Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
AIR-21-10
June 29, 2021
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin is to advise owners and
operators of Piper Aircraft, Inc. PA-28, PA-32, PA-34, and PA-44 (see
list of specific models in “Background” section) airplanes of the
potential for corrosion of the forward spar to fuselage attach
fittings, in an area that may not be easily accessible for inspection
We have determined that no regulatory action is necessary at this time
because the airworthiness concern is not an unsafe condition that would
warrant an FAA AD under 14 CFR part 39.
Background
Piper Aircraft, Inc. issued Service Bulletins (SB) 789A, 977, and 1244B
to inspect for corrosion on the aft wing spar to fuselage attach
fittings. At the time the service bulletins were written, the corrosion
was attributed to water intrusion, and forward attach fittings were not
considered to be subject to the water intrusion issues affecting the
aft attach fittings. Therefore, inspections of the forward attach
fittings were not included in those service bulletins.
Since then, the FAA became aware of several cases of severe corrosion
on the forward attach fittings from operators in Florida. While no
evidence exists of water intrusion at the forward locations, the
potential exists for galvanic corrosion between the dissimilar metals
of the steel fittings and aluminum spar. Due to the restricted
accessibility of the forward attach fittings in some airplanes, owners
may be neglecting to have this area inspected. See Figures 1 through 3
depicting corrosion location and characteristics.
The FAA is recommending that owners take special care to ensure that
the forward wing attach fittings are visually inspected during annual
or 100-hour inspections in accordance with the applicable Piper
Aircraft, Inc. Maintenance Manual. Some operators have had inspection
panels or borescope inspection holes installed to facilitate inspection
(contact Piper Aircraft, Inc. for acceptable options). “Powdery” rivets
in the attach fitting are indicative of corrosion between the steel and
aluminum surfaces. Particularly susceptible are those airplanes
operating in coastal or otherwise corrosive environments.
For Further Information Contact
Dan McCully, Aviation Safety Engineer, Atlanta ACO Branch, FAA, 1701
Columbia Avenue, College Park, GA 30337; phone: (404) 474-5548; fax:
(404) 474-5605; email: william.mccully@faa.gov.
