AD 59-05-04

59-05-04 ERCOUPE: Applies to All Models 415-C, 415-CD, 415-D, E and G. Compliance to be accomplished within the next 100 hours of operation. Frequent failures of the rear spar center section have been found on Ercoupe Model aircraft. These failures follow the same pattern in that the rear spar P/N 415-13048 L/R failed due to cracking of the upper flange in the area of the intersection of the rear spar with the fuselage side on either the right or left spar assembly. Repairs made in the field with gusset plates have been found to be only partially satisfactory and in most instances did not keep the crack from progressing into the spar web. This damage to the spar has been attributed to the following: (1) Rough landings coupled with a lack of fluid in the oleo struts. (2) Taxiing at high speeds over rough terrain. (3) A combination of (1) and (2) with the structure weakened by corrosion due to no protective coating of the spar. In view of the above, it is mandatory that therear spar on Forney (Ercoupe) aircraft be inspected and action taken as follows: (1) If no damage or cracks are found, the spar must be reinforced by stiffener angle P/N F-13109 or equivalent. The spar may be considered satisfactory if previously reinforced with P/N 415-13108 or equivalent. (2) If damage or crack exists but does not extend into the spar web, a repair may be made by the addition of stiffener P/N F-13109 or equivalent provided an inspection every 100 hours of service life thereafter discloses no further progressive damage. If damage is found to progress, then a new spar and stiffener must be installed. If damage or crack extends into the spar web, the spar must be replaced. (3) If a new spar and stiffener is installed, the 100-hour inspection requirement in (2) above may be eliminated. (Forney Manufacturing Company, Aviation Division, Fort Collins, Colorado, Service Memorandum 53A supersedes Service Memorandum 53 and covers this same subject.) This supersedes AD 57-13-03.