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Safety Recommendation Details

Safety Recommendation A-85-002
Details
Synopsis: ON DECEMBER 6, 1984, A PROVINCETOWN-BOSTON AIRLINES, INC., EMBRAER BANDEIRANTE (EMB-110), N96PB, OPERATING AS FLIGHT 1039, CRASHED SHORTLY AFTER TAKEOFF FROM THE JACKSONVILLE INTERNATIONAL AIRPORT, JACKSONVILLE, FLORIDA. ALL 13 PERSONS ON BOARD WERE KILLED, AND THE AIRPLANE WAS DESTROYED. THE NATIONAL TRANSPORTATION SAFETY BOARD'S CONTINUING INVESTIGATION HAS DISCLOSED THAT THE AIRPLANE'S ELEVATORS AND HORIZONTAL STABILIZER SEPARATED IN FLIGHT, RENDERING THE AIRPLANE UNCONTROLLABLE. EVIDENCE TO DATE INDICATES THAT THE HORIZONTAL STABILIZER SEPARATED FROM THE FUSELAGE AT BULKHEAD 33 ALONG THE TOP RIGHTHAND CORNER OF THE STABILIZER ATTACHMENT FITTING. THIS AREA OF THE BULKHEAD IS SUPPORTED BY C-SHAPED, P/N 4A-1411-08, AND U-SHAPED, P/N 4A-1411-07-17, CHANNELS WHICH ARE RIVETED TOGETHER. THE FUNCTION OF THESE CHANNELS APPEARS TO BE TO TRANSFER THE AFT AND DOWNWARD LOADS ON THE FORWARD ATTACHMENT POINTS OF THE STABILIZER TO THE MONOCOQUE STRUCTURE THROUGH LONGERONS AND THE OUTER FUSELAGE SKIN.
Recommendation: THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: REVISE AIRWORTHINESS DIRECTIVE (AD) 83-14-09 TO REQUIRE WITHIN A SPECIFIED PERIOD THAT THE HORIZONTAL STABILIZER ATTACHMENT STRUCTURE OF EMB-110P1 AND -110P2 MODEL AIRPLANES BE MODIFIED IN A MANNER SIMILAR TO THAT DESCRIBED IN AMENDMENT 39-452, PARAGRAPH (D) OR (E), WHICH REQUIRES THAT THE REPAIR OF ANY CRACKS IN THE WEB OF BULKHEAD 33 AND THE REPLACEMENT OF THE ORIGINAL "C" CHANNELS WITH REDESIGNED CHANNELS AND MODIFIED RIVET PATTERNS. REVIEW THE CRACK REPAIR PROCEDURES OF THE AD FOR ADEQUACY, AND REQUIRE MODIFICATION OF THE PROCEDURES TO ELIMINATE "BUCKING" OF RIVETS AT LOCATIONS DIFFICULT TO ACCES AND OTHER PROCEDURES LIKELY TO DAMAGE EXISTING STRUCTURE. (URGENT)
Original recommendation transmittal letter: PDF
Overall Status: Closed - Unacceptable Action
Mode: Aviation
Location: JACKSONVILLE, FL, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA85AA004
Accident Reports: Provincetown-Boston Airlines Flight 1039, Embraer Bandeirante, EMB-110P1, N96PB
Report #: AAR-86-04
Accident Date: 12/6/1984
Issue Date: 1/8/1985
Date Closed: 6/24/1986
Addressee(s) and Addressee Status: FAA (Closed - Unacceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 6/24/1986
Response: We also have reviewed the results of the Embraer tests referred to in your letter. We agree that the tests showed that the stabilizer forward attachment structure at bulkhead 33 would carry ultimate stabilizer static loads even though weakened by cracks and the removal of fasteners in the bulkhead web. However, Embraer did not conduct any tests to verify that the fatigue life of the structure comprising the redundant load path is unaffected by the damage to the bulkhead 33 web and the removal of U- to C-channel attachment rivets. Since there has been no change in the FAA's position, we are classifying this recommendation in a "Closed--Unacceptable Action" status.

From: FAA
To: NTSB
Date: 2/4/1986
Response: "THE STRUCTURAL TESTS REFERRED TO IN MY LETTER DATED MAY 20, 1985, HAVE BEEN COMPLETED BY EMBRAER. IT HAS BEEN DEMONSTRATED BY THESE TESTS, WHICH WERE WITNESSED BY THE BRAZILIAN AIRWORTHINESS AUTHORITY, THAT WITH EXTENSIVE CRACK DAMAGE TO THE BULKHEAD 33 AREA AND WITH 10 RIVETS REMOVED FROM THE U-C CHANNEL ATTACHMENT, THE EMPENNAGE WILL CARRY ULTIMATE LOAD WITHOUT FAILURE OR PERMANENT DEFORMATION. REFERENCE REPORT 110P1-EM-49, COPIES OF WHICH WERE PROVIDED TO THE BOARD OF EMBRAER AND THE FAA. IN RESPONSE TO THE SECOND PART OF THIS RECOMMENDATION, I CONSIDER THE CRACK REPAIR PROCEDURES OF AD 83-14-09 TO BE ADEQUATE, SINCE THE ABOVE TESTS HAVE SHOWN THAT THIS AREA IS NOT CRITICAL AND THE BUCKING OF THE RIVETS CAN BE ACCOMPLISHED WITHOUT DAMAGE TO THE STRUCTURE."

From: FAA
To: NTSB
Date: 5/20/1985
Response: The FAA is continuing its intensive coordination with the Brazilian airworthiness authority (CTA). Preliminary results have been received from the CTA and Embraer on the structural test referred to in our letter dated January 11, 1985. These tests were conducted to determine the residual strength and stiffness of the existing horizontal tail fuselage attachment on an empennage having significant induced failures. Damage was induced in bulkhead 33 in four steps. Condition 1. Three rivets were removed from the "U" channel on one side of the airplane and a 5/16-inch crack induced in the bulkhead. Condition 2. Condition 1 was retested with the 5/16-inch crack expanded to 3 inches total length. Condition 3. Condition 2 was retested with two additional rivets removed from the "U" channel. Condition 4. All 10 rivets were removed from the upper right-hand "U" channel to "C" channel connection in addition to the 3-inch total crack length. Stiffness and frequency tests were run in Conditions 1, 2, 3, and 4, and compared to an undamaged empennage. Preliminary reports indicate no significant changes were measured. Additionally, Condition 4 was tested to ultimate load. Preliminary results indicate that the empannage withstood ultimate load with no failure and no apparent deformation. We are presently reviewing data from the formal tests. Embraer is conducting three additional tests, including an in-flight strain survey, Data Source: NTSB Recommendations to FAA and FAA Responses to further define the residual strength of the stabilizer attachment structure. The FAA and the CTA are participating in these tests. We continue to believe that results and verification of these tests of stiffness and residual strength will have significant bearing on our response to this recommendation. We will provide the Board with a status update on progress within 60 days.

From: FAA
To: NTSB
Date: 1/11/1985
Response: FAA LTR: RECOMMENDATIONS A-85-2 AND -3 ARE BEING GIVEN PRIORITY CONSIDERATION BY THE FAA WORKING JOINTLY WITH THE CTA. AS INDICATED BY THE CTA'S JANUARY 9 MESSAGE TO FAA, ADDITIONAL STRUCTURAL TESTS ARE UNDERWAY AT EMBRAER, UNDER CTA SURVEILLANCE, THAT WILL ANSWER THE OPEN QUESTIONS CONCERNING THE RESIDUAL STRENGTH OF THE EXISTING HORIZONTAL TAIL TO FUSELAGE ATTACHMENT AREA WITH SIGNIFICANT INDUCED FAILURES. IN A FEW DAYS WE EXPECT THE RESULTS OF THESE TESTS, WHICH WILL HAVE A SIGNIFICANT BEARING ON OUR RESPONSE TO RECOMMENDATIONS A-85-2 AND -3. WE WILL KEEP THE BOARD ADVISED AS THE ADDITIONAL DATA IS RECEIVED.