Source: When is an Aircraft Too Old? AOPA
The author begins the article by comparing the aircraft to a person. When people and airplanes grow older they tend to become more “maintenance intensive” requiring more attention to details and replacing of parts. He also says that there are owners who tend to take more out of the airplane then they can and thus they have accidents. If you were to compare this to people I would assume this to be death.
Like many aviation professionals know, airplanes are built with a certain number of cycles in mind. A cycle is usually defined as a pressurization and depressurization of the cabin, or a takeoff or landing. Before Aloha 243, not a lot of people paid much attention to the cycle count on aircraft. After the accident of Aloha 243, (which N7311 had 89680 cycles on the airframe.) manufactures started to pay much more attention to high frequency pressurized flying.
This leads into Corrosion. Something that came up in the Aloha 243 accident was the climate that the 737s were flying in. They were aluminum built aircraft flying in wet and salty, sometimes humid climate which definitely contributes to aircraft ageing. According to AOPA, aircraft in a dry climate will rot a lot slower in a dry, cool climate. This is not hard to understand.
Corrosion of the airframe is not the only danger. Corrosion of the engine and casing can be very dangerous. Like airframes, engines have a defined life and there are several variables that can affect their longevity. Believe it or not frequent use is actually a good thing for the engine. It keeps the everything moving and flowing to prevent the tendency to rot. When the airplanes are parked in the desert or when the FAA grounds an airline (in the case of Valujet) Bright yellow or distinct covers are put into place to prevent humidity and other particles from entering the engine itself and rusting or damaging the engine.
The question that AOPA has probed is does accidents increase with aircraft ages. The author states “as a general rule, no” but I want to rebut for the sake of argument really tweaking his words. I think the author needs to specify which may be redundant to the article but still, mention that “as a general rule with proper care or overhaul no.” If we look at Valujet’s fleet age with a average age of 27years (now, being 21 ½ I’m not saying 27 is old by any means for a person) the DC-9s were in desperate need of some sort of proper care from new parts to possibly new engines completely. I can even tie this example into corrosion and cycles because Valujet got their DC-9s from a hot, humid environment of third world countries that were using these aircraft for high frequency travel.
Another thing that author mentions is parking the airplanes increasing the aging process. It’s not an immediate safety problem according to AOPA but it puts the burden on the owners to pay for the maintenance when we bring those airplanes back into service. If the aircraft is outside, the aircraft tends to corrode much faster. Are we seeing a pattern yet? Corrosion is the root of evil. Window age with parking aircraft is another issue the author brings up. It tends to make a permanent haze which starts to make it harder to see and avoid other aircraft. Solution? Big airpark owners put foil on the aircraft’s windows and landing gear to prevent sun ageing and to prevent the heat build up to cause fire.
Fire can be created by a number of things with heat being a big one when insulation fails on older aircraft. Wiring is another one. If older wiring is not paid attention to, a fire may not occur (Copa 291) but a 737 can crash into the jungle from aging instrumentation wiring. Speaking of which, Gyros are usually the first instruments to go. This is because of the tendency of them to move. But how would you know exactly what failed?
An NTSB investigator knowing how structures works would be able to tell when something was corroded or rubbed together by leaving marks or fracture. Gaskets and hoses or anything that continually rubs against something else will need periodic attention to prevent contamination of fuels. This like the 25 cent Sabertech incident, a two dollar rubber ring could save an aircraft from a fatal problem all together.
In summary prolonging the life of the aircraft is like humans. If we take care of our aircraft (our body) we won’t have an accident. It’s a good theory butt accidents will happen, but maintain the airplane, we are reducing the likelihood it will happen.