# Boeing Service Letter 787-SL-25-025: No revision named - Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2023-1648; AD 2023-25-10 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Boeing Service Letter 787-SL-25-025](https://openairdocs.org/service-documents/boeing/787-sl-25-025.md) - Title as filed: 787-SL-25-025 - Pages: 7 - PDF: https://openairdocs.org/files/sha256/ae/e4/aee4f6df8c4ff22694f62302e31d4cbae2da84bb7fd63eb011575155e2234d05 - Page: https://openairdocs.org/service-documents/boeing/787-sl-25-025/file/aee4f6df8c4f ## Text Some pages are OCR from a scan. OCR can misread letters and numbers. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 BCA Customer Support SERVICE LETTER 787-SL-25-025 ATA : 2500-00 06 September 2022 SUBJECT : FLIGHT ATTENDANT SEAT TRACK ATTACHMENT FASTENERS MODEL : 787 MINOR MODELS : -8,-9,-10 APPLICABILITY : All 787 standard model 2787 and high comfort model 2788 attendant seats installed on all 787 aircraft prior to Line Position 1108. REFERENCES Reference Type Reference Number Revision Number Reference Date a) Component Mainten ance Manual (CMM) 25-21-70 b) Aircraft Maintenance Manual (AMM) 25-25-06 EXPORT COMPLIANCE STATEMENT: No license is required for the dissemination of the commercial information contained herein to foreign persons other than those from or in the terrorist supporting countries identified in the United States Export Administration Regulations (EAR)(15 CFR 730-774). It is the responsibility of the individual in control of this data to abide by U.S. export laws. SUMMARY: This Service Letter is to address a Suspect Discrepancy Report (SDR). Please see Service Letter 787-SL-00-004 for more information about the Boeing SDR process. This Service Letter is being issued to address a quality escapement observed on some attendant seat installations where the seat track fitting nuts were under-torqued. There have been no indications or reports of properly torqued nuts loosening in service, and therefore this is a one-time service action to re-torque all 787 free standing attendant seats. This includes both standard model 2787 and high comfort model 2788 attendant seats. BACKGROUND: In production, a flight attendant seat was discovered to be loose after final installation. The investigation found the floor attach fitting nuts to be significantly under-torqued. A Production line check revealed similar conditions on downstream airplanes. A Quality Assurance investigation revealed that the attachment nuts were torqued using a yoke-type U-Joint adapter to mitigate clearance issues during the final torque process. Per installation process requirements, these adapters are not allowed for final torque as they can result in lower than intended torque values. The subject seat track fitting attachment nuts are to be torqued to 140-150 in-lbs per BAC5009. Review of quality assurance inspection findings showed a few nuts with essentially 'zero' torque (finger tight), and many installations within 30 to 130 in-lbs range. Disclaimer: This document contains BOEING PROPRIETARY, Export Controlled ECCN:9E991 information, Encrypted emails required for forwarding via Email. Document Generated on 09/14/2022 by Fleet Team Digest-Service Letter. Page 1 of 3 ### Page 2 787-SL-25-025 ATA : 2500-00 06 September 2022 DISCUSSION: A safety evaluation was performed including static testing on an attendant seat with undertorqued fittings. This finding was processed through the Continued Operational Safety Program (COSP) and was determined to be Not a Safety Issue. It is important to use the proper installation tools (as shown in the Attachments of this Service Letter) to ensure proper installation torque values of all attendant seats. It is also important to note that the existing engineering is correct. This was a production escapement that has been corrected by updating the installation instructions to eliminate undertorqued seat track attachment fittings. BOEING ACTION: All 787 attendant seats in production will be re-torqued to 140 -150 in-lbs prior to airplane delivery. Boeing has corrected this condition for all 787 airplanes starting at Line Position 1108. As of airplane Line Position 1108 and on, the updated installation instructions provide improved procedures for use of the proper tooling so the same issue of under torqued fasteners will not occur. At the time of publication of this Service Letter, the Aircraft Maintenance Manual (AMM) tasks for removal and installation of the cabin attendant seats (both Standard and High-Comfort models) will be revised to clarify proper tool usage and to note that the yoke-type adaptor or socket should not be used (see Suggested Operator Action section below). This change will be available to operators by 30-Nov-2022. SUPPLIER ACTION: No Supplier Action is required. SUGGESTED OPERATOR ACTION: For all 787 aircraft prior to Line Position 1108 operators are recommended to retorque all free standing attendant seats for both standard model 2787 and high comfort model 2788 to ensure seat track attachment fittings have been properly torqued using the following steps. 1. Obtain access to quantity 4 seat track attachment fasteners by opening the under-seat stowage compartment door and removing the stowed equipment such as life vest, PBE/smoke hood, fire gloves, and/or fire extinguisher (if present), noting installation locations and securing methods. Flashlight (if present) may remain installed. 2. Loosen each of the 4 fasteners by turning nut a minimum of 1/2 turn (180 degrees) CCW. 3. Tighten fasteners in a cris-cross fashion using the appropriate tools (7/16 in. 12-point socket with wobble extension adaptor, swivel socket or adaptor, or crowfoot socket; 1/4 inch drive wrench recommended) to between 140 and 150 in- lbs using an approved torque procedure (BSS7083 or equivalent) and calibrated torque wrench. Do NOT use a yoke- type U-joint adaptor or socket as these may give a false high torque indication, leading to the actual torque on the nut being lower than the desired torque value. If using a wobble or swivel socket or adaptor, ensure that offset angle does not exceed 15 degrees. If using a crowfoot-type socket, ensure proper procedure is followed to account for possible additional moment arm added by socket offset. If in doubt, repeat step 2 above and re-torque nut. 4. Shake the seat to be sure there is no looseness or movement between seat, seat track fittings, and seat tracks. 5. Replace life vest, and PBE/smoke hood, fire gloves, and/or fire extinguisher (if present) in same manner as they were originally installed and close under-seat stowage compartment door. ESTIMATED LABOR HOURS: An estimated 0.2 labor hours per flight attendant seat, up to 2.4 labor hours per airplane, are needed to correctly torque the suspect fasteners. Disclaimer: This document contains BOEING PROPRIETARY, Export Controlled ECCN:9E991 information, Encrypted emails required for forwarding via Email. Document Generated on 09/14/2022 by Fleet Team Digest-Service Letter. Page 2 of 3 ### Page 3 787-SL-25-025 ATA : 2500-00 06 September 2022 INDUSTRY SUPPORT INFORMATION: Boeing warranty remedies are available for 787 airplanes in warranty as of August 24, 2021. For labor-hour and/ or material reimbursement for airplanes in warranty as of that date, send a warranty claim to Boeing Warranty. The warranty remedies described above will expire eight years from the original release date of this service letter. To receive the warranty remedies stated above, warranty claims must be received by Boeing Warranty through the Boeing MyBoeingFleet (MBF) Warranty portal no later than 24 months after work is accomplished. INTERCHANGEABILITY: Interchangeability is not affected. There are no new parts or part changes being introduced by this service letter. PARTS AVAILABILITY: There are no changes to existing parts, and no new parts are required. Fasteners, if needed, are available commercially and through Boeing Material Management (www.myboeingfleet.com, PARTPage). SUPPLIER INFORMATION: Attendant Seat Supplier: Collins Aerospace 1275 N. Newport Rd. Colorado Springs, CO 80916-2279 Original: Dated: 06 September 2022 First publish. Attachments • Attendant Seat Background • Attendant Seat Instl 2 • Attendant Seat Instl 1 • Installation tool Information Disclaimer: This document contains BOEING PROPRIETARY, Export Controlled ECCN:9E991 information, Encrypted emails required for forwarding via Email. Document Generated on 09/14/2022 by Fleet Team Digest-Service Letter. Page 3 of 3 ### Page 4 Background: • A flight attendant seat was discovered to be loose after final installation. Investigation found the floor attach fitting nuts to be significantly under-torqued. Production line check revealed similar condition on downstream airplanes. • A quality assurance investigation revealed that the attach nuts were torqued using a yoke- type U-Joint adapter to mitigate clearance issues during final torque process. Per installation process requirements these adapters are not allowed for final torque as they can result in lower than intended torque values. • The subject seat track fitting attachment nuts are to be torqued to 140-150 in.-lbs. per BAC5009. Review of quality assurance inspection findings showed a few nuts with essentially ‘zero’ torque (finger tight), and many installations within 30 to 130 in.-lbs. range. Typical Attendant Seat Installation ### Page 5 (OCR) Circled in Green show attendant seat attachment nut locations Model capture with FL7 pointing to difficult to reach Nut, opposite side of seat is similar (behind life vest in photo capture below). FL 7 FL 7 || THREAD THE FOUR NUTS, REMOVED IN 'FL 1', ONTO BOLTS. TORQUE EACH BOLT TO A TORQUE VALUE OF 140 TO 150 INCH-LBS (16 TO 17 Nm), PER BAC5009. [URL ERE OF COUR AME TADE ARE SEAN OF FLOOD RAN BILL FANAND 84622000-1204 VESTI CHILA AI Inside lower stowage compartment, attachment nuts indicated, 1 of 4 hidden by life vest (life vest not installed at time of fastener installation) ### Page 6 • Each attendant seat is attached to two floor tracks using four attachment fittings. Each fitting includes a special high-strength 3/8 in. bolt, with the threaded portion pointed upward. • Seat structure sits on top of seat floor pan and fittings and is secured using high tensile strength nuts with designated torque requirement of 140-150 in.-lbs. This torque ensures proper preload and proper load transfer during high-G events. ### Page 7 Root Cause: • Tool selection requirements of BSS7083 were not uniformly adhered to when torqueing the flight attendant seat floor attach fitting nuts. • Back fittings (as seated) cannot be reached solely with a torque wrench and socket combination due to geometry constraints. Use of an offset adapter (Crow’s Foot, Wobble extension, Ball/Swivel adapter with angle limitation) is required. BSS7083 allows for use of above noted offset adapters, however the Yoke-type U-joint adapter which had been used for some seat installations is specifically disallowed. Torque Wrench head with socket installed is too bulky to fit in pocket in seat side panel- offset type of adapter is required Wobble Extension (top), Std. Extension, 12-pt Crow’s Foot socket ALLOWED Std. Extension (bottom) ALLOWED ALLOWED Std. Extension with Yoke-type U-joint adapter and socket NOT ALLOWED --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain, except the copies of manufacturers’ service documents, which belong to their rights holders.