# AD 75-12-09 R2: Inadvertent Structural Failure - Type: Airworthiness directive - Status: Current - Products: Twin Commander 500, 500-A, 500-B, 500-S, 500-U, 520, 560, 560-A, 560-E, 560-F, 680, 680-E and 3 more - Effective: November 28, 1981 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small airplane - Amendment: 39-4246 - Registered aircraft: 250 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E6B0342B1F07A30C86256A38005DFF32.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/75-12-09-R2 ## The airworthiness directive 75-12-09 R2 ROCKWELL: Amendment 39-2223 as amended by Amendment 39-4166 is further amended by Amendment 39-4246. Applies to Models 500, 500A, 500B, 500S, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680F(P), and 720, through Serial Number 3323 airplanes certificated in all categories. Compliance is required as indicated. Within the next 300 hours' time in service after the effective date of this AD, to prevent inadvertent pilot induced structural failure, install "bob weights" in accordance with Rockwell International Service Bulletin No. 128, Revision 1, dated April 24, 1975, or No. 129, Revision 2, dated May 9, 1975, or No. 136, Revision 1, dated May 9, 1975 (or later FAA approved revision), or an equivalent procedure approved by the Chief, Engineering and Manufacturing Branch, Southwest Region, Federal Aviation Administration, Fort Worth, Texas, unless already accomplished in accordance with the above revised service bulletins. Aircraft that have complied with Service Bulletin No. 129 prior to Revision 2 or Service Bulletin No. 136 prior to Revision 1, must comply with Rockwell Service Bulletin No. 152 dated May 9, 1975, or an equivalent approved by the Chief, Engineering and Manufacturing Branch, Southwest Region, Federal Aviation Administration, Fort Worth, Texas, unless already accomplished. Compliance with Service Bulletin No. 152 is required within 300 hours' time in service after the effective date of this AD. Aircraft that have complied with the bob-weight installation in accordance with Service Bulletin No. 129, prior to Revision 4 dated January 26, 1981, or Service Bulletin No. 136 prior to Revision 3 dated January 26, 1981, must comply with Service Bulletin No. 179 dated January 26, 1981, or an equivalent approved by the Chief, Engineering and Manufacturing Branch, Southwest Region, Federal Aviation Administration, Fort Worth, Texas, unless already accomplished. Compliance with the inspection specified in Service Bulletin No. 179 is required as follows: a. Models 500, 500A, 500B, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680F(P), 720, and 500S, through Serial Number 3246 aircraft certificated in all categories which have had the provisions of Service Bulletin No. 129 prior to Revision 4 dated January 26, 1981, or Service Bulletin No. 136 prior to Revision 3 dated January 26, 1981, and Service Bulletin No. 152 dated May 9, 1975, which required the bob-weight installation or an equivalent approved by the Chief, Engineering and Manufacturing Branch, Southwest Region, Federal Aviation Administration, Fort Worth, Texas, accomplished; within 25 hours' time in service after August 9, 1981. When compliance with the repair or strengthening of the supports in accordance with Service Bulletin No. 129, Revision 4, or Service Bulletin No. 136, Revision 3, has been accomplished, the repetitive 25-hour inspection of Service Bulletin No. 179 may be discontinued. b. Model 500S, Serial Numbers 3247 through 3323, aircraft certificated in all categories; within 25 hours' time in service after the effective inspection of Service Bulletin No. 179. This repetitive 25-hour inspection may be discontinued when the repair or strengthening of the supports is accomplished in accordance with Part II of Service Bulletin No. 179. In accordance with FAR 21.197, a ferry flight is permitted to a base where the inspection, repair or modification required by this AD may be accomplished. Copies of these bulletins may be obtained by contacting the Service Manager, Gulfstream American Corporation, 5001 North Rockwell Avenue, Bethany, Oklahoma 73008. Amendment 39-2223 became effective July 2, 1975. Amendment 39-4166 became effective August 9, 1981. This amendment 39-4246 becomes effective November 28, 1981. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 6A1](https://openairdocs.org/tcds/6A1): Twin Commander Aircraft LLC; names 9 of 9 models: 500, 500A, 500B, 500U, 520, 560, 560A, 560E… - [TCDS 2A4](https://openairdocs.org/tcds/2A4): Twin Commander Aircraft LLC; names 5 of 21 models: 680-F, 680-E, 560-F, 720, 680 ## 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: 250 (250 by airframe model, 0 by engine model) - Makers: Aero Commander 231, Rockwell International 19 Models with the most aircraft: - [Aero Commander 500-B](https://openairdocs.org/model/aero-commander-500-b): 85 aircraft (airframe model) - [Aero Commander 500 S](https://openairdocs.org/model/aero-commander-500-s): 45 aircraft (airframe model) - [Aero Commander 500-A](https://openairdocs.org/model/aero-commander-500-a): 23 aircraft (airframe model) - [Rockwell International 500-S](https://openairdocs.org/model/rockwell-international-500-s): 19 aircraft (airframe model) - [Aero Commander 500](https://openairdocs.org/model/aero-commander-500): 12 aircraft (airframe model) - [Aero Commander 520](https://openairdocs.org/model/aero-commander-520): 12 aircraft (airframe model) - [Aero Commander 680](https://openairdocs.org/model/aero-commander-680): 12 aircraft (airframe model) - [Aero Commander 680-F](https://openairdocs.org/model/aero-commander-680-f): 11 aircraft (airframe model) - [Aero Commander 560-A](https://openairdocs.org/model/aero-commander-560-a): 10 aircraft (airframe model) - [Aero Commander 560-F](https://openairdocs.org/model/aero-commander-560-f): 6 aircraft (airframe model) - [Aero Commander 560-E](https://openairdocs.org/model/aero-commander-560-e): 5 aircraft (airframe model) - [Aero Commander 680-E](https://openairdocs.org/model/aero-commander-680-e): 4 aircraft (airframe model) - [Aero Commander 500-U](https://openairdocs.org/model/aero-commander-500-u): 3 aircraft (airframe model) - [Aero Commander 560](https://openairdocs.org/model/aero-commander-560): 2 aircraft (airframe model) - [Aero Commander 720](https://openairdocs.org/model/aero-commander-720): 1 aircraft (airframe model) All 15 models: https://openairdocs.org/ad/75-12-09-R2/models.md Every aircraft: https://openairdocs.org/ad/75-12-09-R2/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; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB ANC97FA143](https://openairdocs.org/ntsb/ANC97FA143), Sep 6, 1997: Aero Commander AC-500A (N543AN), Ketchikan, AK, destroyed, 2 fatal. Probable cause: The rupture of the right engine fuel supply line as a result of inadequate inspection by the pilot/mechanic, and the pilot's excessive pull up which resulted in exceeding the design stress limits of… --- 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.