79-10-15: Cracks in Wing Structure

79-10-15 CESSNA: Amendment 39-3473 as amended by Amendment 39-3652 is further amended by Amendment 39-3711. Applies to Models 401, 401A, 401B, 402, 402A, 402B, 411 and 411A airplanes. COMPLIANCE: Required as indicated, unless already accomplished. To detect fatigue cracks in critical components of the wing structure, accomplish the following: A) On all 401, 401A, 401B, 402, 402A, and 402B airplanes within 100 hours' time-in-service after the effective date of this AD on aircraft with 6,400 or more hours' time-in-service, or upon the accumulation of 6,500 hours' time-in-service for aircraft with less than 6,400 hours' time-in-service and at each 1,000 hours' time-in-service interval thereafter, and On all 411 and 411A airplanes within 100 hours' time-in-service after the effective date of this AD on aircraft with 5,400 or more hours' time-in-service or upon the accumulation of 5,500 hours' time-in-service, for aircraft with less than 5,400 hours' time-in-service and at each 1,000 hours' time-in-service interval thereafter: Inspect areas of the front wing spar lower cap and wing front spar root attach fittings identified as Areas A and B in Figures 1 and 2 of Cessna Multiengine Service Information Letter ME 79-16, Revision 3, dated February 8, 1980, for fatigue cracks using eddy current inspection methods at six (6) locations along the wing front spar lower cap (3 locations on the right wing and 3 identical locations on the left wing) in accordance with Part 2 of the instruction provided in the Service Information Letter. (Note: High frequency eddy current inspection is used for Areas A and B.) B) On all 401, 401A, 401B, 402, 402A and 402B airplanes within 100 hours' time-in-service after the effective date of this AD on aircraft with 6,400 or more hours' time-in-service, or upon the accumulation of 6,500 hours' time-in-service for aircraft with less than 6,400 hours' time-in-service and at each 400 hours' time-in-service interval thereafter, and On all 411 and 411A airplanes within 100 hours' time-in-service after the effective date of this AD on aircraft with 5,400 or more hours' time-in-service or upon the accumulation of 5,500 hours' time-in-service for aircraft with less than 5,400 hours' time-in-service and at each 400 hours' time-in-service interval thereafter: Inspect right and left front wing spar lower cap areas identified as Area C (crosshatched areas) in Figure 3 of Cessna Multiengine Service Information Letter ME 79-16, Revision 3, dated February 8, 1980, for fatigue cracks using eddy current inspection methods in accordance with Part 3 of the instructions provided in said Service Information Letter. (Note: Low frequency eddy current inspection is used for Area C.) NOTE: Inspections previously accomplished in complying with earlier versions of this AD are still valid and Revision 3 to ME 79-16 leaves inspection intervals unchanged. C) If cracks are found as a result of anyinspection performed pursuant to Paragraphs A and B of this AD, prior to further flight, contact Cessna Aircraft Corporation for repair or replacement instructions approved in accordance with its Delegation Option Authorization and satisfactorily perform said instructions. D) As an alternative, inspection intervals set forth in Paragraphs A and B of this AD may be adjusted up to maximum intervals of 1,050 and 420 hours' time-in-service respectively to allow said inspections to be performed at regularly scheduled inspections or maintenance periods. The 1,000 hours repetitive inspections required by Paragraph A may be accomplished at 800 hour intervals (every other 400 hour inspection required by Paragraph B) if owners/operators elect to do so. If Paragraph A inspections are performed at 800 hour intervals, the interval may be adjusted up to a maximum of 840 hours' time-in-service to permit accomplishment at previously scheduled maintenance inspections or maintenance periods.E) When the front wing spar lower cap is modified by the installation of Cessna Service Kit SK402-36 or SK411-56, as appropriate, per Cessna Multi-engine Service Information Letter ME 79-16, Revision 3 dated February 8, 1980, the repetitive inspection made mandatory by Paragraph B) of this AD are no longer required. NOTE: Airplanes so modified may be subject to new mandatory inspection procedures at a later date. F) Aircraft may be flown in accordance with Federal Aviation Regulation 21.197 to a location where the inspections required by this AD can be performed. G) Any equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. NOTE: Cessna Aircraft Company requests, in Part 5 of ME 79-16, Revision 3, reporting of the initial inspection results to their Customer Service Department. The FAA encourages mechanics and owners/operators to comply with this request to facilitate the manufacturer's monitoring of this inspection program. This AD supersedes AD 77-02-05, Amendment 39-2815 (39 FR 20784). Amendment 39-3473 became effective May 25, 1979. Amendment 39-3652 became effective December 26, 1979. This amendment 39-3711 becomes effective February 27, 1980.