Maintenance Service Types are concerned with 'MRO' (Maintenance, Repair, or Overhaul) and used to define the different maintenance functions. These can be selected as filters in the Maintenance - Fleet Maintenance to show operator specific airframe check inspections intervals and in Maintenance Contracts to report Operator and MRO relationships.
All these Maintenance Service Types are associated with Airframe Maintenance and as such also relate to the Inspection Intervals Programme. These "Letter Checks" reflect an industry-wide convention but are not the only way of talking about Airframe Maintenance but are accepted and widely understood.
A Check - Typically occurring on a monthly frequency or Flight Hours (FH) equivalent (typically between 500-1000FH) depending on Aircraft type.
B Check - A mid-level Maintenance Event between the monthly A-Check and the bi-annual C-Check. Not widely used. Tends to apply for older Boeing types or smaller regional Aircraft. Typically only used for Inspection Interval data and not for Maintenance Contracts.
C Check - Typically occurring on a bi-annual frequency but there are variations depending on Aircraft type, generally between 18-36 months.
Heavy Check - This is the generic term for the more significant heavy maintenance check that typically occurs at around 6 years. This term is used for Maintenance Contracts only. Inspection Intervals data uses either of the next two terms which tend to be OEM specific.
4C/8C Check - Airbus preferred convention for Heavy Maintenance, referencing the C-Check number - only used in Inspection Intervals data.
D Check - The Boeing preferred convention for Heavy Maintenance - only used in Inspection Intervals data.
Structural Inspection - Typically occurring around 12 years
These are other Maintenance activities that occur on the Airframe, mainly concerning specific components or specialist areas.
Landing Gear - Concerning landing gear maintenance
Wheels/Tyres/Brakes - Concerning the maintenance of wheels, tyres, or brakes
Components - Concerns maintenance of other components on an aircraft
Composites - Concerns maintenance of composites (typically surfaces) on an airframe
Strip/Paint - Concerns Painting or Livery work on an airframe
This is maintenance work that focuses on the engines
Overhaul - Off wing maintenance for Engines
Engine Components - Concerns maintenance of Engine specific components
Thrust Reversers/Nacelles - Concerns maintenance of thrust reversers or nacelles
This is maintenance work that focuses on the Auxiliary Power Units (APUs)
Overhaul - Concerning full overhaul maintenance of APUs.