# AD 47-20-05: Belly skin reinforcement - Type: Airworthiness directive - Status: Current - Products: Univair 415-C, 415-CD and 415-D - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small airplane - Registered aircraft: 1,005 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E4FE6FF417D42E4486256A5600708410.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/47-20-05 ## The airworthiness directive 47-20-05 ERCO: (Was Mandatory Note 13 of AD-718-6.) Applies to 415-C, -CD and -D Aircraft Serial Numbers 800 Through 2037. Compliance required prior to October 1, 1947. Cracks have occurred in the belly skin at the rearmost rivet attaching the center section belly skin outer stiffeners (Erco P/N 415-13056 L/R) to the belly skin. To prevent similar failures where cracks have not yet developed, install 0.064-inch 24ST alclad angles 1/2-inch wide with legs of 1 3/32 inches and 1/2 inch (Erco P/N 415-13068). Attach the 1 3/32-inch leg to the outboard side of the aft end of each belly skin outer stiffener with two AN 470AD3-4 rivets (3/32-inch diameter, universal head, A17ST, 1/4-inch long) and to the center section rear beam with one AN 470AD3-5 rivet. (AN 430 type round head rivets may be used.) If cracks are found in the belly skin, drill relief holes at the ends of the cracks and install triangular shaped patch plates as follows in addition to the angle stiffeners described above. Prepare the patch plates of 0.032-inch 24ST alclad material of such a shape that it will pick up the last two rivets which attach the aft end of the belly skin outer stiffener to the belly skin and the three rivets attaching the rear beam to the belly skin which are in line with and to either side of the stiffener. Remove the above-mentioned existing rivets and attach the patch plates through these holes using AN 470AD3-3 and -4 rivets. Attach the patch plate to the belly skin with six additional AN 470AD3-3 rivets, three through each side of each plate. (Erco's Ercoupe Service Department Bulletin No. 18 dated January 9, 1947, covers this same subject.) ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A-718](https://openairdocs.org/tcds/A-718): Univair Aircraft Corporation; names 2 of 2 models: 415-CD, 415-C - [TCDS A-787](https://openairdocs.org/tcds/A-787): Univair Aircraft Corporation; names 1 of 8 models: 415-D ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 1,005 (1,005 by airframe model, 0 by engine model) - Makers: Ercoupe 772, Engineering & Research 200, Forney 20, Erco 12, Univair 1 Models with the most aircraft: - [Ercoupe 415-C](https://openairdocs.org/model/ercoupe-415-c): 623 aircraft (airframe model) - [Engineering & Research 415-C](https://openairdocs.org/model/engineering-research-415-c): 160 aircraft (airframe model) - [Ercoupe 415-D](https://openairdocs.org/model/ercoupe-415-d): 101 aircraft (airframe model) - [Ercoupe 415-CD](https://openairdocs.org/model/ercoupe-415-cd): 48 aircraft (airframe model) - [Engineering & Research 415-D](https://openairdocs.org/model/engineering-research-415-d): 24 aircraft (airframe model) - [Forney 415-C](https://openairdocs.org/model/forney-415-c): 17 aircraft (airframe model) - [Engineering & Research 415-CD](https://openairdocs.org/model/engineering-research-415-cd): 16 aircraft (airframe model) - [Erco 415-C](https://openairdocs.org/model/erco-415-c): 7 aircraft (airframe model) - [Erco 415-D](https://openairdocs.org/model/erco-415-d): 4 aircraft (airframe model) - [Forney 415-D](https://openairdocs.org/model/forney-415-d): 2 aircraft (airframe model) - [Forney 415-CD](https://openairdocs.org/model/forney-415-cd): 1 aircraft (airframe model) - [Erco 415-CD](https://openairdocs.org/model/erco-415-cd): 1 aircraft (airframe model) - [Univair 415-D](https://openairdocs.org/model/univair-415-d): 1 aircraft (airframe model) All 13 models: https://openairdocs.org/ad/47-20-05/models.md Every aircraft: https://openairdocs.org/ad/47-20-05/aircraft.md Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.