axle assembly area for corrosion and cracks, removal of the MLG spring strut to expose the fuselage attachment clamp area and axle as sembly area, or the use of nondestructive inspection (NOl) techniques. The Safety Board notes that a d etailed inspection of the MLG spring strut near the fuselage attachment clamp area and the axle as se mbl y area for corrosion a nd cracks can only be accom plished if the spring strut is removed from the fuselage and the axle is removed from th e spring strut. Despite the inspection s required by 14 CF R Part 43 and recom mend ed in the Cessna Aircraft service manual, MLG spring strut failures continue to occur. Visual inspections have not prevented all spring strut failures and do not ade quately detect the relatively small fatigue cracks before failure occurs. The lack of a requirement for de tailed inspection s of the MLG spring strut fus e lage attachment clamp area and axle assembly area allows airplanes with corrosion and cracks in the spring strut to experi enc e fatigue failures. An initial inspection, involving the removal of the MLG spring strut and the use of NDI techniques to examine the spring strut, should aid in the de tection of fatigue cracks that cannot be identified through visual inspec tions, th e reby re ducing the possibility of an incident or acci dent. The Safety Board notes that initial inspections, although benefi cial, might not be enough to monitor whether corrosion and cracks are developing in the spring struts . Rep etitive inspections per formed at ap propriate intervals 4 should further reduce the possibil ity of fatigue failure incidents or accidents. Therefore, th e Na tional Trans portation Safety Board recommends that the Federal Aviation Adminis tration: Issue an airworthiness directive to req uire an initial inspection of
Cessna 170, 180, 185, 190, and 195 series airplane main landing gear spring struts, involving the removal of the spring struts from the fuse lag e attachm ent clamp and axle assembly and the use of nonde structive inspection techniques to exa mine the upper and lower ends of the spring struts for corrosion and cracks, at the next 100-hour or annual inspection, whichever oc curs first . (A-Ol-Ol) Issue an airworthiness directive to require repetitive inspections of Cessna 170, 180, 185, 190, and 195 series airplane main landing gear spring struts, involving the removal of the spring struts from the fuse lage attachm ent clamp and axle assembly and the us e of nonde structive inspection techniques to examine the upper and lower ends of the spring struts for corrosion and cracks, at appropriate intervals. (A-01-02) Vice Chairman HALL5 and Mem bers BLACK and CA RMODY concurred in these recommenda tions. Members HAMMERSCHMIDT and GOGLIA did not concur. Original signed by: Carol]. Ca r mody, Acting Chairman Footnotes:
1. Th e Safety Board contacted Cessna regarding MLG spring stmt fa tigue failures, but Cess na had no record ofsuch failures. 2 . Eleven of th e 16 failures oc curred from 1993 to 1999. 3. The Safety Board notes that Cessna tail wheel-equipped airplanes and Cessna nose wheel-equipped air planes have MLG spring struts similar in design. However, a review ofBoard reco rds indicated that from 1984 to th e prese nt, only 5 of the approxi mately 118,000 Cess na nos e wheel-equipped airplan es in service have experienced MLG spring strut fa tigue failures. In addition, a review of the FAA's SDR data indica ted that from 1972 to th e present, no reports exist of cracked or failed MLG spring struts in Cessna nose wheel-equipped airplanes. On the basis of this review, the Board notes that the fatigue failure
rate of MLG spring struts in Cessna nose wheel-equipped airplanes is sig nificantly lower than that in Cessna tail wheel-equipped airplanes; there fore, the Board is only addressing spring strut fatigue failures in Cessna tail wheel-equipped airplanes in this letter. However, the Board will monitor the spring strut fatigue failure rate in Cessna nose wheel-equipped airplanes to assess whether additional safety rec ommendations are necessary. 4. Appropriate intervals would al low ea rly evidence of corrosion and fatigue cracks in MLG spring stmts to be detected before a failure occurs. The Safety Board notes that the Cessna Aircraft Company Model 100 Series Continued Airworthiness Program con tain s an in spection of the MLG outboard spring supports of Cess na 180 and 185 series airplanes that in volves removing the MLG spring struts from the airplane every 1,000 hours or every 3 years. 5. Vice Chairman Hall was serving as the Safety Board's Acting Chairman at the time of his concurrence. You can obtain a PDF electronic copy of this lette r on the NTSB's website at www.ntsb.gov/recs/
letters/2001/A 01_01 _02.pdf As we were going to press, we had not been notified of the FAA's inten tions, but we are certain an Airworthiness Concern Sheet will be issued, similar to the one just issued regarding Piper lift strut attachment fittings. You can read about that is sue starting on page 4. For continued updates on the Cessna landing gear issue, please visit EAA's website at www.eaa.org. TULSA FLY-IN AND BIPLANE EXPO The 15th annual Biplane Expo and Convention at Bartlesville, Ok lahoma , originally scheduled for June 1-2 has been rescheduled be cause of delayed taxiway con struction at the Bartlesville airport. It will now take place in conjunc tion with the Tulsa Regional Fly-In, September 21-22. Please see the Fly In Ca lendar on page 28 for more information. .... VINTAGE AIRPLANE 3