CAA-T-AD-1-004/98

Effective date: upon receipt

T98-02-51 BOEING

TRANSMITTED AS FOLLOWS IS TELEGRAPHIC AIRWORTHINESS DIRECTIVE T98-02-51 FOR IMMEDIATE TRANSMITTAL TO ALL OWNERS AND OPERATORS OF BOEING MODEL 737-300, -400, AND -500 SERIES AIRPLANES.

ON DECEMBER 19, 1997, A BOEING MODEL 737-300 SERIES AIRPLANE OPERATED BY SILKAIR AIRLINES WAS INVOLVED IN AN ACCIDENT AFTER TAKEOFF FROM JAKARTA SOEKARNO HATTA AIRPORT IN JAKARTA, INDONESIA. THE ACCIDENT IS UNDER INVESTIGATION BY THE INDONESIAN AUTHORITIES WITH ASSISTANCE FROM THE NATIONAL TRANSPORTATION SAFETY BOARD (NTSB) OF THE UNITED STATES, THE MANUFACTURER, THE OPERATOR, AND OTHER AVIATION ORGANIZATIONS.

ALTHOUGH THERE HAS BEEN NO DETERMINATION OF THE CAUSE OF THE ACCIDENT, PRELIMINARY REPORTS FROM THE ON-SITE ACCIDENT INVESTIGATION INDICATE THAT THE HORIZONTAL STABILIZER MAY HAVE SEPARATED FROM THE AIRPLANE PRIOR TO IMPACT IN THE MUSI RIVER. ON-SITE INVESTIGATION HAS REVEALED THAT APPROXIMATELY 26 FASTENERS WERE MISSING FROM CERTAIN LEADING EDGE STRUCTURE ON THE RIGHT-HAND (RH) HORIZONTAL STABILIZER (12 FROM THE UPPER SURFACE, AND 14 FROM THE LOWER SURFACE). ADDITIONALLY, EARLY REPORTS INDICATED THAT AT LEAST ONE FASTENER MAY HAVE BEEN MISSING FROM AN ELEVATOR ATTACHMENT FITTING IN AN OUTBOARD SECTION OF THE RH HORIZONTAL STABILIZER. SUBSEQUENTLY, THERE HAS BEEN A REPORT OF EVIDENCE THAT THE FASTENER WAS ACTUALLY INSTALLED. HOWEVER, THE FAA HAS RECEIVED A REPORT THAT AN OPERATOR FOUND ONE LOOSE FASTENER DURING INSPECTION OF AN IN-SERVICE AIRPLANE. (THERE HAVE BEEN NO REPORTS TO DATE OF ANY FASTENERS MISSING FROM THE LEFT-HAND (LH) HORIZONTAL STABILIZER.)

THERE IS, AS OF YET, NO EVIDENCE LINKING THESE MISSING OR LOOSE FASTENERS TO THE CAUSE OF THE ACCIDENT.

LOOSE OR MISSING FASTENERS ON THE LH OR RH HORIZONTAL STABILIZER COULD REDUCE THE STRUCTURAL INTEGRITY OF THE HORIZONTAL STABILIZER.

BECAUSE THE AIRPLANE HAD BEEN PLACED IN SERVICE A RELATIVELY SHORT TIME AGO (FEBRUARY 14, 1997), IT IS POSSIBLE THAT THE FASTENERS WERE MISSING BECAUSE THEY HAD NOT BEEN INSTALLED DURING MANUFACTURE. IF SUCH A QUALITY CONTROL FAILURE OCCURRED ON THIS AIRPLANE, IT MAY ALSO HAVE OCCURRED ON OTHERS PRODUCED AT APPROXIMATELY THE SAME TIME.

SINCE AN UNSAFE CONDITION HAS BEEN IDENTIFIED THAT IS LIKELY TO EXIST OR DEVELOP ON OTHER AIRPLANES OF THIS SAME TYPE DESIGN, THIS TELEGRAPHIC AIRWORTHINESS DIRECTIVE IS ISSUED TO REQUIRE A ONE-TIME GENERAL VISUAL INSPECTION TO DETECT ANY MISSING FASTENERS ON THE TOP AND BOTTOM OF THE LEADING EDGE SKIN WHERE IT ATTACHES TO THE FRONT SPAR OF THE HORIZONTAL STABILIZER. THIS TELEGRAPHIC AD ALSO REQUIRES A ONE-TIME DETAILED VISUAL INSPECTION TO DETECT ANY LOOSE OR MISSING FASTENERS OF THE ATTACHMENT OF THE ELEVATOR HINGE PLATES TO THE HORIZONTAL STABILIZER REAR SPAR FITTINGS. IF A LOOSE OR MISSING FASTENER IS DETECTED, THIS TELEGRAPHIC AD REQUIRES INSTALLATION OF A NEW OR SERVICEABLE FASTENER.

THIS AD ALSO REQUIRES THAT OPERATORS SUBMIT A REPORT OF ALL INSPECTION FINDINGS TO THE FAA. SINCE THE CAUSE OF THE MISSING FASTENERS OF THE LH AND RH HORIZONTAL STABILIZER IS CURRENTLY UNKNOWN, THE INTENT OF THE REQUIRED REPORTS IS TO ENABLE THE FAA TO DETERMINE HOW WIDESPREAD SUCH DISCREPANCIES MAY BE IN THE AFFECTED FLEET. BECAUSE THE INVESTIGATION IS CONTINUING, FURTHER ACTION MAY BE NECESSARY. THEREFORE, THIS TELEGRAPHIC AD IS CONSIDERED TO BE INTERIM ACTION; AND THE FAA MAY CONSIDER ADDITIONAL RULEMAKING.

THIS RULE IS ISSUED UNDER 49 U.S.C. SECTION 44701 (FORMERLY SECTION 601 OF THE FEDERAL AVIATION ACT OF 1958) PURSUANT TO THE AUTHORITY DELEGATED TO ME BY THE ADMINISTRATOR, AND IS EFFECTIVE IMMEDIATELY UPON RECEIPT OF THIS AD.

T98-02-51 BOEING: TELEGRAPHIC AD ISSUED ON JANUARY 8, 1998. DOCKET 98-NM-04-AD.

APPLICABILITY: MODEL 737-300, -400, AND -500 SERIES AIRPLANES HAVING LINE POSITIONS 2765 THROUGH 2977 INCLUSIVE; CERTIFICATED IN ANY CATEGORY.

NOTE 1: THIS AD APPLIES TO EACH AIRPLANE IDENTIFIED IN THE PRECEDING APPLICABILITY PROVISION, REGARDLESS OF WHETHER IT HAS BEEN MODIFIED, ALTERED, OR REPAIRED IN THE AREA SUBJECT TO THE REQUIREMENTS OF THIS AD. FOR AIRPLANES THAT HAVE BEEN MODIFIED, ALTERED, OR REPAIRED SO THAT THE PERFORMANCE OF THE REQUIREMENTS OF THIS AD IS AFFECTED, THE OWNER/OPERATOR MUST REQUEST APPROVAL FOR AN ALTERNATIVE METHOD OF COMPLIANCE IN ACCORDANCE WITH PARAGRAPH (E) OF THIS AD. THE REQUEST SHOULD INCLUDE AN ASSESSMENT OF THE EFFECT OF THE MODIFICATION, ALTERATION, OR REPAIR ON THE UNSAFE CONDITION ADDRESSED BY THIS AD; AND, IF THE UNSAFE CONDITION HAS NOT BEEN ELIMINATED, THE REQUEST SHOULD INCLUDE SPECIFIC PROPOSED ACTIONS TO ADDRESS IT.

COMPLIANCE: REQUIRED AS INDICATED, UNLESS ACCOMPLISHED PREVIOUSLY.

TO PREVENT REDUCED STRUCTURAL INTEGRITY OF THE HORIZONTAL STABILIZER DUE TO LOOSE OR MISSING FASTENERS OF THE LEFT- OR RIGHT-HAND HORIZONTAL STABILIZER, ACCOMPLISH THE FOLLOWING:

(A) WITHIN 5 FLIGHT CYCLES OR 24 CLOCK HOURS AFTER RECEIPT OF THIS TELEGRAPHIC AD, WHICHEVER OCCURS LATER, PERFORM THE FOLLOWING INSPECTIONS OF THE LEFT- AND RIGHT-HAND SIDES OF THE HORIZONTAL STABILIZER:

(1) PERFORM A GENERAL VISUAL INSPECTION TO DETERMINE IF ANY FASTENERS ARE MISSING ON THE TOP AND BOTTOM OF THE LEADING EDGE SKIN WHERE IT IS ATTACHED TO THE FRONT SPAR.

(2) PERFORM A DETAILED VISUAL INSPECTION TO DETECT LOOSE OR MISSING FASTENERS OF THE ATTACHMENT OF THE ELEVATOR HINGE PLATES TO THE LEFT- AND RIGHT-HAND SIDES OF THE HORIZONTAL STABILIZER REAR SPAR FITTINGS. ENSURE TORQUE SEALANT HAS NOT BEEN BROKEN ON THE FASTENERS.

(B) IF NO DISCREPANCIES ARE FOUND, NO FURTHER INSPECTIONS ARE REQUIRED BY THIS TELEGRAPHIC AD.

(C) IF ANY FASTENER IS LOOSE OR MISSING, OR IF THE TORQUE SEALANT HAS BEEN BROKEN ON ANY FASTENER, PRIOR TO FURTHER FLIGHT, INSTALL A NEW OR SERVICEABLE FASTENER.

(D) WITHIN 5 DAYS AFTER ACCOMPLISHING THE INSPECTIONS REQUIRED BY THIS AD, REPORT INSPECTION RESULTS, POSITIVE OR NEGATIVE, TO THE MANAGER, SEATTLE AIRCRAFT CERTIFICATION OFFICE (ACO), FAA, TRANSPORT AIRPLANE DIRECTORATE, 1601 LIND AVENUE, SW., RENTON, WASHINGTON 98055-4056; FAX (425) 227-1181. INFORMATION COLLECTION REQUIREMENTS CONTAINED IN THIS REGULATION HAVE BEEN APPROVED BY THE OFFICE OF MANAGEMENT AND BUDGET (OMB) UNDER THE PROVISIONS OF THE PAPERWORK REDUCTION ACT OF 1980 (44 U.S.C. 3501 ET SEQ.) AND HAVE BEEN ASSIGNED OMB CONTROL NUMBER 2120-0056.

(E) AN ALTERNATIVE METHOD OF COMPLIANCE OR ADJUSTMENT OF THE COMPLIANCE TIME THAT PROVIDES AN ACCEPTABLE LEVEL OF SAFETY MAY BE USED IF APPROVED BY THE MANAGER, SEATTLE ACO. OPERATORS SHALL SUBMIT THEIR REQUESTS THROUGH AN APPROPRIATE FAA PRINCIPAL MAINTENANCE INSPECTOR, WHO MAY ADD COMMENTS AND THEN SEND IT TO THE MANAGER, SEATTLE ACO.

NOTE 2: INFORMATION CONCERNING THE EXISTENCE OF APPROVED ALTERNATIVE METHODS OF COMPLIANCE WITH THIS AD, IF ANY, MAY BE OBTAINED FROM THE MANAGER, SEATTLE ACO.

(F) SPECIAL FLIGHT PERMITS MAY BE ISSUED IN ACCORDANCE WITH SECTIONS 21.197 AND 21.199 OF THE FEDERAL AVIATION REGULATIONS (14 CFR 21.197 AND 21.199) TO OPERATE THE AIRPLANE TO A LOCATION WHERE THE REQUIREMENTS OF THIS AD CAN BE ACCOMPLISHED.

(G) TELEGRAPHIC AD T98-02-51, ISSUED ON JANUARY 8, 1998, BECOMES EFFECTIVE UPON RECEIPT.

FOR FURTHER INFORMATION CONTACT: GREGORY L. SCHNEIDER, AEROSPACE ENGINEER, AIRFRAME BRANCH, ANM-120S, FAA, TRANSPORT AIRPLANE DIRECTORATE, SEATTLE AIRCRAFT CERTIFICATION OFFICE, 1601 LIND AVENUE, SW., RENTON, WASHINGTON 98055-4056; TELEPHONE (425) 227-2028 OR (425) 227- 2557; FAX (425) 227-1181.