Aircraft Maintenance - Why do we maintenance?

Hello guys. Yesterday I said I'm going to talk more about ICAO, but I'm too tired to focus on one topic for a long time.
As the result, I'm going to write something not so boring today, and it's also a little part of my "Program Planning and Controlling" course. As usual, I won't finish everything in one article, and I will keep trying to improve the presenting way to make you guys feel easier on my articles.

Why do we do maintenance??

So, First we know that the machine has a special property called Bathtub Curve.
Actually, different types of components would have different styles bathtub curve.
I just put the most common and classical one in the figure below.
When our machine is very young, we may need to adapt to it, then the probability of failure may be high. That's one of the reason why airline could pay less if they buy the newest type aircraft in the beginning. They're kind of helping manufacturer testing the aircraft.
After a period, the machine gets stable, then the failure may come from human errors, or some early fatigue.
Of course, when our machine get old, there would be more failures which come from bearing, corrosion, and fatigue..etc
So, we know in different periods, the failures may be different.
Manufacturer can predict at what time what could happens on their machine.

Then, when do we do the maintenance?
During the machine operated, the machine is deteriorating, but we may not notice where it is deteriorating.
As the result, we need to do the maintenance after we can find it and before it becomes dangerous.



As the conclusion, we definitely need maintenance plans for our machine!

But.. How to manage it?

Who perform the plans?

What is Maintenance Program??

It's a maintenance plan or schedule to define at what time we should do what for maintenance.
For Airline, they have a manual called Maintenance Requirement (different airline companies may have different name of it) to define the maintenance schedules.
However, the airlines won't know when their machines may go wrong. As I told you in Bathtub Curve and Maintenance Timing, the manufacturers should know it!
The aircraft manufacturers would provide the airline operators a manual called Maintenance Planning Document to tell them when and what for the maintenance of each aircraft.

Then I give you some example of routine maintenance you may hear easily.
Line Maintenance which is at the airport around the aircraft you took on every trip.
It takes very short time to ensure your aircraft is safe for it's next flight immediately.
Before the first flight everyday, it's pre-flight check.
Before any other flights in the same day, it's transit check.
After the last flight in that day, it's Daily check.
Line Maintenance is rush but important. They are the last ditch for your flight safety.

For the other base maintenance, we may have A check, C check, D check...etc
They may have different flight hour period between each check.
The airline operators may define their flight hour depends on their environment, using frequency, and any other conditions.
I may talk about them more in the future.

What about Reliability Program?

Reliability Program is a system to ensure the aircraft airworthiness and quality.
Engineers may collect all the data during the maintenance, and analyze how to improve the situation or how to prevent some problem, then they will modify the maintenance plan for the future maintenance.
The objective is to achieve applicability, rationality and optimization.

Then we can tell this story in another word called PDCA.
We have a plan (not a pen), and we do the maintenance according to the plan.
Then, we found some issues, so we need to analyze what's the problem, and how to prevent it.
Then we do the Action to modify the plan.
And we loop to the beginning that we do the maintenance in accordance to our modified plan.


So, we know how they manage the aircraft maintenance.
I give you the list of all the maintenance we may have below.
For the routine maintenance, as I told you, it's following the Maintenance Requirement.
But there may be some special requirement come from aviation authority, manufacturers, or company policy. This kind of special requirement you don't need to repeat the action. You may finish it in one time or only few times, ex. remove some structure because they found out that it may rub some wires during the flights, or you don't know when you need to do for the next time, ex. debuggin, aircraft washing.
There may also be some surprise that we don't expect it happens. Then they belong to the Non-Routine Maintenance.


I hope it's clear for you in this article.
If it's not clear, tell me below the article! I may write another article to solve your question!
I want to stop here. See you guys next time.

Ciao~