{"id":"F2012L00161","name":"AD/PA-31/37 Amdt 11 - Airframe Retirement Lives","slug":"ad-pa-31-37-amdt-11-airframe-retirement-lives","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":142468,"registerId":"commonwealth-F2012L00161-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Piper PA-31 Series Aeroplanes","sectionType":"division","heading":"Piper PA-31 Series Aeroplanes","content":"### Piper PA-31 Series Aeroplanes\n\n| AD/PA-31/37 Amdt 11 | Airframe Retirement Lives | 3/2012 |\n| ------------------- | ------------------------- | ------ |\n\n```html\n

Applicability:

All Models.

Requirement:

1. a. Retire the wing main spar lower cap and the pressure cabin (where applicable) before exceeding the times in service shown in the Retirement Schedule below; or

b. Adopt a CASA approved inspection program to allow operation beyond the retirement life specified in the Retirement Schedule below. Refer to Note 2 and Note 5 for guidance on developing an inspection program.

2. a. Retire the remainder of the airframe after the expiration of two wing main spar lower cap lifetimes, Note 2 refers; or

b. Adopt a CASA approved inspection program to allow operation beyond the retirement limit of requirement 2.a. Refer to Note 2 and Note 5 for guidance on developing an inspection program.

RETIREMENT SCHEDULE

Model

Wing Main Spar
Lower Cap (hours)

Pressure Cabin (pressurised flights)

*PA-31

11000

N/A

*PA-31-300

15500

N/A

*PA-31-325

11000

N/A

*PA-31-350

13000

N/A

PA-31P

14000

10000

PA-31P-350

28000

10000

PA-31P-350 with 3368kg MTOW (STC 72-6)

23900

10000

\n```\n\n```html\n

PA-31T

12000

10000

PA-31T1

14500

10000

PA-31T1 with optional tip tanks

12000

10000

PA-31T2

11400

10000

PA-31T3

17400

N/A

PA-31T3 with optional tip tanks

13800

N/A

* Aircraft which have been modified in accordance with Gippsland Aeronautics Pty Ltd. Engineering Release PA31-0001 (Model PA-31, -300, -325) or PA31-0002 (Model PA31-350), and which are subject to the related ongoing inspection program of ER PA31-0003, are exempt from the wing fatigue life limitation. The airframe life limitation of Requirement para 2 still applies.

Note 1: The wing main spar lower cap comprises the complete spar cap assembly including the “T” section element, the nesting angles, and the reinforcing strips. It is recommended, but not essential, that the centre section splice plate be retired with the spar cap.

Note 2: The available fatigue data covers wing main spars and pressure cabins only. The durability of other parts of the airframe has not been evaluated, and is therefore unknown.

Based on experience, the Authority is prepared to credit unevaluated structure with a retirement life equal to double the life for the wing spar (Requirement para 2). An extension beyond this may be available, but any application must be supported by a fatigue substantiation covering all the remaining primary structure. This should include empennage, wing centre section, wing rear spar, control surfaces, unpressurised fuselages, etc. The substantiation may take the form of a sufficiently rigorous inspection program to ensure that any fatigue cracking which could occur in service will be detected before the aircraft is endangered.

Revised airframe lives approved against earlier issues of this Directive still apply.

Note 3. The model designations in the Retirement Schedule are as listed in FAA Type Certificate Data Sheets A2050 and A8EA. The variation between the popular and the official designation for some models has caused confusion in the past; AAC Articles 133-5 (August 1982) and 135-5 (October 1982) refer. All PA-31 series aircraft have life-limited wings. If your model is not listed in the Retirement Schedule, or if you are uncertain of the official model designation for your aircraft, please contact your CASA District Office.

\n```\n\n| | Note 4. The requirement for tracking weights and average flight times has been removed as a result of a sensitivity analysis that was conducted. To operate beyond the retirement life refer to requirements 1.b. & 2.b.Note 5. In developing an inspection program consideration must be given to the principles of damage tolerance. A Damage Tolerant analysis of critical parts is required such that inspections include probable locations of damage due to fatigue, corrosion or accidental damage per FAR 23.573(b). For guidance on this aspect, refer to FAA Advisory Circular 23-13A “Fatigue, Fail-Safe, and Damage Tolerance Evaluation of Metallic Structure for Normal, Utility, Acrobatic, and Commuter Category Airplanes”. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | Forthwith. |\n| | This Amendment becomes effective on 2 February 2012. |\n| Background: | The retirement lives promulgated in this Directive are based on fatigue tests and analyses conducted by the manufacturer. According to these evaluations, the risk of airframe cracking increases to an unacceptable level beyond the specified life limitations.Amendment 11 provides alleviation to the retirement requirement of paragraphs 1.a. and 2.a. by allowing a CASA Approved Damage Tolerance inspection program as an alternative.Amendment 10 became effective on 25 February 1999 and removed the requirement to record average weight and flight times. This was a result of a sensitivity analysis carried out by CASA on the relative effects of different sortie profiles and their relative effect on true fatigue life.Amendment 9 of this Airworthiness Directive became effective on27 December 1990.Amendment 8 of this Airworthiness Directive became effective on 7 September 1975.The original issue of this Airworthiness Directive became effective on31 March 1975. |\n\n![](image.001.png)\n\nMike Higgins \nDelegate of the Civil Aviation Safety Authority\n\n2 February 2012","sortOrder":0},{"sectionNumber":"AD/PA-31/37 Amdt 11","sectionType":"part","heading":"AD/PA-31/37 Amdt 11","content":"## AD/PA-31/37 Amdt 11","sortOrder":1},{"sectionNumber":"Airframe Retirement Lives","sectionType":"part","heading":"Airframe Retirement Lives","content":"## Airframe Retirement Lives","sortOrder":2},{"sectionNumber":"3/2012","sectionType":"part","heading":"3/2012","content":"## 3/2012","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"Yes. Amendment 11 adds an alternative CASA‑approved damage‑tolerance inspection pathway allowing continued operation beyond the numeric retirement lives (altering the original strict retirement-only approach). Amendment 10 removed the requirement to track weights and average flight times, narrowing operational data obligations. The AD also preserves conditional exemptions for aircraft modified under specified Gippsland engineering releases while retaining an overall airframe life limit."},"complexity_factors":["Model‑specific numeric life limits for wing main spar lower caps and pressure cabins across many PA‑31 variants (Retirement Schedule).","Dual compliance path: mandatory retirement at specified hours or adoption of a CASA‑approved damage‑tolerant inspection program (Requirement 1.a/1.b; 2.a/2.b).","CASA approval introduces administrative discretion and a certification burden on operators developing inspection programs.","Inspection programs must address damage‑tolerance principles and reference FAR 23.573(b) / FAA AC 23‑13A for guidance (Note 5), raising technical complexity and likely specialist engineering cost.","Exemption for aircraft modified under Gippsland ER PA31‑0001/0002 from the wing fatigue life limitation, while the airframe life limit still applies (asterisk note) — creates conditional carve‑outs tied to specific STCs/ERs.","Allowance to credit unevaluated structure up to double the wing spar life (Note 2) but further extension requires full fatigue substantiation covering primary structure — creates variable scope depending on available substantiation.","Removal of the earlier tracking requirement for weights and average flight times (Amendment 10 / Note 4) reduces operational data obligations but shifts reliance to inspection substantiation.","Immediate/forthwith compliance and specified effective date impose prompt operational and recordkeeping actions on operators (Compliance: Forthwith; effective 2 Feb 2012).","Interplay between component retirement (spar cap, centre splice recommendation) and whole‑airframe retirement after two spar lifetimes introduces lifecycle planning and replacement timing complexity (Requirement 2 / Note 1)."],"plain_english_summary":"Sets flight‑hour retirement limits for wing main spar lower caps (and pressurised cabins where applicable) on Piper PA‑31 series aeroplanes, and requires operators to either retire the parts/airframe at those hours or adopt a CASA‑approved damage‑tolerance inspection program to continue operating. Affects PA‑31 owners/operators who pay for parts, inspections and for obtaining CASA approval; CASA decides whether an inspection program is acceptable. The directive is based on manufacturer fatigue tests showing increased cracking risk beyond the specified lives."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"Originally this directive appears to have been a straightforward retirement mandate (retire parts at X hours). Amendment 11 significantly expanded the scope by introducing an alternative compliance path — allowing CASA-approved damage tolerance inspection programs instead of mandatory retirement. This transformed the directive from a simple 'scrap it' rule into a complex regulatory framework accommodating extended operations through engineering substantiation. The removal of weight tracking requirements (referenced in background) also shifted from prescriptive to performance-based regulation."},"complexity_factors":["Multiple model variants with different hour limits (12 distinct model configurations in the Retirement Schedule)","Cross-references to external documents (FAA Type Certificate Data Sheets A2050 and A8EA, FAA Advisory Circular 23-13A, Gippsland Aeronautics Engineering Releases)","Conditional logic: two alternative compliance paths (retirement vs. approved inspection program)","Nested applicability: exemption for Gippsland Aeronautics modifications with ongoing inspection program","Technical terminology requiring definitions (damage tolerance, fatigue substantiation, MTOW, STC)","Cumulative life calculations (double wing spar life for remainder of airframe)","Amendment history references (Amendments 8-11) creating contextual dependencies"],"plain_english_summary":"This CASA Airworthiness Directive requires retirement or replacement of critical structural items on Piper PA-31 series aircraft after set service limits — notably the wing main spar lower cap and, for pressurised models, the pressure cabin — and calls for the rest of the airframe to be retired after double the spar life unless approved otherwise. It affects owners, operators and maintainers, but lets operators use a CASA-approved damage-tolerance inspection program to extend service if safety is proven."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-31-37-amdt-11-airframe-retirement-lives","history":"/api/acts/ad-pa-31-37-amdt-11-airframe-retirement-lives/history","analysis":"/api/acts/ad-pa-31-37-amdt-11-airframe-retirement-lives/analysis","conflicts":"/api/acts/ad-pa-31-37-amdt-11-airframe-retirement-lives/conflicts","importantCases":"/api/acts/ad-pa-31-37-amdt-11-airframe-retirement-lives/important-cases","documents":"/api/acts/ad-pa-31-37-amdt-11-airframe-retirement-lives/documents"}}