AD/Gas/1 Amdt 10 Inspection, Test and Retirement (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below repeals Airworthiness Directive (AD) AD/GAS/1 Amdt 9 and issues the following AD under subregulation 39.001 (1) of CASR 1998 and subsection 33 (3) of the Acts Interpretation Act 1901. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct an unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Compressed Gas Cylinders

AD/GAS/1 Amdt 10 Inspection, Test and Retirement 5/2016

Applicability:

For aircraft to which Part 42 of CASR 1998 applies:

All rechargeable compressed gas cylinders except for those used:

(a)   as fire extinguishers installed or intended to be installed in an aircraft, or

(b)   in a hot air balloon; and,

for which a system of maintenance detailing the procedures for inspection, test and retirement of compressed gas cylinders and valves and/or regulators has not been approved.

Requirement:

1.    Applicable compressed gas cylinders shall be emptied. The gas cylinder assembly, which includes the valve, must be inspected. The gas cylinders are to be hydrostatically tested and have their markings updated to conform with their manufacturer's, Australian Standards or DOT specification except as varied below:

(a)   Cylinders with a working pressure of less than 1MPa are exempted from hydrostatic testing.

(b)   USA cylinders which have an outside diameter of less than 51 mm and length less than 610 mm are exempted from hydrostatic testing.

(c)   The retest of aircraft compressed gas cylinders must include a visual internal and external inspection together with a test by interior hydrostatic pressure in a water jacket or other apparatus of suitable form for the determination of the expansion of the cylinder. Permanent volumetric expansion must not exceed 10% of total volumetric expansion at test pressure or a permanent increase in volume of more than 1/5000 of its original volume.

(d)   Where a cylinder specification or CGA Pamphlet does not adequately define damage limits, 50% of the damage tolerances stated in AS2030 shall be applied.

(e)   USA cylinders marked 3HT must be inspected and tested in accordance with the USA Compressed Gas Association Pamphlet C-8 (Standards for Visual Inspection of Compressed Gas Cylinders (1972), 49 CFR §180.209 and 180.213(c) (2) refer).

(f)   A hydrostatic proof test is an acceptable alternative to a hydrostatic stretch test only where permitted by a particular cylinder specification.

2.    Inspect and test of the valve and/or the regulator in accordance with the manufacturer’s specifications. If no manufacturer’s specification is available then the valve is to be inspected in accordance with AS2337.1-2004 paragraph 10.2.2.

3.    Retire cylinder from service.

4.    Cylinders which do not comply with their scheduled inspection limits or test requirements shall be rendered unfit for further use in accordance with AS2030.

Compliance:

1.    Unless it can be positively established and certified when the last hydrostatic testing was carried out and is again due, testing should be carried out within 1 year after 31 August 1986 and thereafter at intervals not exceeding 5 years except for:

(a)   3HT cylinders are to be tested at intervals not exceeding 3 years, and

(b)   DOT-E type cylinders are to be tested in accordance with the latest revision of the applicable DOT Special Permit or 3 years.

2.    In accordance with the manufacturer’s requirements or at the same time as the cylinder inspection whichever is the lesser.

3.    In accordance with whichever of the following occurs first:

(a)   the manufacturer's specification,

(b)   for 3HT cylinders:

(i)    4 380 pressurisations (cycles), or

(ii)   24 years from date of manufacture; or

(c)   HOLASW 1** cylinders:

(i)    5 000 pressurisations (cycles), or

(ii)   25 years from date of manufacture.

(d)   for fibrewrapped cylinders:

(i)    the limit specified in the applicable DOT-Exemption, or

(ii)   15 years from the date of manufacture.

4.    Immediately following Requirement 3.

Note 1:  Not all specifications include a retirement requirement.

Note 2:  From the effective date of this amendment, and where the number of pressurisation cycles prior to this amendment have not been recorded, or cannot be substantiated, and where a cylinder is, or has been:

(a)   installed only for emergency purposes, it is to be assumed to have consumed 1 cycle every 2 days since date of manufacture; or

(b)   installed or used for the normal provision of supplementary oxygen above an altitude, or cabin altitude of 10 000 feet, it is to be assumed to have consumed 1 cycle each day since the date of manufacture.

The effective date of this AD is 26 February 2016.

Background:

Amendment 7 recognised the cycle life limit of USA 3HT, and UK HOLASW cylinders. It has been established for emergency oxygen systems that the normal frequency of topping up, and only cycling pressure from despatch limits to maximum, will allow this class of cylinder where applicable, to retain its full remaining calendar life. However, where no records exist, cylinders for routine high altitude use must be assumed to have been fully cycled from empty to full, and on a regular basis.

Amendment 8 aligned the Directive with the change in the Australia Standard AS 2337.1 which requires the valve to be inspected along with the gas cylinder and regulator.

Amendment 9 was issued because US DOT Exemption E 8162 had been superseded by US DOT Special Permit SP 8162 dated May 11, 2007. US DOT-SP 8162 changes the hydrostatic test interval of lightweight composite oxygen cylinders from 3 years to 5 years for cylinders that have been tested after July 1, 2006.

Amendment 10 is issued to limit the applicability of the AD to Part 42 aircraft only. This AD will be repealed after the requirements are incorporated into a future amendment of the Part 42 Manual of Standards.

Pieter van Dijk
Delegate of the Civil Aviation Safety Authority

22 February 2016