Safety Recommendation A-01-007

Notation 8437: The National Transportation Safety Board (NTSB) has reviewed the Federal Aviation Administration’s (FAA) notice of proposed rulemaking (NPRM), titled “Airworthiness Directive; Piper Aircraft, Inc. Airplanes,” which was published at 76 Federal Register 45979 on August 2, 2012. The NPRM proposes to adopt a new airworthiness directive (AD) applicable to Piper models PA-28, PA-32, PA-34, and PA-44 series airplanes that would require inspecting the horizontal stabilator control system for damage to control cables and turnbuckles and replacing parts as necessary to prevent failure of the stabilator control system.

This proposed AD was prompted by reports of control cable assembly failures that may lead to failure of the horizontal stabilator control system and could result in loss of pitch control. The NTSB has previously recommended the proposed action. Between March 1998 and April 2001, the NTSB learned of six airplanes on which flight control cable terminals had fractured. 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 terminal in the stabilator control system, and three of the fractures occurred in flight.

As a result, on April 16, 2001, the NTSB issued Safety Recommendations A-01-6 and -7: Issue appropriate airworthiness directives, applicable to Piper PA-28, Piper PA 44, and Cessna 172 series airplanes older than 15 years, to require recurrent visual inspections, on an appropriate, calendar-based interval, for evidence of corrosion pits or cracking on control cable terminals that were or may have been constructed from SAE-AISI 303 Se stainless steel. The inspections should be performed after removal of any safety wire or safety clips on the terminals. Require that any terminals with signs of corrosion or cracking be removed from service immediately. (A-01-6)

Determine which currently certificated aircraft models are authorized to have control cable terminals made from SAE-AISI 303 Se stainless steel, evaluate the need to require recurrent visual inspection, on an appropriate, calendar-based interval, of the terminals on these aircraft, and require such inspections if needed. (A-01-7) In a January 30, 2002, response to these recommendations, the FAA indicated that it found 18 reported cases of corrosion in the terminals of Piper PA-12, -14, -18, -28 and -28R airplanes in a fleet of 14,564. For the Cessna 172, the FAA found 11 reported cases of broken/frayed cables in a fleet of 24,925 aircraft.

All aircraft certification offices also confirmed with their respective aircraft manufacturers that most aircraft use SAE-AISI 303 Se stainless steel terminals and they are an industry standard design. Based on the results of its evaluation, the FAA did not believe that action by way of an AD was warranted at that time.

The Safety Board notes that the FAA has determined which aircraft are authorized to use SAE-AISI 303 Se steel, evaluated the need for visual inspections, and determined that no inspections are needed. Accordingly, Safety Recommendation A-01-7 is classified "Closed--Acceptable Action."

Letter Mail Controlled 02/07/2002 9:50:55 AM MC# 2020126 All aircraft certification offices have contacted their respective aircraft manufacturers and the type clubs to determine which aircraft models have control cable terminals made from SAE AISI 303 Se stainless steel. The manufacturers have confirmed that most aircraft use SAE AISI 303 Se stainless steel terminals to MIL Spec MS21260 and they are of industry standard design. There are approximately 375,000 general aviation airplanes in service. The FAA believes that the review conducted by Piper and Cessna in response to Safety Recommendation A-01-6 is an adequate sample of the total fleet to determine if a safety concern exists.

The results of the evaluation indicate that there is no safety concern to warrant mandating additional inspection requirements. All aircraft manufacturers mandate the inspection of control cable attach fittings at annual or l00-hour inspection intervals. None of the occurrences mentioned in response to Safety Recommendation A-01-6 resulted in any serious accidents, and most of the occurrences were discovered during maintenance activity. On November 1, 2001, FAA issued SAIB CE-02-05 recommending that owners or operators of rotary and fixed-wing aircraft inspect the flight control cables at 100 flight hour intervals or at each annual inspection.

If corrosion is found, it is recommended that the control cable attach fittings be replaced even if the manufacturer's maintenance manual does not recommend replacement of corroded fittings. A copy of the SAIB is enclosed for the Board's information. I consider the FAA's action to be completed in response to this safety recommendation.

Again, the Safety Board is pleased with the FAA's rapid response to this safety recommendation. Because of the large number of aircraft manufacturers and aircraft models that could be affected by this recommendation, the Board requests that the FAA provide a list of all manufacturers contacted as a result of this safety recommendation and a list of all aircraft models that the manufacturers identify as having this type of control cable terminals. Pending analysis and further action by the FAA, Safety Recommendation A-01-007 is classified "Open--Acceptable Response."

Letter Mail Controlled 06/08/2001 11:54:36 AM MC# 2010473 The FAA has requested that all aircraft certification offices contact their respective aircraft manufacturers to determine which aircraft models are affected and to discuss the research and method of inspection procedures to address this safety recommendation. The FAA's Small Airplane Directorate will develop an appropriate course of action based on the results of this review. I will keep the Board informed of the FAA's progress on this safety recommendation.