SAIB AIR-21-10

FAA Aviation Safety

SPECIAL

AIRWORTHINESS

INFORMATION BULLETIN

SUBJ: Wing, Attach Fittings (JASC 5740) This is information only. Recommendations aren’t mandatory.

SAIB: AIR-21-10 Date: June 29, 2021

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 specific Piper Aircraft, Inc. models affected are: PA-28-140, PA-28-150, PA-28-151, PA-28- 160, PA-28-161, PA-28-180, PA-28-181, PA-28-201T, PA-28-235, PA-28-236, PA-28R-180, PA- 28R-200, PA-28R-201, PA-28R-201T, PA-28RT-201, PA-28RT-201T, PA-28S-160, PA-28S-180, PA-32-260, PA-32-300, PA-32-301, PA-32-301FT, PA-32-301T, PA-32-301XTC, PA-32R-300;

PA-32R-301 (HP), PA-32R-301 (SP), PA-32R-301T, PA-32RT-300, PA-32RT-300T, PA-32S-300, PA-34-200, PA-34-200T, PA-34-220T, PA-44-180, and PA-44-180T.

Recommendations

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.

35630 38643 101

SKETCH A SECTION A-A BOLT NAS1104-17 WASHER AN960-416L (UNDER HEAD) WASHER AN960-416 (UNDER NUT) NUT MS21045-4 SEE NOTE

0.12 MIN.

0.35 MAX.

TORQUE NUT 50-60 IN-LBS NOTE MINIMUM OFHEN UNDER NUT.

AN960-416 OR AN960-416L AS

REQUIRED TO LEAVE A MAXIMUM OF 1 1/2

THREADS OR MINIMUM

OF BOLT CHAMFER

EXPOSED Figure 1. Forward Attach Fitting

Figure 2. PA-28 Corroded Forward Attach Fitting and Spar Section (removed)

FORWARD FITTING INSIDE WING

LEADING EDGE SHOWING

CORRODED RIVET HEADS Figure 3. Wing Interior Showing Galvanic Corrosion