Broad findings - Ageing Aircraft Management Plan (AAMP) Stage 1 Report
CASA fully supports the continued operation of ageing aircraft in Australia - provided it can continue to be done safely.
• Aircraft owners may not be able to continue operating 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 ageing aircraft. We will recommend a number of approaches to address these issues in Stage 2 of the AAMP.
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, stored, upgraded etc.
A large percentage of aircraft on the Australian register were designed and manufactured in the 1950s, 60s and 70s.
The certification basis of the aircraft, also known as the standard to which the aircraft has been built, significantly impacts the ageing process. Some aircraft designed and built in the 1950s and 60s had little or no fatigue considerations built into their design. The later the design of the aircraft, the more comprehensive the certification basis.
Other factors such as methods of manufacture & assembly, quality of surface protections etc. have all evolved significantly since these post-war times and all have a large 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 the Australian fleet for some time.
Also, many business models revolve around the use of older aircraft (with cheaper purchase price but significantly higher maintenance costs) as opposed to the use of more recently manufactured aircraft (with higher purchase prices but lower maintenance costs).
CASA’s main concerns are for General Aviation (GA) aircraft
CASA’s initial focus will be on ageing GA aircraft, particularly those involved in some form of fare paying passenger operations.
The average age of GA aircraft (aircraft less than 5,700 kg) is much higher than the average age of Regular Public Transport (RPT – aircraft greater than 5,700 kg).
Also, RPT aircraft tend to have:
• on-going manufacturer’s support on ageing issues
• comprehensive Systems of Maintenance
• higher levels of resources to support them.
No 'one size fits all' solution
There are no blanket solutions 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. Therefore, each aircraft needs to be considered individually.
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, for example:
• the existence of any manufacturing flaws
• the application of insufficient protective coatings
• the existence of swarf in wiring bundles, miss-aligned drill holes.
All of these examples can initiate a premature ageing process in a new aircraft.
Minimal monitoring of aircraft ageing data
CASA has recognised the benefits of increasing available data on the factors that contribute to the ageing process. The extent to which this occurs will be determined by CASA in the near future under AAMP – Stage 2.
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 increased knowledge and awareness campaign on the science behind the ageing process.
As a result, CASA will deliver seminars that cover basic concepts of the ageing process. For more information about the seminars and how to register, go to Ageing Aircraft Awareness & Industry Feedback Program seminars.
Addressing the ageing issue will take resources
Many older GA aircraft have minimal instructions for continuing airworthiness. In many cases, owners have used CASA Maintenance Schedule 5 as the default System of Maintenance for their aircraft.
As the ageing process becomes better understood, the adequacy or otherwise of such minimalist Systems of Maintenance may need to be reviewed.