A robust management program should keep an older airplane safe, but at what point does the need to keep it safe cross over with the need to replace it, asks Mario Pierobon…
For purposes of operational effectiveness, ideally pilots should only worry about flying the aircraft. Likewise, maintenance staff should only think about the aircraft when in the shop – it’s in safe hands away from the hangar… Such confidence can only be possible through effective and thorough management of the aircraft’s airworthiness.
Continuing airworthiness management (CAM) is essentially the structured set of processes and tasks performed to ensure that an aircraft’s airworthiness requirements are met and the vehicle is in a condition that is safe for operation throughout its life. CAM is a necessary pre-condition for the safety of flight and is the responsibility of the aircraft operator, whereas any actual performance of maintenance is more often outsourced.
The principle of continuing airworthiness management and the appropriate execution of CAM tasks are meant to serve as control mechanisms, ensuring that aircraft are always ‘fit to fly’. As a result of CAM, there should be no difference in aircraft safety performance that can be attributed to aircraft age.
CAM tasks include the development and control of a maintenance program for the managed aircraft, including:
• Any applicable reliability program;
• The management of the approval for modification and repairs;
• The assurance that all maintenance is carried out in accordance with the approved maintenance program and released in accordance with requirements on the aircraft’s release back into service;
• The assurance that all applicable airworthiness directives and operational directives with a continuing airworthiness impact are applied;
• The assurance that maintenance is performed by appropriately approved maintenance organizations as necessary;
• The management and archiving of all continuing airworthiness records and operators’ technical logs; and
• The assurance that the weight and balance statement reflects the current status of the aircraft.
“Theoretically, it’s technically possible, assuming an aircraft’s airworthiness is adequately and thoroughly performed, to keep an aircraft airworthy for an indefinite period of time,” notes Roberto Mario, a CAM professional working in the Business Aviation field. “That’s without prejudice to specific restrictions or life limits imposed by authorities or aircraft OEMs.
“In practice, however, cost efficiency leads to fleet changes as business needs evolve and aircraft performance deteriorates over time. It’s also true that as aircraft assets age they become less reliable. This has obvious implications in terms of operational readiness, but may also impact safety performance…”
Business aircraft are maintenance intensive, and this only increases as aircraft age. “Life limits (i.e. hours or cycles of operation) of business aircraft are generally defined in the prototype stages as a result of fatigue tests,” Mario highlights. “These life limits are generally more restrictive than those of airliners.
“In some cases these life limits may be attributable to the assurance of performance - even of specific installations or parts - but in most cases life limits are shorter for economic reasons."
“Concepts such as ‘Progressive Maintenance’, which sub-divides inspection phases to reduce aircraft downtime, or ‘Reliability/MSG-3-based Maintenance’, which applies statistical methods to increment the intervals for the off-wing maintenance of components are more typically employed in CAM programs for the airlines, and are less common in Business Aviation CAM. Thus, Business Aviation maintenance becomes somewhat more intensive compared with commercial airliner maintenance.”
Navigate the ‘Safety Space’
The decision on whether making aircraft airworthiness management more intensive (with higher running costs), or buying a new aircraft (with necessarily higher ownership costs) exemplifies how to healthily navigate the ‘Safety Space’, a notion derived from the ‘Economics of Safety’.
Decisions are made within the ‘safety space’ so long as a condition of equilibrium is reached between the amount of resources made available for performing flying missions (‘Production’), and the resources made available for targeting the safety risks associated with flying (‘Protection’). A massive upfront investment - such as buying a new aircraft - is often justified in safety and economic terms in comparison with recurrent, expensive repairs and preventive maintenance, plus increasing uncertainty over equipment reliability.
Keeping Up Vs. Selling Up…
What methods should corporate flight department managers use when they need to keep up with the increasing maintenance needs of an aircraft? Obviously the safety of flight should not be traded-off in favour of short-term productivity gains. Maintenance needs must continue to be performed in accordance with the approved aviation maintenance program if the aircraft continues to be operated.
The case is more for trade-offs of a financial nature. In the face of increasing maintenance and operating costs (e.g. fuel efficiency) decisions may lean towards buying aircraft. This requires a monitoring of aircraft utilization to estimate when maintenance will start to become more expensive, as well as when the maximum number of flying hours (life limit) will be reached. This monitoring should support an advanced planning for alternatives.
Fleet planning decisions are never easy as fleet planning is far from a perfect science with several, often unpredictable variables. Currently low oil prices are making older aircraft economically viable that only a couple of years ago looked ripe to be scrapped.
In determining fleet needs and related timings, also consider frequency of operations, average sector length, seating capacity, crew qualification, performance requirements at frequented airports, and specific operational approvals needed. Depending on the sophistication of the operation, the use of mathematical models can support fleet planning and decision-making.
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