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Safety Recommendation Details

Safety Recommendation A-73-078
Details
Synopsis: THE NATIONAL TRANSPORTATION SAFETY BOARD'S INITIAL INVESTIGATION INDICATES THAT ONE OR MORE FAULTS IN A BOEING 707-331B LONGITUDINAL CONTROL SYSTEM MIGHT HAVE BEEN CONTRIBUTORY TO THE CAUSE OF A RECENTACCIDENT INVOLVING TRANS WORLD AIRLINES FLIGHT 742, ON AUGUST 28, 1973. ALTHOUGH THE INVESTIGATION HAS NOT YET BEEN COMPLETED, THE SAFETY BOARD BELIEVES THAT THE INITIAL FINDINGS ARE SUFFICIENT TO JUSTIFY CERTAIN INTERIM ACTIONS DESIGNED TO PRECLUDE THE SERIOUS CONSEQUENCES WHICH MAY RESULT FROM SIMILAR OCCURRENCES.
Recommendation: REQUIRE CHANGES IN THE APPROVED MAINTENANCE MANUAL FOR ALL BOEING 707/720 AIRCRAFT TO: (A) SPECIFY A MORE PRECISE METHOD OF MEASURING THE NET ELEVATOR HINGE FRICTION THROUGHOUT THE ENTIRE RANGE OF CONTROL SURFACE TRAVEL; AND (B) SPECIFY A MORE DEFINITIVE METHOD FOR ADJUSTING THE BALANCE PANEL SEALS WITHIN THE DESIRABLE TOLERANCE. AT PRESENT, THE MANUAL SPECIFIES A 0-0.020-INCH FIT BETWEEN THE BALANCE PANEL SEAL AND THE STABILIZER STRUCTURE. A -0.020-INCH MEASUREMENT IMPLIES SEAL COMPRESSION WHICH IS EXTREMELY DIFFICULT TO MEASURE ACCURATELY.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: Los Angeles, CA, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: LAX74AL019
Accident Reports: Trans World Airlines, Inc., Boeing 707-331B, N8705T
Report #: AAR-74-08
Accident Date: 8/28/1973
Issue Date: 10/5/1973
Date Closed: 10/2/1974
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 10/2/1974
Response: Closed--acceptable action.

From: FAA
To: NTSB
Date: 11/2/1973
Response: REVISIONS TO THE MAINTENANCE MANUAL ARE EXPECTED AS SOON AS IMPROVEDPROCEDURES CAN BE DEVELOPED.10/2/74 THE BOEING COMPANY ISSUED SERVICE BULLETIN NO.3164 ON JULY 19, 1974. THIS BULLETIN DESCRIBES THE ELEVATOR BALANCE PANEL SEAT MODIFICATION AND ACCOMPLISHES PART OF THE DESIRED ACTION. THE BOEING COMPANY BELIEVES THATPRESENTLY DESCRIBED METHODS FOR MEASURING ELEVATOR HINGEFRICTION ARE ADEQUATE. THE BUREAU IN VIEW OF INVESTIGATIONSUBSEQUENT TO ISSUANCE OF RECOMMENDATION 73-78 ACCEPTS THISASSESSMENT. THE FAA LETTER DATED AUGUST 20, 1974 ACKNOWLEDGES THE BOEING SERVICE BULLETIN AND CHANGES TO THE MAINTENANCE MANUALS ON JULY 2. FAA APPROVAL OF THESE CHANGESCONSTITUTES COMPLIANCE WITH THE SECOND PART OF THIS RECOMMENDATION.