47-20-06 ERCO: (Was Mandatory Note 14 of AD-718-6.) Applies Only to 415-C, -CD and -D Aircraft Serial Numbers 113-3784, Inclusive, Except the Following Which Have New Design Incorporated: 3719, 3720, 3723, 3724, 3726, 3729, 3732, 3735, 3738, 3741, 3742, 3744, 3745, 3747, 3750, 3753, 3756, 3759, 3762, 3764, 3765, 3767, 3768, 3771, 3774, 3777, 3780, 3783.
Compliance required not later than next 100-hour inspection unless visual inspection indicated immediate repair is required.
Flexing of the lower aileron skin has resulted in fatigue cracks in the beam in the balance weight area. Inspect the beam and lower aileron skin carefully for cracks and drill relief holes at the ends of all cracks. Then add reinforcement plates (Erco P/N 415-16039-5 and -6) to the front face of the aileron beam and lower surface of the lower aileron skin, respectively, following the procedure outlined in Ercoupe Service Department Bulletin No. 20. (Blind, Type A, AN 450-4-10 may be used in lieu of DupontExplosive DR134A-8 and DR134A-10 rivets, respectively.) Use new longer AN 526C632-7 truss head screws to reinstall the balance weight. Check the aileron rigging and the aileron bellcrank pushrod for freedom from binding in the rod end under full aileron travel before again placing the airplane in operation.
(Ercoupe Service Department Bulletin No. 20 dated February 17, 1947, covers this subject in greater detail.)