# AD 76-21-03: Main Landing Gear Struts - Type: Airworthiness directive - Status: Current - Products: Allied Ag Cat Productions G-164, G-164A, G-164B, G-164B-15T, G-164B-20T, G-164B-34T, G-164B (with 73 inch wing gap), G-164C, G-164D and G-164D (with 73 inch wing gap) with STC SA647WE - Effective: October 20, 1976 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small airplane - Amendment: 39-2746 - Registered aircraft: 564 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D6610B23D6F3F8C986256A5400702CFD.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/76-21-03 ## The airworthiness directive 76-21-03 GRUMMAN AMERICAN: Amendment 39-2746. Applies to Model G-164 airplanes certificated in all categories incorporating Frenco Co. main landing gear struts P/N 1428, installed in accordance with STC SA647WE. Compliance required as indicated. To prevent possible hazards associated with main landing gear strut failures, accomplish the following: (a) Within the next 100 landings after the effective date of this airworthiness directive, unless accomplished within the last 1900 landings, and thereafter at intervals not to exceed 2000 landings from the last inspection, remove the main gear struts, Frenco Co. P/N 1428, and inspect the struts for cracks using dye penetrant and a glass of at least 10 power or magnetic particles inspection. "Note: During the inspection required by paragraph (a) particular attention should be directed to the upper bend radius, and fuselage attachment area." (b) If cracks are found, before further flight, replace the cracked strut with an unused strut of the same part number. (c) For the purpose of complying with this airworthiness directive, subject to the acceptance by the assigned FAA maintenance inspector, the number of landings may be determined by dividing each airplane's hours' time in service by the operator's fleet average time from takeoff to landing for the airplane type. (d) Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Aircraft Engineering Division, FAA Western Region may adjust the repetitive inspection interval specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator. (e) Equivalent inspection procedures or parts may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region. This amendment becomes effective October 20, 1976. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 1A16](https://openairdocs.org/tcds/1A16): Allied Ag Cat Productions Inc.; names 8 of 10 models: G-164B, G-164D (with 73 inch wing gap), G-164C, G-164, G-164B-20T, G-164A, G-164B-34T, G-164B-15T ## 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: 564 (564 by airframe model, 0 by engine model) - Makers: Grumman Acft ENG Cor-Schweizer 325, Grumman 119, Schweizer 64, Gulfstream-Schweizer A/C 36, Grumman American Avn. 12, Ag-Cat 5, Grumman/Schweizer 2, Gulfstream Schweizer A/C 1 Models with the most aircraft: - [Grumman Acft ENG Cor-Schweizer G-164B](https://openairdocs.org/model/grumman-acft-eng-cor-schweizer-g-164b): 157 aircraft (airframe model) - [Grumman Acft ENG Cor-Schweizer G-164A](https://openairdocs.org/model/grumman-acft-eng-cor-schweizer-g-164a): 150 aircraft (airframe model) - [Grumman G-164A](https://openairdocs.org/model/grumman-g-164a): 63 aircraft (airframe model) - [Schweizer G-164B](https://openairdocs.org/model/schweizer-g-164b): 56 aircraft (airframe model) - [Grumman G-164](https://openairdocs.org/model/grumman-g-164): 52 aircraft (airframe model) - [Gulfstream-Schweizer A/C GULFSTREAM AM G-164B](https://openairdocs.org/model/gulfstream-schweizer-a-c-gulfstream-am-g-164b): 33 aircraft (airframe model) - [Grumman Acft ENG Cor-Schweizer G-164C](https://openairdocs.org/model/grumman-acft-eng-cor-schweizer-g-164c): 18 aircraft (airframe model) - [Grumman American Avn. G-164B](https://openairdocs.org/model/grumman-american-avn-g-164b): 6 aircraft (airframe model) - [Ag-Cat G-164B](https://openairdocs.org/model/ag-cat-g-164b): 5 aircraft (airframe model) - [Grumman American Avn. G-164](https://openairdocs.org/model/grumman-american-avn-g-164): 3 aircraft (airframe model) - [Grumman American Avn. G-164A](https://openairdocs.org/model/grumman-american-avn-g-164a): 3 aircraft (airframe model) - [Gulfstream-Schweizer A/C GULFSTREAM AM G-164D](https://openairdocs.org/model/gulfstream-schweizer-a-c-gulfstream-am-g-164d): 3 aircraft (airframe model) - [Schweizer G-164B-20T](https://openairdocs.org/model/schweizer-g-164b-20t): 3 aircraft (airframe model) - [Grumman G164C](https://openairdocs.org/model/grumman-g164c): 2 aircraft (airframe model) - [Grumman G-164B](https://openairdocs.org/model/grumman-g-164b): 2 aircraft (airframe model) - [Grumman/Schweizer G-164D](https://openairdocs.org/model/grumman-schweizer-g-164d): 2 aircraft (airframe model) - [Schweizer G164B-34T](https://openairdocs.org/model/schweizer-g164b-34t): 2 aircraft (airframe model) - [Gulfstream Schweizer A/C GULFSTREAM AM G-164C](https://openairdocs.org/model/gulfstream-schweizer-a-c-gulfstream-am-g-164c): 1 aircraft (airframe model) - [Schweizer G164A](https://openairdocs.org/model/schweizer-g164a): 1 aircraft (airframe model) - [Schweizer G-164C](https://openairdocs.org/model/schweizer-g-164c): 1 aircraft (airframe model) All 22 models: https://openairdocs.org/ad/76-21-03/models.md Every aircraft: https://openairdocs.org/ad/76-21-03/aircraft.md ## Related documents - [STC SA647WE](https://openairdocs.org/stc/SA647WE): Modified landing gear.. Frenco Company, Named in the applicability --- 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.