Wing Spar Eddy Current Inspection
The test spar ADs rely on to find cracks you can't see.
Eddy current testing finds cracks in metal without taking the part apart.
A probe carrying alternating current induces small electrical currents in the aluminum. A crack or a thin spot disturbs those currents, and the instrument shows the change. It reaches places a flashlight and mirror can't, like the inside of a bolt hole.
That's why the FAA wrote it into each of the Piper and Cessna spar ADs covered on this site.
Where spar ADs call for it
- Piper PA-28 and PA-32 Wing Spar Inspection: the lower outboard bolt holes of the main spar caps (AD 2020-26-16)
- Cessna 210 Carry-Thru Spar Inspection: the kick area of the carry-thru spar lower cap (AD 2020-03-16 and AD 2023-02-17)
- Cessna 177 Cardinal Carry-Thru Spar Inspection: the same area on the Cardinal (AD 2023-02-17)
A September 2024 proposal, still not a final rule, would also call for a one-time eddy current inspection of the lower main spar bolt holes on more PA-28 and PA-32 models once a spar reaches 12,000 hours, or sooner if the logbooks are incomplete. SeePiper PA-28 and PA-32 Wing Spar Inspection.
Who is qualified
An A&P certificate alone doesn't cover eddy current work. Spar inspections are done by inspectors certified to Level II or III under recognized NDT standards such as NAS 410. Many work as mobile inspectors and come to your hangar.
What it costs
The FAA priced the eddy current step at about $600 in both the Piper and Cessna ADs. Mobile inspectors often add travel, and some charge less per airplane when several airplanes at one airport are inspected together. Access labor is separate: about $360 on the Piper (opening up and closing up) and about 20 hours on a Cessna 210 or 177, by the FAA's estimates.
When the inspection finds something
A crack, or corrosion past the AD's limits, has to be dealt with before the airplane flies again. See Wing Spar Corrosion Repair.