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Broad findings - AAMP stage 1 report
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- CASA fully supports the ongoing operation of ageing aircraft in Australia - provided it can continue to be done safely.
- Registered operators (owners) may not be able to operate the existing fleet of ageing aircraft indefinitely, with only a minimal amount of maintenance, and expect the inherent risks to remain at an acceptable level.
- The identified ageing issues are impacting on the continuing airworthiness of aircraft.
Australia has an ageing aircraft problem
The airworthiness of an ageing aircraft is influenced by many factors, including chronological age and how it is flown, maintained, modified, repainted, repaired, overhauled and stored.
A large percentage of aircraft on the Australian register were designed and manufactured in the 1950s, 60s and 70s. In many cases, these aircraft were designed with a notional life of 20 years.
Other factors, such as certification standards, methods of manufacture and assembly, quality of surface protections etc. all have a significant impact on the airworthiness status of ageing aircraft.
Ageing aircraft are here to stay
As the rate of renewal of the Australian aircraft fleet is relatively low, ageing aircraft will continue to form a large part of it.
Many business models revolve around the use of older aircraft, which are cheaper to buy but can have significantly higher maintenance costs. This is opposed to the use of more recently manufactured aircraft, with higher purchase prices, but with generally lower maintenance costs, and also the added benefit of higher levels of inherent safety and crashworthiness.
CASA’s initial concerns are for general aviation (GA) aircraft
The following statistics for GA aircraft (aircraft less than 5,700kg) were obtained from the Australian transport safety bureau's How old is too old? report:
- single and multi-engined fixed wing aircraft – average age was 30 years in 2005
- multi-engined piston aircraft category – over 97% are older than the typical 20-year design life.
Aircraft that are mainly used for high-capacity regular public transport (RPT) - aircraft greater than 5700kg - are of considerably lower average age by comparison. In addition, these RPT aircraft tend to have:
- ongoing manufacturer’s support for ageing issues
- comprehensive systems of maintenance
- higher levels of resources to support them.
As a result of this study, CASA’s initial focus is on ageing GA aircraft, particularly those involved in any form of fare-paying passenger operation.
No 'one size fits all' solution
There is no blanket solution to ensure the continued airworthiness of Australia’s ageing aircraft fleet. Every aircraft is unique in the way it ages as a result of many independent factors.
As with cars, boats and any other machine, each aircraft ages from the moment it leaves the factory. Some ageing mechanisms are already determined at this stage. Examples include:
- existence of any manufacturing flaws
- application of insufficient protective coatings
- existence of swarf in wiring bundles, misaligned drill holes, etc.
These are only some of the processes that can initiate premature ageing in a new aircraft.
The certification basis of the aircraft also significantly impacts the ageing process. The later the design of the aircraft, the more comprehensive its certification basis (also known as the standard to which the aircraft has been built). For example, some aircraft designed and built in the 1950s and 60s had little or no fatigue considerations incorporated in their design.
As the aircraft progresses through its operational life, other factors also contribute to the ageing process. For example:
- the number of flight hours, cycles, and pressurisation cycles (where applicable)
- the standard of maintenance applied to the aircraft over its life
- where the aircraft is operated over its life (gravel, dirt, grass etc)
- accident damage and modifications
- whether the aircraft is hangared, cleaned regularly and/or kept near the ocean.
All these factors influence and can accelerate the ageing process in different ways. Each aircraft needs to be considered individually.
Minimal awareness of the science of ageing
The AAMP Stage 1 industry consultation process revealed that many owners, operators and maintenance personnel would benefit from an awareness campaign and industry feedback on the science behind the ageing process in aircraft.
As a result, a comprehensive education and awareness campaign has been conducted involving:
- issuing all registered operators with a copy of the CASA ageing aircraft publication take a closer look, outlining basic ageing aircraft concepts, as well as the registered operators responsibilities with respect to owning an ageing aircraft
- undertaking a comprehensive ageing aircraft awareness and industry feedback program in Australia’s capital cities and at flying clubs around the country
- the development of an ageing aircraft discussion paper to increase awareness of education in relation to ageing aircraft issues
- the release of an ageing aircraft awareness eLearning course aimed at registered operators/owners
- the trialing of a web-based prototype 'matrix tool' to provide educational feedback to individual registered operators as to the likelihood that their aircraft might be affected by ageing aircraft-related issues.