By Geoff Fein
For the second time in almost 10 months, the Navy has issued an inspection bulletin for the F/A-18A-D Hornet fleet, this time for cracks discovered in some horizontal stabilator actuator support fittings, known as bootstraps, the service said.
The Navy issued the inspection bulletin for all 566 legacy Hornet aircraft last Friday after discovery of cracks during recent high flight hour inspections, Lt. Clayton Doss, Navy spokesman, said on Monday.
“We issued the bulletin as a precautionary, risk-reduction measure to ensure our aircraft are structurally sound and safe for operational flight,” he said.
The bulletin calls for inspections of each Boeing [BA] F/A-18 A-D aircraft’s horizontal stabilator “bootstrap” within the next 25 flight hours. Aircraft with cracked “bootstraps” as a result of missing fasteners will be flight restricted until safety of flight is achieved through material replacement or repair. The estimated replacement time is two weeks, while repair time will be on a case-by-case basis. “Bootstraps” can be replaced in the field by a depot field team, Doss said
He added the inspections and any repairs will not impact the Navy’s operations. That’s because aircraft will be inspected once they hit 25 flight hours.
During recent high flight hour inspections, “bootstraps” in two aircraft were discovered to have missing fasteners, resulting in fatigue cracking. Because the “bootstrap” is a fracture critical/critical safety item, its failure could result in loss of control to the horizontal stabilator, which is the primary flight control surface responsible for maneuvering the aircraft.
As of late Monday, the service had already inspected approximately 100 aircraft. Of those inspections, three were found to be missing fastners and two of those had cracks in the horizontal stabilator actuator support fittings, thus requiring replacement, Doss noted.
Initial stress analysis has shown that missing fasteners caused increased loads, which resulted in cracks and reduction in stiffness. These “bootstraps” are part of a high flight hour inspection that grants flight hour extension, Doss said.
“Five hundred sixty-six of the 622 F/A-18 A-D aircraft in the Navy and Marine Corps inventory are being inspected within the next 25 flight hours. All other aircraft have been inspected or are not operational. There are 111 Hornets in a deployed status–384 in CONUS in training, 38 reserve and 90 in depot status. Ten early-model aircraft are not affected by this bulletin,” Doss said.
In October 2008, the Navy issued an aviation bulletin to inspect all 636 A through D Hornets for cracks on F/A-18 Hornets’ outer wing panels (Defense Daily, Nov. 7).
During those inspections, the Navy grounded 10 aircraft and placed flight restrictions on an additional 20 aircraft. Of the deployed aircraft, two were grounded and eight were flight restricted, Doss said last November.
Since 2000, the Navy has been reviewing the potential to extend the life of its legacy Hornet fleet. The effort was divided into the Service Life Assessment Program Phases 1 and 2 and a Phase 1 Service Life Extension Program (SLEP). SLAP phase 1 began in December 2001 and ended in October 2005. The study looked to extend the number of catapult take- offs, trap landings and field landings, as well as stretch the Hornet’s flight hours from 6,000 to 8,000 (Defense Daily, July 24).
The average age of the Hornet fleet is approximately 18 years, and the Navy has planned to keep the Hornet in service until 2023.