Overhaul and replacement requirements consist of components of the aircraft that are simply replaced at a certain time rather than simply inspected and returned to the aircraft. Many overhaul and replacement components also have periodic inspection requirements up to the time they are replaced, but in the end they are consumable or include consumable parts. An overhaul component for example will include pieces that are always replaced during the overhaul process as well as pieces that are thoroughly inspected (to a specified standard) and reassembled with the overhauled assembly prior to return to service. Replacement items are simply removed and replaced with new regardless of their condition. The engineers have determined that these components are subject to wear and tear that may not be obviously visible to the naked eye and that replacement or disassembly and overhaul are the only adequate means of ensuring the safe continued operation of the aircraft.
Airworthiness limitation is a specific term used in our industry to identify items whose overhaul or replacement is critical to the airworthiness of the aircraft. These items are specifically identified during the type certification process of the aircraft due to the critical nature of their purpose in the operation of the aircraft and are listed in a document specifically called an Airworthiness limitations listing. In most cases, little or no wear is acceptable and the replacement or in some cases overhaul, is critical.
We group service information and Airworthiness Directives together because they are very similar in nature. However, Airworthiness Directives are much more critical because they are literally regulations themselves. Both service information and Airworthiness Directives are issued to resolve some safety, quality, or configuration issue that has been found, generally after the type certification of the aircraft. Most commonly a specific problem is identified by issuance of a Service Bulletin by the aircraft manufacturer. When the problem is most critical in nature, the FAA will subsequently issue an Airworthiness Directive that echoes the Service Bulletin and in most cases refers directly to the Service Bulletin.
Weighing the inspection components
Those are the basic components of the aircraft inspection and maintenance program, now lets talk about the weight of each component. When we refer to “weight” what we are talking about is this. We are working in a regulated industry with specific guidelines that create levels of severity, or criticality when it comes to the components of an inspection program. Like it or not, some things simply matter more that others.
Part 91.409 (e) requires that the aircraft be inspected as outlined in the inspection program regardless of whether the inspection program is the one specifically recommended by the manufacturer or one submitted by the owner operator to the FAA and approved. The rule tells us to inspect the aircraft in accordance with that program and correct discrepancies found or it is not airworthy. As most of us know, that inspection program can consist of hundreds and sometimes thousands of specific items. Because that aircraft must be inspected in order to maintain its airworthy status, inspection items carry the same weight as the regulation itself.
Lubrication and servicing requirements are not specifically called out by the regulation and therefore carry a little less weight than inspections. We have discussed several times the fact that the inspection program includes lubrication and servicing references.
Some are of the mindset that simply because the lubrication or servicing requirement is included in the inspection program it carries the weight of the inspection program. Not so. FAA Order 8300.10 specifically addresses this issue in an effort to eliminate the confusion.
Obviously we must properly lubricate and service the aircraft, the idea here is that when a scheduled lubrication requirement comes due ahead of an inspection, we have the latitude to wait until the aircraft is down for the inspection to accomplish the lubrication.
Similarly, the overhaul and replacement items are not considered inspections and can be scheduled to coincide with the next inspection. When the manufacturer considers an overhaul or replacement item as critical, it simply calls it an Airworthiness limitation. Again, looking at Part 91.409 (e) we see that the term inspection is used specifically and that the regulation also calls out Airworthiness limitations specifically. This is not to say that we don’t need to overhaul or replace items that the manufacturer suggests. Again, we believe they are listed because the component is subject to wear that may not be visible to the naked eye. If that is the case, not replacing these components or not overhauling them as scheduled could be cause for concern as an inspector. But we do have a little latitude here for scheduling the aircraft down.
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