By Jack Hessburg
Talking with Greg Napert recently, he reminded me of some comments I made during a presentation at a technical seminar. I frequently used the expression, "As a mechanic, I push tin." He said he at first didn't understand what I meant.
It suddenly became apparent to me that many may not understand that in the air carrier world there are different types of maintenance. It takes a different kind of mechanic to do the jobs unique to each type; both in technical skills and personality. Air carrier maintenance is divided into three distinct categories; bench, hangar, and line.
Bench maintenance consists of repair, overhaul or refurbishment of LRUs or major assemblies (i.e. powerplants), which have been removed from the airplane. Usually work is confined to one or more LRUs or at least to a given specialty (i.e. sheet metal work, accessory overhaul, etc.). There is a predictable workload. Proficiency in a number of maintenance disciplines is not required. Knowledge of the entire airplane and its systems is not required.
Hangar maintenance is that activity normally affiliated with work on the airplane when it is removed from the revenue schedule. It is predominately, though not exclusively, associated with the heavy checks (C & D) of scheduled maintenance; AD accomplishment; theincorporation of aircraft alterations; and structural repairs. Corrosion control tasks and discretionary work is also included.
Hangar maintenance is also predictable. It is performed in a benign atmosphere. Many times, it is in a nice, warm hangar rather than outside exposed to the adverse weather common to many stations. There is a defined work package. Maintenance arising from discrepancies that are found during inspection is less demanding, for time is allocated in the work package to correct discrepancies. Heavy checks may take from 5 to 25 days.
Line maintenance is that maintenance activity performed while the airplane is committed to the revenue schedule. It may be subdivided into turnaround or gate. Turnaround maintenance, also known as overnight maintenance, is performed at terminating locations in the flight schedule. Time available may be 8 to 16 hours or more. The environment is less demanding than when the airplane is committed to the revenue schedule. The work is predictable. Many times it is accomplished by line maintenance mechanics. The work usually consists of a daily check. Logbook discrepancies including outstanding MEL deferrals are corrected. Passenger service equipment discrepancies are corrected. Servicing is accomplished. Additionally scheduled maintenance (i.e. portions of a phased check) may be performed at stations having a long turnaround. Depending upon time and manpower availability, discretionary tasks may be included. AD note accomplishment may also be included in the work package.
Gate maintenance is performed prior to the airplane departure either originating a flight or handling a transit flight. This is the job that I refer to as "pushing tin." It is incidental to scheduled flight operations. Time available is normally limited to usually 40 to 60 minutes, but may be as low as 20 minutes. Equipment and manpower are also limited. Work mostly consists of a visual check of the airplane exterior with particular attention to indications of fuel or oil leaks, obvious discrepancies such as worn or flat tires, low shock struts, fuselage or wing damage and a review of aircraft log discrepancies.
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