SERVICE LETTER NO. 1346

inch to ensure the uniform depth of rotation and to aid in reducing lift-off effects. Automated scanning systems may be used. Bolt hole probes shall match as closely as possible, but not exceed, the bolt hole diameter. Split core probes may be expanded to a maximum of 0.050 inch beyond the probe's nominal diameter (based on the probe manufacturer's recommendation). The fill factor shall be 80 % minimum. Holes being inspected shall be no larger than 10% of the expanded bolt hole diameter. Aright angle (90-degree) surface probe may be used for further detail indication, if needed. Reference Standard: • • • • • Any reference standard used shall be of the same conductivity 2024-T3 within ±15% IACs. It shall have electrical discharge machining (EDM) notches for simulating defects as calibration references. The surface finish shall be 63 RHR or better. The reference standard shall have a corner notch size of 0.030 x 0.030 inch (screen set at minimum of three divisions vertical with a phase signal of between 45 and 120 degrees separation from the horizontal lift-off). Frequency used shall be between 100 and 500 kHz. The calibration shall be checked at the beginning and end and every 30 minutes during inspections. SERVICE LETTER NO. 1346 PAGE 4 of 9 Equipment Guidelines: Fluorescent Penetrant Inspection Method: The following is a list of equipment capable of performing the inspections described in this service letter. The following optional inspection equipment has been shown to be adequate to conduct this procedure and is provided as an example only. Other equipment meeting the requirements under the heading “Equipment" may be used. NOTE: Other manufacturers offer equivalents to what is listed here (including GE, Hocking, Rohman, Uniwest, VM, and Zetec). • • • NORTEC 500D or 600D Series Portable Eddy Current Flaw Detector - Olympus Bolt hole probe, 0.375 in. with 0.062 inch shielded coil – Olympus - A bolt hole probe must first be used to inspect the bolt holes; an Olympus right angle (90-degree) surface probe with 0.062 inch shielded coil may be used for a more detailed inspection, if needed. For the calibration standard (NIST traceable) for bolt holes and surface, use the Air Force General Purpose Eddy Current Standard with the following criteria: • • • Bolt Hole Inspection: 0.030 x 0.030 inch corner notch, 0.030 inch radial notch Surface: 2024-T3: 0.008, 0.020, and 0.040 inch depth EDM notches Frequency 300-500 kHz, EDM notch set at five (5) divisions screen height Acceptance: Using the successive evaluation procedure provided under instructions relevant crack or crack-like indications with amplitudes equal to or greater than 50 % of the reference level signal shall be rejected and documented (i.e., such an amplitude reading may mean that the spar box bar does not meet type design requirements and must be reported to Piper Aircraft, Inc. for disposition; fluorescent penetrant inspection is to be accomplished on relevant indications as part of the evaluation). The pass-fail criteria of this inspection is only applicable to a crack in the spar box. Damage in the other areas mentioned should be reported to Piper Aircraft, Inc. for disposition. It is possible for non-crack damage, such as elongated holes, fay gaps, thread marks, gouges, or edge chips in the bolt holes of the spar box to return a flaw indication similar to that of a crack. Multiple indications or broad indications may be associated with fay gaps or swarf within these fay gaps and may not be representative of cracks. If an indication is observed, the hole should be carefully inspected for non- crack damage to eliminate the possibility of false crack indications. To avoid false indications, holes with damage shall be cleaned, per instructions under "Cleaning Surface Imperfections" on page 5, prior to any Eddy Current Inspection. If there is paint in the inspection area, remove it from the area specified using only chemical processes. Abrasives or other mechanical methods for paint removal will hide the existence of any cracks, making it impossible to do an accurate inspection. Use isopropyl alcohol to wipe clean the areas to be inspected where paint was removed. Perform a fluorescent penetrant inspection for cracks as described in FAA AC 43.13-1B, "Acceptable Methods, Techniques, and Practices – Aircraft Inspection and Repair" Chapter 5, Section 5. If no cracks are detected during the inspection, wipe the area of inspection clean with isopropyl alcohol. Apply primer to the areas where paint was removed for inspection using MIL-PRF-85582 Type I Class C2 primer. Alternatively, use any primer conforming to MIL-PRF-23377 and apply per the primer manufacturer's instructions. Any non-crack damage, including elongated holes, should be reported to Piper for disposition. (See "Contact Piper" on page 5.) SERVICE LETTER NO. 1346 PAGE 5 of 9 Contact Piper: INSPECTION AREA CARE: Any indications that is discovered as a result of inspections should be reported to Piper Aircraft Inc., at CustomerService@piper.com or (+1) 772-299-2141. Piper's normal business hours are Monday through Friday, 7:30 a.m. to 4:30 p.m. (Eastern). Care for Bolts and Bolt Holes Cleaning Surface Imperfections: To facilitate bolt removal and avoid damage to the bolt holes, follow this guidance. • • • • • Within the instructions for wing removal found in the applicable Piper AMM, there is the statement, "Arrange and put in place a suitable fuselage cradle and supports for both wings." Proper placement of these supports can neutralize the shear loading of the bolt at the interface of the wing spar and spar box, easing bolt removal. Apply penetrating oil around all washers in the inspection area. Capillary action will draw the oil to the bolt shank to facilitate removal. One such oil is Kroil Penetrating Oil Aerosol, from Kano Laboratories (visit www.kroil.com and see "Where To Buy"). Remove the nut and washers. After removing the nut, apply torque to the bolt head to rotate the bolt approximately one turn, to help draw in the penetrating oil and break the bolt shank free from the hole. Do not wrench the bolt out of its hole, because this can result in thread marking of the hole. Before removing a bolt from its hole, thoroughly clean all debris from the exposed threaded end. Use a nylon bristle brush, as necessary, to remove all debris from the threads and solvent clean using acetone. Ideally, three people should work simultaneously to remove the bolts. This approach should not demand a lot of effort from the group, as follows: • One person adjusts the wing supports or deflects the wing tip up and/or down to neutralize the shear loading. • A second person underneath the aircraft pushes the threaded end of the bolt to move it up and out of the hole. • A third person, in the aircraft, would receive and remove the pushed bolt. • For the person underneath the aircraft: a suitable non-marring tool (such as a 1/4-inch wooden dowel) may be used to push the bolt completely upwards through the hole. If necessary, use a rubber mallet or equivalent to very gently tap the lower end of the tool upwards - do not to make contact with the hole bore. Clean the inspection areas using acetone. Surface imperfections (blemishes, drag marks or scratches) in the hole bore can be cleaned – deburred, smoothed, and polished – using a medium (brown colored) or fine (rust colored) rubberized abrasive, either a point or cylinder, on a 1/16-inch mandrel in a rotary tool. At no point shall the diameter exceed 0.379 inches over the entire shank. • Cratex Q8M or Q8F - 1 x 9/32 bullet point • Cratex Q6M or Q6F - 7/8 x 1/4 cylinder The best results are obtained between 7,500 and 15,000 RPM, using light work pressure. To procure Cratex points, call 800-800-4077 or visit www.cratex.com. SERVICE LETTER NO. 1346 PAGE 6 of 9 INSTRUCTIONS: WARNING: FLIGHT WITH KNOWN CRACKS IN THE AIRCRAFT STRUCTURE IS NOT PERMITTED. AN AIRPLANE WITH A CRACK IN THE STRUCTURE DOES NOT MEET ITS TYPE DESIGN AND NO LONGER POSSESSES ITS REQUIRED TYPE DESIGN STRENGTH. ANY CRACK DISCOVERED IN THE AIRCRAFT STRUCTURE MUST BE REPAIR PRIOR TO THE NEXT FLIGHT. CAUTION: DO NOT DRIVE OUT MAIN WING SPAR BOLTS. TAKE EXTREME CARE NOT TO DAMAGE BOLT HOLES. CAUTION: DO NOT ROTATE BOLTS WHEN THE THREADS ARE INSIDE THE BOLT HOLE. NOTE: The instructions contained within this service letter are applicable only to aircraft that conform to type design at the interface of the main wing spar and spar box. Any previously approved repairs or modifications may require alternate methods, instructions, and hardware. NOTE: Temporary removal of interior components, fairings, and/or access panels may be required in order to accomplish the instructions contained in this service letter. NOTE: Refer to the applicable Piper Airplane Maintenance Manual (AMM) or Service Manual (SM) for model specific details. Refer to the applicable Piper Parts Catalog (IPC) for the type and size of replacement hardware. NOTE: These instructions apply to both the left and right wings. 1. 2. For each bolt removed from the lower wing cap that secures the main wing spar to the spar box, perform the Visual Inspection method, as described page 3, on the inner surface of each spar box bolt hole for damage (scratches, gouges, thread marks, etc.). See Figure 1 for a view of the spar box and main wing spar that identifies the bolt holes and inspection areas. • If no damage is discovered in any bolt hole, proceed to step 6. If damage is discovered in one or more bolt holes, proceed to step 2. Clean the subject spar box bolt holes with damage as described under Cleaning Surface Imperfections on page 5. Then perform the Visual Inspection method again on the inner surface of each subject spar box bolt hole. • If no damage is discovered in any bolt hole, proceed to step 6. • If damage is still discovered in one or more bolt holes, proceed to step 3. 3. 4. 5. For each spar box bolt hole with damage, perform the Eddy Current Inspection (ECI) method following the guidance under Inspection Methods on page 3. • If no ECI indications are present, then proceed to step 6. • If an ECI indication is present, proceed to step 4. NOTE: If there is any uncertainty when performing an eddy current inspection (ECI), uncertainty in the results of an ECI, or when performing an ECI it is believed that a noisy condition exists, Piper Aircraft, Inc. recommends consulting with a NAS 410 (or equivalent standard per FAA AC 65-31B) Level III technician. Perform the fluorescent penetrant inspection (FPI) method on the subject spar box bolt holes and the surrounding area local to each subject bolt hole. FPI improves situational awareness of the inspection area and potential contributors to false positives (e.g., fay gaps, swarf, etc.); it can further identify potential false positives and corroborate eddy current findings (additional ECIs are appropriate, as necessary). Follow the guidance under Inspection Methods on page 3. NOTE: If the technician accomplishing FPI is not the ECI technician, then the ECI technician shall observe the FPI to gain situational awareness of the inspection area for the benefit of the ECI in step 1. Consult with a NAS 410 (or equivalent standard per FAA AC 65-31B) Level III technician to interpret the NDT results and provide final determination of indications. • If ECI indications are determined not to be damage, then proceed to step 6. • If ECI indications are determined to be damage, proceed to "Contact Piper" on page 5 for further action. 6. Make a logbook entry documenting compliance with this service bulletin. Spar Box Inspection Figure 1 (Sheet 1 of 2) MAIN WING SPAR 2701 IOI SERVICE LETTER NO. 1346 MAIN WING SPAR INSTALLATION PERSPECTIVE VIEW (PA-28-181 SHOWN, OTHERS SIMILAR) WING SPAR BOX PAGE 7 of 9 SERVICE LETTER NO. 1346 INBD ± VIEW A-A LOOKING FWD (LH SHOWN, RH OPPOSITE) WING SPAR BOX MAIN WING SPAR INSPECTION AREA VIEW C-C WING SPAR CROSS SECTION SHOWN AS INSTALLED IN WING SPAR BOX (LH SHOWN, RH OPPOSITE) ここここ Figure 1 (Sheet 2 of 2) Spar Box Inspection UP L INBD מים שים שים םים VIEW B-B LOOKING AFT (LH SHOWN, RH OPPOSITE) UP FWD PAGE 8 of 9 SERVICE LETTER NO. 1346 MATERIAL REQUIRED: N/A EFFECTIVITY DATE: This service letter is effective on November 12, 2024. SUMMARY: NOTE: PAGE 9 of 9 Please contact your Piper Approved Service Center to make arrangements for compliance with this service letter in accordance with the compliance time indicated. Please notify the factory of any address/ownership corrections. Changes should include aircraft model, serial number, and current owner's name and address. Corrections and/or changes should be directed to: PIPER AIRCRAFT, INC. Attn: Customer Service 2926 Piper Drive Vero Beach, FL 32960 or: CustomerService@piper.com Please include in subject line: "Aircraft ownership update"