Back in August, over half of the Lockheed-Martin F-16Ds in the USAF inventory were removed from flight after cracks were identified along the canopy sill longeron. This particular longeron in located between the front and back seat of the Viper. Longeron fatigue cracks are always a concern because of their relationship to the structural integrity of an aircraft.

Aging fleets coupled with consistent air combat operations in multiple countries over the last 25 years has meant an increased focus on extending airframe hours. Probably the most recent notable incident involving longeron cracks was when the cockpit section of a Missouri ANG F-15C separated in flight back in 2007.

In this instance, one longeron with fatigue cracks resulted in multiple failures in the same area and caused a complete structural failure just aft of the cockpit. The aircraft literally broke into two pieces mid-flight and miraculously, the pilot, Major Stephen Stilwell, ejected from the stricken aircraft, but suffered serious injuries and disfigurement as a result of the incident, cutting short his flying career.

The USAF and Lockheed-Martin identified a long-term fix near the beginning of September. The solution involved installing a strap over the cracked longeron to give it structural stability and increased strength to withstand the wicked G-loads the Viper is capable of.

A temporary fix was identified sooner, one that could have gotten the Vipers back in the air, but the nature of these cracks was deemed too high-risk. With engineers cognizant of the F-15 incident and unwilling to further risk the lives of airmen all over the world flying the F-16, the temporary solution was ultimately canned.

More than one-third of the aircraft identified as having cracks belong to the 56^th Fighter Wing based at Luke Air Force Base in Glendale, Arizona. The importance of having these aircraft in the fight is significant due to Luke being the only home for active duty F-16 pilot training in the Air Force.

Back in November, the first of 32 Luke F-16D’s was returned to full flying duties. Maintainers from Luke and depot field teams from Hill Air Force Base in Ogden, Utah have been working 12-hour days, six days per week, to get Luke’s shaggin’ wagons back in the air. As a direct result of their hard work and dedication, the last two aircraft are expected to be ready for flight at the beginning of January.