AD Issued for Aeronca (Rogers) Sedan Wing Inspection
Aeronca 15AC Sedans like this one are the subject of an AD issued by the FAA for potential cracks, intergranular exfoliation, and corrosion in the upper and lower main spar cap angles on both wings.
By H.G. Frautschy, Executive Director - Vintage Aircraft Association, EAA 203490
March 15, 2012 – The FAA recently issued Airworthiness Directive AD 2012-04-10 requiring owners of the Aeronca 15AC Sedan to have initial inspections of the exposed trailing edges on both the upper and lower main spar cap angles on both wings. The inspections are looking for signs of cracks, intergranular exfoliation, and corrosion. While a wing failure has not occurred in any of the approximately 255 Sedans on the FAA registration rolls, corrosion in the structure of a few Sedans was discovered and prompted the FAA to issue the AD. This is only the fourth airworthiness directive issued against the Sedan's airframe over its 62-year history.
The first inspection must be accomplished within 25 hours time-in-service (TIS) after April 17, 2012 (the effective date of the AD), or within the next six months after that date. If the wing has been repaired within the past 10 years, different inspection intervals come into effect.
If significant corrosion is found, the wing must be repaired by replacement of the spar cap angles, and no splicing of those components is allowed.
If the initial inspection does not reveal cracks, intergranular exfoliation, and corrosion, a more in-depth inspection must be accomplished within 12 months after April 17, 2012. The installation of inspection panels and associated doubler plates is needed to accomplish a visual inspection of the entire length of the spar. The inspection and installation of the panels and plates must be done in accordance with Burl's Aircraft LLC Mandatory Service Bulletin No. 15AC06-08-10, dated June 8, 2010; Burl's Aircraft LLC Mandatory Service Bulletin No. 15AC06-08-10, Amendment A, dated June 23, 2010; or Burl's Aircraft LLC Mandatory Service Bulletin No. 15AC06-08-10, Amendment B, dated June 23, 2010, Rev. Original, September 15, 2011; and FAA Advisory Circular (AC) 43.13 - 1B, Change 1, Chapter 6. (The aircraft is known to the FAA as the Burl A. Rogers 15AC Sedan, since Burl's Aircraft is the owner of the type certificate previously held by William Brad Mitchell, who had acquired the TC from Aeronca, the original manufacturer.)
You'll note the identification number of the three versions of the Burl's bulletin is the same; only the revision letter changes. Rogers advised us that the inspection method is identical in all three of the references. Some changes to inspection intervals and additional language required by the FAA were added in subsequent revisions. You can download Service Bulletin No. 15AC06-08-10, Amendment B, dated September 15, 2011 from the the company's website. Frankly, it would have been simpler to understand if only one reference to the inspection service bulletin were listed.
After each of the inspections, it is recommended that the spar be treated with a corrosion-inhibiting compound.
In the event the spar cap angles must be replaced, the FAA estimated that each wing could cost $8,000 to repair, if the work were hired out to a shop that charged $85 per hour for the estimated 80 man-hours needed to accomplish the job.
While we were under the impression that comments and procedures for an alternate method of compliance (AMOC) were submitted to the docket during the public comment period, the FAA stated that when it issued the AD a written, detailed procedure had not been submitted. The agency further mentioned it would consider an AMOC. We understand that an inspection procedure has been created using a borescope to thoroughly inspect the wing, but without the installation of a large number of inspection holes.
We would also expect that some may wish to submit an AMOC for the installation of inspection panels and doublers of their own design. In most cases, Sedan owners will have to repeat the inspection on an annual basis after the initial in-depth inspection is accomplished.