Airplanes are no doubt the most expensive means of transportation in the world. The sheer cost of designing, manufacturing, and maintaining aircraft make them such costly commodities to own. It, therefore, becomes imperative that airplane manufacturers take these factors into consideration when producing new planes. This is why airplanes are made to be some of the most durable vehicles around. Statistics show that planes last 3 times longer than automobiles. In fact, they are sometimes considered to be much tougher than they actually need to be. But no matter how durable hardware is, it still needs to retire at some point.
On average, most commercial airplanes remain in use for approximately 20 to 30 years before they are finally retired. Interestingly, the rugged DC-9-14 which first flew in 1966 is believed to have survived over 50 years of service.
But just like any other vehicle, the lifespan of an aircraft has more to do with its total number of flying hours than its mere age in years. In aviation, lifespan is calculated in cycles and not necessarily in months or years.
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Factors that Determine the Lifespan of Airplanes
All around the world, over 700 aircraft are retired on a yearly basis. Despite the huge amounts of investment airlines dedicate to them, some factors make it impossible for airplanes to continue flying.
When talking about the lifespan of an aircraft, a very important term to take into consideration is what aviation engineers call “pressurization cycles”. A pressurization cycle is the measure of the amount of time a plane is exposed to high levels of stress during flight. Due to the nature of air travel, airplanes are built to withstand tremendous degrees of heat, pressure, and velocity. These forces, however, affect different parts of the plane differently. The most pressurized part of the plane during flight is the fuselage. This is why the most critical technical factor that determines the lifespan of a plane is its fuselage health.
- Fuselage health: At take-off and landing, the fuselage of an airplane experiences very drastic changes in pressure. This change is due to the pressure difference between the air in the cabin and the air outside the plane. Relatively higher cabin pressures apply more load on the fuselage. During take-off and through the course of a flight, cabin pressurization leads to the expansion of the fuselage. Contrarily, when landing, the cabin is depressurized causing the fuselage to contract.
This fluctuation in pressure difference impacts the health of the fuselage greatly and generally decides how healthy and airworthy a plane is. Long-haul aircraft—which make fewer cycles—can typically withstand 40,000 pressurization cycles. On the other hand, short-haul aircraft can take as much as 111,000 of such cycles. Quite ironically, short-haul airplanes are known to use up these cycles much faster than the long-haul planes due to the number of flights they embark on daily.
However, asides fuselage health, there are also other important non-technical factors that decide when airplanes retire. These factors are mostly economic.
- Fuel economy: Airlines spend huge amounts of money to the tune of billions of dollars fuelling their fleet every year. It isn’t uncommon to see them retire well functioning planes on the account of fuel efficiency. With improving technology, most newer planes tend to be more fuel-efficient than their older counterparts.
- Maintenance costs: Airplanes frequently undergo very elaborate maintenance procedures. But there are times when something really expensive needs to be fixed in an aircraft and the airline chooses to retire the whole thing.
- Consumer taste: Just like every other industry, aviation is also strongly influenced by the changing tastes of customers. Passengers generally feel more comfortable flying newer planes.
Are Older Airplanes More Dangerous?
Many passengers generally tend to feel less secure when they fly on older, less-sophisticated aircraft. But it is logically wrong to associate how safe a plane is with its age in years. Technically speaking, there’s no such thing as an old aircraft. A plane is either certified airworthy or it is not. If you fly frequently, the chances that you’ve been on a 20-year old aircraft before are very high. In fact, there are no statistics to support the reasoning that older planes crash more often than newer ones.
Plane crashes are more related to pilot errors than the condition or age of the plane. Other flight safety factors that take preeminence over age are natural factors (snow, lightning, etc.), poor communication between pilot and ground control, foreign object debris, and engine failure.
Without a doubt, new planes are more convenient. Passengers are prone to experience flight delays due to mechanical issues less often. But once an old plane is certified airworthy, it is just as safe as an absolutely new one.
However, it is also true that newer planes have more advanced features. Features like glass cockpit avionics, modern autopilot, onboard weather monitoring, better radios, and more powerful engines are designed to make flight safer. Nevertheless, this simply means that older airplanes will generally require more skill to fly.
Maintenance Is Everything
Airplanes are able to stay airworthy over such a long period of time due to maintenance. Well maintained planes can often survive several pressurization cycles without developing any serious mechanical fault. Aircraft maintenance engineers ensure to inspect planes regularly using non-destructive testing (NDT). Non-destructive testing is a method used to examine aircraft so as to detect flaws and cracks in their materials.
Though manufacturers determine the lifespan of a plane, there are government authorities that regulate aircraft maintenance standards. Based on these standards, the national aviation authority in every country issues an airworthiness certificate for any plane registered in that country. All airlines demand this certificate before admitting a new plane to their fleet.
In the case where an airplane is found not to be in optimal condition, they aren’t rendered absolutely inoperable. The plane’s service time limit can be prolonged after overhauling—a procedure that can be carried out multiple times during a plane’s lifespan. Time between overhauls (TBO) is fixed according to the manufacturer’s recommendations and often ranges between 3,000 to 5,000 flight hours.
Are Aircraft Parts Recyclable?
Yes. More often than not, parts of retired airplanes are removed for reuse or resale. Almost every aircraft part gets a second life. Even after decommissioning, airplane parts remain very valuable and are in high demand in the secondhand market. A typical plane consists of hundreds of thousands of parts and these parts can be disassembled using a maintenance manual that comes from the manufacturer.
On arrival at the recycling facility, the mechanics first rid the plane of dangerous substances like batteries, oil, and fuel. Then they begin to take out the most valuable parts. Parts like the engine, windshield, and landing gear can be used on other planes after proper inspection, sanitization, and repair. Other parts like the cockpit can be employed as flight simulators for training pilots. Aircraft sections have been used in the most interesting ways in the past. Some end up in museums, get sold to filmmakers and even turned to furniture.
But not all airplane parts are recyclable. Airplane interiors fall in this category the most. The challenge with interiors is that they are made with materials that are either non-recyclable or relatively too costly to dismantle and sort. Once the useful parts are taken out, the rest of the plane’s frame is turned to scrap aluminum. Manufacturers aim to keep at least 95% (by mass) of the plane’s parts recyclable (real figures are at 85 to 90% at the moment). This idea is known as modularization.
Where Do Retired Planes Go?
After planes serve their time, they are taken to a storage facility called an aircraft boneyard or graveyard. Most boneyards have enough room to accommodate hundreds to thousands of aircraft at the same time. Some planes remain in this facility for years while some are taken apart in a few months after arrival. These boneyards are often located in very dry regions like deserts where the climate helps to minimize metal corrosion.
Here is an interesting video showing a visit to an airplane boneyard.
Summary
In conclusion, airplanes are extremely durable large chunks of metal and one can always expect at least 25 years of service from them. It’s also necessary to remember that an older plane does not necessarily mean a less safe one. So, the next time you’re boarding that plane that probably looks as old as you, you should remember that it’s okay to trust the engineers.
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