78-26-03 GRUMMAN: Amendment 39-3369. Applies to Models G-164, G-164A and G-164B aircraft, certificated in all categories, that have been in service for either more than 500 hours or six months.
Compliance is required as indicated:
To detect corrosion of the lower wing attachment fittings, P/N's A1050-1, -3, -4, -101, -102, -103, -104, -13, -19, -20, -411, -412 and 3050-13, -14, -15, -16, accomplish the following:
(a) Within the next 25 hours in service and thereafter at intervals not to exceed 500 hours in service or six months, whichever comes first, since the last inspection, visually inspect the lower wing panel attachment fittings for corrosion.
(b) If surface corrosion (corrosion which is evidenced by dulling, pitting, blistering, scaling, roughness, or localized discoloration of the metal surface) is found on the attachment fittings, remove the wing and the corrosion. If it is required to clean up corrosion of the rear fittings follow the procedure below:
1. Press wing attachment bolt bushing below corroded surface. Do not fully remove the bushing.
2. Remove corrosion.
3. Equalize the amount the bushing extends from each surface of the fitting.
4. Measure gap in fuselage fitting.
5. Fabricate shims for both sides of fitting so that total width of fitting does not exceed gap of fuselage and bushing does not exceed width of fitting by more than .020".
If the front or rear wing attachment fitting dimensions are found to be in excess of the minimum limits specified in paragraph (c), (d), or (e), protect the surface from further corrosion in accordance with FAA Advisory Circular 43.13-1A, Paragraph 250(b) or equivalent.
(c) For G-164 aircraft S/N's 001 thru 400: If after removal of the corrosion, the thickness of the front or rear fitting is found to be less than the .231", or the distance from the edge of the fitting is found to be less than .290", install an unused fitting of the same part number or an equivalent.(d) For G-164A aircraft S/N's 401 and up. If after removal of the corrosion, the thickness of the front or rear fitting is found to be less than .220", or the distance from the edge of the hole to the edge of the fitting is found to be less than .340", install an unused fitting of the same part number or an equivalent.
(e) For G-164B aircraft S/N's 001 and up. If after removal of the corrosion, the thickness of the front or rear fitting is found to be less than .230", or the distance from the edge of the hole to the edge of the fitting is found to be less than .515", install an unused fitting of the same part number or an equivalent.
Equivalent parts and corrosion protection must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.
Upon request, with substantiating data submitted through an FAA Maintenance Inspector, the compliance times specified in this AD may be adjusted by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.
The aircraft may be flown in accordance with FAR 21.197 to a location where the AD can be accomplished.
Grumman Service Bulletin No. 65 dated October 16, 1978, covers this same subject.
This amendment is effective December 20, 1978.