# AD 77-13-21: Prevent Landing Gear Collapse - Type: Airworthiness directive - Status: Current - Products: Piper PA-24, PA-24-250, PA-24-260, PA-24-400, PA-30 and PA-39 - Effective: December 16, 1977 - Published: December 12, 1977 - Issued: December 2, 1977 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small airplane - Amendment: 39-3093 - Registered aircraft: 3,192 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/4F788F3D9BBD884086256E01005C35A3.0001 - DRS record last changed: November 21, 2025 - Page: https://openairdocs.org/ad/77-13-21 ## The airworthiness directive 77-13-21 PIPER AIRCRAFT CORPORATION: Amendment 39-2946 as amended by Amendment 39-3093. Applies to airplane models PA-24, PA-24-250, and PA-24-260; model PA- 24-400, except S/N 1; and models PA-30 and PA-39, certificated in all categories. For aircraft having 1000 hours or more in service on the effective date of this AD, compliance is required within the next 100 hours in service, and for aircraft having less than 1000 hours in service, compliance is required prior to 1100 hours in service, unless already accomplished in either case. To prevent collapse of the landing gear after manual extension; (a) Accomplish the inspection described on page 3 of Piper Aircraft Corporation Service Letter No. 782A, dated March 21, 1977, and replace components exceeding the specified wear limits, or an equivalent inspection and replacement procedure approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region. (b) Inspect the main landing gear bungee cords for frayed protective covering, breaks, soft areas, and replace cords exhibiting these conditions. In addition, replace cords every 500 hours in service, or every three years, whichever occurs first. (c) Repeat paragraph (a) at each 1000 hours in service after the prior inspection, and repeat paragraph (b) at each 500 hours in service after the prior inspection, or within one year after the prior inspection, whichever occurs first. (d) Airplanes may be flown in accordance with FAR 21.197 to a base where repairs can be performed. The Chief, Engineering and Manufacturing Branch may adjust the inspection interval upon submission of substantiating data submitted through an FAA maintenance inspector. Amendment 39-2946 became effective July 6, 1977. This amendment 39-3093 is effective December 16, 1977. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 1A15](https://openairdocs.org/tcds/1A15): Piper Aircraft Inc.; names 4 of 4 models: PA-24, PA-24-260, PA-24-250, PA-24-400 - [TCDS A1EA](https://openairdocs.org/tcds/A1EA): Piper Aircraft Inc.; names 2 of 3 models: PA-30, PA-39 ## 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: 3,192 (3,192 by airframe model, 0 by engine model) - Makers: Piper 3,192 Models with the most aircraft: - [Piper PA-24-250](https://openairdocs.org/model/piper-pa-24-250): 1,222 aircraft (airframe model) - [Piper PA-30](https://openairdocs.org/model/piper-pa-30): 878 aircraft (airframe model) - [Piper PA-24-260](https://openairdocs.org/model/piper-pa-24-260): 590 aircraft (airframe model) - [Piper PA-24](https://openairdocs.org/model/piper-pa-24): 345 aircraft (airframe model) - [Piper PA-39](https://openairdocs.org/model/piper-pa-39): 82 aircraft (airframe model) - [Piper PA-24-400](https://openairdocs.org/model/piper-pa-24-400): 75 aircraft (airframe model) All 6 models: https://openairdocs.org/ad/77-13-21/models.md Every aircraft: https://openairdocs.org/ad/77-13-21/aircraft.md Its text cites no advisory circulars or STCs. ## NTSB investigations that cite this AD (4) 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 WPR23LA116](https://openairdocs.org/ntsb/WPR23LA116), Feb 20, 2023: Piper PA-24-260 (N9267P), San Jose, CA, substantial damage. Probable cause: A landing gear collapse due to an inadequately maintained landing gear extension and retraction system. - [NTSB WPR18LA153](https://openairdocs.org/ntsb/WPR18LA153), May 21, 2018: Piper PA24 (N244TW), San Jose, CA, substantial damage. Probable cause: A landing gear retraction during the landing rollout for reasons that could not be determined based on the available evidence. - [NTSB DEN07LA160](https://openairdocs.org/ntsb/DEN07LA160), Aug 31, 2007: Piper PA-30 (N22HW), Lawrence, KS, substantial damage. Probable cause: Total failure of the landing gear retraction/extension assembly. Contributing factors in this accident were worn parts in the landing gear retraction/extension assembly, and mechanical binding of the… - [NTSB ANC06LA041](https://openairdocs.org/ntsb/ANC06LA041), Mar 30, 2006: Piper PA-24-250 (N6744P), Mammoth Lake, CA, substantial damage. Probable cause: The collapse of the right main landing gear during landing, which resulted in a loss of directional control and an on-ground encounter with a snowbank. A factor associated with the accident was other… --- 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.