Recommendation

The Civil Aviation Safety Authority accepts this recommendation
and is now considering how best to clarify the intent of CAO
108.26, paragraph 3.1, for relevant operators.

I refer to an email dated 28 May 2002...... requesting an update
of CASA's actions to clarify the intent of the Civil Aviation Order
(CAO) 108.26, paragraph 3.1 in relation to Recommendation
R20000289.



CASA has reconsidered its original response dated 2 February 2001
to Recommendation R20000289. A copy of the response is attached.
The original response was misleading and CASA now wishes to clarify
the status of CAO 108.26 and, in particular, paragraph 3.1.



Some of the requirements in CAO 108.26 are Australian design
standards. These design standards were intended to be applied to
the oxygen systems of types and models of aircraft when those types
and models were first offered for acceptance in Australia. In 1990
the Civil Aviation Authority abandoned its practice of applying
Australian design standards to aircraft that were manufactured
outside Australia and certificated in any of five major aviation
countries.



New legislation promulgated in 1990 facilitated the entry to
Australia of new aircraft types and models without having to comply
with Australian design standards. The design standards to which
these aircraft were certificated in any of the five major aviation
countries were accepted by the Civil Aviation Authority as being
adequate. Consequently the design standards in CAO 108.26 are not
consistent with regulations in force since the early 1990s and the
design standards have not been applied to any type and model of
aircraft that has entered Australia since that time.



The effect of the amendment to CAO 108.26, paragraph 3.1, in July
1987 was to require warning of cabin depressurisation at a cabin
pressure altitude of 10,000 feet. This design standard is no longer
consistent with the Civil Aviation Regulations and CASA does not
apply it to new types and models of aircraft.



All pressurised aeroplanes certificated in the country of
manufacture to Part 25 of the USA Federal Aviation Regulations, or
to Part 23 at amendment 23-17 or later, will have a warning of
cabin depressurisation at 10,000 feet so paragraph 3.1 will not
have an impact. The only aeroplanes on which paragraph 3.1 had an
impact were those of a type and model certificated prior to Part 23
at amendment 23-17; which are intended to be operated above 25,000
feet; and which entered Australia in the period between July 1987
and promulgation of regulation 22A in 1990. It is likely there is
no such aeroplane in Australia.



Further information is provided in an Attachment to this
letter.



ATTACHMENT



In April 2002 CASA issued Notice of Proposed Rule Making 0216CS
"Proposal for aural warning to operate with cabin altitude warning
systems". During preparation of this NPRM CASA gave renewed
consideration to Recommendation R20000289 and it is now clear that
CASA should revise the response provided on 2 February 2001.



CAO 108.26 contains requirements of two kinds. Some requirements
are directed at operators and pilots in command of aircraft
equipped with oxygen systems. These requirements relate to the
amount of oxygen and the number of oxygen dispensers that must be
carried on a particular flight, and at what altitudes oxygen must
be used. The remainder of the requirements are design standards
applicable to aircraft equipped with oxygen systems and intended to
be operated above 10,000 feet. These design standards were intended
to be met prior to issue of a certificate of airworthiness and
compliance would need to be shown whenever the aircraft was
repaired or modified in a way that affected the oxygen
system.



By the end of the 1980s Australia had a large number of design
standards applicable to aircraft. Most were published in Part 101
of Civil Aviation Orders. Others were published in Parts 105, 108
and elsewhere in Civil Aviation Orders. The design standards in CAO
108.26 are an example. These design standards were a controversial
part of Australian aviation legislation. In the late 1980s the
Board of the Civil Aviation Authority commissioned Mr Ronald Yates
to investigate these design standards.



Mr Yates advised that the design standards were inappropriate when
applied to aircraft which had already been certificated by
competent aviation authorities and he recommended their use be
discontinued. The Board accepted the recommendation and, as a
result, Australia's aviation legislation was amended in 1990 to
introduce the concept of automatic acceptance of aircraft type
certificates issued by the aviation authority in certain recognised
countries. This was achieved by promulgation of regulation 22A, and
amendment of regulation 24, of the Civil Aviation Regulations. The
effect of this change was to render Australian aircraft design
standards ineffective when new aircraft types were introduced to
Australia, even though those design standards had not been
cancelled.



The amendment to CAO 108.26 in July 1987 reducing the activation
altitude for depressurisation warnings from 14,000 to 10,000 feet
was only applied to new types and models of aircraft entering
Australia from July 1987 until promulgation of regulation 22A in
about late 1990. It was also only applied to pressurised aircraft
intended to be operated above 25,000 feet.



The Australian design standards were not actively applied
throughout the 1990s. In October 1998 most of the design standards
in CAO Part 101 were cancelled. After that, CASA promoted a
procedure for re-issue of the certificate of airworthiness to allow
aircraft operators to legally abandon modifications that had been
introduced to comply with the Australian design standards. If any
operator had enquired about how to eliminate a burden associated
with any of the design standards in CAO 108.26 CASA would have
recommended re-issue of the certificate of airworthiness.



Since the early 1990s CASA management has advocated harmonisation
with major aviation countries and avoidance of uniquely Australian
requirements except where they can be publicly justified.
Successive Australian governments have supported this approach to
aviation regulation. As a result the Australian design standards
were first rendered ineffective and are now being progressively
cancelled.

I wish to clarify an issue relating to CASA's response to ATSB
Recommendation R20000289, repeated below:



The ATSB recommends that CASA advise relevant operators of its
interpretation of CAO 108.26 in relation to the applicability of
the requirements for a device to provide flight crew of pressurised
aircraft with a warning whenever the cabin pressure altitude
exceeds 10,000 feet.



The Recommendation was made in ATSB investigation report 199902928
covering an in-flight pilot incapacitation that occurred on the
21st June 1999.



Section 108.26 of Civil Aviation Orders ("CAO") contains
specifications for oxygen systems in aircraft intended for
operation at altitudes up to 40,000 feet. These are mostly
pressurised aircraft. CAO 108.26 was amended occasionally but the
amended specifications were only applied to new types and models of
pressurised aircraft entering Australia for the first time after
the date of the amendment. Amendments were never intended to be
applied to aircraft of a type and model already established in
Australia, nor were they intended to be applied retroactively to
aircraft which already had certificates of airworthiness. In 1990
Australia adopted a process of automatic acceptance of aircraft
type certificates issued in any of five major aviation countries.
Uniquely Australian standards for aircraft, including the design
specifications in CAO 108.26, have not been applied to new types
and models entering Australia since the introduction of automatic
acceptance. CAO 108.26 remains applicable to pressurised aircraft
which received their Australian certificates of airworthiness prior
to implementation of automatic acceptance.



Despite automatic acceptance of aircraft type certificates, certain
requirements in CAO 108.26 are specified in CAO 20.4 and therefore
remain in force. Sub-section 3 of CAO 20.4 requires that oxygen
storage, dispensing and control equipment, and minimum rates of
oxygen flow must be in accordance with CAO 108.26. Sub-section 3 of
CAO 20.4 specifies only a small number of operational requirements
in CAO 108.26 and these do not include the area in contention (CAO
108.26, para 3.1) which refers to inclusion of a warning
device.



The changing role of Australian design standards for aircraft has
contributed to confusion among people who do not have an
understanding of the process for issue of certificates of
airworthiness. CASA is therefore considering amendment of CAO
108.26 to delete all requirements except the operational
requirements imposed by CAO 20.4, sub-section 3, and the
specification for protective breathing equipment imposed by CAO
20.4, sub-section 10.



If CAO 108.26 is amended the background to the amendment will be
explained in an article in Flight Safety Australia.

On 12 July 2002 I wrote to you regarding the above
Recommendation which states:



The ATSB recommends that CASA advise relevant operators of its
interpretation of CAO 108.26 in relation to the applicability of
the requirements for a device to provide flight crew of pressurised
aircraft with a warning whenever the cabin pressure altitude
exceeds 10,000 feet.



In my 12 July letter I stated that CASA was considering amendment
of CAO 108.26 to delete all requirements except the operational
requirements imposed by CAO 20.4, sub-section 3, and the
specification for protective breathing equipment imposed by CAO
20.4, sub-section 10. I am pleased to advise that CASA has now
formally taken the decision to initiate an Advanced Regulatory
Change project to carry out this amendment. Consequently I can give
you a commitment that the work will be done. I expect the CAO to be
amended before the end of 2002.



An article will be published in Flight Safety Australia to explain
the amended CAO and the background to the change.

CASA advised on 4 December 2002 that CAO 108.26 was revised
today by Amendment No. 101 and was on CASA's web site at the
following address:



www.casa.gov.au/avreg/rules/orders/108.htm

The following response, dated 28 February 2003, was received
from the Civil Aviation Safety Authority on 5 March 2003:



ATSB Recommendation R20000289 states: "The ATSB recommends that
CASA

advise relevant operators of its interpretation of CAO 108.26 in
relation to the

applicability of the requirements for a device to provide the
flight crew of pressurised

aircraft with a warning whenever the cabin pressure altitude
exceeds 10,000 feet."



CASA and ATSB have corresponded on several occasions about the need
to amend CAO 108.26 so that its meaning is clear to aircraft
operators and others. The effect of CAO 108.26 was altered
significantly in 1990 by the promulgation of regulation 22A of the
Civil Aviation Regulations which introduced automatic acceptance of
foreign type certificates. I wrote to you on 30 August 2002
advising that CAO 108.26 would be amended to delete superfluous
material.



I am now able to advise that the amendment to CAO 108.26 was signed
on

27 November 2002 by the Director of Aviation Safety, Mr Mick
Toller. That amendment became effective upon gazettal on Wednesday
4 December 2002. A revised version of the CAO now appears on CASA's
web site. CASA is also planning an explanatory article in Flight
Safety Australia.

The Civil Aviation Safety Authority provided the following
response on 23 April 2004.<br><br>Civil Aviation Order
(CAO) 108.26 was substantially amended in November 2002 to delete
all references to audible warning systems and other confusing
elements. Therefore, explanatory material on the interpretation of
the CAO is no longer necessary.<br><br>