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" The trouble started on Nov. 2, when a Missouri Air National Guard F-15C crashed during an exercise. The incident quickly blossomed into a temporary, global shutdown of all F-15 flights, so that the planes--including those owned by overseas customers in countries such as Israel, Saudi Arabia and Japan--could be examined. This was the fourth crash involving an F-15 model this year. &amp;quot;First, only noncritical flights in the U.S. were grounded,&amp;quot; says Guy Ben-Ari, a research fellow at the Center for Strategic and International Studies. &amp;quot;Then it was broadened to include all noncritical flights in combat operations. Then it was broadened to all flights. That doesn&amp;#039;t happen very often.&amp;quot; Equally rare is the fact that international customers of the airplane followed the United States&amp;#039; lead in grounding their F-15s. &amp;quot;Makes you wonder what information they are receiving,&amp;quot; he says. Most media reports have emphasized the age of the aircraft, which debuted in 1975. However, newer variants--particularly the F-15E Strike Eagle--have also been grounded, and the last F-15 went into service in 2004. Now, comments from military officials to Popular Mechanics concerning the examination of structural parts common to all variants hint at a potentially serious problem with the airplane&amp;#039;s structural integrity. Inspecting America&amp;#039;s 700 F-15s is a massive undertaking that involves thousands of maintenance crews around the world. In what is called an Immediate Action Time Compliance Technical Order, a list of detailed instructions was handed down to those maintainers whose daily duty is to keep the complex planes flying. &amp;quot;This is done at the base level,&amp;quot; says Maj. Tom Crosson, spokesman for Air Combat Command. &amp;quot;The average wrench-turner goes through the checklist.&amp;quot;    How the Inspections Work According to those involved, 13 hours worth of testing is required per airplane before it can pass inspection, with results reported back to Air Force headquarters. Each bolt to be twisted, every panel to be removed and each line to be checked is listed in detail. In the case of the F-15 investigation, Crosson says, specific attention is being paid to the hydraulic system lines, environmental control systems that regulate the cockpit, and structural frames called longerons. Longerons are metal strips that run along the length of the airplane&amp;#039;s fuselage and transfer aerodynamic loads from the skin of the airplane to internal frame--not a place where you want to see signs of weakness. The longerons require four hours to examine after the jet has been prepared by removing panels to gain access, according to Lt. Col. Al Porter, deputy maintenance group commander for the 366th Fighter Wing. &amp;quot;The maintainers are looking for any cracks in the upper and lower longerons or any other structural deficiency, including any problems around fastener holes or the fasteners themselves,&amp;quot; he says.  Part of the inspection uses a non-invasive surface scan that can detect cracks that may be invisible to the naked eye. Electricity is passed through a tightly wound coil, creating a current that will be interrupted by any anomalies, according to Porter. Any suspected cracks are followed up by placing dye in the suspect area and viewed with an ultraviolet light that will confirm a crack. &amp;quot;We have detected no cracks in our inspections so far,&amp;quot; Porter says. &amp;quot;The longerons that we are inspecting now are not part of the current phase inspection work cards. It is too early to know if this will become part of future phase inspections.&amp;quot; When maintenance problems arise in airplanes, fingers quickly point at the operational tempo of operations: In other words, the more hours a plane flies, the more likely it is to develop problems. With a military aircraft, however, the pace is less important than where it&amp;#039;s flying and what it&amp;#039;s called on to do.  During combat operations in Afghanistan and Iraq, sand and large differences between day and nighttime temperatures can take their toll on an airplane. On the other hand, the missions are relatively easy on F-15s. &amp;quot;These aircraft were designed for superior maneuverability and acceleration while dogfighting,&amp;quot; Ben-Ari says. &amp;quot;[In Iraq and Afghanistan] there are no enemy fighter jets or anti-aircraft missiles to outmaneuver.&amp;quot; Instead, the planes are logging many flight hours simply loitering in circles, waiting for information on where to drop bombs to help ground forces.    Operations like environmental duct reinstallation can take Air Force maintainers up to 13 hours to complete. &amp;quot;We have detected no cracks in our inspections so far,&amp;quot; one tells PM. (Photographs Courtesy fo the U.S. Air Force) Debunking a Conspiracy Theory It may seem logical to ground airplanes after a series of crashes, but there is another explanation for why the Pentagon has been keeping many of its F-15s on the ground. Skeptical analysts and defense watchers on Web boards have speculated that what&amp;#039;s really at stake isn&amp;#039;t safety, but future budget fights.  The 2008 defense bill passed last week by Congress designates $3.15 billion to purchase an additional 20 F-22 Raptor jets, , a successor to the F-15, from Lockheed Martin. Over the next several years, the Air Force wants to maintain or even step up spending on both Raptors and the F-35 Lightning II (aka the Joint Strike Fighter). But some in Congress have been pushing to limit Air Force spending in order to beef up ground forces. According to the online rumor mill, the well-publicized shutdown of F-15s is meant to provide the Air Force with some leverage when the bean counters come knocking. So is there any credence to the idea that the Air Force was eager to prove a point by shutting down their fighters? Not really. &amp;quot;The F-22 [consideration] was a side effect,&amp;quot; says military analyst and author Jim Dunnigan. &amp;quot;An idea like that would not withstand scrutiny by engineers or historians.&amp;quot; Ben-Ari agrees that the &amp;quot;conspiracies don&amp;#039;t hold water.&amp;quot; He points out that the Pentagon&amp;#039;s operational need for F-22s is well known, and would not likely change based on a stunt that crash investigators could refute. Besides, why try manipulating thousands of savvy engineers and mechanics, when Congress is such a soft target? Traditional lobbying is easier and more effective, Ben-Ari maintains. &amp;quot;I am hoping there is no mix of safety and politics,&amp;quot; he says.  10 Plane Crashes That Changed Aviation &amp;amp;gt;&amp;amp;gt;&amp;amp;gt;  New legislation will send billions of dollars toward Lockheed Martin for its F-22 fighter jets, but experts say the engineering holds up against speculation that money got in the way of the F-15 stand-down. (Photograph Courtesy of the U.S. Air Force) Skeptical analysts and defense watchers on Web boards have speculated that what&amp;#039;s really at stake in the massive investigation into F-15s isn&amp;#039;t safety, but future budget fights. (Photograph by Getty Images) "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/military/a4627/4231807/>