AIRCRAFT MAINTENANCE DATA

Maintenance data are maintenance information and instructions required to maintain an aircraft or product in an airworthy condition. The maintenance data are used to ensure the continuing airworthiness of aircraft throughout its life and are required to be kept up to date and accessible to maintenance personnel performing maintenance and inspection on aircraft. Maintenance data are sometimes referred to as technical data or airworthiness data either approved or accepted. This paper examined the regulatory requirement for maintenance data and types of maintenance data. The paper looked at the various categories of maintenance data and their sources with emphases on the organization issuing or publishing such maintenance data and importance. The availability of maintenance data to persons or organization performing maintenance, the need for the currency of maintenance data, the permissibility of making changes to maintenance data, and the use of work cards and/or worksheets were examined including the requirements.

EASA Part M.A.401(a) requires the person or organization maintaining an aircraft to have access to and use only applicable current maintenance data in the performance of maintenance including modifications and repairs. The maintenance data could be any of the following:

1. Instruction for Continued Airworthiness (ICA) issued by the aircraft manufacturer or Original Equipment Manufacturer (OEM) who owns the type certificate for the aircraft type/product or the holder of a supplemental type certificate for the aircraft type;
2. Airworthiness Directives (ADs) or other mandatory airworthiness requirements like Certification Maintenance Requirements (CMRs) or Airworthiness Limitation issued by the regulatory authority of the State of Design or ADs issued by the regulatory authority of the State of Registry;
3. Airworthiness data issued by the Part 21 organizations or other similar approved organization; and
4. Maintenance data issued by the engineering department of an air operator or modified by a Part 145 organization in accordance with a procedure approved the regulatory authority with safety oversight responsibility on that aircraft.

The maintenance data could be once only issued data or subject to revision by the issuer or publisher. At any point in time, only the current issue/revision of the maintenance data is permitted to be used in performing maintenance on aircraft and products by various regulations. Let us now examine the various maintenance data held by operators or organizations performing maintenance on aircraft or products.  

Categories of Maintenance Data

Airworthiness Directives (ADs) are issued by regulatory authorities of the State of Design and/or the State of Registry. According to 14 CFR Part 39, an AD is issued when an unsafe condition exists in the aircraft or product and the condition is likely to exist in aircraft or products of similar design. ADs are an example of Mandatory Continuing Airworthiness Information (MCAI) is required to be provided by the State of Design and must be complied with by the aircraft owner or operator. Most regulations forbid any person from operating an aircraft for which an AD has been issued except in accordance with the terms and conditions of the AD.

Instruction for Continued Airworthiness (ICAs) are published by the type certificate holders (aircraft manufacturers/OEMs) or the supplemental type certificate holders for the aircraft or product. The aircraft owner, operator and maintenance organizations must have access to these ICAs and use them in performing maintenance on the aircraft or products. Some examples of ICAs are: Maintenance Planning Document or Guide (MPD or MPG) that contains Maintenance Review Board Report (MRBR), CMRs, and AWL; Aircraft Maintenance Manuals (AMM); Troubleshooting Manual; Structural Repairs Manual (SRM), Component Maintenance Manual (CMM), among others. These ICAs contains maintenance information or instructions for maintaining the aircraft in airworthy condition by the person performing maintenance.

Airworthiness data are issued by Part 21 organisations for modifications or repairs in accordance with procedures approved by the regulatory authority having safety oversight over the aircraft. Sometimes this type of airworthiness data is required to be approved by the regulatory authority to determine that the airworthiness data comply with the applicable airworthiness requirements. Such airworthiness data includes major repair scheme.

Maintenance data published by the engineering department of an air carrier in the form of engineering order or maintenance data published or modified by an approved maintenance organisation in the form of engineering drawing.

Availability of Maintenance Data

Apart from the fact that persons and maintenance organisations performing maintenance should have access and use current maintenance data, both EASA Part M and Part 145 require maintenance data to be made available to mechanics and certifying staff maintaining aircraft in close proximity to the aircraft or component being maintained. Where maintenance data is accessed through computer systems, sufficient computer terminals should be situated in the hangar for easy access.

Currency of Maintenance Data

The organisations performing maintenance on aircraft are required by regulations to establish procedure to ensure the amendment status of the maintenance data being used is monitored and kept up to date and where the maintenance data is supplied by the owner or operator, the maintenance organisation should obtain a written confirmation that the maintenance data is the latest amendment. Another suitable means should be established to verify the amendment status of any maintenance data. Most organisations have technical library under the Quality Manager that monitors amendment status of maintenance data and produce an amendment status list for circulation among workshops and offices. If a maintenance data is out of date, that is enough ground for nullifying the maintenance carried out on the aircraft.

Changes to Maintenance Data

Maintenance organisations performing maintenance on aircraft are permitted by regulations to modify maintenance instruction where it is found to be inadequate or ambiguous. This must be done in accordance with the procedure approved by their regulatory authority in their maintenance procedures manual.  However, the organisation modifying must demonstrate that the changes will result in equivalent or improved maintenance standards and shall inform the publisher of such changes.

Work Cards or Worksheets

EASA Part 145 permits the maintenance organisation transcribe accurately the maintenance data onto such work cards or worksheets, or make precise reference to the particular maintenance task(s) contained in such maintenance data. This means the maintenance organisation should use a common work card or worksheet systems throughout the organisation that would differentiate and specify, when relevant, disassembly, accomplishment of task, reassembly and testing. The work cards or worksheet may be computer generated to safe guard unauthorised alteration and the maintenance organisation may also use the work cards or worksheets of the operator where it so desire but a procedure must be established to ensure correct completion of the work cards or worksheets.

Conclusion

            O’Brien (2014) opined that maintenance data are also referred to as approved data or accepted data based on the regulatory jurisdiction, FAA or EASA. Maintenance data when used for performing maintenance or repair on an aircraft are required to be up to date and be made part of the certification of the maintenance and permanent maintenance records of the aircraft. The maintenance data are required to be kept with the worksheet or work cards used as the maintenance records of the aircraft. Maintenance data is also called technical data, and airworthiness data by the industry. The maintenance data must contain self-explicit instructions, procedures and information in performing applicable maintenance or inspection task. Most of them contains warning, and caution for persons performing maintenance and standards to which the maintenance must be performed to.