Understanding the cycle.

Today we would like to stand back and take a 50K foot view of the business aircraft maintenance cycle and discover the points within that cycle that play a role in efficiently performing maintenance.

The maintenance cycle

Aircraft go through a repeatable and predictable series of events we refer to as the maintenance cycle. The maintenance cycle is made up of four basic components or segments: flight, inspection, corrective action, and modification. Let's look at each segment in series to help us understand how they affect each other as well as the importance of each.

Flight — Once the aircraft is delivered to the owner for use (either new from the factory or fresh out of maintenance or modification), the flight segment of the maintenance cycle begins. The flight segment is the only time in which the aircraft is making money. Even aircraft that are not used commercially should be considered to be costing the operator when the aircraft is not flying. In all cases, the aircraft was purchased to fly.

The length of the flight segment is limited by two primary factors: 1) scheduled maintenance and 2) component failure. It is important to keep in mind that the scheduled inspection program, which is made up of several scheduled maintenance events, is purposely designed to minimize component failure as well as downtime. As the aircraft is operating in this flight segment, it is accumulating hours, cycles, and calendar time and as such is constantly moving closer to its next scheduled maintenance event.

Inspection — The next segment of the maintenance cycle is the inspection segment. Recurring inspections performed on a scheduled basis help to identify potentially unsafe conditions. Correction of these unsafe conditions ensures continued safe operation of the aircraft. The inspection segment describes the physical action taken by qualified persons trained to isolate the unsafe conditions which developed as a result of the use of the aircraft during the flight segment(s).

Prior to beginning the inspection phase, it is important to examine the maintenance records (logbook) and/or computerized maintenance status to determine the current status of the aircraft's inspection and maintenance program and identify possible deficiencies in the aircraft's maintenance records.

An aircraft inspection is required to be performed using a checklist. The obvious purpose of the checklist is to avoid forgetting any portion of the inspection as well as allow the inspection program to be divided up into a logical and efficient schedule. Any discrepancies found while inspecting the aircraft are recorded and, with few exceptions, must be corrected prior to returning the aircraft to service.

Maintenance/corrective action — The next segment in the maintenance cycle is the corrective action segment. The corrective action segment consists of the performance of hands-on maintenance in order to correct any physical defects found as well as any records deficiencies identified within the records. Proper correction of the discrepancies found will determine the airworthiness of the aircraft. Once each item has been corrected, a second inspection should be conducted to verify complete and safe correction of the discrepancy. If all discrepancies that affect "airworthiness" have been corrected, the aircraft may then be approved for return to service. The approval for return to service is a written certification (by a properly certificated person or agency) that specifies the aircraft meets all regulatory airworthiness requirements and is safe for continued operation.

If any of the defects found by the inspection, that impact the airworthiness of the aircraft are left undone, the inspection performed must still be recorded as accomplished, however in such case, "a list of uncorrected discrepancies" must be provided to the aircraft owner-operator and the aircraft may not be operated until those items are corrected. With FAA approval, the aircraft may be flown to another location to have the corrective action performed.

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