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Show NEWS - 6 workers 1 " f cracks pursue on daily basis I i , ' - , ... . J ... j ' . " ' .... i t ' j I a i'V .Vj V Hilltop Times : t F-- .Aug. 2, 1991 ' by Gary Hatch w II ' jr Hilltop Times editor Repairing and preventing fatigue cracks has been part of the workaday world of the F-- 1 6 system program manager for years. Col. Gary Austin pursues cracks most of which are microscopic in the Fighting Falcon's wings and substructure with the same care he gives to any other facet of the upkeep of the Air Force's multi role fighter. Durability tests and engineering studies alerted the Air Force to the possibility of cracks developing in the aircraft since the earliest models came off the assembly line 15 years ago. Accordingly, engineers set up an extensive tracks to ing system with a wide variety of F-1 6. stay ahead of a potential problem on any An article in Jane's Defense Weekly two weeks ago about cracks in the wings of some F-- 1 6s sent members of the news media clamoring for answers to questions about flight safety for the versatile cross-check- I - 1 lVfc-fe- et f ..... ... ...m llll,lll,nllll. U.S. Air Force Photos by Doug James reporter Jack Ford in Bldg. 225, clearing up misconceptions some people were having about stress cracks in Col. Gary Austin talks with KSL-T- V s. 5 rX Safety uncornpromisod five-plat- ,i . Clearing the air fighter. The answer: "The cracks are not a flight safety issue at all. They are a durability issue," Austin told a group of reporters gathered July 26 at Hill AFB's big maintenance hangar, Bldg. 225. "No Air Force F-- 1 6 has ever been grounded because of any of these cracks, and we've never had an aircraft accident because of them. "We don't view this as a crisis. It's routine maintenance," Austin said. In fact, for more than a year workers have been to prevent anticipated performing a wing "beef-up- " F-1 6s that come in for programmed cracking on all maintenance. During the stopover, all the sysdepot tems and structures of each aircraft are thoroughly inspected, tested and repaired. More than 60 jets have been modified so far. The Air Force's approximately 1,700 F--1 6s are all expected to be fitted with the beef-up-, most at Hill, the service's primary repair depot for the fighter. e Aircraft workers are installing a patch wide an area by approximately covering long on the top skin of the wing near where it attaches to the fuselage. It covers three access panels into the wing. oyr - ' 3) Steady eddy MSgt. James Turner, 388th Equipment Maintenance Squadron, demonstrates the use of an electrical eddy current to find minute imperfections in metal surfaces. 3-fe- et Preventive maintenance This modification began because durability tests conducted at General Dynamics, the primary contractor of the jet, found cracks could develop in that area after several thousands of hours of flight. At the 4,000-hou- r mark, tiny fractures were found in all three access holes. The modification was installed to prevent further cracking, which could lead to a more expensive repair later. The most heavily flown of the fighters are just beginning to approach the 4,000-hou- r mark. The modification should enable the fighter to life expectancy, Austin said. reach its 8,000-hou- r Cracks can occur at a variety of locations on the plane. Most that have been found cannot be seen by the naked eye. Aircraft technicians rely on a battery ld electrical eddy current, microof tests using scopes, ultrasonic sound waves, penetrating fluorescent dyes and magnetic currents. Workers are guided to problem areas not only by engineering studies but also by the compiled, computer-cruncheflight data of each plane. That data is then compared to a baseline flight profile to identify vulnerable areas. Cracks found around holes drilled through the infrastructure to route hydraulics or other lines may be repaired by a cold reworking process that realigns the molecular structure by expanding the hole slightly and compressing the metal around the hole, r 'm Austin aioW X-ray- d s, Other cracks are repaired using a doubler, or patch, and some cracks can simply be watched for some period of time before they need to be repaired. Badly cracked pieces are usually replaced, Austin said. Some fatigue cracks can be fixed by wing units at the base level and some must be taken to a major repair facility. The F-- 1 6 was originally designed as a lightweight fighter with a narrowly defined mission primarily Austin said. i 1 .. .:. : at-r- UpB . xf 9 J W ifcgfm it air-to-grou- Additional rolos However, new missions, including more roles, have been added. The new tasks required modifications avionics equipment, munitions or structural strengthening that added weight to the aircraft. In addition, the plane is being flown more aggressively than anticipated. These factors put more stress on the aircraft and contribute to the incidence of fatigue cracks, Austin said. None of the 388th Tactical Fighter Wing's more than 70 F-- 1 6s have experienced any fatigue cracks. Some have been found on a few of the 419th TFW's planes. The Air Force plans to modify and strengthen the structure more extensively beginning in 1993, providing funding is approved. Austin said the Air Force doesn't yet know where the majority of that workload might be done or how much the project would cost to complete, if ap- proved. -- .n-. air-to-a- ir F-16- 's Thick skinned Colonel Austin details procedures aircraft workers take to beef up an area on the top skin of an 1 6 wing. The modification is expected to be completf ed on all 1,700 of the Air Force's multi-rol- e efSwhethrvCacks.haye PJS&f jss. F-- |