Piper PA-31 Series Aeroplanes

AD/PA-31/37

Amdt 10

Applicability: All models.

Airframe Retirement Lives 2/99

Requirement: 1. 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.

2. The remainder of the airframe must be retired after the expiration of two wing main spar lower cap lifetimes, Note 2 refers.

RETIREMENT SCHEDULE

Model Wing Main Spar Pressure Cabin

* 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.

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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 safe life assessment, or a sufficiently rigorous revised inspection schedule 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.

Note 4. The requirement for tracking weights and average flight times has been removed. However, whilst the lives listed provide a degree of safety for all aircraft irrespective of individual aircraft history, such data when analysed by a CAR 35 engineer may justify an increase of fatigue lives for individual aircraft.

Compliance: Forthwith.

This Amendment becomes effective on 25 February 1999.

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 10 removes the requirement to record average weight and flight times. This is as 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 on 27 December 1990.

Amendment 8 of this Airworthiness Directive became effective on 7 September 1975.

The original issue of this Airworthiness Directive became effective on 31 March 1975.