What Happens During An Aircraft’s C-Check

Aircraft maintenance procedures are a critical piece in the larger puzzle of keeping airline fleets active. There are several different kinds of these, of which a term that you may have come across more frequently than others is a ‘C-check.’ But what exactly does this entail?

Delta Airbus A330neo
C-checks generally take place in hangars, and sideline aircraft for several weeks. Photo: Airbus

What does a C-check entail?

With C-checks taking several weeks to complete, they require a lot of work to be done on a given aircraft. This will typically include a thorough inspection of the majority of the plane’s components. However, Qantas also notes that it will sometimes use the time to undertake cabin refurbishment projects, seeing as the aircraft is on the ground anyway.

According to Aviation Pros, the goal of a C-check is to assess an aircraft’s functionality and serviceability at the time of the inspection. Certain inspections are done visually, such as those for the condition of the entry door seals. However, some aspects require greater scrutiny, comprising the use of specialist tools and equipment.

The National Aviation Academy reports that other parts of the aircraft that are subjected to these thorough examinations include load-bearing components on the wings and fuselage. It is important to ascertain that these have not been damaged or corroded. At the same time, engineers will lubricate the plane’s cables and other fittings.

Lufthhansa Technik Hamburg Getty
C-checks see the majority of an aircraft’s components be inspected. Photo: Getty Images

How often do they take place?

With C-checks being incredibly thorough procedures, they are not regular occurrences. On a general level, they take place every 20-24 months, depending on the aircraft in question. However, in some cases, a C-check may instead occur once a particular plane has reached a given number of flight hours. The procedure requires around 6,000 hours of work.

In some instances, usage also plays a factor. For example, aircraft from the Airbus A320 family are also eligible for a C-check every 5,000 flight cycles. Among the most frequently checked aircraft are ATR’s 42 and 72 turboprops, which undergo this procedure every 5,000 flight hours. At the other end of the scale, the ultra-long-range Bombardier Global 7500 business jet can reportedly go as long as 8,500 cycles or 12 years between C-checks!

Czech Airlines ATR72
The ATR 72 and its smaller ATR 42 counterpart have C-checks every 5,000 flight hours. Photo: Jake Hardiman | Simple Flying

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Not always at an airline’s base

It is important to note that an aircraft’s C-check won’t necessarily occur at one of its airline’s maintenance bases. For particular aircraft, generally with smaller production outputs, a C-check will sometimes require a trip away from home. For example, Alitalia is the only European carrier whose maintenance division is certified to C-check the Airbus A330neo.

As such, the Italian flag carrier has carried out maintenance procedures on aircraft that don’t fly for the airline itself. An example of these was an Air Senegal A330neo, whereby Alitalia finished the job on May 12th this year. The procedure clearly went well, as the aircraft in question set the record for the longest A330neo flight just two days later (Beijing-Dakar).

Did you know what happens during a plane’s C-check? Have you ever worked in aircraft maintenance yourself? Let us know your thoughts and experiences in the comments.