What Determines the Life Span of an Airplane?

What Determines the Life Span of an Airplane

October 21, 2021 | By JETechnology Staff

An airplane is an expensive investment. Boeing aircraft can cost anywhere from $89 million to more than $442 million, depending on the model. At some point, it becomes necessary to replace an aging aircraft with a new one. However, the high cost makes it especially important to preserve its useful life span as much as possible. The longer your plane can operate, the more cost-effective your initial purchase is, and the longer you can delay another multi-million dollar acquisition.

Because of the considerable expense involved in purchasing a new aircraft, many aircraft equipment buyers may consider used aircraft. In that case, it becomes even more important to be aware of the plane’s life span and how you can extend it.

While many factors influence an airplane’s life span, you can also do many things to preserve it.

Is an Older Aircraft Unsafe?

Aviation safety is a critical issue for aircraft equipment buyers. When looking at aircraft above a certain age range, it’s natural to question whether it remains safe for flight. However, studies have shown that there is no correlation between accident rates and age for airplanes up to 18 years old and no correlation between fatal accident rates and age for aircraft up to 27 years old. Airplanes more than 20 years old have a weak correlation between age and accident rates.

That said, it’s essential to consider the overall condition of an aircraft, the maximum life span and the components that can age and may need replacement. Besides the plane’s age in years, you might look at the number of flight cycles and flight hours it has experienced.

A more critical safety factor than the age of the aircraft is how well it’s been maintained. Components such as engines, wiring, structural elements and instrumentation may experience wear, corrosion, fatigue or other symptoms of aging before the aircraft reaches the end of its life span. These parts may need replacement or an overhaul to keep an aircraft safe as it ages.

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How Is an Aircraft’s Life Span Determined?

Aircraft life spans depend on a range of factors. According to data on Western-built aircraft from 2005 to 2018, the average passenger jet is retired at 23.6 years. However, aircraft constructed by reliable manufacturers can last even longer, possibly up to 30 years, depending on the make, model and attention to maintenance.

However, while chronological age is important, the life span is more affected by pressurization cycles and flight hours. Airplane manufacturers may set a specific retirement age by flight hours or pressurization cycles.

The Federal Aviation Administration (FAA) requires all planes to have a limit of validity (LOV), which can be listed in aircraft flight cycles, flight hours or both. The LOV is the limit before which widespread fatigue damage is unlikely to occur so long as the required maintenance schedule is followed. Planes may not operate past their LOV unless an aircraft owner applies and gets FAA approval for an extended LOV.

Limit of Validity

Let’s discuss the most critical factors affecting a plane’s life span, flight cycles and flight hours.

Pressurization Cycles

When an aircraft ascends, it must increase the air pressure so that crew members and passengers can receive enough oxygen. As the plane descends, it must depressurize to return the aircraft to ground-level air conditions. Every time an aircraft cycles through pressurization and depressurization, it can experience stress, particularly on the fuselage and wings. Both of these components are large sheets of metal joined with fasteners. Those fasteners may begin to crack when going through pressurization cycles.

Because the main factor contributing to this is the pressure changes the plane experiences, a plane that takes frequent, short flights, such as domestic flights, will age faster than a long-haul international jet plane. Manufacturers usually determine the maximum number of takeoff and landing cycles an aircraft can endure. For example, Boeing lists an anticipated LOV for the 747 as 35,000 cycles. However, some of their models, including the MD-80 and DC-10, can last up to 110,000 cycles.

Flight Hours

Another factor to consider is the number of flight hours a plane has endured. While the figure doesn’t say much about the aircraft’s age on its own, the flight hours should be considered alongside the pressurization cycles. A plane that’s flown for fewer hours with more pressurization cycles may be more aged than a plane with more flight hours and fewer pressurization cycles. Still, the hours in flight can contribute heavily to fatigue, which is a type of aging that affects the fuselage, wings and engines.

Airplane manufacturers often list maximum flight hours as part of the anticipated LOV. For example, a Short Range Boeing 747 can last up to 135,000 flight hours, while a 400 Domestic 747 can last up to 165,000 flight hours.

Other Factors Determining an Aircraft’s Life Span

An aircraft may be retired long before it reaches its established LOV due to some other factors affecting a plane’s retirement age. An important factor here is the maintenance costs. While an aircraft may be repairable after certain types of damage or aging, the airliner or fleet manager may determine that the costs to repair outweigh the value of keeping the plane in commission. In other words, maintenance needs, which rise in cost and complexity as a plane ages, become too costly to justify, and purchasing a new or used plane becomes the better investment.

Fleet managers may also factor in fuel burn when determining whether an aircraft is worth fixing or ready for retirement. A less fuel-efficient plane may be retired even while it could still be airworthy because the high costs of jet fuel make repairs less cost-effective. A new plane will have a more favorable fuel burn rate. In the case of commercial aircraft, airlines might also retire aged planes to meet customer expectations since they can charge more for a luxurious flight on a new airplane.

Other forms of aging, such as corrosion, can also play a role in the life span. Corrosion occurs when the aircraft’s metal experiences chemical or electrochemical degradation. It’s common for an aircraft’s structure to experience corrosion over time, and the electrical connectors and flight control cables can experience corrosion, too.

Calendar age is a contributing factor in corrosion, and so is exposure to the elements. Airplanes parked outside will experience paint fading and chipping in the sun, which exposes the metal to corrosion. Aircraft in coastal areas, such as seaplanes, will be exposed to humidity and saltwater, which also accelerates corrosion.

What Is the Average Life Span of an Aircraft Engine?

Average Life Span of an Aircraft Engine

Aircraft engines have a metric similar to LOV for various parts of the engine. An engine part’s approved life is a threshold after which the component must be replaced. Another specification known as time between overhauls (TBO) is used to recommend a maintenance schedule for aircraft engines. However, TBO is not a definitive measure of how long an aircraft engine should last between overhauls. It’s instead a recommendation, and an engine could feasibly last longer or need repairs before reaching its TBO.

Aircraft engine life spans can be influenced by many factors, including:

Oil Consumption Rate

It’s critical to track an engine’s oil consumption and be able to identify when that rate increases. When the oil consumption rate spikes, many causes could be at play, and it’s usually a sign that an engine needs repair.

Engine History and Chronological Age

It’s crucial to consider the engine’s maintenance history alongside its chronological age. An engine that’s required little maintenance is an excellent candidate to outlast its recommended TBO. However, an engine that’s needed frequent repairs may not last until its TBO.

Engines that aren’t used often tend to deteriorate faster than engines that fly regularly. Because of this, engine manufacturers usually list a TBO in calendar years and flight hours. If an engine has reached the limit in either chronological age or flight hours, it could be time for an overhaul, depending on the other factors at play.

Operation Conditions

The circumstances under which the engine operates can also affect how quickly it deteriorates. For example, running for long stretches at high power or in dusty conditions can increase wear on the engine. When the engine does not operate under manufacturer-recommended conditions, it can cause premature aging.

Maintenance History

Aircraft engines require maintenance according to a recommended schedule provided by the manufacturer. This schedule should include regular inspections and proactive maintenance. Engines last longer when they aren’t allowed to run until something goes wrong. Instead, the engine should receive service and parts replaced when they are nearing the end of their useful life but haven’t yet stopped performing as intended. It’s also essential to keep a detailed maintenance activity log to reference when determining if an overhaul is necessary.

Spark Plug Condition

As part of regular maintenance, aircraft engine mechanics should also remove and inspect the spark plugs. Their coloration and condition can indicate what’s happening inside the engine. For example, cracked spark plug porcelain is sometimes a sign of preignition. Meanwhile, a brownish grey deposit indicates a healthy engine and spark plug component.

Engine Compression

The engine should receive regular differential compression checks after every 100 flight hours and during its annual inspection. It should also receive an assessment if an engine experiences:

  • Loss of power during flight.
  • High oil consumption.
  • Soft spots while pulling the prop.

Typically, compression checks performed regularly can reveal deterioration over time.

Aircraft Engine Overhauls

When an engine reaches the end of its life span, the aircraft may not need to retire. Usually, the engine simply requires an overhaul. By overhauling the engine on the recommended schedule or when the engine needs repair, you can extend the life of an aircraft.

Engine overhauls can entail many different things. The manufacturer’s operating manual will list the tasks which a technician must complete during an overhaul. And within the aviation industry, there are two types of overhauls — a major overhaul and a top overhaul. A major overhaul involves completely disassembling the engine, inspecting all parts and repairing and replacing each component as necessary.

For a top overhaul, the technician only disassembles and replaces components outside the crankhouse. It may involve cylinder, valve and piston-related repairs or replacement. Not all engines and manufacturers recommend top overhauls, and some may require a major overhaul for any repairs to this extent.

An overhaul does not reset the engine’s flight hours. Even if many parts are replaced during the repair, the engine is still considered to have flown the same number of hours. However, overhauling an engine can offer many advantages for maximizing the life of an aircraft, such as:

Extending the Engine’s Life Span

An aircraft engine goes through significant stress. Individual components can experience stress and wear due to the heating and cooling cycles inside the engine, and improper lubrication can cause metal-on-metal wear. As they experience wear, they may affect other parts of the engine and cause further damage. By replacing these parts all at once when they’re starting to show signs of wear, you’ll prevent the damage from worsening without having to replace the parts that are still in good condition. You’ll also preserve the components that still work.

Improving Aircraft Performance

An engine overhaul is an opportunity to examine all parts and how they perform together as a unit. An airplane engine technician will recalibrate and rebalance all moving parts during the reassembly process. Disassembling and reassembling the engine’s working parts while replacing underperforming parts allows the engine to operate with decreased vibrations and increased thrust output.

Boosting Resale Value

An engine that’s regularly overhauled according to its TBO schedule shows a solid maintenance history, which can be critical during the buying process. Just as you scrutinize the maintenance history of the used aircraft you consider adding to your fleet, other buyers do the same for your planes when you decide to resell them.

Also, depending on the type of plane and the buyer, an overhaul can be more valuable than an engine replacement. That’s because some buyers, usually for smaller planes, look for an original engine frame and serial number, with only original equipment manufacturer replacement parts.

Practices to Extend an Aircraft’s Life Span

Practices to Extend an Aircraft Life Span

Whether purchasing new aircraft for your fleet or looking to get the longest service life possible out of your current aircraft, the choices you make can extend the life span of your aircraft for many years. Some best practices to keep in mind include:

  • Inspect aircraft thoroughly: Before purchasing an aircraft, and then periodically after that, you should conduct a complete inspection on any plane. This measure ensures a plane is in good condition before you purchase it and lets you detect any issues before they worsen and potentially cut the aircraft’s service life short.
  • Maintain aircraft consistently: Factor the manufacturer’s recommended maintenance schedule into your budget and schedule repairs, routine servicing and inspections accordingly. To improve upon the recommended maintenance, work with a maintenance crew that can make recommendations for your aircraft’s unique operating conditions and current state. They may be able to implement proactive and predictive maintenance plans that let you service your aircraft before issues appear.
  • Implement a service life assessment program: To extend the service life of your fleet and safely increase the average fleet age, you should consider a formalized service life assessment and extension program. This can involve using various data and real-time monitoring to identify issues as they arise rather than using an interval-based maintenance schedule. It can also include rotating aircraft to different tasks as they move through different phases of the aircraft life cycle. Consider using your newest aircraft for the most stressful flights, and transition them to less demanding activities as they age.

Learn More About the Aerospace Field

JETechnology Solutions, Inc. is an expert aircraft maintenance stand manufacturer serving military and commercial aircraft. With over 75 years of combined experience in the aviation industry, our team has a wealth of aerospace maintenance and fall protection knowledge. To learn more about the aviation field, explore the JSI blog and feel free to contact our team with any questions.

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