SERVICE LETTER - MANDATORY MEL-57-01

Access Panel Installation for Forward Spar or service kits SK402-49, and SK421-152 - Access Panel Installation and Stub Wing Fitting Removal/Installation. These panels are directly below the forward spar wing fitting. • Model 401 and 402 series airplanes remove panels 32 and 94. (Refer to the Model 401 and 402 (1967-1978) Service Manual.) • Model 402C airplanes remove panels 511AB, 511AT, 512BT, 611AB, 611AT and 612BT. (Refer to the Model 402C (1979-1985) Maintenance Manual.) • Model 411 airplanes remove panels 35 and 57. (Refer to the Model 411/411A (1965-1968) Service Manual.) • Model 414 airplanes remove panels 34, 35 and 41. (Refer to the Model 414/414A (1970-1985) Service Manual.) • Model 414A airplanes remove panels 511AB, 511AT, 512AT, 611AB, 611AT and 612AT. (Refer to the Model 414/414A (1970-1985) Service Manual.) • Model 421, 421A, and 421B airplanes remove panels 35, 57 and 93. (Refer to the Model 421, 421A, 421B Series (1968-1975) Service Manual.) MEL-57-01 December 18, 2017 Page 3 MEL-57-01 Page 4 December 18, 2017 Multi-engine SERVICE LETTER MANDATORY MEL-57-01 • Model 421C airplanes remove panels 511AB, 511AT, 512AT, 611AB, 611AT and 612AT. (Refer to the Model 421C (1976-1985) Service Manual.) A. (Airplanes with the forward spar access panels. Refer to Figure 1, Detail A.) Remove the 5292032-4 or 5292031-10 Forward Spar Access Panel if installed with MEB-57-01, MEB-57-02 or SK425-49. NOTE: Forward spar access panels were installed with either service bulletins MEB-57-01 or MEB-57-02 - Access Panel Installation for Forward Spar or service kits SK402-49, or SK421-152 - Access Panel Installation and Stub Wing Fitting Removal/Installation. These panels are directly below the forward spar wing fitting. B. (Airplanes without the forward spar access panels. Refer to Figure 1, Detail B.) Remove rivets as necessary from the left and right lower stub wing skin sufficient to get access to the bottom surface of the lower carry through spar cap for the visual inspection. CAUTION: Use caution when removing fasteners along the two lateral rows of rivets just forward and aft of the fitting. These two rows are common to the lower carry through spar web flanges. CAUTION: To prevent cracking dimples or damaging understructure, when removing rivets from dimpled holes, drill a hole into the rivet shank before driving it out. (1) Remove all rivet butts, drill shavings, and foreign object debris. 3. Clean the lower surface of the left and right side of the carry through spar cap as follows: A. Use a suitable solvent to remove all grease and dirt from the lower spar cap area. B. Wash the remaining solvent off with soap and water and let air dry. 4. (Refer to Figure 1, Detail C.) Do a detailed visual inspection of the left and right side of the carry through spar cap as follows: NOTE: A detailed inspection is described as an intensive visual examination of a specific structural area, system, installation or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate by the inspector. Inspection aids such as mirrors, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required. A. Use a suitable light source and a 10X Magnifying Lens to inspect the bottom surface of the left and right side of the carry through spar cap inboard of the lower fittings in the area extending 1-inch inboard to 1-inch outboard of the two rows of fasteners and around all 10 fasteners. WARNING: Further flight with a cracked carry through spar cap is prohibited. The carry through spar cap must be replaced before further flight. B. If a crack is found, no further flight is permitted. Contact Cessna Structures at: csstructures@txtav.com, or phone: 316-517-6061. C. If an area is questionable, do a surface eddy current examination, go to Step 5. D. If no cracks or questionable areas are found, go to Step 6. 5. Do a surface eddy current examination of the suspect area on the carry through spar cap. (For surface eddy current instructions refer to inspection documents listed below.) • Model 401 and 402 series airplanes refer to the Model 401 and 402 (1967-1978) Service Manual, Supplemental Inspection Number 57-10-10 - Lower Carry-Thru Main Spar Cap • Model 402C airplanes refer to the Model 402C (1979-1985) Maintenance Manual, Supplemental Inspection Number 57-10-14 - Wing Lower Carry-Thru Front Spar Cap • Model 411 airplanes refer to the Model 411/411A (1965-1968) Service Manual, Supplement Inspection Number 57-10-10 - Lower Carry-Thru Main Spar Cap • Model 414 airplanes, refer to the Model 414/414A (1970-1985) Service Manual, Supplement Inspection Number 57-10-10 - Lower Carry-Thru Main Spar Cap • Model 414A airplanes, refer to the Model 414/414A (1970-1985) Service Manual, Supplement Inspection Number 57-10-14 - Lower Carry-Thru Front Spar Cap Multi-engine SERVICE LETTER MANDATORY MEL-57-01 • Model 421, 421A, 421B airplanes, refer to the Model 421, 421A, 421B Series (1968-1975) Service Manual, Supplement Inspection Number 57-10-10 - Lower Carry-Thru Main Spar Cap • Model 421C airplanes, refer to the Model 421C (1976-1985) Service Manual, Supplement Inspection Number 57-10-14 - Lower Carry-Thru Front Spar Cap NOTE: The eddy current technician must be qualified and certified to Level 2 or 3 per the requirements of NAS 410 or equivalent. A. If a crack is found. Contact Cessna Structures at: csstructures@txtav.com, or phone: 316-517-6061. 6. Complete the attached INSPECTION RESULTS FORM and return to Cessna Structures at csstructures@txtav.com. (Refer to the attached INSPECTION RESULTS FORM.) NOTE: Return the INSPECTION RESULTS FORM to Cessna Structures even if no crack is found. 7. (Airplanes without forward spar access panels.) Install MS20426AD4-X and MS20470AD4-X Rivets to secure the stub wing skin. NOTE: Rivet length can vary, determine correct length at time of install. 8. Install all removed access panels. 9. Remove the maintenance warning tags and connect the airplane battery. 10. Make a logbook entry that states the recurring inspection is due at the specified flight hour interval as listed in the COMPLIANCE section of this service letter. NOTE: An example of a log book entry on an airplane that currently has 25,500 flight hours, the next inspection is due at 25,550 flight hours. MEL-57-01 Forward Lower Spar Cap Inspection must be accomplished at or before 25,550 flight hours. 11. Make an entry in the airplane logbook that states compliance and method of compliance with this service document. MEL-57-01 December 18, 2017 Page 5 MEL-57-01 Page 6 December 18, 2017 Multi-engine SERVICE LETTER MANDATORY MEL-57-01 Figure 1. Carry Through Spar Cap Inspection (Sheet 1) Multi-engine SERVICE LETTER MANDATORY MEL-57-01 Figure 1. Carry Through Spar Cap Inspection (Sheet 2) MEL-57-01 December 18, 2017 Page 7 MEL-57-01 Page 8 December 18, 2017 Multi-engine SERVICE LETTER MANDATORY MEL-57-01 Figure 1. Carry Through Spar Cap Inspection (Sheet 3) Multi-engine SERVICE LETTER MANDATORY MEL-57-01 MATERIAL INFORMATION No parts are required to complete this service document. MEL-57-01 December 18, 2017 Page 9 Multi-engine ATTACHMENT MANDATORY MEL-57-01 SPAR CAP INSPECTION RESULTS FORM Airplane Model Number Airplane Serial Number Total Airframe Hours Left Engine Hours Forward Lower Spar Cap Hours Right Engine Hours Owner's Name Inspection Facility Name Owner's address Inspection Facility Address List all STC installed on the airplane In the table that follows please provide detailed and dimensioned descriptions of any crack(s). Attach pictures to this form as necessary. Multi-engine ATTACHMENT MANDATORY MEL-57-01 SPAR CAP INSPECTION RESULTS FORM CONTINUED Was a crack found: Yes/No? Detailed description: (Attach pictures and additional details as necessary, if a crack was found with visual inspection or with a surface eddy current inspection?) Send completed form/attachments to Cessna Structures at csstructures@txtav.com Multi-engine OWNER ADVISORY MEL-57-01 TITLE WINGS - FORWARD LOWER SPAR CAP INSPECTION TO: Cessna Model 401, 401A, 401B, 402, 402A, 402B, 402C, 411, 411A, 414, 414A, 421, 421A, 421B, 421C Aircraft Owner REASON Cracks have been found in the forward lower carry through spar cap. An undetected crack can cause the spar cap to break which could result in flight instability and potential loss of control. COMPLIANCE MANDATORY. This service document must be accomplished as follows: Model With Flight Hours Of Flight Hours To Comply With Initial Inspection Flight Hours For Recurring Inspection Interval All Airplanes 25,000 or more 25 Flight Hours Every 50 Flight Hours 421, 421A, 421B, 421C 12,000 thru 24,999 50 Flight Hours Every 50 Flight Hours 401, 401A, 401B, 402, 402A, 402B, 402C, 411, 411A, 414, 414A 15,000 thru 24,999 50 Flight Hours Every 50 Flight Hours NOTE: Airplanes that have less than the minimum required number of flight hours upon receipt of this service letter must comply with this inspection within 50 flight hours of reaching the minimum flight hours listed in the above table. MATERIAL AVAILABILITY No parts are required to complete this service document. WARRANTY None NOTE: As a convenience, service documents are now available online to all our customers through a simple, free-of-charge registration process. If you would like to sign up, please visit the Customer Access link at www.txtavsupport.com to register. MEL-57-01 December 18, 2017 Page 1 of 1 Textron Aviation Customer Service, P.O. Box 7706, Wichita, KS 67277, U.S.A. 1-316-517-5800 This document contains technical data and is subject to U.S. export regulations. This information has been exported from the United States in accordance with export administration regulations. Diversion contrary to U.S. law is prohibited. ECCN: 9E991 COPYRIGHT © 2017