Aircraft Maintenance Continued from page 57 as well as plan for, what can be, a high-cost item. The overhaul decision, in turn, leads to choosing the appro- priate facility. Choosing a maintenance provider/facil- ity is, of course, another article and Jeopardy! topic. Back to TBO, if you are operating a turbo-prop engine, the regulations change to some degree; how- ever, TBO is still recommended. The limitations that are mandatory with a turbine engine are life-limited parts. These parts are airworthiness limitations and listed in the Type Certificate Data Sheet (TCDS). The other regulation in play for TBO is 14 CFR 91.409, which requires the owner or operator to select an inspec- tion program under paragraph (f). These programs are either (i) a continuous airworthiness inspection pro- gram that is part of a continuous airworthiness mainte- nance program under 14CFR Part 121, (ii) an approved aircraft inspection program approved under Part 135, or (iii) what I call the owner-produced inspection pro- gram, which must also be approved by the FAA. Notice how we moved from discussing overhaul require- ments, which is a maintenance function, to inspection pro- grams. That was not a trick, just a natural progression, since industry folks usually discuss the two together and that is where the rest of the confusion lies and what prompted the FAA to issue its most recent policy, FAA Notice 8900.410. The term “maintenance” has been around for a long time and is defined in the regulations. According to the recent Notice, the elements that comprise maintenance—overhaul and inspection—have not always been clearly understood. The Notice addresses the difference between inspection programs and maintenance programs. An inspection program only captures a list of scheduled inspections, whereas a maintenance program can encom- pass many elements, including inspections, overhaul requirements, repair schemes, Corrosion Prevention and Control Programs (CPCP), and the scheduled replacement of parts, such as life-limited parts. Overhaul is a maintenance function, not an inspec- tion, and is not included in an inspection program. Overhauls are part of the manufacturer-recommended maintenance program. While recommended, Part 91 operators are not required to comply with a manu- facturer’s entire maintenance program; to that end, overhauls are not mandatory for Part 91 operators. Part 43 describes overhaul as disassembly, cleaning, inspection, repair, reassembly and testing. According to the recent FAA Notice, these functions restore an article to a known good condition that provide reason- able assurance of operation for a specified amount of time, referred to as the “Time Between Overhauls (TBO).” Inspecting individual components is an integral part of an overhaul. For example, during the inspec- tion phase in an overhaul, a mechanic may be prompted to replace a part after inspecting it, even though it is not broken and is still performing its intended function. But, the wear might be such that the manufacturer does not have confidence the part would make it to the next overhaul period. Inspecting for condition, and wear, in this case, is a result of a maintenance instruction and does not mean it is the same as an inspection item in an inspection program as described in Part 91.409. The FAA Notice also describes how, in the past, manufac- turers used TCDS Notes to insert maintenance requirements as another form of ICA. The FAA is clear in the new Notice and stated in FAA Order 8110.121, Type Certificate Data Sheet (TCDS) Notes, that TCDS Notes are not mandatory and the notes are used to describe the certification basis of the engine, not the maintenance requirements of the engine. Let’s do a bit of a recap before the final exam. Just kidding, this is Jeopardy!, not a class. ■■ Engine TBO is a manufacturer recommenda- tion and not required by FAA regulation as long as you are operating as Part 91. An overhaul is not an inspection; it is a maintenance action described under Part 43. An overhaul may have an inspec- tion action to determine wear; however, that is not the same as an inspection program under Part 91. ■■ There are airworthiness limitations that pertain to the life-limited parts inside a turbine engine. The limitations are listed in the TCDS Notes as part of the certification basis of the engine, not to meet the ICA manufacturer requirement of Part 33. ■■ Manufacturer-recommended inspection and maintenance programs are ICAs and do meet the requirement under Part 33. ■■ The FAA issued Notice 8900.410 that discusses TBO and other “fun” facts regarding the use of ser- vice bulletins and their use by the manufacturer as instructions on performing an engine overhaul. Continued at bottom of page 59 58 Aviation Business Journal | 2nd Quarter 2017
