Aircraft Aging has many exterior factors instead of just the initial age of the aircraft. Some of the exterior factors can be how the aircraft is maintained and where it is stored. When an aircraft is improperly stored and maintained the aircraft tends to "age" more rapidly or in a sense reach it's life limit far sooner than manufacturers recommendation. Some areas of aircraft are more likely to have corrosion happen then others based on the materials that are exposed to the elements. Examples of these areas are (Aviation Safety Bureau, 2010):
- The battery compartments
- Bilge areas
- Bulkheads
- Wheel wells and landing gear
- Water entrapment areas
- Wing flap and spoiler recesses
- Areas hit by exhaust steam
- Cooling air vents
In order to maintain the aircraft in good working condition there are various ways in order to assist in preventing such corrosion to happen. One of the major reasons is to follow recommended intervals for maintenance and to have a maintenance facility capable of handling all necessary repairs. When an aircraft is in storage it is important to cover all open areas to prevent animals and moisture from entering these areas and causing excess damage. Also storage in a warm arid place assists in preventing damage.
Where not to store an aircraft:
Old hangers that have not been maintained properly. Moisture can easily be trapped in these hangers causing ideal conditions for corrosion to exist. There may even be heath issues associated with lead paint or asbestos in hangers such as these.
Near salt water. Salt water easily starts to cause corrosion not just on the airframe but also inside the engine. It is recommended that after being near salt water that an engine wash and an aircraft cleaning are done.
Corrosion Prevention and Control:
Due to the amount of damage that is caused by corrosion all operators of aircraft are expected to have a corrosion prevention and control program (CPCP). According to the Federal Aviation Administration (1993) the Baseline Program for CPCP recognizes three levels of corrosion that are used to assess effectiveness:
- Level 1 Corrosion found during the accomplishment of the numbered Corrosion Task indicates an effective program.
- Level 2 Corrosion indicates that program adjustments are necessary.
- Level 3 Corrosion is an urgent airworthiness concern requiring expeditious action on the part of the operator to project its entire model fleet. The FAA must be notified immediately upon determination of Level 3 Corrosion.
Level 2 and Level 3 Corrosion finding must be reported to the manufacturer for evaluation and possible Baseline Program adjustment. Corrective fleet actions resulting from Level 3 Corrosion findings must be reported to the FAA.
Although baselines are provided by the manufacturer of an aircraft model it is always the operators responsibility to ensure proper care and treatment of the aircraft. The manufacturer is no longer responsible for the aircraft an any issues resulting from improper care once the operator accepts the aircraft. This is often negated in regards to a new aircraft model that has safety of flight issues that may result in grounding of the entire model and as such the manufacturer may take additional steps in order to ensure customer satisfaction.
Proper Maintenance
In order for an airline to be considered airworthy they have to have a proper maintenance program in place. Many regulatory authorities require to know where the maintenance will be performed and if that maintenance facility has the correct type certificate to perform the work for the commercial aircraft.
To become a certified 14 CFR Part 145 Repair Station there are 5 major phases (Federal Aviation Administration, 2013):
Phase 1 - Preapplication
- Submit a preapplication statement of intent (PASI) to show intent to initiate the certification process.
- Preapplication meeting: held in the district office allowing applicant to become familiar with assigned FAA personnel.
- Application for Repair Certificate and/or Rating: applicant is instructed on how to complete the application
- Formal Application Attachments: Requirements for application attachments are discussed to include the following: Develop and evaluate a repair station manual (RSM) and quality control manual (QCM), Letter of Compliance is completed to ensure compliance with regulations and how the repair station will comply with them
- Letter stating compliance with 14 CFR 145.53(c) or (d)
Phase 2 - Formal Application
- A team of certification team members and all key management personnel will meet with the FAA to ensure all documents are ready for processing and any questions are answered.
- Corporation Papers: If a corporation is making the application the FAA requires a copy of the Certificate of Incorporation by the State.
- Drug and Alcohol Program: A copy of the program must be approved by the FAA.
Phase 3 - Document Compliance
- Application is thoroughly reviewed for approval or disapproval.
- Manual and related attachments are reviewed for acceptance or rejection.
Phase 4 - Demonstration and Inspection
- Certification team ensures the applicants proposed procedures are effective and the facilities and equipment met regulatory requirements.
Phase 5 - Certification
- Once applicant meets regulatory requirements of CFR Part 145 the repair station certificate and operations specifications with the appropriate ratings are issued.
Even with a properly certified repair station performing the work it is ultimately the owner of the aircraft's responsibility to ensure that all maintenance procedures and practices are being followed. Many times maintenance is performed in a different country then where the aircraft is operated and as such may require additional oversight to ensure the airworthiness of the aircraft.
Conclusion:
Although there are ways to prevent an aircraft from rapidly aging it is still recommended to understand what the ultimate life of the aircraft is as recommended by the manufacturer and FAA. Once the aircraft has reached the determined flight hours or flight cycles which deem the aircraft past economic life it is recommended that the aircraft be retired. Just because the airframe reaches its life expiration does not prevent the operator from using parts from the airplane to continue operation of the fleet. There has been little evidence that there is an economic life for engines, landing gear, electronics, or other components that are installed on the aircraft. This may result in many "hanger queens" which tend to be aircraft used for parts only.
Ultimately the responsibility of the airworthiness and safety of an aircraft lies with the operator of the airplane. Outsourcing maintenance to appropriately certified maintenance facilities is not an excuse for anything that is missed during maintenance. An operator has the right to request additional non-routine work in order to ensure that all maintenance tasks and airworthiness directives are complied with in a timely manner even if the required task or AD is not required for an additional amount of time. It is always better to pull forward maintenance that can assist in preventing added aging then to ignore it.
Aviation Safety Bureau. (2010). How to Prevent Aircraft Corrosion. Retrieved July 2, 2014, from Aviation Safety Bureau website: http://www.aviation-safety-bureau.com/aircraft-corrosion.html
Federal Aviation Administration. (1993, November 29). 8300.12 Corrosion Prevention and Control Programs. Retrieved July 2, 2014, from Regulatory and Guidance Library Web site: http://www.faa.gov/regulations_policies/orders_notices/index.cfm/go/document.information/documentID/11770
Federal Aviation Administration. (2013, March 19). Become a Certificated 14 CFR Part 145 Repair Station. Retrieved July 2, 2014, from Federal Aviation Administration Web site: http://www.faa.gov/aircraft/repair/become/
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