As aircraft get older, they will begin to have problems that could affect the safety of the aircraft. However, new design methods, newer materials, and proper maintenance procedures have increased the lifespan of aircraft over the years and determining the lifespan of any particular aircraft is not always based on a ‘just a number’.
An aircraft’s lifespan is not measured directly in years but is based on ‘Pressurization Cycles’. A pressurization cycle involves the takeoff and landing of the aircraft which is the amount of time that the aircraft is kept under pressure during a flight. The pressurization and depressurization of the aircraft during flight stresses the fuselage and wings and weakens the fasteners and rivets on the aircraft frame. In time this will allow cracks to form due to fatigue creating a dangerous flight condition.
The number of pressurization cycles is determined by the aircraft manufacturer and is based on the proper completion of the manufacturer’s maintenance programs. The more an aircraft is used, the faster it will reach its maximum service limitations.
The average age of a general aviation aircraft is roughly 30 years with a significant number of aircraft over 40 years old. Commercial airline fleets average around 15 years old with some aircraft still in service after 20 years.
Most passengers would not know that they are flying on an older aircraft. Most aircraft parts and components can be replaced and with proper maintenance, a majority of items required to operate the aircraft can be nearly new, including upgrades to the cabin areas with new seating, carpeting, Wi-Fi, and other features.
The age of an aircraft certainly also depends on where it is stored. If the aircraft is stored outside instead of in a protective hangar additional damage to the aircraft will be accelerated due to the additional moisture, sunlight and other environmental factors that will affect the aircraft.
Aircraft Maintenance Programs
A solid manufacturer maintenance program with regular inspections can keep an aircraft flying for years. The FAA has also enacted several programs to address age-related problems with air transport aircraft. Non-Destructive Testing (NDT) and inspection techniques are available that can detect minor cracks and corrosion and prevent or replace the items damaged before they become catastrophic problems.
Airlines and aircraft owners are usually content to replace aging parts at regular intervals on their existing aircraft than to want to spend significant sums on large costly repairs or new aircraft due to poor maintenance practices.
The major factors that contribute to the aging of an aircraft are corrosion, structural fatigue, and electrical wiring problems.
Corrosion detection and prevention is a constant challenge for all aircraft. Corrosion causes a deterioration of the surface of the aircraft and can be accelerated in wet or salty environments. Corrosion can literally eat away a component until it no longer functions as intended.
Structural fatigue causes the airframe structure or fastening components on the aircraft to become damaged and crack from the continual forces that are applied to them during flight. The fatigue in the components builds during each flight until the item is weakened to the point that it does not have the required strength to hold the area together.
Problems in the electrical wiring of an aircraft are often difficult to identify and repair. The wiring is created in large wiring bundles and is often routed in areas that are difficult to access. This makes the detection of any damaged or and broken wires especially difficult if the wire is in the middle of the wiring bundle. A single burnt wire could potentially burn through many wires in the bundle and create a dangerous situation.
To determine whether it is time for an aircraft to be retired, it often depends on the economics surrounding the decision. If the upkeep cost of the aircraft becomes substantial or a major repair is suddenly required, the decision will need to be made if the expense to fix the aircraft is justified and if the repairs will maintain the safety of the aircraft.
As newer aircraft are built, decisions are also based on the advantages of upgrading to the newer designs. Aircraft are constantly manufactured with newer features that aid in the enjoyment and comfort of passengers, such as in-flight Wi-Fi, built-in video screens, etc. Newer aircraft are also typically more fuel-efficient during flight so upgrades over older models could save thousands of dollars in fuel costs.
Aircraft that do get retired get stored in an ‘aircraft graveyard’ in a dry desert location with other retired aircraft or aircraft that are stored due to an aircraft surplus. The dry desert air helps to preserve the aircraft until they are either entered back into service or scrapped for parts or recycled metal.
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