GENERAL INFORMATION

NARRATIVE

[O] On August 15, 1998, about 0955 eastern daylight time, a Piper PA-18-150, N3981Z, operated by Sky Signs, Inc., experienced an in-flight structural failure of the left wing and crashed during an attempted banner tow pick-up at a private airstrip in Conway, South Carolina. The commercial pilot, the sole occupant, received minor injuries, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was operated under 14 CFR Part 91 and originated about 5 minutes before the accident. [Recommendations] A-00-22. Require The New Piper Aircraft, Inc., to develop a recurrent inspection procedure adequate to detect corrosion of any portion of the lift strut attach fittings installed on high-wing Piper airplanes and require that owners of these airplanes implement those recurrent inspection procedures. [Responses] FAA LTR DTD: 4/26/00 The New Piper Aircraft, Inc., is reviewing the service history and the engineering data to determine what action may need to be taken to address this safety recommendation. It is anticipated that the review will be completed by June 2000. I will inform the Board of the Federal Aviation Administration's course of action to address this safety recommendation as soon as the review is completed. NTSB LTR DTD: 6/6/00 The FAA reports that the New Piper Aircraft, Inc., is reviewing the service history and the engineering data to determine what action may need to be taken to address this safety recommendation. The Safety Board believes this is a constructive first step. Pending the development of an adequate recurrent inspection procedure, Safety Recommendation A-00-22 is classified "Open-Acceptable Response." FAA LTR DTD: 8/14/00 The Federal Aviation Administration (FAA) has reviewed this safety recommendation and agrees that an unsafe condition existed on the subject airplane. The FAA also agrees that adding inspection provisions for the forward wing strut attach fittings would be beneficial. However, the FAA does not agree that this condition is likely to occur in other airplanes and, therefore, airworthiness action is not warranted. The FAA reached its conclusion after reviewing service difficulty and accident data, inspecting similar airplanes, and considering the facts from the accident investigation. In addition to the three reports of corroded fittings cited in the Board's letter dated February 23, 2000, the service difficulty and accident data bases show only one other occurrence of corrosion on the subject lift strut attach fitting. This is significant because there were over 51,000 airplanes built using this fitting, the majority of which were built prior to 1960 with the first service in 1936. Also, periodic recovering of the wings of the airplane will not allow inspection of the fittings attached to the front of the spar because the wing leading edges of these airplanes are made with aluminum sheet metal. Recovering the wings does not require removing the metal and, without taking it off, access for inspection of the fitting is limited. On October 21, 1998, the FAA issued Special Airworthiness Information Bulletin (SAIB) 99-01 to registered owners of all Piper high-wing airplanes. The bulletin alerted registered owners of the potential for corrosion of the subject wing attach fittings and recommended inspecting the visible areas of the fittings for any evidence of corrosion. No additional reports of corrosion have been received since the issuance of SAIB 99-01. The Board's Materials Laboratory Factual Report 99-49 states that the forward attach fitting failed due to corrosion at the second bolt hole from the bottom of the fitting. From the pictures of the failed fitting in the report, it can be determined that corrosion would have been visible externally from the lower side of the wing (see enclosed pictures of similar Piper high-wing airplanes and sketches showing the failed area). Report 99-49 also notes that the aft fitting failed at the third hole from the bottom of the fitting. This fitting also had evidence of visible corrosion. The report also states that forward and aft fittings on the other side of the airplane were subjected to slight to moderate corrosion damage, with most of the damage confined to the lower end of the fittings. The corrosion on the aft fittings would have been readily visible through an inspection panel in the wing. Since detectable corrosion was evident on the visible portions of all four fittings and no action was taken to rectify the airplane's condition during any previous inspections, the FAA believes that the additional inspection provisions recommended by the Board would have provided no additional benefit for this particular airplane. SAIB 99-01 recommends that airplane owners inspect the inaccessible areas of the forward fittings if any evidence of corrosion is found on the visible portions of the fittings. However, the Board stated in its letter dated February 23, 2000, that SAIB 99-01 does not specify how to inspect the forward attach fittings if corrosion is detected on exposed surfaces that protrude beneath the wing. The Board further states that the surface condition in the aft area of the fittings may not adequately represent the surface condition in the area of the forward portion of the fitting that protrudes into the bottom skin of the wing and is hidden from view. The FAA does not agree with the Board's assessment. A properly trained and licensed airframe mechanic can determine a method of inspection suitable to a particular airplane. There are several methods that may be used--inspection mirrors and a flashlight may provide sufficient inspection, a borescope may be used in conjunction with a small hole drilled through the covering, or an inspection hole can be installed. This last modification is within the scope of FAA Order 8300.10, Airworthiness Inspector's Handbook, for a field approval. Advisory Circular 43.13B, Chapter 4, section 2-14 supplies instructions on how to install these rings and covers. These inspection rings and covers are inexpensive and readily available from several aviation supply sources. On July 27, 2000, The New Piper Aircraft Company, Inc., issued Service Bulletin 1044 to provide detailed inspection techniques for the lift strut attachment fitting on the forward side of the front spar and to provide details for the inspection of wing components for corrosion. I have enclosed a copy of the service bulletin for the Board's information. I believe that this bulletin meets the full intent of this safety recommendation, and I consider the FAA's action to be completed. NTSB LTR DTD: 11/16/00 The FAA reports that on July 27, 2000, The New Piper Aircraft Company, Inc., issued Service Bulletin (SB) 1044 to provide detailed inspection techniques for the lift strut attachment fitting on the forward side of the front spar and to provide details for the inspection of wing components for corrosion on high-wing piper airplanes. The Safety Board has reviewed the SB and determined that if its recommended actions were mandated by the FAA the intent of the recommendation would be met. However, the FAA states that it does not believe that such corrosion is likely to occur in other airplanes and, therefore, that airworthiness action is not warranted. The FAA states that it reached its conclusion after reviewing service difficulty and accident data, inspecting similar airplanes, and considering the facts from the accident investigation. The Safety Board is disappointed that the FAA has reached this conclusion. The Board notes that Piper's SB states across the top that "PIPER CONSIDERS COMPLIANCE MANDATORY." The FAA based its decision, in part, on information contained within the Service Difficulty Report (SDR) database. However, the Safety Board believes that, currently, the SDR data are not reliable for evaluating the extent of safety-related service difficulty problems. The FAA indicates it believes that a properly trained and licensed mechanic would have discovered the corrosion in the accident airplane. However, the Board is concerned because the corrosion was not detected and holds that without a mandate for a specific procedure, such as that outlined in Piper's SB, to detect corrosion, the potential for a repeat of this accident is too high. Although the FAA feels that the condition of the corrosion inside the wing leading edge is the same as the condition outside of it (that is, visible portion), the Board does not agree. The Board contends that it is possible to have areas of severe corrosion in the bottom, hidden area of the leading edge where water and debris can become trapped. The Safety Board urges the FAA to reconsider its decision not to require mandating the actions recommended in Piper's SB. Pending such action, Safety Recommendation A-00-22 is classified "Open Unacceptable Response." FAA LTR DTD: 4/17/01 The Federal Aviation Administration (FAA) has reviewed the Board's letter dated November 16, 2000, and continues to believe that this corrosion condition is not likely to occur in other airplanes and, therefore, airworthiness action is not warranted. The information obtained from the service difficulty reports (SDR) is adequate to evaluate the extent of safety-related problems. The SDR data, in conjunction with the accident data, the inspection of similar airplanes, and the evaluation of the facts from the accident investigation are reliable means for determining if additional airworthiness action is warranted. As stated in the FAA's letter dated August 14, 2000, Special Airworthiness Information Bulletin (SAIB) 99-01 was issued October 21, 1998, to alert registered owners of the potential for corrosion of the subject wing attach fittings and recommended inspecting the visible areas of the fittings for any evidence of corrosion. No additional reports of corrosion have been received since the issuance of SAIB 99-01. On July 27, 2000, The New Piper Aircraft Company, Inc., issued Service Bulletin 1044 to provide detailed inspection techniques for the lift strut attachment fitting on the forward side of the front spar and to provide details for the inspection of wing components for corrosion. I believe that the FAA has addressed this safety issue completely, and I consider the FAA's action to be completed. NTSB LTR DTD: 7/25/01 In an August 14, 2000, letter, the FAA informed the Safety Board that Special Airworthiness Information Bulletin (SAIB) 99-01 had been issued on October 21, 1998, alerting registered owners of the potential for corrosion of the wing attach fittings and recommending inspection of the visible areas of the fittings for any evidence of corrosion. The FAA also stated that no additional reports of corrosion had been received since the issuance of SAIB 99-01. The FAA further stated that, on July 27, 2000, The New Piper Aircraft Company, Inc., issued Service Bulletin (SB) 1044 to provide detailed inspection techniques for the lift strut attachment fitting on the forward side of the front spar and to provide details for the inspection of wing components for corrosion. The FAA concluded by stating that it does not believe that such corrosion is likely to occur in other airplanes and, therefore, that airworthiness action is not warranted. The FAA noted that it had reached its conclusion after reviewing service difficulty report (SDR) and accident data, inspecting similar airplanes, and considering the facts from the accident investigation. In a November 16, 2000, letter, the Safety Board indicated that it was disappointed that the FAA had reached this conclusion. The Board noted that SB 1044 states across the top that "PIPER CONSIDERS COMPLIANCE MANDATORY." As the FAA noted, it based its decision, in part, on information contained in the SDR database; however, the Board believes that the SDR data are not reliable for evaluating the extent of safety-related service difficulty problems. The FAA indicated that it believes that a properly trained and licensed mechanic would have discovered the corrosion in the accident airplane. However, the Board stated that it was concerned because the corrosion had not been detected and held that, without a mandate for a specific procedure, such as that outlined in SB 1044 to detect corrosion, the potential was too high for a repeat of the type of structural failure that occurred on the accident airplane. The Board further stated that it did not agree with the FAA that the condition of the corrosion inside the wing leading edge was the same as the condition outside of it (that is, visible portion). The Board stated that it was possible to have areas of severe corrosion in the bottom, hidden area of the leading edge where water and debris could become trapped. In its April 17, 2001, letter, the FAA reports that it has reviewed the Safety Board's November 16, 2000, letter, and continues to believe that the corrosion found on the accident airplane is not likely to occur in other airplanes and, therefore, that airworthiness action is not warranted. The FAA states that information obtained from the SDR database is adequate to evaluate the extent of safety-related problems. The FAA believes that SDR data, in conjunction with accident data, the inspection of similar airplanes, and the evaluation of the facts from the accident investigation, are reliable means for determining whether additional airworthiness action is warranted. The Safety Board continues to believe that the FAA should mandate the actions recommended in SB 1044. However, because the FAA has indicated that it considers its action completed and plans no further action, Safety Recommendation A-00-22 is classified "Closed Unacceptable Action." 5

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