SERVICE BULLETIN NO. 1377

If an indication is observed, the hole should be carefully inspected for non-crack damage to eliminate the possibility of a false crack indication. Any non-crack damage, should be cleaned per ‘Cleaning Surface Imperfections’, below, and inspected again. If cleaning results in an diameter measurement greater than the maximum allowed for a nominal hole size, a repair hole size may be permissible per the below instructions. If an indication is still observed, contact to Piper Aircraft, Inc. for disposition. See contact information below. Cleaning Surface Imperfections: Surface imperfections (blemishes, drag marks or scratches) in the hole bore can be locally 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: • 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. To Contact Piper: Any unresolved crack indication(s) 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 Standard Time). SERVICE BULLETIN NO. 1377 PAGE 4 of 9 INSTRUCTIONS: WARNING: FLIGHT WITH KNOWN CRACKS IN THE AIRCRAFT STRUCTURE IS NOT PERMITTED. ANY CRACKS DISCOVERED IN THE AIRCRAFT STRUCTURE MUST BE REPAIRED PRIOR TO THE NEXT FLIGHT. AN AIRPLANE WITH A CRACK IN THE STRUCTURE DOES NOT MEET ITS TYPE DESIGN AND NO LONGER POSSESSES ITS REQUIRED TYPE DESIGN STRENGTH. NOTES: • Prior to any inspection, wipe surfaces clean using a soft cloth dampened with isopropyl alcohol, mineral spirits, naphtha, or other suitable cleaning agent. • Refer to the appropriate section of the applicable Airplane Maintenance Manual or Service Manual for the procedures to jack the airplane and for model-specific instructions for the removal and installation of the main landing gear. • Instructions below apply to both left and right sides of the aircraft. • The inspections described in this service bulletin shall be accomplished using a 10X magnifier, a mirror, and a suitable light source or other equipment capable of providing equal or better resolution. 1. Place the airplane on jacks. 2. Remove the MLG truss brackets, two (2) each per aircraft, as shown in Figure 1. Replace any truss bracket hardware (bolts, nuts, and washers) on condition. Other components, including lubricator fittings, that are in serviceable condition may be retained for reinstallation. 3. Visual Inspection for Cracks Examine all surfaces covered by the main gear truss bracket for cracks, fretting wear, or other damage. Repair or replace on condition. a. If there is paint on the inspection area of the main wing spar, as shown in Detail A of Figure 1, remove it from the area specified using only chemical processes. Abrasives or other mechanical methods for paint removal may hide the existence of any cracks, making it impossible to do an accurate inspection. Use isopropyl alcohol to wipe clean where paint was removed in the inspection area. b. After paint is removed from the inspection area, 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. c. Any cracks that are discovered must be reported to Piper. Regardless of findings, the inspection results must be reported to Piper electronically as described in step 5, below. If no cracks are found, wipe clean with isopropyl alcohol and apply primer to bare metal surfaces using MIL-PRF-85582D Type I Class C2 primer. Alternatively, use any primer conforming to MIL-PRF-23377 and apply per the primer manufacturer’s instructions. SERVICE BULLETIN NO. 1377 PAGE 5 of 9 TRUSS BRACKET FWD MAIN LANDING GEAR ASSEMBLY ISOMETRIC VIEW LEFT SIDE SHOWN (RIGHT SIDE OPPOSITE) DETAIL A INSPECTION AREA LOOKING FORWARD AT MLG TRUSS BRACKET AND MAIN WING SPAR LEFT SIDE SHOWN (RIGHT SIDE OPPOSITE) TRUSS BRACKET MAIN WING SPAR INSPECT SPAR ALONG THE MATING SURFACES INBD UP INBD UP INSPECTION AREA SEE DETAIL A Figure 1 Main Landing Gear Truss Bracket Figure 2 Truss Bracket Rivet Head Protrusion WING SPAR SURFACE RIVET HEAD 0.005 INCH MAXIMUM PROTRUSION SERVICE BULLETIN NO. 1377 PAGE 6 of 9 4. Rework of Nonconforming Rivets Identify all countersink rivet heads in the main wing spar that are covered by the MLG truss brackets when installed. Depending on the aircraft model, these rivets could be associated with a wing rib, a nut plate, or some other airframe component. Measure the height of each rivet head above the local surface as shown in Figure 2. If the rivet head protrusion exceeds 0.005 inches, rework is required. Remove the nonconforming rivet and rework the 100° countersunk hole to achieve a rivet installation that is flush (+0.005 / -0.003 inch) to the adjacent surface. Install replacement MS20426AD-series rivet (NAS523 Code: BB), procured locally. Alternatively, use a rivet shaver to achieve the flushness requirement. 5. Inspection Feedback Report After inspection, complete the Feedback Form at https://techpubs.piper.com/feedback. 6. Bolt Hole Inspection NOTE: Unless stated otherwise, all dimensions are in inches. a. Measure the bolt holes common to the MLG truss bracket and the main wing spar (three holes through the web, two holes through the lower flange). Compare measured holes sizes against the acceptable maximum hole sizes shown in Table 1. • If all bolt holes do not exceed the values shown in Table 1, then no oversize repair bolts are required. Proceed to step 7. • If one or more bolt holes exceed the values shown in Table 1, replacement of the factory original hardware with a 1/64 or 1/32 oversize repair bolt is required. Proceed to Step b. NOTE: If bolts have signs of damage, they must be replaced and an eddy current inspection performed on the corresponding bolt holes in the spar following the guidance under Inspection Methods, above. A qualified NDT level II or III inspector is required to perform this inspection to ensure the spar does not have crack indications. NOTE: If the oversized bolt hole condition is limited to the MLG truss bracket and does not apply to the main wing spar, replace the MLG truss bracket and reinstall factory original hardware. TABLE 1 ORIGINAL DESIGN ORIGINAL BOLTS WITH MAXIMUM BOLT HOLE SIZES Nominal Original Bolt Size Maximum Allowable Bolt Hole 1/4 0.2510 5/16 0.3130 SERVICE BULLETIN NO. 1377 PAGE 7 of 9 b. For each bolt hole exceeding the maximum allowable bolt hole shown in Table 1, determine if the use of an oversize bolt is permissible. See Table 2 for permissible oversize bolt and reworked hole sizes. 1) For oversized holes in the spar web, measure the local thickness of the spar web near the affected bolt hole. • If the web thickness measures 0.0908 or greater, a 1/64 or 1/32 oversized bolt is permissible. 2) For oversized holes in the spar flange, measure the local thickness of the spar flange near the affected bolt hole. • If the flange thickness measures a minimum of 0.2694, a 1/64 oversized repair bolt is permissible. • If the flange thickness measures 0.2713 or greater, a 1/64 or 1/32 oversized repair bolt is permissible. If the spar flange thickness measures less than 0.2694, it may still be possible to address the discrepant condition with an oversized repair bolt. The following method requires an accurate measurement of the width of the spar flange; to gain access, the temporary removal of rivets common to the spar and the lower wing skin may be required. Use the following formula: D = W − (0.5942 ÷ T) D = Maximum permissible reworked hole size, as calculated. W = Measured width of the flange near the affected screw hole. T = Measured thickness of the flange near the affected screw hole. • If D does not exceed 0.2664, a 1/64 oversize repair bolt is permissible. • If D does not exceed 0.2820, a 1/32 oversize repair bolt is permissible. Example: W = 2.4930, T = 0.2675 D = 2.4930 − (0.5942 ÷ 0.2675) D = 2.4930 − 2.2213 D = 0.2717 In the example above, D = 0.2717. Since D exceeds 0.2664, a 1/64 oversize repair bolt is not permissible; but, since D does not exceed 0.2820, a 1/32 oversize repair bolt is permissible. c. To ensure a good fit between the repair bolt and oversized bolt hole, it is permissible (but not required) to ream the bolt hole within the minimum and maximum tolerances defined in Table 2. Refer to AC 43-13-1B for clean reaming procedures. If a bolt hole cannot be cleaned up to within the specified tolerances or the local thickness of the spar where the bolt hole is located is insufficient, an alternative repair is required, which is outside the scope of this service bulletin. 7. Procure replacement installation hardware including oversize repair bolts as required. Refer to the appropriate Airplane Parts Catalog (APC) and Table 2 for part numbers. 8. Reinstall the MLG truss brackets. Torque all 1/4 inch bolts to 65−100 in·lb and all 5/16 inch bolts to 160−200 in·lb. 9. Perform a functional check on any systems that were disturbed during this inspection. 10. Remove the airplane from jacks. 11. Make a logbook entry documenting compliance with this service bulletin. SERVICE BULLETIN NO. 1377 PAGE 8 of 9 Nominal Original Bolt Size Repair Bolt Size Repair Bolt (Through Web) (1) Repair Bolt (Through Flange) (2) Minimum Bolt Hole Size Maximum Bolt Hole Size 1/4 1/64 oversize shank NAS6204 -* X NAS7404-*X 0.2654 0.2664 1/32 oversize shank NAS6204- * Y NAS7404-*Y 0.2810 0.2820 5/16 1/64 oversize shank NAS6205- * X NAS7405-*X 0.3279 0.3289 1/32 oversize shank NAS6205- * Y NAS7405-*Y 0.3435 0.3445 (1) Repair Bolt Example: NAS6204 -* X OVERSIZE GRIP (X DENOTES 0.0156 OVERSIZE) (Y DENOTES 0.0312 OVERSIZE) GRIP DASH NUMBER IN 0.0625 INCREMENTS NAS NUMBER REPAIR BOLT NAS7404 -* X OVERSIZE GRIP (X DENOTES 0.0156 OVERSIZE) (Y DENOTES 0.0312 OVERSIZE) GRIP DASH NUMBER IN 0.0625 INCREMENTS NAS NUMBER REPAIR BOLT (2) Repair Bolt Example: ERSIZE) ERSIZE) NTS NAS7404 -* X OVERSIZE GRIP (X DENOTES 0.0156 OVERSIZE) (Y DENOTES 0.0312 OVERSIZE) GRIP DASH NUMBER IN 0.0625 INCREMENTS NAS NUMBER REPAIR BOLT TABLE 2 OVERSIZED REPAIR PART NUMBERS AND BOLT HOLE TOLERANCES SERVICE BULLETIN NO. 1377 PAGE 9 of 9 MATERIAL REQUIRED: Per aircraft: • As required, bolts, per the applicable Piper APC and/or Table 2 • As required, washers and nuts, per the applicable Piper APC and/or Table 2 • As required, MS20426AD-series rivet (NAS523 Code: BB), procure locally AVAILABILITY OF PARTS: Procure locally and/or at your Piper Approved Service Center – Find your local service center at https://www.piper.com/ EFFECTIVITY DATE: This service bulletin is effective on January 22, 2024. SUMMARY: Please contact your Piper Approved Service Center to make arrangements for compliance with this service bulletin in accordance with the compliance time indicated. NOTE: 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”