Problem Found During Restoration Of An Ercoupe 415-C
The FAA has issued a Special Airworthiness Information Bulletin concerning elevator controls in Ercoupe 415 model airplanes. The FAA received a field report of a loose elevator horn on an Ercoupe 415-C during restoration of the airplane. Although the external appearance of the elevator was unremarkable, teardown of the elevator revealed the elevator horn attach bracket had only one secure fastener out of four as a result of severe corrosion where the steel elevator control horn attached to the aluminum lateral stiffener. Investigation indicated dissimilar metals (steel attached to aluminum), and the corrosion prevention means of this vintage, were the primary cause of the corrosion. Similar undetected corrosion could occur on other airplanes of this type featuring elevators with a continuous compared to the split-type) trailing edge.
Later model Ercoupe series airplanes using an aluminum (not steel) elevator control horn in conjunction with the split-type trailing edge are not subject to this SAIB. As originally designed, this area of the elevator has no adequate means of internal inspection. Univair Aircraft Corporation has issued Service Bulletin No. 34, dated January 4, 2013, to address this limitation and minimize the potential of corrosion going undetected before it exceeds 25 percent of the cross sectional area. The service bulletin adds two round holes (aft of the aluminum elevator stiffener) and one trapezoidal hole (forward of the stiffener) to provide inspection access through the lower elevator skin.
The FAA recommends that all owners and operators of the Univair airplanes identified in the introduction of this SAIB comply with Univair Aircraft Corporation Service Bulletin No. 34, dated January 4, 2013. If corrosion is found upon compliance with this service bulletin or during subsequent inspections, the FAA recommends it be reported it to the FAA.
(Ercoupe 415-C image from file released to Public Domain)