AD 81-18-05 ACTIVE

81-18-05 GENERAL DYNAMICS: Amendment 39-4487. Applies to Model 240 and military models eligible or to be made eligible for civil use under Type Certificate A-793, and all such model airplanes converted to turbopropeller power, certificated in all categories.

Compliance required as indicated, unless previously accomplished.

To prevent structural failure of the wing structure, which could result from corrosion and cracking at the wing outer panel/wing center section joint, accomplish the following:

(A) On or before September 15, 1981, and thereafter at intervals not to exceed 100 hours of additional time in service until compliance with the complete internal inspection required by paragraph (B) of this AD has been completed:

1) Conduct an external visual inspection of the wing in the area of the spar rails, both upper and lower, front and rear, from ten (10) inches inboard of bulkhead 15(WS323) to ten (10) inches outboard of bulkhead 17(WS346) in accordance with Figure 3 of General Dynamics 600 (240D) Service Bulletin No. 57-4A dated February 13, 1973, hereinafter referred to as S.B. No. 57-4A, for evidence of internal structural corrosion which may be indicated by some out-of-alignment or bulging of the external surface.

If any indication of surface out-of-alignment, bulging, corrosion, cracks, or failed rivets is found, before further flight, conduct a complete internal inspection in accordance with paragraph (B) of this AD.

2) Conduct an internal visual inspection of the center wing to outer panel attach fittings upper and lower, front and rear, upper and lower bulkhead rails, and associated structure for corrosion and/or cracks as identified in S.B. No. 57-4A, Figures 1 through 3. This includes the structure at and between bulkheads 15(WS323) and 17(WS346). Remove all dirt from the corners, front and rear, and clear drain holes to allow for drainage of moisture. Access to this dry area is via the outer panel access door indicated on S.B. No. 57-4A, Figure 2.

If any indication of surface out-of-alignment, bulging, failed rivets, corrosion, or cracks is found, before further flight, conduct the complete internal inspection in accordance with paragraph (B) of this AD.

(B) On or before December 1, 1981, and thereafter at intervals not to exceed 3,000 hours of additional time in service or one year since the last such inspection, whichever occurs earlier:

Conduct an internal visual inspection of the wing in accordance with S.B. 57-4A, paragraph 2, including spar rails (upper and lower, front and rear), center wing to outer panel attach fittings, upper and lower bulkhead rails, and associated structure for corrosion and/or cracks from bulkhead 14(WS300) to bulkhead 18(WS361), after cleaning all surfaces in accordance with the procedures shown in S.B. 57-4A, Figures 1 through 4. In addition to the visual inspection required above, using a dye penetrant method, inspect for cracks in spar rails and chordwise bulkhead tee rails, after removal of all dirt, paint, and integral fuel tank sealant, in the following areas at the specified stations.

Upper and lower spar rails

Six (6) inches spanwise inboard and outboard of bulkhead 15(WS323) and bulkhead 17(WS346) on the forward facing surface of the front spar rails and the aft facing surface of the rear spar rails.

Upper and lower chordwise tee rails

On the outboard facing surfaces at bulkhead 15(WS323) and the inboard facing surfaces at bulkhead 17(WS346) a minimum total of two (2) inches extending fore and aft chordwise from each of the forward and aft ends of the tee rails in the radius (or where the radius would exist prior to cut-out of a tee leg) in exposed areas accessible without fitting interference. Access to this "dry" wing area between bulkhead 15 and 17 is possible by removal of the outer panel access door indicated in S.B. 57-4A, Figure 2, page 5.

The above dye penetrant inspections at bulkhead 17(WS346) are required only for those aircraft with integral fuel tanks installed in the wing outer panels outboard of bulkhead 17.

(C) If corrosion or cracking is detected, repair in a manner approved by the Manager, Western Aircraft Certification Field Office, FAA, Northwest Mountain Region, Hawthorne, California.

(D) Military aircraft being converted for civil airworthiness certification and those civil aircraft which have been out of service for one year, shall, prior to further flight after the effective date of this AD, be inspected in accordance with paragraph (B) of this AD.

(E) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections required by this AD.

(F) Alternate inspections, modifications, or other actions which provide an equivalent level of safety may be used when approved by the Chief, Western Aircraft Certification Field Office, FAA, Northwest Mountain Region, Hawthorne, California.

(G) Reports of the discrepancies found are requested. The reports would provide surveillance of the propagation of fatigue cracking and corrosion in these aircraft. The reports should cite: airplane "N" number and serial number, nature of defect and part identification, total airplane operating hours, time since last inspection, and AD compliance paragraph.

Forward reports to Manager, Western Aircraft Certification Field Office, FAA Northwest Mountain Region, 15000 Aviation Boulevard, Hawthorne, California 90261, by mail.

This supersedes Amendment 39-4117, AD 81-11-08 (46 FR 28149).

This Amendment 39-4487 becomes effective November 15, 1982, and was effective earlier to those recipients of priority mail AD 81-18-05 dated August 26, 1981.