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53-23-03 REPUBLIC: Applies to All Model RC-3 Aircraft.
Compliance required within the next 25 hours of operation but not later than December 1, 1953, and thereafter at each 25-hour period of operation or every 6 months, whichever occurs first.
Cases of severe corrosion of the right and left upper and lower lift strut fittings, fuselage wing lift strut fittings and wing lift strut fittings have been reported. Since the strength of these fittings are of primary importance to the safe operation of the airplane, the following inspections should be made and corrective action taken.
Fitting 17W22002 is located on the upper end of the lift strut and fitting 17W22003 is located on the lower end of the lift strut. Fitting 17F11013 is located in the fuselage and is attached to fitting 17W22003. Fitting 17W22004 is located in the wing and is attached to fitting 17W22002.
Inspect thoroughly and test the fitting with a pointed instrument to determine whether corrosion is present. One 1 1/4-inch diameter inspection hole should be cut in the upper and one in the lower surface of the wing in accordance with Republic Aviation Service Bulletin No. 25, Supplement No. 2, in order to accomplish the inspection of the portion of the fitting 17W22004 which lies inside the wing skin. This inspection will require the aid of a light as well as a sharp-pointed instrument. The holes should be covered with United Carr Fastener Corp. Plug Button No. 51021, Seabee spare parts item No. 1379, or equivalent.
A fitting may appear satisfactory but actually may be corroded under the surface. Such corrosion which may be intergranular in nature may actually result in a much greater loss of strength than would be indicated by the loss of metal from the surface. If the fitting has only slight surface corrosion, the corrosion should be carefully removed and the fitting should be suitably treated against further corrosion. Fittings which have deteriorated beyond slight surface corrosion should be replaced.
(Republic Aviation Service Bulletin No. 25, including Supplements Nos. 1 and 2, covers this same subject in detail.)
This supersedes AD 50-30-01.
NOTE: This AD also applies to Model UC-1 aircraft (see note 3 on TCDS A6EA.)
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