# AD 59-05-04: Rear spar reinforcement - Type: Airworthiness directive - Status: Current - Products: Univair 415-C, 415-CD, 415-D, 415-E and 415-G - Published: May 9, 1959 - Issued: May 4, 1959 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small airplane - Registered aircraft: 1,037 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/EE202AB60CD844D286256A4D004BDD05.0001 - DRS record last changed: November 21, 2025 - Page: https://openairdocs.org/ad/59-05-04 ## The airworthiness directive 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. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A-787](https://openairdocs.org/tcds/A-787): Univair Aircraft Corporation; names 3 of 8 models: 415-D, 415-G, 415-E - [TCDS A-718](https://openairdocs.org/tcds/A-718): Univair Aircraft Corporation; names 2 of 2 models: 415-CD, 415-C ## 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: 1,037 (1,037 by airframe model, 0 by engine model) - Makers: Ercoupe 793, Engineering & Research 210, Forney 21, 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) - [Ercoupe 415-E](https://openairdocs.org/model/ercoupe-415-e): 18 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) - [Engineering & Research 415-E](https://openairdocs.org/model/engineering-research-415-e): 7 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) - [Engineering & Research 415-G](https://openairdocs.org/model/engineering-research-415-g): 3 aircraft (airframe model) - [Ercoupe 415-G](https://openairdocs.org/model/ercoupe-415-g): 3 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) - [Forney 415-E](https://openairdocs.org/model/forney-415-e): 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 18 models: https://openairdocs.org/ad/59-05-04/models.md Every aircraft: https://openairdocs.org/ad/59-05-04/aircraft.md Its text cites no advisory circulars or STCs. ## NTSB investigations that cite this AD (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB LAX04FA150](https://openairdocs.org/ntsb/LAX04FA150), Mar 9, 2004: Ercoupe 415-C (N93707), Oakdale, CA, destroyed, 2 fatal. Probable cause: the in-flight separation of the main spar due to corrosion in the wing center section not detectable by inspection methods described in manufacturer's service bulletins and FAA Airworthiness… --- 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.