What is an Ageing Aircraft?
Just as a human being starts ageing from the day he is born, similarly an aircraft starts ageing from the day it is manufactured. The dilemma however is, how old is too old? Some aviation experts feel that if an aircraft is properly maintained as per schedule the chronological age of an aircraft does not matter much in the final performance review. But is that really true? Let’s find out more…
A lot of factors come into play while calculating the ageing process of an aircraft like the number of flight hours or the number of flight cycles that the aircraft has flown till date. Even if we do get a specific age, the different components of an aircraft age differently based on their functions, use and maintenance. Factors like these make the age calculation of an aircraft difficult. Apart from these other factors like maintenance on an aircraft, the type of aircraft operations, and the operational environment also matter while calculating the aircraft age.
Understanding aircraft aging is critical for the fleet management to decide when an aircraft needs to be replaced.
Common ageing problems faced by an aircraft and their causes
Fatigue is the most common sign that an aircraft has started ageing. It includes fatigue of the basic type design, widespread fatigue damage (WFD), corrosion, fatigue of changes and repairs, and continued operation with unsafe levels of fatigue cracking. Due to the repeated flight cycles and frequent use, the metal elements of planes weaken over time, and eventually require attention and repair. This weakness manifests in cracks in structures of panes, which are microscopic at first but later prove to be fatal. The maintenance issues which have particularly arisen with aging aircraft structural failure have generally been seen as arising from fatigue or corrosion, with corrosion sometimes initiating fatigue effects.
- Metallic corrosion: Most of the older aircraft are made used two dissimilar metals making them an easy target for metallic corrosion due to chemical action thereby causing deterioration of the metal surface. As this effect mostly occurs at the microscopic grain boundaries within a metal alloy, there are chances that it might go undetected resulting in loss of integrity of metallic structure.Selection of better design and non-metallic composite is the best solution to avoid the problem.
- Pitting corrosion – It is a localized corrosion by which small cavities or holes are formed on the surface of metals. This is one of the more dangerous corrosions because of its limited detection and the persistence of pitting formations.These small holes and cavities can lead to a catastrophic failure of the engineering systems.
- Maintenance –
- Better understanding of the detailed effects of corrosion
- Study of the ground environment where the aircraft is parked
- Improved inspections including the use of non-destructive testing or NDT
- Corrosion management by effective repair techniques, mapping technologies and recording
- Use of coating or inhibitor treatments
- Use of composite doublers as a cost-effective method to safely extend the life of aircraft. They are able to withstand extensive damage and non-optimum installations while improving fatigue life and ultimate strength.
- Use of drones for detecting cracks or structural deformities on the fuselage instead of manual inspection
Apart from the above, Degradation and failure of aircraft wiring insulation results in potentially flight safety critical system failure or in smoke and fire due to arcing. With two air accidents in recent years involving great loss of life caused by wiring failure, the integrity of aging aircraft wiring is a significant and growing concern for aviation regulators, aircraft operators and maintainers.
Aircraft retirements & Teardowns in 2021
As per IATA about 16,000 commercial aircraft have been retired over 35 years and about 700 per year are reaching the end of their lives. This trend is steadily rising with around 11,000 aircraft are expected to retire over the next decade. The pandemic has definitely played a catalytic role in this process with many operators announcing earlier than expected fleet retirement programs. Older and inefficient aircraft are being retired and being replaced by more efficient next-generation Boeing 787 Dreamliner and Airbus A350 XWB. Virgin Atlantic Airways retired its Airbus A340-600 aircraft ahead of time while KLM Royal Dutch Airlines retired its Boeing 747-400 aircraft in March. Iconic quad-engine aircraft such as the Boeing 747 and Airbus A380 have disappeared from the global airline fleets only to be replaced with twin-engine aircraft. Aging twin-engine aircraft are also on retirement line-up, with airlines seeking newer types that provide their passengers with better experiences and relief for their bottom lines. American Airlines retired its entire fleet of Boeing 767-300ER wide-body aircraft. Newer wide-body aircraft including the Boeing 787 Dreamliner have taken the place of the 767. Lufthansa grounded its Airbus A380s due to reduction in demand.
Once the aircraft ages and retires, the next step is the teardown process. During teardown the completely aircraft is stripped down and reusable spare parts and components are removed. These parts hold a very high value in the market.
The future trend is in aircraft teardowns. Instead of bearing the brunt of maintenance of ageing aircraft, operators and lessors are opting for more value-driven and increasingly favourable teardown options. During teardown the spare parts removed from the retired aircraft can be repaired and re-certified before being released into the marketplace. Generally, aftermarket components are more affordable and readily available than OEM parts.
Naturally many aerospace companies across are expanding into aircraft modification and teardown facilities. Recently J&C Aero opened their first aircraft teardown site in Lithuania.
Commenting on the new site opening, Laurynas Skukauskas, the CEO at J&C Aero says, “The pandemics, despite all its challenges, also provided new opportunities as airlines and aircraft owners seek more flexibility with their fleets. That is why we decided to expand J&C Aero’s existing DOA/POA and CAMO capabilities and launch our own MRO center. In addition, seeing a rising demand for used spare parts and supporting the industry’s efforts to be more sustainable, we have also decided to launch the region’s first aircraft teardown site with a capacity of several aircraft per month.”
Conclusion
Until very recently the issues arising due to aircraft ageing were neither recognised nor addressed till fatal accidents occurred. It was then that system deterioration started receiving attention from maintenance and airworthiness officials. The United States, which has seen most examples of accidents attributed to aging aircraft problems, has a joint civil-military organisation called the Joint Council on Aging Aircraft (JCAA) to co-ordinate the development of risk management solutions for the various types of aging aircraft problem, especially structures.
