Flying Fortresses grounded pending wing spar inspection

According to the FAA document, “This AD was prompted by a report indicating that the left front spar lower fitting had completely separated at the wing-to-fuselage joint, and the equivalent joint on the right side of the airplane was cracked. This AD requires inspections of the wing terminal-to-spar chord joints, and repair if necessary.”

The AD applies to 18 aircraft registered in the United States, though only three of those aircraft are considered airworthy, while others are in various stages of restoration. Aircraft that are operated under experimental airworthiness certificates have also been included in the AD because of “the risks associated with passenger-carrying operations frequently conducted by these airplanes.”

The AD continues, “This condition, if not addressed, could result in fatigue cracking of the wing terminal-to-spar chord joints, which could result in loss of control of the airplane and reduced structural integrity of the airplane.”

The defect was originally found on EAA’s B—17 Aluminum Overcast. The organization reported on its website that the crew “discovered a fitting inside the wing that showed signs of fatigue. Following safety protocols, the airplane was grounded for a full inspection that determined that replacing the part was necessary. Because of that, EAA’s B-17 national tour is on hiatus for the time being. The airplane will remain in Florida at this time until a repair schedule is finalized.”

Operators of the nearly 80-year-old fleet have been aware of the potential of the AD and have made the decision to ground affected aircraft until inspections and any required repairs can be made.

Travis Major, Commemorative Air Force Airbase Arizona leader, said, “Members of CAF Airbase Arizona operate and maintain the Commemorative Air Force’s B-17 Sentimental Journey. CAF Airbase Arizona has been working closely with the FAA regarding the latest concerns related to the wing spars of the B-17 aircraft. We are currently working through the inspection procedure and process as called for in the FAA’s recently issued airworthiness directive and we are looking forward to having our B-17 flying again this summer on the Flying Legends of Victory Tour."

This isn’t the first time wing spars have been a problem for the B–17 fleet. In 2001, the FAA released an AD that required “inspections to detect cracking and corrosion of the wing spar chords, bolts and bolt holes of the spar chords, and wing terminals; and correction of any discrepancy found during these inspections.” The now 32-year-old AD was also prompted by reports of cracked wing spars and affected B–17 models E, F, and G.

Now, the FAA states that the required inspection from the 2001 AD was not effective in reliably finding the cracks in the steel fitting inside the spar chord tube. The new AD requires a new inspection method.

The AD gives operators two inspection options: a magnetic particle inspection of the terminal fittings and an eddy current inspection of the spar chord, or an eddy current bolt hole inspection of the steel terminal fitting and aluminum spar chord.

The AD also requires that any cracking or corrosion be repaired, and all inspection results must be sent to the FAA. The FAA will use inspection reports to determine the “nature, cause and extent” of the concern, evaluate the risks, and come up with a long-term resolution.

The AD goes into effect June 1, 2023, and comments can be submitted until July 3. Comments can be submitted using the procedures outlined in 14 CFR 11.43 and 11.45.