A significant milestone in the history of naval aviation maintenance and repairs is coming to an end.
The Navy’s Center Barrel Replacement (CBR) program that was created by Fleet Readiness Center Southwest (FRCSW) in 1991 inducted its last F/A-18 legacy Hornet fighter (RA52) to undergo the CBR procedure March 17 at Naval Air Station North Island (NASNI).
The CBR procedure was developed after a crash-damaged F/A-18 aircraft with very low flight hours was brought to FRCSW (then Naval Aviation Depot North Island) for analysis. The area damaged was the center fuselage section – the center barrel – where the wings and main landing gear attach.
Instead of scrapping the plane for parts, the engineers and artisans of FRCSW were challenged to find a way to make the repair. After a thorough examination, it was determined that replacing the center barrel would be the most viable and cost-effective option.
In less than two years the project was complete, and at a cost of $4 million, it totaled less than 10 percent of the aircraft’s replacement value.
The new capability later evolved into the CBR + program which played a major role in extending the initial 6,000-flight-hour service life of the aging legacy (A-D models) Hornet aircraft.
The CBR + program targeted an aircraft’s fatigue life expectancy (FLE), a formula derived from the usage history of an individual aircraft and based upon stress-related factors affecting key areas of the airframe, such as the wing attachment points, and included replacement of the forward and aft dorsal decks, and the forward, aft, and keel longerons (structural beams).
Significant service life extension programs began in 2006 with the High Flight Hour (HFH) program that included an array of airframe inspections to ensure operational safety of an aircraft to 8,000 flight hours.
The HFH program typically included procedures in conjunction with routine Planned Maintenance Interval-One cycle (PMI-1). The PMI-1 cycle was an analysis as to the scope of repairs or replacement to the aircraft’s major components and other vital parts.
Three years later, the Service Life Extension Program (SLEP) was created through combining the CBR+ program with the HFH inspections to extend the 8,000 flight hours by 600 hours. A 2011 revision to SLEP added an additional 1,000 flight hours.
Aircraft are scrapped upon reaching 10,000 flight hours.
Aerospace manufacturer Northrop Grumman builds the center barrels, and corresponding kits contain about 12 components.
A staff of 49 artisans work in FRCSW’s CBR+ program. Disassembly and assembly phases are performed in Building 94 and 378, while the Center Barrel phases take place in Building 378.
“The CBR+ program requires very technical artisanship because an average of 20 to 22 thousand fasteners of many types are removed. Where the fastener is removed the artisan drills up the hole to the next size to accommodate the new fastener. We have a very diverse work force that also consists of aircraft mechanics, electricians, machinist and the sheet metal mechanics who perform 85 percent of the work,” FRCSW CBR Deputy Program Manager Pedro Duran said.
Each CBR+ averages about 25,000 manhours at a total cost of $2.5 to $3 million per aircraft.
FRCSW and FRC Southeast (FRCSE) are the only naval maintenance facilities authorized to perform the CBR+ procedure.
“There are approximately five aircraft going through at FRCSE,” Duran said. “We still have six Center Barrel aircraft going through the process. When RA52 is completed and returned to the fleet, then the program will end.”
“We will continue to bring in aircraft for other programs and or any other maintenance or platform that is brought in for us to repair,” he added.
With 7,782 flight hours, RA52 has undergone all HFH inspections and PMI-1 in conjunction with CBR+.
When complete it may return to Marine Fighter Attack Squadron 232 (VMFA 232) based at Marine Corps Air Station (MCAS) Miramar or be assigned elsewhere by the Marine Corps.
“Many hours of work have gone in pushing through 135 CBR aircraft, and when RA52 is finished a total of 141 aircraft would have gone through Building 378, the birthplace of the CBR program,” Duran said.