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WING INSPECTION FOR CESSNA 336s & 337s WITH WING TIP EXTENSIONS |
On March 16, 2010, the FAA issued a Special Airworthiness Inspection Bulletin then ammended it on May 12, 2010 with a revised Special Airworthiness Inspection Bulletin (SAIB) for Cessna Models 336, 337, and F337 (Reims). The SAIB also referenced a preliminary NTSB report associated with the bulletin. The bulletin discusses a potential issue with aircraft that have been modified with an STC for extended wingtips. If your airplane is equipped with extended wingtips, we recommend that during your preflight inspections you carefully look for smoking rivets on both the top and bottom surfaces of the wings near the inboard aileron hinge. You should also look for wrinkles, cracks, or any signs of distress in the upper wing skins, near unreinforced access holes, and along both front and rear spars. Check the wingtips, too, to ensure none of the fasteners are missing and that none of them are loose. We also recommend that you modify your preflight checklist to include all these items so that you have a writen reminder to yourself to look for them. Another good time to inspect the wings is after your flight when you are finished for the day. Take a damp rag to your plane, clean the bugs off the leading surfaces, and look for imperfections while you're at it. Additionally, we recommend that during your annual inspections, you double check with your mechanic to ensure that he or she has taken a close look at the particular wing stations idendified in the SAIB as potential problem areas and has carefully reviewed Cessna Service Newsletter SNL06-6 and Aviation Enterprises Wing Extension Service Letter AE01-11-00. |
Flight Controls – Frayed Flap Extend Cables |
On April 6, 2012, the FAA issued a Special Airworthiness Information Bulletin for Cessna models 336 and 337 and all their derivatives. The SAIB discusses the possibility of frayed flap extend cables. Inside the wings on Cessna 336s and 337s, the flap extend cables make a tight bend around a bellcrank an inch or two away from the cable tension adjusting nut. The cables can wear along the inside radius of the bend as they wrap around the bellcrank. Most importantly, the cable in this area is not visible if someone is inspecting it without the help of a second person. To adequtately inspect the cable, one person (an IA) needs to carefully look at it while the second person operates the flaps through their full movement of travel. In this manner, all portions of the cable can be inspected for broken wires, corrosion, fraying, or other damage. The FAA recommends that maintenance personnel perform specific inspections of the cable every 100 hours or 12 months, every 600 hours or 12 months, and every 800 or four years. They also suggest that maintenance personnel review AC 43.13-1B, Chapter 7, paragraph 7-149., “Cable System Inspection.” As with all inspections, we recommend you insist that your IA use the most current inspection checklist published by Cessna rather than merely adhering to the list provided by the FAA under FAR 43 CFR Appendix D. The manufacturer's checklist will always be more detailed. We further recommend that you ensure your IA has access to - and uses - all supplemental inspection documents related to your particular model. We also suggest that you ask your IA about the cables when you bring the plane to her or him for its annual or 100 inspection. We further recommend that you look at the inspection checklist before you take delivery of the plane and ensure it has been appropriately marked in accordance with the work that was done. According to data collected by the FAA, flap extend cables in 336s and 337s last between 2,450 hours and 4,500 hours. If you are buying either of these models, and if the airframe logbooks do not indicate installation of new cables in the near past, we suggest you negotiate a purchase price that takes into account cable replacement. |