# Martin-Baker Alert Service Bulletin 92-25-026

Copy: No revision named ("Sikorsky S-92 Helicopter ASB 92-25-026 (includes Martin-Baker SIL Nos. 831 and 833)"), 24 pages: PDF https://openairdocs.org/files/sha256/0e/9a/0e9a454014322e804cb1de72cc454b8f2dc9fd55537c9d4da53a17ef88ee8ee9; text https://openairdocs.org/service-documents/martin-baker/sb-92-25-026/file/0e9a45401432.md. Rights: © Martin-Baker. Filed by the FAA in regulations.gov docket FAA-2021-0106, the docket of AD 2021-19-17. Not covered by OpenAirDocs’ CC0 dedication.

## Details

- Manufacturer: [Martin-Baker](https://openairdocs.org/service-documents/martin-baker.md)
- Type: Service bulletin (Alert Service Bulletin)
- Number: 92-25-026
- Page: https://openairdocs.org/service-documents/martin-baker/sb-92-25-026

## ADs that cite it (1) (OpenAirDocs)

Newest first, with the revision each names, as OpenAirDocs read it from the AD's text.

- [AD 2021-19-17](https://openairdocs.org/ad/2021-19-17.md), effective Nov 22, 2021: No revision named

## Text (24 pages)

Rights: © Martin-Baker. Filed by the FAA in regulations.gov docket FAA-2021-0106, the docket of AD 2021-19-17. Not covered by OpenAirDocs’ CC0 dedication. Each page's text from the PDF; open the PDF at a page with #page=N.

### Page 1

Page 1 of 8 
ATA
25-22-05
ONE-TIME 
INSPECTION 
S-92® HELICOPTER 
ALERT SERVICE  
BULLETIN 
NOTICE TO ALL PERSONS RECEIVING THIS DOCUMENT: 
WARNING: THIS DOCUMENT, OR AN EMBODIMENT OF IT IN ANY MEDIA, DISCLOSES INFORMATION WHICH IS PROPRIETARY, IS THE PROPERTY OF LOCKHEED MARTIN CORPORATION AND/OR ITS SUBSIDIARIES, IS 
AN UNPUBLISHED WORK PROTECTED UNDER APPLICABLE COPYRIGHT LAWS, AND IS DELIVERED ON THE EXPRESS CONDITION THAT IT IS NOT TO BE USED, DISCLOSED, REPRODUCED, IN WHOLE OR IN PART 
(INCLUDING REPRODUCTION AS A DERIVATIVE WORK), OR USED FOR MANUFACTURE FOR ANYONE OTHER THAN LOCKHEED MARTIN CORPORATION AND/OR ITS SUBSIDIARIES WITHOUT ITS WRITTEN CONSENT,
AND THAT NO RIGHT IS GRANTED TO DISCLOSE OR SO USE ANY INFORMATION CONTAINED HEREIN. ALL RIGHTS RESERVED. ANY ACT IN VIOLATION OF APPLICABLE LAW MAY RESULT IN CIVIL AND CRIMINAL 
PENALTIES. 
S-92® IS A REGISTERED TRADEMARK OF SIKORSKY AIRCRAFT CORPORATION. 
ASB 92-25-026 
Basic Issue ▪ March 5/20 
SUBJECT: EQUIPMENT FURNISHINGS – Side Facing Utility Seat – One Time Inspection of Side 
Facing Utility Seat (MBCS12410AA001) and Observer Seat (MBCS12200, and MBCS7301-
2) and Repair with New Tube Assembly if Necessary 
Section 1. PLANNING INFORMATION 
A. Effectivity All S-92A helicopters serial numbers 920006 through 920296 equipped with side 
facing utility seats (MBCS12410AA001) and observer seats (MBCS7301-2 and 
MBCS12200,) including spares, delivered as of the release date of this ASB. 
B. Purpose To identify side facing utility seats (MBCS12410AA001) and observer seats 
(MBCS7301-2 and MBCS12200) that were fabricated with an alternate tube 
assembly finishing process, that does not meet Sikorsky requirements, and repair 
if necessary. 
C. Background During dynamic testing, a utility seat (MBCS12410AA001) became detached from 
wall attachment points on one side of the utility seat. The root cause was identified 
as changes to the finishing process of the main back tube (MBCS4109) of the 
utility seat. This caused increased surface friction in the direction of the seat 
attenuation which prevents utility seat attenuation as required during a crash 
event. The main back tube (MBCS4109) is also common to observer seat 
(MBCS12200). Impact analysis has shown the observer seat may exhibit 
excessive lumbar loads in a crash event due to the affected main back tube 
(MBCS4109). A procedure was developed to inspect for affected seats, and repair 
as necessary. 
Sikorsky Aircraft Corporation
6900 Main Street P.O. Box 9729 
Stratford, Connecticut 06615-9129 
(203) 386-4000
WARNING – This file contains export controlled information subject to the EAR. ECCN 9E991

### Page 2

S-92 ALERT ASB 92-25-026 
SERVICE BULLETIN Basic Issue ▪ March 5/20 
Page 2 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 1. PLANNING lNFORMATION (Continued) 
D. Description  
 For association between the Martin Baker seat part numbers and Sikorsky part 
numbers, see Tables 1 and 2. 
 Utility seat (MBCS7301-2) is a lower level assembly to observer seat 
(MBCS12200). 
Helicopter is prepared for maintenance. Martin Baker Special Information Leaflet (SIL) No. 831 
and Martin Baker SIL No. 833 are complied with. Helicopter is returned to service. 
E. Compliance Compliance is essential. The repair outlined herein shall be accomplished no later 
than March 5, 2021. 
F. Approval The design change specified by this document is FAA approved in accordance 
with the applicable requirements of United States Federal Aviation Regulations 14 
CFR Part 29. FAA approval constitutes EASA, Transport Canada, ANAC, and 
JCAB approval under the terms of current bilateral agreement procedures. 
G. Manpower (Estimated) 
Task No. of Men No. of Hours Man-Hours* 
Performance of Martin Baker SIL No. 831 1 2.0 2.0 
Total Man-Hours (per side facing utility 
seat (MBCS12410AA001)) 
2.0 
Performance of Martin Baker SIL No. 833 1 2.0 2.0 
Total Man-Hours (per observer seat 
(MBCS12200, and MBCS7301-2)) 
2.0 
*Estimate does not include time required to prepare helicopter or return it to flight status. 
H. Tooling 
Qty Nomenclature Part No. Source 
1 Roller  Commercially available (1) 
* Refer to Martin Baker SIL No. 831 and Martin Baker SIL No. 833 
(1) Available through normal supply channels. 
NOTE: 
This file contains export controlled information. See WARNING on first page.

### Page 3

ASB 92-25-026 S-92 ALERT
Basic Issue ▪ March 5/20 SERVICE BULLETIN
Page 3 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 1. PLANNING lNFORMATION (Continued) 
I. Weight and Balance 
Not affected. 
J. Electrical Load Data 
Not affected. 
K. Software Load Data 
Not changed. 
L. References 
(1) Martin Baker SIL No. 831  
(2) Martin Baker SIL No. 833 
M. Publications Affected 
None. 
N. Attachment 
(1) Martin Baker SIL No. 831  
(2) Martin Baker SIL No. 833 
Section 2. MATERIAL INFORMATION 
A. Procurement Requirements: 
NOTE: Only top-level kits should be ordered. For part(s) inventory, see Bill of Material Table. 
New Part No. Qty Nomenclature Instructions/
Disposition 
MBCS12995 1 Repair Kit, Utility Seat (1)(2) 
MBCS12992 1 Repair Kit, Observer Seat (1)(3) 
(1) Part are available at no cost. For parts availability and lead time requirements, contact your 
Customer Service Representative at Sikorsky Commercial Inc. (SCI). Submit a no-cost 
purchase order referencing this ASB number and the side facing utility seat and observer 
seat serial number(s) on which these parts will be used. This will allow SCI and the 
operator to track shipment and receipt of parts. Orders will be accepted by letter, 
telephone, or through the SCI website: https://customerportal.sikorsky.com. For prompt 
shipment, reference address of each shipping destination. Direct your order to: 
This file contains export controlled information. See WARNING on first page.

### Page 4

S-92 ALERT ASB 92-25-026 
SERVICE BULLETIN Basic Issue ▪ March 5/20 
Page 4 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 2. MATERIAL INFORMATION (Continued) 
Sikorsky Aircraft Corporation 
Commercial Systems and Services 
Mailstop K100 
124 Quarry Road 
Trumbull, CT 06611 U.S.A. 
Attn: Account Service Manager 
Telephone: (203) 416-4000 
https://customerportal.sikorsky.com
(2) Refer to Martin Baker SIL No. 831 for affected side facing utility seat serial numbers. 
(3) Refer to Martin Baker SIL No. 833 for affected observer seat serial numbers. 
B. Basis for Material Data 
Per helicopter. 
C. Bill of Material 
NOTE: Referenced parts below are for part(s) inventory of top-level kit(s). For top-level kit 
ordering, see Procurement Requirements Table. 
New Part No. Qty Nomenclature Old Part No. Reference 
MBCS12995 1 Repair Kit, Utility 
Seat 
Consisting of: 
MBCS12834  1 Tube Assembly, 
Back Main  
MBCS4148  2 Label Ident 
Warning  
P37689  9 in. Scotchmate 25mm 
Blk Hook  
P38733  2 Pin, Split 1/16 dia 
x 0.50 (SP90-C4)  
P38774  4 Pin, Split 1/16 dia 
x 0.375 (SP90-C3) 
P35789  1 Strap, Tie Down 
MS3367-1-0  
MBCS12992 1 Repair Kit, Observer 
Seat 
This file contains export controlled information. See WARNING on first page.

### Page 5

ASB 92-25-026 S-92 ALERT
Basic Issue ▪ March 5/20 SERVICE BULLETIN
Page 5 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 2. MATERIAL INFORMATION (Continued) 
New Part No. Qty Nomenclature Old Part No. Reference 
Consisting of: 
MBCS12834  1 Tube Assembly, 
Back Main  
MBCS4148  2 Label Ident 
Warning Seat 
Attenuated  
P37689  9 in. Scotchmate 25mm 
Blk Hook  
P38774  4 Split Pin 1/16 dia x 
0.375 (SP90-C3)  
P38765  2 Split Pin 5/32 dia x 
0.625 (SP90-H5)  
P35789 1 Strap, Tie Down 
MS3367-1-0  
D. Consumable Material 
Qty 
Nomenclature Part No. Source 
A/R  Cheesecloth CCC-C-440, or equivalent (1) 
A/R Isopropyl alcohol  TT-I-735, or equivalent (1) 
A/R 3M™ Dual Lock  SJ3541, or equivalent (1) 
A/R 3M™ double sided tape No. 468MP, or equivalent (1) 
* Refer to Martin Baker SIL No. 831 and Martin Baker SIL No. 833. 
(1) Available through normal supply channels. 
OBSERVE ALL CAUTIONS AND WARNINGS ON CONTAINERS 
WHEN USING CONSUMABLES. WHEN APPLICABLE, WEAR 
NECESSARY PROTECTIVE GEAR DURING HANDLING AND USE. IF 
A CONSUMABLE IS FLAMMABLE OR EXPLOSIVE, MAKE CERTAIN 
CONSUMABLE AND ITS VAPORS ARE KEPT AWAY FROM HEAT, 
SPARK AND FLAME. MAKE CERTAIN FIREFIGHTING EQUIPMENT 
IS READILY AVAILABLE PRIOR TO USE. FOR ADDITIONAL 
INFORMATION ON TOXICITY, FLASHPOINT AND FLAMMABILITY 
OF CHEMICALS, CONSULT YOUR MEDICAL DEPARTMENT OR 
THE MANUFACTURER OF THE CONSUMABLE. 
This file contains export controlled information. See WARNING on first page.

### Page 6

S-92 ALERT ASB 92-25-026 
SERVICE BULLETIN Basic Issue ▪ March 5/20 
Page 6 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 3. ACCOMPLISHMENT INSTRUCTIONS 
A. Prepare helicopter for modification: 
(1) Turn off all helicopter electrical and hydraulic power. 
(2) Engage rotor brake. 
NOTE: Tables 1 and 2 can be used to associate the Martin Baker seat part numbers with 
Sikorsky part numbers. 
B. Inspect side facing utility seats (MBCS12410AA001) and observer seats (MBCS12200, and 
MBCS7301-2) for serial numbers listed in Table 2 of Martin-Baker SIL No. 831 and Martin-Baker 
SIL No. 833.  
C. Remove existing placards (06092A01F100-2, 06092A01F100-3, and 06092A01F100-4) from aft 
side of seat (MBCS12410AA001) as required. 
D. Review and comply with attached Martin-Baker SIL No. 831 and Martin-Baker SIL No. 833. 
E. Reinstall previously removed placards (06092A01F100-2, 06092A01F100-3, and 
06092A01F100-4) on aft side of seats (MBCS12410AA001) in previously installed location as 
follows: 
(1) Clean bonding surface of aft side of seats using cheesecloth (CCC-C-440) and isopropyl 
alcohol (TT-I-735). 
NOTE: 3M ™ Dual Lock (SJ3541), shall be cut as necessary for best fit. 
(2) Using 3M ™ Dual Lock (SJ3541), install placards (06092A01F100-2, and 06092A01F100-
3) on aft side of seat. 
(3) Using 3M ™ double sided tape (No. 468MP), install placard (06092A01F100-4) on aft side 
of seat. 
(4) Using a roller (commercially available), apply firm pressure to placards (06092A01F100-2, 
06092A01F100-3, and 06092A01F100-4) to obtain intimate contact to the bonding surface 
of aft side of seat. 
F. Inspect for remaining FOD. Clean as required. 
G. Return helicopter to service. 
TO PREVENT ELECTRICAL SHOCK OF PERSONNEL OR 
POSSIBLE DAMAGE TO HELICOPTER COMPONENTS, MAKE 
SURE TO TURN OFF ALL ELECTRICAL POWER. 
MAKE SURE ALL FOREIGN OBJECT DEBRIS (FOD) IS REMOVED 
BEFORE RETURNING HELICOPTER TO SERVICE. 
This file contains export controlled information. See WARNING on first page.

### Page 7

ASB 92-25-026 S-92 ALERT
Basic Issue ▪ March 5/20 SERVICE BULLETIN
Page 7 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 3. ACCOMPLISHMENT INSTRUCTIONS (Continued) 
TABLE 1 – S-92 SIDE FACING UTILITY SEAT 
Supplier Part Number Sikorsky Part Number Kit Part Number 
MBCS12410AA001 
N/A 92276-20022-014 
92500-82735-101 92073-95001-015 
92500-82011-012 
92500-82011-015 
92500-82735-105 92073-95001-015 
92500-82011-012 
92500-82011-015 
TABLE 2 – S-92 OBSERVER SEAT 
Supplier Part Number Supplier/Sikorsky Part 
Number 
Assembly Part Number Kit Part Number 
MBCS7301-2 
MBCS12200 
92500-02833-041 92500-02833-011 
92500-02833-102 
This file contains export controlled information. See WARNING on first page.

### Page 8

S-92 ALERT ASB 92-25-026 
SERVICE BULLETIN Basic Issue ▪ March 5/20 
Page 8 
ATA
25-22-05
ONE-TIME 
INSPECTION 
Section 3. ACCOMPLISHMENT INSTRUCTIONS (Continued) 
H. Record of compliance: 
(1) Make helicopter logbook entries to show compliance with this ASB as follows: 
(a) Make helicopter level logbook entry on form SA7343-15 (Aircraft ASB Release 
Signoff). 
(b) When ASB modifies a component that can be removed from this helicopter: 
1. Make component log card entries on forms SA7343-22 (Aircraft Component 
Log Cards) and SA7343-21 (Component Log Cards), as applicable. 
2. If a component modified by this ASB does not have a log card and the ASB 
does not create one, then annotate compliance on the next higher assembly 
that the component belongs to which does have a log card. 
NOTE: If access to www.Sikorsky360.com is unavailable, complete attached ALERT 
SERVICE BULLETIN COMPLIANCE RECORD CARD and return it to Sikorsky 
Aircraft Corporation. 
(2) Make an appropriate electronic compliance entry in the E-Notification section at 
www.Sikorsky360.com. Refer to User Guide located on the www.Sikorsky360.com/E-
Notification Search page. 
This file contains export controlled information. See WARNING on first page.

### Page 9

(Fold over and tape closed) 
SIKORSKY AIRCRAFT CORPORATION 
FACSIMILE NUMBER (817) 762-6715 
EMAIL ADDRESS: product_safety.gr-sik@lmco.com 
ATTENTION: Gr-SIK, Product_Safety 
SIKORSKY AIRCRAFT CORPORATION 
(Fold Up to Arrows)
IMPORTANT NOTICE 
Upon COMPLIANCE with the attached ASB, Sikorsky requests your cooperation 
in completing and returning this ENTIRE PAGE by MAIL, FAX, or scan & 
EMAIL. 
Please fill in the requested information at the bottom of the page, so we may maintain 
proper records documenting the configuration of your aircraft. This information is useful 
when determining configuration and effectivity of issues affecting fielded aircraft. 
This request is in keeping with our policy to assure that our customers receive the latest 
information applicable for the maintenance of your aircraft. Thank you. 
ALERT SERVICE BULLETIN:  ________________  Compliance Record Card 
TITLE:  ___________________________________________________________________  
 ___________________________________________________________________  
 ___________________________________________________________________  
OWNER/OPERATOR:  _____________________________________________________  
SUBMITTED BY:  ___________________________  DATE:  ____________________  
FOLLOWING SERIAL NUMBERS ARE NOT AFFECTED BY THIS ASB 
ASB HAS BEEN COMPLIED WITH ON HELICOPTER SERIAL NUMBERS: 
 ___________   ___________   ___________   ___________   ___________   ___________  
 ___________   ___________   ___________   ___________   ___________   ___________  
92-25-026
EQUIPMENT FURNISHINGS – Side Facing Utility Seat – One Time Inspection of 
Side Facing Utility Seat (MBCS12410AA001) and Observer Seat (MBCS12200, and 
MBCS7301-2) and Repair with New Tube Assembly if Necessary

### Page 10

No Postage 
Necessary 
BUSINESS REPLY MAIL 
FIRST-CLASS MAIL PERMIT NO. 432 BRIDGEPORT CT 
POSTAGE WILL BE PAID BY ADDRESSEE 
SIKORSKY AIRCRAFT CORPORATION 
Commercial Systems and Services 
Mailstop K100
124 QUARRY ROAD 
TRUMBULL, CT 06611 U.S.A. 
ATTENTION:   
Gr-SIK, Product_Safety 
Please complete the form on the reverse side and FAX to 
FACSIMILE NUMBER (817) 762-6715 
Or scan and email to: 
EMAIL ADDRESS: product_safety.gr-sik@lmco.com 
or fold and return ENTIRE form to Sikorsky Aircraft Corporation

### Page 11

7 
 1 
      SPECIAL INFORMATION   
  
 
 
  
  
SPECIAL INFORMATION LEAFLET No. 831 
 
SAFETY ADVISORY NOTICE 
 
A. SIKORSKY S-92 UTILITY SEAT MBCS12410 ATTENUATION SYSTEM 
DEGREDATION OF PERFORMANCE 
 
EFFECTIVITY 
 
B. This Special Information Leaflet is applicable to Tube Assembly, Back Main 
MBCS12834 fitted to Martin-Baker crashworthy seats detailed below: 
 
MBCS12410AA001 
 
NOTE: See Table 2 below for details of affected seat serial numbers. 
 
C1. It was found during dynamic testing of a S-92 utility seat conducted by Martin-
Baker with 10° wall deformation applied per AS8049A requirements that the 
seat became detached from the attachment points on one side and potential for 
increased lumbar loads was observed.  
 
C2. Martin-Baker identified the root cause of the test failure to be changes to the 
finishing process of Tube Main Back MBCS4109 (a detail of Tube Assy, Back 
Main MBCS12834) circa July 2012. The change in process resulted in increased 
surface friction in the direction of seat attenuation. Increased surface friction 
prevented seat attenuation as required during a crash event. 
 
C3. Martin-Baker have conducted a System Safety Risk Assessment (SSRA) in 
relation to this issue. SSRA conducted indicates the reported issue to present a 
medium safety risk for a Severity 1 hazard, Hazard Risk Index (HRI) 12 – 
acceptable with review. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 of 7      
Martin-Baker Aircraft Company Limited 
Higher Denham, near Uxbridge, 
Middlesex UB9 5AJ, 
England 
Tel: (Reception) +44 (0) 1895 832214 
Telefax: +44 (0) 1895 832587 
 
WARNING – This file contains export controlled information subject to the EAR. ECCN 9E991

### Page 12

7 
 2 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 831 
 
C4. The purpose of this Special Information Leaflet is to: 
 
C4.1 Inform Customers of the issue. 
 
C4.2 Identify S-92 Utility Seats MBCS12410AA001 where finishing of detail Tube 
Back Main MBCS4109 (a detail of Tube Assembly, Back Main MBCS12834) 
has been completed using the changed process which require repair action to 
be completed. 
 
C4.3 Provide recovery actions for identified seats, as recommended by Martin-
Baker. 
 
D1.  Timing for Embodiment of this Instruction 
 
D1.1 Customers are requested to locate all fielded and inventoried S-92 Utility 
Seats MBCS12410AA001 and inspect serial number of each seat against 
Table 2 below. For each seat identified by serial number listed in Table 2 
below, order replacement parts in accordance with instruction in paragraph 
E1 below. Repair actions detailed in paragraph D2 below shall be completed 
following receipt of replacement items. 
 
NOTE: Seat part and serial number information is marked on identification 
label affixed to underside of the sitting platform assembly. 
 
D2. Work Required 
 
WARNING: 
 
 FOLLOW ALL APPLICABLE WARNINGS AND CAUTIONS IN THE 
RELEVANT MARTIN-BAKER TECHNICAL MANUAL WHEN 
UNDERTAKING WORK DEFINED IN THIS SPECIAL INFORMATION 
LEAFLET. 
 
CAUTION: 
 
 USE APPROPRIATE PERSONAL PROTECTIVE EQUIPMENT (PPE) 
WHEN UNDERTAKING WORK DEFINED IN THIS SPECIAL 
INFORMATION LEAFLET. 
 
D2.1 Tools and Materials Required: 
 
D2.1.1 Tools – standard mechanics set of tools. No special tools, fixtures or 
equipment required. 
 
D2.1.2 Materials – See Martin-Baker technical publication MB570 (Issue 2, 
dated December 2011 current at SIL No. 831 issue) 
 
 
 
2 of 7    
This file contains export controlled information. See WARNING on first page.

### Page 13

7 
 3 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 831 
 
D2.2 Parts Required: 
 
Part Number  Description Quantity per Seat 
MBCS12834 Tube Assembly, Back Main 1 
MBCS4148 Label Ident Warning 2 
P37689 Scotchmate 25mm Blk Hook 9 inches 
P38733 Pin, Split 1/16 dia x 0.50 (SP90-C4) 2 
P38774 Pin, Split 1/16 dia x 0.375 (SP90-C3) 4 
P35789 Strap, Tie Down MS3367-1-0 1 
 
Table 1 – Parts Required for SIL831 Repair Actions 
 
D2.2.1 Required parts identified in Table 1 above are included in Kit 
Components Utility Seat Repair, MBCS12995.  
 
D2.3 Locate affected seats, remove the seat from the aircraft (if installed) and 
transfer to an appropriate maintenance facility. 
 
NOTE: Seat part and serial number information is marked on identification label 
affixed to underside of the sitting platform assembly. 
 
D2.4 Disassemble the seat in accordance with procedures in Martin-Baker 
technical publication MB570 to the extent necessary to remove discrepant 
Tube Assembly, Back Main MBCS12834 (Section 1, pages 301 to 302 
inclusive refer). 
 
D2.5 Examine all removed components for damage, deterioration and wear in 
accordance with Martin-Baker technical publication MB570 procedures. 
Replace components as required. 
 
D2.6 Assemble seat with replacement Tube Assembly, Back Main MBCS12834 in 
accordance with Martin-Baker technical publication MB570 procedures 
(Section 1, pages 701 to 703 inclusive refer). 
 
D2.6.1 With reference to Figure 1 below, attach fastener, 25mm hook P37689 
to underside of the top of the main back tube assembly. 
 
D2.6.2 With reference to Figure 2 below, attach warning ident label 
MBCS4148 to either side of the main back tube assembly. 
 
D2.6.3 Replace split pins P38733 and P38774 and tie down strap P35789 
removed at paragraph D2.4 above with new supply items. 
 
D2.7 Complete all checks and operational tests necessary in accordance with 
Martin-Baker technical publication MB570 procedures in order to recover 
the seat to operational use. 
 
 
 
 
3 of 7  
This file contains export controlled information. See WARNING on first page.

### Page 14

7 
 4 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 831 
 
D2.8 Using Edding 780 ink pen (white colour), or equivalent, mark legend 
‘SIL831 incorporated’ to the underside of the Sitting Platform Assembly 
MBCS4111 adjacent to identification labels. Seal marking with clear matte 
acrylic lacquer. 
 
D2.9 Discrepant main back tube assemblies MBCS12834 shall be positively 
destroyed to prevent re-use. Disposal of destroyed discrepant main back 
tube assemblies MBCS12834 shall be in accordance with local rules. 
 
D2.9.1 Discard removed split pins part number P38733 and P38774 and tie 
down strap P35789 in accordance with local rules. 
 
D2.10 Record completion of SIL No. 831 in all applicable engineering 
documentation for subject seat. 
 
 
 
E1. Customers are requested to place free of charge purchase orders for Kit 
Components Utility Seat Repair, part number MBCS12995 (as identified in 
paragraph D2.2 above) for seats identified in Table 2 via Sikorsky in the first 
instance quoting SIL No. 831 as reference. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4 of 7    
This file contains export controlled information. See WARNING on first page.

### Page 15

7 
 5 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 831 
 
Part Number 
Seat 
Serial 
Number 
From 
Seat 
Serial 
Number 
To 
MBCS12410AA001  
PE1278 PE1286 
PE1287 PE1295 
PE1296 PE1304 
PE1315 PE1317 
PE2307 PE2315 
PF0235 PF0244 
PF0245 PF0254 
PF0041 PF0049 
PF0060 PF0068 
PF0255 PF0263 
PF1054 PF1057 
PK0486 PK0487 
PK0540 PK0547 
PK0710 PK0719 
PE1355 PE1363 
PE1364 PE1372 
PE1373 PE1374 
PF1405 PF1414 
PF1415 PF1424 
PH0171 PH0179 
PH0978 PH0985 
PH1008 PH1015 
PH1020 PH1025 
PH0180 PH0180 
PH0777 PH0784 
PH0785 PH0792 
PH0805 PH0812 
PH0813 PH0820 
PH0847 PH0853 
PJ1092 PJ1099 
PJ1100 PJ1102 
PF0789 PF0798 
PG1240 PG1247 
PG1231 PG1239 
PH0001 PH0008 
PH0009 PH0016 
PH0017 PH0024 
PH0025 PH0030 
PG1301 PG1308 
 
Table 2 - S-92 Utility Seats, Part Number MBCS12410AA001, Requiring Rework Actions 
5 of 7   
This file contains export controlled information. See WARNING on first page.

### Page 16

7 
 6 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 831 
 
 
Figure 1 – Position of Fastener, 25mm Hook P37689 on Tube Assembly, Back Main MBCS12834 
 
 
6 of 7   
View on underside of seat. 
1.50 ± 0.12 long 
Fastener, 25mm 
Hook (P37689) 2 
places. 
5.00 ± 0.12 long Fastener, 
25mm Hook (P37689). 
All dimensions in inches. 
Seat fabric and harness 
omitted for clarity. 
 
This file contains export controlled information. See WARNING on first page.

### Page 17

7 
 7 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 831 
 
 
 
 
Figure 2 – Position of Warning Ident Label MBCS4148 (Typical) 
 
 
 
 
 
PSD/831 
10th July 2019 
 
Customer enquiries are to be sent to 
SILEnquiries@martin-baker.co.uk 
 
 
 
7 of 7 
Bracket, Upper MBCS4214 
(RH)/MBCS4215 (LH). 
All dimensions in inches. 
Warning Ident. Label MBCS4148 to be 
positioned without red background showing. 
This file contains export controlled information. See WARNING on first page.

### Page 18

7 
 1 
      SPECIAL INFORMATION   
  
 
 
  
  
SPECIAL INFORMATION LEAFLET No. 833 
 
SAFETY ADVISORY NOTICE 
 
A. SIKORSKY S-92 OBSERVER SEAT, POTENTIAL FOR HIGHER LUMBAR 
LOAD 
 
EFFECTIVITY 
 
B. This Special Information Leaflet is applicable to Tube Assembly, Back Main 
MBCS12834 fitted to Martin-Baker crashworthy seats detailed below: 
 
MBCS12200 MBCS7301-2 
 
NOTE (1): See Table 2 below for details of affected seat serial numbers. 
 
NOTE (2): MBCS7301-2 is a lower level assembly of MBCS12200. 
 
C1. It was found during dynamic testing of a wall mounted crashworthy seat 
conducted by Martin-Baker increased lumbar loads from original qualification 
data were observed.  
 
C2. Martin-Baker identified the root cause of the recorded increased loads to be 
changes to the finishing process of Tube Main Back MBCS4109 (a detail of 
Tube Assy, Back Main MBCS12834) circa July 2012. The change in process 
resulted in increased surface friction in the direction of seat attenuation. Whilst 
increased surface friction caused the increase in lumbar loads, the loads 
recorded were within allowable limits. 
 
C3. Impact analysis conducted by Martin-Baker following the test has identified 
that there is a theoretical risk, unconfirmed by test, that the pole mounted S-92 
observer seat may exhibit excessive lumbar loads in a crash event with affected 
Tube Main Back MBCS4109 fitted. Due to the perceived safety risk Martin-
Baker have concluded that rework action for the identified seats is required. 
 
C3. Martin-Baker have conducted a System Safety Risk Assessment (SSRA) in 
relation to this issue. SSRA conducted indicates the reported issue to present a 
medium safety risk for a Severity 1 hazard, Hazard Risk Index (HRI) 12 – 
acceptable with review. 
 
 
 
 
 
 
1 of 7      
Martin-Baker Aircraft Company Limited 
Higher Denham, near Uxbridge, 
Middlesex UB9 5AJ, 
England 
Tel: (Reception) +44 (0) 1895 832214 
Telefax: +44 (0) 1895 832587 
 
This file contains export controlled information. See WARNING on first page.

### Page 19

7 
 2 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 833 
 
C4. The purpose of this Special Information Leaflet is to: 
 
C4.1 Inform Customers of the issue. 
 
C4.2 Identify S-92 observer seats where finishing of detail Tube Back Main 
MBCS4109 (a detail of Tube Assembly, Back Main MBCS12834) has been 
completed using the changed process which require repair action to be 
completed. 
 
C4.3 Provide recovery actions for identified seats, as recommended by Martin-
Baker. 
 
D1.  Timing for Embodiment of this Instruction 
 
D1.1 Customers are requested to locate all fielded and inventoried S-92 observer 
seats (MBCS12200/MBCS7301-2) and inspect serial number of each seat 
against Table 2 below. For each seat identified by serial number listed in 
Table 2 below, order replacement parts in accordance with instruction in 
paragraph E1 below. Repair actions detailed in paragraph D2 below shall be 
completed following receipt of replacement items. 
 
NOTE (1): Seat part and serial number information is marked on identification 
label affixed to underside of the sitting platform assembly. 
 
NOTE (2): Quantity 4 seats listed in Table 2 below were sold as, and marked on 
their identification label as, part number MBCS7301-2 (Seat GA S-
92 Utility Seat). 
 
D2. Work Required 
 
WARNING: 
 
 FOLLOW ALL APPLICABLE WARNINGS AND CAUTIONS IN THE 
RELEVANT MARTIN-BAKER TECHNICAL MANUAL WHEN 
UNDERTAKING WORK DEFINED IN THIS SPECIAL INFORMATION 
LEAFLET. 
 
CAUTION: 
 
 USE APPROPRIATE PERSONAL PROTECTIVE EQUIPMENT (PPE) 
WHEN UNDERTAKING WORK DEFINED IN THIS SPECIAL 
INFORMATION LEAFLET. 
 
 
 
 
 
 
 
 
2 of 7    
This file contains export controlled information. See WARNING on first page.

### Page 20

7 
 3 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 833 
 
D2.1 Tools and Materials Required: 
 
D2.1.1 Tools – standard mechanics set of tools. No special tools, fixtures or 
equipment required. 
 
D2.1.2 Materials – See Martin-Baker technical publication MB610 (Issue 1, 
Revision 2, dated June 2019 current at SIL No. 833 issue) 
 
D2.2 Parts Required: 
 
Part Number  Description Quantity per Seat 
MBCS12834 Tube Assembly, Back Main 1 
MBCS4148 Label Ident Warning Seat Attenuated 2 
P37689 Scotchmate 25mm Blk Hook 9 inches 
P38774 Split Pin 1/16 dia x 0.375 (SP90-C3) 4 
P38765 Split Pin 5/32 dia x 0.625 (SP90-H5) 2 
P35789 Strap, Tie Down MS3367-1-0 1 
 
Table 1 – Parts Required for SIL833 Repair Actions 
 
D2.2.1 Required parts identified in Table 1 above are included in Kit 
Components Observer Seat Repair, MBCS12992.  
 
 
D2.3 Locate affected seats, remove the seat from the aircraft (if installed) and 
transfer to an appropriate maintenance facility. 
 
NOTE (1): Seat part and serial number information is marked on identification 
label affixed to underside of the sitting platform assembly. 
 
NOTE (2): Quantity 4 seats listed in Table 2 below were sold as, and marked on 
their identification label as, part number MBCS7301-2 (Seat GA S-
92 Utility Seat). 
 
D2.4 Disassemble the seat in accordance with procedures in Martin-Baker 
technical publication MB610 to the extent necessary to remove discrepant 
Tube Assembly, Back Main MBCS12834 (Section 1, pages 301 to 303 
inclusive refer). 
 
D2.5 Examine all removed components for damage, deterioration and wear in 
accordance with Martin-Baker technical publication MB610 procedures. 
Replace components as required. 
 
 
 
 
 
 
 
 
3 of 7    
This file contains export controlled information. See WARNING on first page.

### Page 21

7 
 4 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 833 
 
D2.6 Assemble seat with replacement Tube Assembly, Back Main MBCS12834 in 
accordance with Martin-Baker technical publication MB610 procedures 
(Section 1, pages 701 to 703 inclusive refer).  
 
D2.6.1 With reference to Figure 1 below, attach fastener, 25mm hook P37689 
to underside of the top of the main back tube assembly. 
 
D2.6.2 With reference to Figure 2 below, attach warning ident label 
MBCS4148 to either side of the main back tube assembly. 
 
D2.6.3 Replace split pins P38774 and P38765 and tie down strap P35789 
removed at paragraph D2.4 above with new supply items. 
 
 
D2.7 Complete all checks and operational tests necessary in accordance with 
Martin-Baker technical publication MB610 procedures in order to recover 
the seat to operational use. 
 
D2.8 Using Edding 780 ink pen (white colour), or equivalent, mark legend 
‘SIL833 incorporated’ to the underside of the Sitting Platform Assembly 
MBCS12215 adjacent to identification labels. Seal marking with clear matte 
acrylic lacquer. 
 
D2.9 Discrepant main back tube assemblies MBCS12834 shall be positively 
destroyed to prevent re-use. Disposal of destroyed discrepant main back 
tube assemblies MBCS12834 shall be in accordance with local rules. 
 
D2.9.1 Discard removed split pins part number P38774 and P38765 and tie 
down strap P35789 in accordance with local rules. 
 
D2.10 Record completion of SIL No. 833 in all applicable engineering 
documentation for subject seat. 
 
 
 
E1. Customers are requested to place free of charge purchase orders for Kit 
Components Observer Seat Repair, part number MBCS12992 (as identified in 
paragraph D2.2 above) for seats identified in Table 2 via Sikorsky in the first 
instance quoting SIL No. 833 as reference. 
 
 
 
 
 
 
 
 
 
 
 
4 of 7  
This file contains export controlled information. See WARNING on first page.

### Page 22

7 
 5 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 833 
 
 
 
Table 2 - S-92 Observer Seats, MBCS12200 and MBCS7301-2, Requiring Rework Action 
5 of 7   
Part Number (As Sold) Seat Serial Number From Seat Serial Number To
B453-00185 B453-00186
C453-00001 C453-00001
C453-00002 C453-00002
B453-00192 B453-00194
B453-00195 B453-00196
B453-00125 B453-00125
B453-00126 B453-00127
B453-00128 B453-00128
B453-00129 B453-00130
B453-00131 B453-00131
B453-00144 B453-00144
B453-00145 B453-00145
B453-00132 B453-00132
B453-00133 B453-00133
B453-00134 B453-00134
B453-00135 B453-00135
B453-00136 B453-00136
B453-00137 B453-00137
B453-00138 B453-00138
B453-00139 B453-00139
B453-00140 B453-00140
B453-00141 B453-00141
B453-00142 B453-00142
B453-00143 B453-00143
B453-00146 B453-00147
B453-00148 B453-00148
B453-00149 B453-00150
B453-00151 B453-00151
B453-00152 B453-00152
B453-00153 B453-00153
B453-00154 B453-00154
B453-00155 B453-00155
B453-00156 B453-00157
B453-00158 B453-00158
B453-00159 B453-00160
B453-00161 B453-00161
B453-00162 B453-00162
B453-00163 B453-00164
B453-00165 B453-00166
B453-00167 B453-00168
B453-00169 B453-00170
B453-00171 B453-00172
B453-00173 B453-00174
B453-00175 B453-00176
B453-00177 B453-00178
B453-00179 B453-00179
B453-00180 B453-00181
B453-00182 B453-00182
B453-00183 B453-00184
B453-00187 B453-00187
B453-00188 B453-00188
B453-00189 B453-00189
B453-00190 B453-00190
B453-00191 B453-00191
MBCS12200
MBCS7301-2
This file contains export controlled information. See WARNING on first page.

### Page 23

7 
 6 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 833 
 
 
Figure 1 – Position of Fastener, 25mm Hook P37689 on Tube Assembly, Back Main MBCS12834 
 
 
6 of 7   
View on underside of seat. 
1.50 ± 0.12 long 
Fastener, 25mm 
Hook (P37689) 2 
places. 
5.00 ± 0.12 long Fastener, 
25mm Hook (P37689). 
All dimensions in inches. 
Seat fabric and harness 
omitted for clarity. 
 
This file contains export controlled information. See WARNING on first page.

### Page 24

7 
 7 
Continuation Sheet 
 
SPECIAL INFORMATION LEAFLET No. 833 
 
 
 
 
Figure 2 – Position of Warning Ident Label MBCS4148 (Typical) 
 
 
 
 
 
PSD/833 
11th July 2019 
 
Customer enquiries are to be sent to 
SILEnquiries@martin-baker.co.uk 
 
 
 
7 of 7 
Bracket, Upper MBCS4214 
(RH)/MBCS4215 (LH). 
All dimensions in inches. 
Warning Ident. Label MBCS4148 to be 
positioned without red background showing. 
This file contains export controlled information. See WARNING on first page.

---
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.