On 2 November 2007, an F-15C Eagle air superiority fighter of the Missouri Air National Guard disintegrated in mid-air, the pilot managing to eject safely from the stricken aircraft. As recounted here on 6 November, the cause of the accident was not immediately apparent, and the entire fleet of F-15s was grounded for precautionary inspections, pending completion of the accident investigation. An astute reader with hands-on experience believed that de-bonding honeycomb structures on the tail and ailerons could be at fault, with potentially grave implications for the airworthiness of the entire F-15 fleet. As it turned out, there were systemic problems, but from an entirely different cause.
The precautionary inspections having failed to reveal any systemic faults in the aircraft, on 21 November the F-15s were cleared to fly once again. According to a message sent by General John D.W. Corley, Commander, Air Combat Command (ACC) to all F-15 pilots and their families:
We evaluated the grounded fleet. First, we focused on the F-15Es. They are the newest F-15s and have been exposed to less stress. They are structurally different than the A-D models. Problems identified during years of A-D model usage were designed "out" of the E-model. Given these differences, and after consultation with Warner Robins ALC and the AIB, we returned the F-15E fleet to flying status following successful inspections.
Next, we concentrated on the remainder of the grounded fleet. The AIB is now focused on the area just aft of the cockpit and slightly forward of the inlets. Warner Robins ALC mandated a thorough inspection and repair of all structural components in this area. I have directed each F-15 aircraft be inspected and cleared before returning to operational status. Today, ACC issued an FCIF and Warner Robins ALC issued an Operational Supplemental Tech Order to further direct and guide your pre-flight and post-flight actions.
However, on 27 November, analysis of the accident investigation revealed what USAF Air Combat Command called "possible fleet-wide airworthiness problems." As detailed in an official ACC press release,
The new findings from the Accident Investigation Board indicate possible fleet-wide airworthiness problems with F-15A/B/C and D aircraft. These findings, based on a metallurgical analysis of the mishap aircraft, have drawn attention to the F-15's upper longerons near the canopy of the aircraft that appear to have cracked and failed. The longerons are major structural components that run along the length and side of the aircraft.
Although the longeron area was covered in general by previous inspections as a result of the Nov. 2 mishap, technical experts with the Warner Robins Air Logistics Center in Georgia, are recommending a specific inspection technique for the suspect area based on the yesterday's findings.
Manufacturer simulations have indicated a catastrophic failure could result in this particular area. In addition, cracks were discovered along the same longeron area during two recent inspections of F-15C aircraft. These aircraft were immediately grounded based upon the inspection findings and are awaiting further engineering instructions.
