NTSB · Safety Recommendation
Safety Recommendation A-01-008
Recommendation
THE NTSB RECOMMENDS THAT THE FAA: IMMEDIATELY NOTIFY ALL MANUFACTURERS OF BOTH ROTARY AND FIXED-WING AIRCRAFT OF THE CRACKING AND CORROSION PROBLEMS CURRENTLY BEING EXPERIENCED WITH TERMINALS MADE FROM SAE-AISI 303 SE STAINLESS STEEL.
Safety Issue and Context
SINCE MARCH 1998, THE NATIONAL TRANSPORTATION SAFETY BOARD HAS LEARNED OF SIX AIRPLANES ON WHICH FLIGHT CONTROL CABLE TERMINALS HAVE FRACTURED. ADDITIONAL TERMINALS FROM SOME OF THESE SIX AIRPLANES AND TERMINALS FROM FOUR OTHER AIRPLANES WERE ALSO EXAMINED AND FOUND TO BE CRACKED. NINE OF THESE 10 AIRPLANES WERE PIPER AIRCRAFT THAT HAD AT LEAST ONE FRACTURED OR CRACKED MS21260-S4 TERMINAL, ILLUSTRATED IN FIGURE 1 (ATTACHED). THE 10TH AIRPLANE WAS A CESSNA AIRCRAFT ON WHICH AN AN669 TERMINAL, THE PRECURSOR TO THE MS21260 TERMINAL, WAS FRACTURED.
METALLURGICAL EXAMINATIONS CONDUCTED BY THE SAFETY BOARD DETERMINED THAT MOST OF THE TERMINALS FRACTURED OR CRACKED THROUGH THE SHAFT ON THE THREADED END OF THE TERMINAL, CLOSE TO THE WRENCH FLATS. A FEW OF THE TERMINALS CONTAINED CRACKING IN THE SWAGED END. THE EXAMINATIONS IDENTIFIED CHLORIDE STRESS-CORROSION CRACKING, WHICH HAD ORIGINATED AT GENERAL CORROSION PITS ON THE SURFACE OF THE PART, TO BE THE FRACTURE MODE OVER MOST OF THE FRACTURE SURFACE OF THE TERMINALS.
Response History
May 17, 2002 · NTSB Correspondence · FAA
The Safety Board appreciates the FAA's effort in verifying that all aircraft manufacturers have been notified of this potential problem. Accordingly, Safety Recommendation A-01-8 is classified "Closed--Acceptable Action." The Board looks forward to continued cooperative efforts with the FAA in making improvements to the safety of America's aviation programs.
January 30, 2002 · Recipient Response · FAA
Letter Mail Controlled 02/07/2002 9:50:55 AM MC# 2020126 The FAA has verified that all aircraft certification offices have notified their respective rotary and fixed-wing aircraft manufacturers of the cracking and corrosion problems experienced with the terminals identified in this safety recommendation. I consider the FAA's action to be completed on this safety recommendation.
September 12, 2001 · NTSB Correspondence · FAA
The Board requests that the FAA also provide documentation showing that all aircraft certification offices have notified their respective rotary and fixed-wing manufacturers of this safety recommendation. The Safety Board believes that FAA actions on this safety recommendation, coupled with the FAA's response to Safety Recommendation A-01-7, will ensure that all affected aircraft manufacturers will be notified of the Board's concerns associated with these particular control cable terminals.
Pending the notification from the FAA that all aircraft certification offices have informed their respective aircraft manufacturers of this recommendation, Safety Recommendation A-01-8 is classified "Open--Acceptable Response."
The Safety Board commends the FAA for the rapid and positive actions it has taken to respond to these safety recommendations.
June 4, 2001 · Recipient Response · FAA
Letter Mail Controlled 06/08/2001 11:54:36 AM MC# 2010473 The FAA's Small Airplane Directorate has requested that all aircraft certification offices notify their respective rotary and fixed-wing aircraft manufacturers of the cracking and corrosion problems experienced with the terminals identified in this safety recommendation. I have enclosed a copy of the letter directing this action for the Board's information. I consider the FAA's action to be completed on this safety recommendation.