Can Safe Aircraft and MSG-3 Coexist in an Airline

WHITE PAPER
Can Safe Aircraft and MSG-3
Coexist in an Airline Maintenance Program?
White Paper By Dave Nakata, VP Consulting Services
Maintenance and engineering professionals at air carriers, MRO suppliers, regulatory authorities and other involved parties
wrestle with this question every day as they attempt to fully understand and implement the latest advances in
maintenance philosophy and practices. It is absolutely clear to all concerned that maintenance activities must help ensure
that the inherent levels of safety and reliability of the aircraft are maintained. It is also clear that maintenance
organizations need to take advantage of the lessons learned over the past thirty years to improve the quality and operating
efficiency of approved maintenance programs. This paper examines the development of maintenance program logic and
offers suggestions for realizing the full safety and economic benefits of those developments.
Background
For years prior to 1968, most major airlines incorporated the base overhaul concept into their total scheduled maintenance
program. This concept essentially required an aircraft to be removed from service periodically, for example, every 5 years,
and that everything on an aircraft that could be removed was removed and sent to the “shop” for overhaul. In those days,
overhaul was the equivalent to what we know today as a total restoration. After many days of work, the aircraft was
reassembled with all overhauled parts, and (in theory) all deterioration, degradation and wear removed from the aircraft.
Thus, a “gold plated” aircraft or, as it was sometimes called, “an aircraft better than new” rolled out of the hangar.
In 1968, the commercial aviation industry was introduced to a new way of maintaining aircraft. The Maintenance Steering
Group-1 (MSG-1) logic was used to develop the initial scheduled maintenance requirements for the Boeing 747-100
aircraft. The Federal Aviation Administration (FAA) accepted the MSG-1 logic process and the initial scheduled
maintenance requirements it generated for the Boeing 747-100.
MSG-1 provided the initial catalyst for a significant technical operations model shift with regard to the development of
scheduled maintenance requirements and the execution of those requirements by aircraft maintenance technicians.
Essentially the necessity for maintenance organizations to produce a “gold plated” aircraft out-of-check ended.
WHITE PAPER
Can Safe Aircraft and MSG-3
Coexist in an Airline Maintenance Program?
MSG-1 introduced three broad processes to classify the scheduled maintenance requirements. The processes were Hard
Time (HT), On-Condition (OC) and Condition Monitoring (CM). OC required that an item be periodically checked or tested
against an appropriate physical standard to determine whether or not the item could continue in service. The introduction
of this process, OC, began an era of new thinking – it was allowable to let an aircraft leave a maintenance check with
known deterioration, degradation or wear if the appropriate physical standard was not exceeded. Approximately a decade
later, between 1978 and 1980, two very significant events occurred: 1) Federal Aviation Regulation (FAR) 25.571
(Damage-Tolerant and Fatigue Evaluation of Structure) was revised to require that transport category aircraft be designed
and manufactured to meet ‘damage tolerant rules for structures’ and 2) Maintenance Steering Group-3 (MSG-3) was
issued by the Air Transport Association of America, Inc. (ATA) and subsequently copyrighted by ATA in 2001.
The MSG philosophy has been tested, revised and used successfully for more than three decades. Aircraft such as the
Boeing 747, 757, 767, 777, DC-9/ MD-80, DC-10, L-1011, MD-11, Airbus A320, 330, 340, and the Canadair Regional Jet are
some of the aircraft types that have had their initial scheduled maintenance requirements developed using MSG.
MSG-3 Implementation Progress
Since the creation of MSG-3 in 1980, all its users have been trained to understand the four basic objectives of an efficient
airline maintenance program generated by MSG-3. They are:
1. To ensure realization of the inherent safety and reliability levels of the equipment.
2. To restore safety and reliability to their inherent levels when deterioration has occurred.
3. To obtain the information necessary for design improvement of those items whose inherent reliability proves inadequate. To accomplish these goals at a minimum total cost, including maintenance costs and the costs of resulting
failures.”
In addition to the MSG-3 requirements, new aircraft usually have a number of mandatory maintenance requirements
generated by compliance to FAR 25.571. These are inspections of structurally significant items for fatigue cracking and
are classified as Airworthiness Limitation Items (ALIs). Additionally, there is usually another set of mandatory
maintenance requirements generated by compliance to FAR 25.1309 (Equipment, Systems and Installations). These are
maintenance tasks that are performed on aircraft systems and/or powerplants and they are classified as Certification
Maintenance Requirements (CMRs). Lastly, most transport category aircraft are delivered with some items that have life
limits, e.g., landing gears, engine disks, pressurized cylinders, etc. These three categories, ALIs/ CMRs/life limited, are
WHITE PAPER
Can Safe Aircraft and MSG-3
Coexist in an Airline Maintenance Program?
usually considered to be safety sensitive. They are basically required to be complied with for the life of the aircraft and are
unchangeable by an air carrier.
Maintenance Operations Culture Change Required
While the initial catalyst, MSG-1, was provided over three decades ago, very few airlines have taken advantage of the
opportunity to change their scheduled maintenance operations culture. A number of air carriers still produce “gold plated”
aircraft out-of-check, not because they are required to do so, but because it is an established ‘habit’.
The MSG philosophy and the requirements of life limited items, CMRs and ALIs form the basis for scheduled maintenance
program requirements that allow transport category aircraft to operate with known degradation, deterioration and/or wear
– even for an aircraft “fresh” out of check.
Additionally, air carriers are required by FAR 121.373 (Continuing Analysis and Surveillance) to, “… establish and maintain a
system for the continuing analysis and surveillance of the performance and effectiveness of its inspection program and
the program covering other maintenance, preventive maintenance, and alterations and for the correction of any deficiency
in those programs, regardless of whether those programs are carried out by the certificate holder or by another person.”
Traditionally, an FAA approved reliability program and a quality assurance audit program form the foundation for an air
carrier’s compliance to this FAR. However, regardless of how compliance is met, this FAR, in part, requires the air carrier to
monitor aircraft performance and to change the scheduled maintenance requirements in order to achieve the best
performance possible. This reinforces the fact that maintenance requirements need to be reviewed continuously and
revised as necessary throughout the life of an aircraft. This continuous review and adjustment of scheduled maintenance
requirements forms another critical element in the overall culture that should be embraced today.
Air carriers that can successfully make the necessary cultural change will provide a safe product to the traveling public and
reduce the total cost of ownership of their fleet of aircraft. This can be realized in several ways, but the most germane is
only accomplishing the maintenance dictated by the air carrier’s approved scheduled maintenance program, and as a
result, reducing the time in-check of the aircraft. After all, airlines do not derive any income from aircraft that are parked in
hangars receiving maintenance.
The required cultural change is not restricted to the air carriers. The regulatory authority, be it the Federal Aviation Authority
(FAA), Transport Canada, Joint Airworthiness Authorities (JAA), or any other aviation authority, must understand and
support this not-so-new maintenance philosophy and offer assistance to air carriers wishing to make the necessary
cultural change.
WHITE PAPER
Can Safe Aircraft and MSG-3
Coexist in an Airline Maintenance Program?
The days of doing maintenance just for the sake of maintenance or because it makes us ‘feel good’ are past. Studies have
revealed that technicians performing maintenance based on ‘tribal knowledge’ rather than the air carrier’s approved
maintenance program have generated errors. In other cases, technicians performing approved maintenance that was not
necessary ave also generated maintenance errors. Each time we provide technicians access to an aircraft, we also
provide the potential for that technician to inadvertently induce an error.
How can an air carrier take advantage of the benefits of FAR 25.571 and MSG-3? Several approaches are possible, but the
first step is to educate all members of the air carrier’s operations team including management and aircraft maintenance
technicians regarding why we need to maintain aircraft differently than we did 25 or 30 years ago. This is the first step in
making that necessary culture change in an air carrier’s maintenance organization.
Dave Nakata, VP, Consulting Services
Dave Nakata has worked in the aircraft maintenance industry for thirty-five
years and actively participated in the initial development of, and the ongoing
revisions to, the MSG-3 Operator/Manufacturer Scheduled Maintenance
Development philosophy and logic.
EmpowerMX Consulting Services Group offers a full range of services in the development and implementation of a MSG-3 based maintenance
schedule as well as CASS and event based reliability programs. Contact Dave Nakata at 651-788-8877 for more information.