Documentation for Aging Aircraft Maintenance

An aging aircraft is capable of retaining its airworthiness from an evaluation of the maintenance program that the FAA conducts. After the airplanes 14th year of service (the calendar time elapsed since the FAA issued an airplane its first U.S. or first foreign airworthiness certificate), certain airplanes must undergo inspections and records reviews by the agency who administered the certificate. This action ensures the maintenance of the airplanes' age-sensitive parts and components has been adequate and timely

(U.S. Department of Transportation, 2009). To ensure that this is being conducted properly the FAA takes sample tasks and records for the airplane and then continues to monitor the air carriers' maintenance program.

When the Advisory Circular 120-84 was put into place on Jan 15 2009 it was assumed that airplanes over 24 years would have inspections done during the next available check and then airplanes 14 years or older had a more extensive period of time to comply with the FAA's request. This was to better accommodate the work load of the FAA personnel doing the inspections of the maintenance records. The airline was also able to request an extension of 90 days if there were unforeseen circumstances that would prevent the FAA from being able to conduct the inspection on the scheduled date.

After the initial inspection then the air carrier is expected to schedule with the FAA 60 days prior to the aircraft going into it's next scheduled shop visit where a repeat inspection is expected. The interval is expected to be every seven years which generally means every Heavy Maintenance Visit (either 4C or a "D" check).

During a records review the following information must be made available to ensure compliance

(U.S. Department of Transportation, 2009):

• Total years in service of the airplane;
• Total time in service of the airframe;
• Total flight cycles of the airframe (not required under Part 135.422(d));
• Date of the last inspection and records review required by the Aging Airplane Safety Rule;
• Current status of life-limited parts of the airframe;
• Time since the last overhaul of all structural components required to be overhauled on a specific time basis;
• Current inspection status of the airplane, including the time since the last inspection required by the inspection program under which the airplane is maintained;
• Current status of applicable Airworthiness Directives (AD), including the date and method of compliance (and if the AD involves recurring action, the time and date when this action is required);
• A list of major structural alterations; and
• A report of major structural repairs and current inspection status for those repairs.

This does not include the fact that the Aging Airplane Safety Rule requires certain airplanes from operating unless damage-tolerance-based inspection and procedures are included in the maintenance or inspection program for each airplane in accordance with a specified schedule. The operator is also expected to asses adverse effects of any repairs or alteration on fatigue-critical structures. There are no specifics mentioned in the AC that tell when these inspections are suppose to occur.

Once the aircraft has been determined to be in compliance with all the requirements for an aging aircraft then it is issues a "Result of Aging Airplane Safety Inspection" document to be maintained with the other records to indicate its compliance.

Example of Results Document

U.S. Department of Transportation. (2009, January 15). Aging Aircraft Inspections and Records Reviews. Advisory Circular. Washington, DC, United States of America: Federal Aviation Administration.

Flow Chart to Determine Aging Aircraft Applicability

The FAA had recognized the dangers of aging aircraft and had published the Aging Airplane Safety Interim Final Rule on December 6, 2002. On February 2, 2005, the FAA published the Aging Airplane Safety Final Rule (U.S. Department of Transportation, 2009).

The final rule specifies the following (U.S. Department of Transportation, 2009):

• Mandatory aging airplane inspections for certain airplanes according to their years in service
• Damage-tolerance-based inspections and procedures to be included in the maintenance programs of certain airplanes
• Operation of these airplanes after specified deadlines will cease unless the maintenance programs under which th eairplanes are maintained include damage-tolerance-based inspections and procedures.

In order to determine the applicability the operator can use the following charts to determine if their aircraft qualify for an aging aircraft.

Decision Logic - Initial Inspections and Records Review Due Date

Decsion Logic - Applicabiltiy of Inspections and Records Review

U.S. Department of Transportation. (2009, January 15). Aging Aircraft Inspections and Records Reviews. Advisory Circular. Washington, DC, United States of America: Federal Aviation Administration.

Maintenance Tasks

Aircraft should be maintained on a regular basis based on manufacturer intervals or their own maintenance program. The maintenance programs are submitted to the appropriate regulatory authority for approval. Operator maintenance programs have to follow a general baseline of the manufacturer’s maintenance program but based on experience with the aircraft can have the life limits and intervals extended.

How does maintenance affect the age of an aircraft?

As an aircraft ages the intervals of the maintenance checks known as "C Checks" merge to create even heavier maintenance visits. These visits end up costing more money than initial checks and more non-routines are generated due to the age of the aircraft. Here is an example of a maintenance program and how the age produces a heavier check.

Note: This is a made up example based on the standard 18 month interval mentioned in the Aviation Maintenance Management book written by Kinnick and is by no means meant to reflect any specific airline maintenance program.

Notice how the third interval of the 4C Check/HMV Check matches with the 3C, 2C, and 1C Checks. At 216 months the aircraft would be 18 years old. By now an operator may start thinking about replacing their aircraft before this maintenance visit happens because of how much it costs to actually conduct this maintenance.

No matter how good the maintenance being conducted is the fact is the aircraft is still aging and certain other tasks start populating because of that. The aircraft bins may need to be painted, the light covers yellow, seat cushions have to be replaced, and this doesn't cover the standard hard time components that life span may be coming due. Some hard time components such as slides have to be sent out for overhaul at about 5 to 7 years and depending on the age of the slide will have to be sent out every year to two years for overhaul. At this point it may be more cost effective to just purchase all new slides instead of overhaul this is no different then determining if continued use of an aging aircraft is worth the cost of the maintenance.

Performing continued maintenance is very important for actually reaching the expected economic life of an aircraft as well. When maintenance isn't performed and the aircraft sits on a ramp or in a storage area then the parts tend to start to corrode a little easier because lubricant may not be applied as often as it would normally. Airplanes that rest too long can become home to animals which can damage wiring and insulation in order to make their nests causing additional maintenance tasks in the future should the aircraft ever be attempted to be reactivated.

Proper maintenance during C Checks is also important. Human factors is a huge issue when it comes to maintenance and many times when an aircraft ends up having an issue the maintenance task performed was done so incorrectly. This was part of the reason why the Aloha flight had the issue. Aloha had been operating the aircraft past its economic life which was one of the reasons why the top part of the fuselage separated from the bottom half. Another reasons was due to improper maintenance procedures. When the airline was under investigation it was determined multiple other airplanes were showing the same cracks and issues as the accident aircraft. This is why proper maintenance and an ultimate life are important when dealing with aircraft.

Conclusion

Over the course of this brief blog post the author has spoken about the importance of continued maintenance on the aircraft. By doing continued maintenance there is a reduced chance of animals nesting or corrosion happening on the aircraft. When performing correct maintenance the life of the aircraft can be expected to meet the ultimate life as what is suggested by the maintenance manufacturer. Overall though it is the responsibility of the airline operating the aircraft to ensure that a replacement plan is in place once the aircraft starts nearing its end of life and to make sure that maintenance is performed in a timely manner to keep the aircraft airworthy.

Quality Assurance

Some of the issues that have come up in regards to aging aircraft is how they are maintained. Quality assurance personnel are responsible for making sure that maintenance cards are carried out in a timely and accurate manner to make sure the aircraft keeps it's airworthiness capabilities. Maintenance planning documents are prepared by the manufacturer, can be customized by the operator, and reviewed by the regulatory authority. The manufacturer is also responsible for determining an ultimate life to assigned to their aircraft or engine model in order to ensure that the aircraft or engine does not exceed limits and becomes a hazard.

Airframe life is important to determine because there is constant stress being applied to the airframe as it pressurizes and depressurizes during a single cycle. Think of the airframe as a rubber band, under continued stretching and release eventually the elasticity weakens and the rubber band breaks. This is the same as what can happen to an airframe as the elasticity of the metal is weakened and eventually becomes brittle and breaks. Under the same rules it's important that when the aircraft is part of a fleet that it is used on a regular basis because exposure to the elements and constant sitting also reduces the properties of the metal.

Most other parts of a particular aircraft have life limits much like that of the airframe. Once a life limit is reached the part must no longer be used. This is true for landing gear and engines. In general for landing gear there is a list of limited parts with an expected life span in cycles and months. For engines the expected life span is expressed in flight cycles or flight hours depending on the part. The manufacturer is responsible for determining these life limits. Keep in mind that when a new engine model is created the life limit may be far lower than the expected ultimate life. Engines are generally utilized differently per airframe model that it is attached to and how the operator uses the aircraft. Aloha air utilized their 737's as "puddle jumper" airplanes and increased the stress put on the engines by using shorter flight hours and more cycles per flight hour. This is different then Alaska air who may be running an engine with one flight cycle per every 4 flight hours.

It is quality assurances responsibility to ensure that the life limits for all parts on the airplane are not exceeded. You wouldn't want an engine coming apart because of a life limited part that has exceeded its recommended life just as you wouldn't want to open a life jacket and realize that the material is degraded because it has exceeded it's expected life as well. Operators have a way to track and monitor this information and do so on a regular basis to ensure that the aircraft is safe for flight. It is quality assurances responsibility to ensure that the maintenance on all components of an aircraft is completed. Aged aircraft just tend to have more frequent maintenance tasks that have to be performed.

Requirements for a Maintenance Program

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/

Aviation Authority Regulations

FAA Regulations for Aging Aircraft

As of November 2010 the major concern of Aging Aircraft was “widespread fatigue damage” (WFD). According to the FAA (Babbitt, 2010):

Fatigue damage to a metallic structure occurs when the structure is subjected to repeated loads, such as the pressurization and depressurization that occurs with every flight of an airplane. Over time this fatigue damage results in cracks in the structure, and the cracks may begin to grow together. Widespread fatigue damage is the simultaneous presence of fatigue cracks at multiple structural locations that are of sufficient size and density that the structure will no longer meet the residual strength requirements.

In the past to prevent this kind of damage the aircraft was supposed to be inspected regularly but due to accidents involving WFD this is no longer the case. Accidents involving AD’s created due to WFD will be discussed later in another blog post.

With the new rule involving WFD from aircraft aging two things are required as per Dorr & Duquette (2010):

• Aircraft manufacturers and certification applicants are required to establish a number of flight cycles or hours a plane can operate and be free from WFD without additional inspections for fatigue. Manufacturers have between 18 and 60 months to comply depending on the particular aircraft type.
• Once limits are established, operators of affected aircraft must incorporate them into their maintenance programs within 30 to 72 months, depending on the model of aircraft. After the limit is in the maintenance program, operators cannot fly the aircraft beyond that point unless the FAA approves an extension of the limit.

All of the limits of validity (LOV) are incorporated in the FAA Final Ruling on WDF. Of course these limits are capable of being extended but only under extreme scrutiny by the FAA.

EASA Regulations for Aging Aircraft

Currently there are still no regulations that the author was able to find in regards to EASA regulations for aging aircraft. There is a working document that currently available online mentioned in the references at the bottom of this blog that discusses aircraft aging and future regulatory requirements. Many of the recommendations gathered in the EASA document are due to the FAA assisting in creating this program. It does appear that there are plans on publishing a final document in second quarter of 2015.

References

Babbitt, J. R. (2010, November 15). Aging Airplane Program: Widespread Fatigue Damage; Final Rule. Federal Register. D.C., Washington, United States of America: Department of Transportation.

Dorr, L., & Duquette, A. (2010, November 12). Press Release – FAA Adopts “Comprehensive Solution” to Widespread Fatigue on Aging Aircraft. Retrieved June 17, 2014, from Federal Aviation Administration Web site: http://www.faa.gov/news/press_releases/news_story.cfm?newsId=12137

European Aviation Safety Agency. (2013, April 23). Notice of Proposed Amendment 2013-07. European Aviation Safety Agency. Cologne, Germany: European Aviation Safety Agency.

Direction of this blog

Background and Reasoning for Study

Currently the author works for a section of the Boeing Company that leases used airplanes to airlines across the world. One of the major focuses that is coming down the pipeline from the FAA is aircraft aging and the effects that is has on the aircraft. Aircraft aging isn't just about the years that pass but has to do with the cyclic impact of using the aircraft on a day to day basis. Every time an aircraft takes and lands (known as a flight cycle) there is wear and tear performed on the aircraft. During the course of a flight cycle the fuselage of the airplane undergoes and expansion and a contraction which produces wear on the material. Continuous wear ends up producing damage and if not caught in time can produce catastrophic results.

Since the author works closely with aged aircraft the importance of understanding Aging Aircraft and how it effects the market is really important to her job. The FAA is starting to crack down and has created a questionare that is to be completed by commerically flown aircraft operating under the FAA. What the issue is now is how to extend those requirements past just the operators in the United States to those in other countries where these requirements may not be prevelant.

Why This Topic is Important

Every day the fleet gets older and people continue to board the airplanes. Humans have trust that no matter the age of the aircraft that it will depart their current airport and land at their destination without fail. This has to be accomplished by correctly maintaining the aircraft. One major question is just how old the fleet is out there. Well the average fleet is about 14 years old according to a study conducted in 2010 by The Airline Monitor. That's based on the major carriers in the United States alone. A well maintained aircraft could easily last longer in the fleet before finally being decommissioned. Other websites suggest that the retirement age on most fleet aircraft are about 25 years old as of 2013.

Why are these airplanes being retired so early? Is it because of the actual age of the aircraft and the fact that they are no longer safe to fly on? No. It's because the aviation community is constantly trying to find more fuel efficient aircraft in order to increase their profit margins. When it does come to an aged fleet there are various other reasons why it might be decommissioned such as:

1. cost of the maintenance being performed
2. aircraft operating economics
3. airframe versatility
4. flexibility

Now add the requirement that the FAA wants operators to complete a survey after the aircraft reaches a certain amount of flight cycles and there is one less desirable reason to keep these assets in their fleet.

So why is this topic really important to everyone? Even though the average age of aircraft being retired is going down this is not sustainable. Eventually as the market for purchasing new aircraft declines the age of the aircraft is going to continue to increase. Aircraft operators are working with engineers to limit the reasons why the aircraft may be retired. Such as issues being engineered out reducing the number of maintenance visits that have to occur or extending the time between maintenance visits. Even with all this happening the aircraft is still being aged by various other factors that can not be ignored.

Definitions, Goals and Objectives

Definitions of all defined terms (terms that are capitalized) will be added to along the course of this blog under the blog labeled "Defined Terms". All terms will be in alphabetical order to ease in location of the term. If a defined term is not the definition that the author is using but a general definition (such as The Boeing Company) proper APA citation will be available below the term to link where the definition was taken from.

Goals and Objectives:

• To give a general definition of what aircraft aging is so that even those without aviation experience can understand
• Provide examples of different ways that aircraft are aged
• Provide examples of different ways to reduce aircraft aging effects
• Explain how the FAA is starting to "crack down" on aircraft aging

Note: Additional goals and objectives may be added at a later date as more research is performed. There may also be posts to this blog that do not pertain to the goals and objectives but provide useful information to the public about Aircraft Aging in general.

References

Compart, A. (2013, February 11). 2013 Could Be Telling For Aircraft Retirement Trend. Retrieved June 11, 2014, from Aviation Week Web site: http://aviationweek.com/awin/2013-could-be-telling-aircraft-retirement-trend

Pawlowski, A. (2010, February 1). How old is the plane you're flying on? Retrieved June 11, 2014, from CNN: http://www.cnn.com/2010/TRAVEL/02/01/planes.age.dreamliner/

Understanding Basic Aircraft Aging

The AOPA provides an excellent short course on aircraft aging based on aircraft that a person may purchase for personal use. There are multiple videos to assist in understanding how aging occurs and that aging is not just caused by time passed.

According the AOPA aging comes from three main reasons:

1. Flight Activities
2. Maintenance Performed
3. Damage History

That aren't the only reasons and any small thing can cause additional aging. Think how the aircraft is stored or animals that get into the aircraft and build nests. All of these can affect the age of an aircraft.

This class is great for pilots that have a Certification because at the end of the course there is a test that will create a certificate. Sadly the author of this blog is not pilot certified and could not get her certificate despite properly completing the course. She would still recommend going through this course for basic knowledge (even if you aren't pilot certified). Even with all the interactions the author was able to complete the course in about 2 hours with an average reading speed.

AOPA. (n.d.). Aging Aircraft. Retrieved June 10, 2014, from AOPA Aging Aircraft Certificate Course: http://flash.aopa.org/asf/agingaircraft/swf/flash.cfm?keycode=FX07CRS&offercode=FX07CRS

Acronyms Used

This blog may use terms that are not well known to people outside the aviation community. When an acronym is used in any of the blogs the correct extended name will be placed here. Should the same acronym be used more than once both will appear and a reference as to what blog it came from will also be available.
AOPA: Aircraft Owners and Pilots Association
EASA: European Aviation Safety Agency
FAA: Federal Aviation Administration
LOV: Limit of Validity
WFD: Widespread Fatigue Damage