Survey finds concern over aircraft wings

Potential or actual wing spar corrosion and fatigue threatens a cohort of (largely piston-powered) aircraft that have been in service for decades, predominantly (so far) single-engine Piper and Cessna piston models. The significant safety implication of weakened wing spars has resulted in heightened scrutiny by the FAA, with the most recent examples published in 2020 and 2021.

In a 2021 directive that applies to a range of Piper Aircraft models and requires eddy current inspection for an estimated 5,440 of the 10,881 airplanes in the applicable models group, the FAA wrote that it “considers this AD to be an interim action,” and that the inspection reports will provide the FAA additional data for determining the number of cracks present in the fleet. The FAA may take further rulemaking action based on data.

The FAA has applied a similar approach to thousands of Cessna Aircraft Co. products, primarily the high-wing (strutless) Cessna 210 series, subject to an AD issued in 2020 following an in-flight breakup of a Cessna T210M in Australia. Investigators found fatigue cracks had initiated from corrosion pits in the accident aircraft's wing spar, weakening this critical part to the point of failure. A proposed AD followed in 2021 adding later Cessna 210 models, as well various iterations of the Cessna 177.

While the FAA has collected comments from individuals, AOPA, and other organizations, it continues to engage and seek feedback from aircraft owners for specific alternatives it should consider to ensure the safety of aircraft wing spars.

A special airworthiness information bulletin (SAIB) issued by the FAA in October for Piper PA–28 and PA–32 airplanes noted that 115 of 2,880 aircraft inspected under the 2020 AD were found to have crack indications, though a quarter of those were determined to be hole damage or corrosion, rather than a crack.

In addition, AOPA developed a survey for impacted Cessna and Piper operators to provide feedback on eddy current compliance, availability, and costs related to current and proposed ADs that rely on eddy current inspections to identify damaged wing spars.

More than 600 respondents provided insight on the current state of compliance with the various active ADs affecting both brands. Of the 333 Piper owner respondents, 33 percent were either required or voluntarily completed an eddy current inspection and a similar rate found for the 163 Cessna respondents.

Availability of eddy current inspections proved better than expected, at least among the survey group: 92 percent of the respondents reported that such services were available within 150 miles, and 77 percent reported eddy current inspection availability within 50 miles. This is an important finding, because ferry permits are not issued to reposition an aircraft for wing spar replacement, should the owner choose to do that, in the event the spar does not pass inspection. However, 86 percent either agreed or strongly agreed that there are very few local mechanics who are qualified to perform eddy current inspections.

Eddy current inspections are also costly, with approximately 44 percent reporting up to $1,000 in added cost to an annual inspection, with 28 percent reporting eddy current inspection costs as high as $2,000.

Reported options available to owners of aircraft that do not pass eddy current inspection are less than encouraging. Across all models, owners tended to agree that replacement wing spars are hard to find. It has also been reported to AOPA that there is limited availability of spars for out-of-production Cessna aircraft, and the Cessna 210 and 177 models both have that distinction.

AOPA Senior Director of Regulatory Affairs Christopher Cooper said that while wing spar ADs published in the last three years have already impacted a significant number of aircraft, due to the severity of the problem that wing spar damage can cause, our concern is that future ADs could be equally significant. It will be important for the aircraft operator community to be proactive and engaged with the FAA to provide safe and accessible options for compliance.

Cooper and others have worked with the FAA in recent years to focus the scope of directed inspections on aircraft that more closely match the characteristics—including time in service—of the accident aircraft that prompted the various ADs. A 2018 AD that originally applied to about 20,000 Piper PA–28 aircraft was reduced by about 8,000 airplanes in 2020. While AOPA and others who comment on proposed FAA rulemaking (specifically, wing spar-related ADs) have continued to urge the FAA to focus on aircraft that are "representative" of accident aircraft, the agency's stance may shift if more inspections reveal potentially dangerous defects.

Cooper said AOPA will continue to gather information from aircraft owners, maintenance shops, and the FAA to inform our advocacy for right-sized solutions for ongoing inspection and maintenance requirements; however, he highly recommends individuals who have specific data, knowledge, or experience with the impacted Cessna and Piper wing spars to contact AOPA.