Paul Lewis/PATUXENT RIVER
The US Navy plans to extend the structural life of about one-quarter of its fleet of Boeing F/A-18C/D Hornet fighters until at least 2019 to make up for the shortfall in planned follow-on Super Hornet numbers.
The navy plans a "destructive tear-down" of a Hornet in 2000 into 1,290mm² (2in²) pieces to validate previous fatigue testing and identify potential problems. "We look for as much lead time as possible - we don't want to be surprised in service," says Bill Taylor, F/A-18 Fleet Support IPT leader.
Also, the USN has awarded Northrop Grumman an initial $4.4 million contract to build four replacement F/A-18C/Dcentre barrel subassemblies. The programme is expected to extend to at least 200 aircraft over the next 10 years - about 25% of the USN's F/A-18A/B and C/D inventory.
The high wear and tear subassembly extends from aft of the cockpit to forward of the engine bay. It encompasses the wing root, main landing gear trunnion and mid-keel, which is the main load path for catapult take-offs and arrester-hook landings.
"Replacing the centre barrel removes 90% of potential problem areas," says Dan Polakovics, head of the tactical aircraft strengths and airframe technical branch.
The new barrels are virtually identical to the earlier subassemblies in terms of material and overall dimension, but have thicker gauge radius and the longerons are reinforced in selected areas. Aircraft will be modified at depot level, using tools and techniques developed to repair damaged F/A-18s.
Boeing designed the F/A-18 for a 6,000h operational life, although some components were bench tested to 24,000h and 2,000 aircraft carrier cycles. Despite accelerated use in the Gulf and Balkans, most of the USN fleet will reach this fatigue ceiling and beyond without modifications. The oldest aircraft are expected to reach the end of their structural life by 2013.
Extending the aircraft's service by six to seven years will require pushing the fatigue life to 9,000-12,000h and, more importantly, 2,700 carrier cycles. "The centre barrel replacement is intended to achieve that," says Taylor.
Having retired the Grumman A-6 and with plans to retire Northrop Grumman F-14A/Ds between 2003 and 2008, the USN will rely increasingly on the F/A-18 until the Joint Strike Fighter is fielded. Cuts have reduced the navy's planned F/A-18E/F purchase from 1,000 to potentially as few as 548 aircraft.
Source: Flight International
