. The procedure must be repeated 24 times to duplicate each individual hole.
Once the new mounts are installed, the wing continues along the line for work on its hydraulics, electronics, fuel cells, sheet metal and under-wing hardpoints used to mount weapons.
When completed, each overhauled wing set is rated for up to 8,000 hours of flight time and installed on an A-10 fuselage that has also undergone a complete refurbishment and upgrades.
Once an aircraft is flight tested, it is ready to return to the warfighter.
16000h de vol qu'ils totaliseront les A-10 au retrait du service
(si l'on ne l'allonge pas encore parce que le JSF c'est pas top pour le CAS)
