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``All F-15 aircraft have been grounded, not just non-mission critical flight ops,'' the Air Force said. ``The grounding will remain in effect until conclusions are made'' by the safety investigation, the service said. Aircraft assigned to Afghanistan and patrols over U.S. airspace will be on ground alert in case of a major emergency, the service said.
In a statement released on 4 November, the US Air Force said the cause of the F-15C crash remains under investigation, but preliminary findings indicate that a possible structural failure of the aircraft may have occurred. It described the suspension of non-mission-critical flight operations as a "precautionary measure".
A report on the incident is expected to be completed in 60 days.
This is the second Missouri ANG Eagle crash this year. The May crash of an F-15D in Indiana was caused by a jammed control cable. Four USAF F-15s have been lost so far this fiscal year, compared with one in FY2006.
Originally posted by Zaphod58
The F-15 was originally designed for 4000 to 8000 flight hours before it hit the end of its structural lifetime. They found that that would be about 7600 "hard" hours, or up to 12,000 "soft" hours. They were planning on the F-15C being around until up to 2030, but that's based on 270 flight hours a year.
[edit on 11/5/2007 by Zaphod58]
The F-15 initial operational requirement was for a service life of 4,000 hours. Testing completed in 1973 demonstrated that the F-15 could sustain 16,000 hours of flight. Subsequently operational use was more severely stressful than the original design specification. With an average usage of 270 aircraft flight hours per year, by the early 1990s the F-15C fleet was approaching its service-design-life limit of 4,000 flight hours. Following successful airframe structural testing, the F-15C was extended to an 8,000-hour service life limit. An 8,000-hour service limit provides current levels of F-15Cs through 2010. The F-22 program was initially justified on the basis of an 8,000 flight hour life projection for the F-15. This was consistent with the projected lifespan of the most severely stressed F-15Cs, which have averaged 85% of flight hours in stressful air-to-air missions, versus the 48% in the original design specification.
Full-scale fatigue testing between 1988 and 1994 ended with a demonstration of over 7,600 flight hours for the most severely used aircraft, and in excess of 12,000 hours on the remainder of the fleet. A 10,000-hour service limit would provide F-15Cs to 2020, while a 12,000-hour service life extends the F-15Cs to the year 2030. The APG-63 radar, F100-PW-100 engines, and structure upgrades are mandatory. The USAF cannot expect to fly the F-15C to 2014, or beyond, without replacing these subsystems. The total cost of the three retrofits would be under $3 billion. The upgrades would dramatically reduce the 18 percent breakrate prevalent in the mid-1990s, and extend the F-15C service life well beyond 2014.