Jet Engine Maintenance: This Is How We Do It

In this blog, we will show you what a jet engine is subjected to during a complete overhaul. Depending on the type, an engine has to be taken apart, cleaned and serviced every 3,000 or more flight cycles. This means an engine receives a major overhaul every five years, in addition to more frequent, less radical visits to the workshop.

Step 1: Defining the work scope

The first step is the arrival of a “dirty engine” at our Schiphol Airport facility. This eco-friendly building is named after Sir Frank Whittle, the British pilot who designed and patented the first turbo jet engine in 1930. Then it’s time to roll up our sleeves.

Jet Engine Maintenance

Each engine is identified by a six-digit serial number and has its own maintenance plan and complete history data. There are all kinds of reasons why an engine might be replaced: deteriorating performance, time on-wing or, most commonly, because it’s reached its cycle limit.

You can read more about flight cycles in our previous blog.

When this cycle limit is reached (e.g. 3,000 cycles), the engine will be removed and serviced. The work package level is then discussed in detail with engineering specialists, the production team and, of course, our customer. Other airlines, besides KLM, make use of our engine maintenance expertise.

The result is an overview of all the work that needs to be done. This is known as the “workscope”.

Step 2: Cleaning & inspection

A mega scrub & go, just like in a wellness centre, involves several baths with different liquids to ensure all the dirt and oil is removed before the visual inspections begin. One of these is a borescope inspection in which a camera is used to carry out an internal examination of the engine. This is the same technique used in hospitals to examine the inside of the human body.

Jet Engine Maintenance

A very small camera attached to a flexible pipe is inserted into the engine through small holes distributed all around the engine. This enables the borescope operator to see right into the heart of the engine and view any irregularities, such as dents or cracks, on a large display. Nothing escapes attention using this technology.

Step 3: “Disassembly”

Components fall into two distinct categories: static parts and rotating parts. Rotating parts are located in the sections where large forces are generated, for example, in the compressor and turbine section. They are, obviously, subjected to more wear and tear than static parts. Just think of your car’s gearbox: constant rotational movement means it wears out faster than other parts.

At a major overhaul, the engine is almost completely dismantled (about 40,000 parts). These parts are inspected and some of them are sent to the engine manufacturer or to other KLM and Air France departments, who are specialised in different parts. There, the mechanics examine and repair the parts, according to the repair manuals, to make them fully functional again.

Jet Engine Maintenance

And who says engineering is a man’s world? Not in our shop. We have female mechanics on our team.

Step 4: Repair & replace

Engine parts are very costly. Life-limited parts at the end of their life cycle have to be replaced with new ones. Some parts can be repaired at our top-notch repair shop, using robots and innovative techniques such as laser cladding or e-beam welding.

Jet Engine Maintenance

Are you wondering what the most expensive part of an engine is? Well, in an engine type CF6-80E that would be the Forward Outer Seal. This component costs USD 1.4 million, and no, this is not a typo. This is equivalent to about five Ferraris (type 458 for the experts) or an ultra-luxury villa with staff and pool. It really is an amazing amount of money for a single engine part!

Forward Outer Seal foto 4

Step 5: Assembling & testing

This is the phase in which we rebuild the engine. All the parts are collected and carefully assembled. Then the engine goes into the test cell. This is an insulated bunker where the engine is subjected to thorough testing under the toughest of conditions and all kinds of circumstances.

Jet Engine Maintenance

If the engine passes the tests, a certified inspector carries out a final inspection and issues a Certificate of Airworthiness.

Now the jet engine has been completely overhauled, the counter is back to zero and it’s ready to fly again for years.

Posted by:   Jacky van Damme and Miranda Stolk-Oele  | 
Join the conversation Show comments



Wow its really good to read this. I always thought engines were sent back to the manufacturer for the servicing.

You learn something new every day! Great blog entry!


Hi Stephen,
We are therefore also very proud that we are authorised to carry out this heavy maintenance on Jet Engines, and find it super interesting to share this with you!
Best regards,

claudio ranghetto

very interesting


Dear Claudio,
Thank you so much for your interest!
Best regards

Sherin Francis

Extremely interesting read! Proud of the ladies who have worked and written this blog :-)


Thank you Sherin,
We feel very privileged to share this with you!
Best regards


hi, its cool to see the women working on this jet engine.. whats her name?
i need to know pls.


Hello Rajat,
It`s definitely cool to work as a woman in the technique,
and we call her ” Power Lady “.
Best regards,


hey jacky,
thanks for the reply.
power lady, sounds cool. now i wanna know the real name, to talk to her on 1 to 1 basis, cuz am a KLM fan & it would be interesting knowing more about the inner stuff. am sure u can help me on this one.


Hello Rajat, great to learn you are a KLM fan and that you are interested in the inner stuff. However it is not in our privacy policy to share personal details about our staff in our blogs. I’m sure you understand.
Regards, Miranda

simon nicolas coster

i love the way everyone claps when we land in spanish countries

in appreciation and thankful trust and never screw up

isa datta de spaghetti de tallitelli or de fettucini so many pipes she must be a genius

is she married i hope she teaches a surgeon doctor consultant and scientist

i bet she swimms with a grip like that and a torquey what a power boat

giver a go on miss geico the gentry eagle all started with a grain dryer


Hi Simon,

I`m not sure exactly what you mean, but we have got indeed well trained staff.

Best regards,

simon nicolas coster




chris Reed

Aircraft maintenance & it’s high levels of professionalism is one of the reasons that your safer in an aircraft than in your own car. Great job men & women in this trade. . I build aircraft and know the responsibility involved in the work. .


Thank you Chris. Let’s keep up the good work in Aviation!

Bryan Schleipen

Hi Jacky,

Is it possible to elaborate on that USD 1.4 million part? Why is it that expensive?



Hi Bryan, thank you for your response. The forward outer seal is a high precision manufactured part which was a challenging design to begin with. Which both add up to the price tag.
Kind regards, Jacky and Miranda


Thanks for the post. Very well written and informative. As a Mechanical engineer myself, I have great respect for engineers. As a fan of Airplanes, I’m fascinated how 360000+ parts are carefully assembled, joined or put in place with such precision. Every time, I board on an Airplane and look down while the aircraft is at the cruising altitude, I thank everyone who makes it possible. From the Pilot to the designers to the maintenance team and the assembly team.

Thank you girls for the awesomeness and I will think of you guys next time I fly KLM!


Thank you for your response Anil. We think of you and all other passengers as well every time a serviceable engine leaves our facility to go do its magic.
Enjoy your future flights!


Hi Chris,
We totally agree with you, in this industry you meet people with a lot of passion
and responsibility for their work. I have also worked for an aircraft manufacturer and thereby gained a lot of knowledge and experience. I wish you all the best with building aircrafts!
Best regards,

Chris Kasteel

Hi Jacky and Miranda,
So interesting to read your fascinating blog, particularly about how often its done and the expensive forward outer seal. My wife and I are flying Vancouver Amsterdam tomorrow and now I won’t be nervous….. Love this blog and THANS!!


Hi Chris,
Thank you so much for your nice comment, don`t be nervous on your flight to Amsterdam, but enjoy it, our crew will take good care.
Kind regards
Jacky & Miranda


welcome to a real world umm awesome


Hi Gibbs,
Indeed, and great to be a part of it!


This is a very valuable blog.An aircraft engineer or a technician can get a general idea about how the eng maintenance are carried out by KLM engineering.Highly appreciated.


You’re welcome Jaqath. And thank you for your response which is appreciated als well.
Kind regards, Jacky and Miranda


Interesting indeed. It’s satisfying to see the expense and thoroughness an airline commits itself to our safety. Certainly an airline to trust.


Thank you for your comment Stuart. Safety is indeed a core value to KLM. We appreciate your recognition.
Kind regards, Jacky and Miranda


Thanks for the blog!
Really interesting


Thank you Yaela,
Keep reading our blog, there are interesting posts coming up that will amaze you.
Have a nice day
Best regards, Miranda & Jackyb


its so good when you have the chance to do what you like to do. And at the same time earns money in a high professional environment. I will star to study for 2 years in high qualified engineers school in order to obtain the license type b1. my goal will get the license some experience in a certificate airline company and definitely try to find a job like a mechanical engineer.. any suggestion …


No coiptamnls on this end, simply a good piece.


I have interested CFM56 engine repair
How & who do contact about CFM56 engine Repair

Kessena Emuakpeje

Hi Kessena Emuakpeje


Wow. This is a great tips.I am a trainee engineer in the engine workshop and this is really good information to know. Thanks for sharing.

Scott Adams

It’s interesting that you talked about how nothing can really be missed by using a bore scope. I have been needing to inspect a plane for a friend of mine, and I was wondering what tools to bring because it’s been a while since I inspected. I can see how it would be important to get my bore scope repaired, so I can make sure that I’m seeing everything.

Powerjet parts

This is a very valuable blog.An aircraft engineer or a technician can get a general idea about how the eng maintenance are carried out by KLM engineering.Highly appreciated.


Hi Jacky and Miranda,

I was wondering the following; when KLM is going to service (overhaul) an engine that is possessed by another airline, does KLM provide a ‘replacement’ engine to the other airline, in order that the other airline can continue its flying schedule? And is the ‘original’ engine when the service is finished installed back on to the plane? Or does the airline continue flying with the ‘replacement’ engine?

Would like to hear from you! Regards, Simon


Great Blog.
What borescope system you use to check inside engines? which brand i mean

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