Part 91

When we take the time to lay out all of the maintenance requirements for an aircraft we will find some interesting scenarios that, when encountered, can cause lots of confusion and discussion.


When we take the time to lay out all of the maintenance requirements for an aircraft we will find some interesting scenarios that, when encountered, can cause lots of confusion and discussion. What is legal? What is right? Does it make sense? Why not? In the end as maintenance personnel we have got to be able to move forward and keep working with little or no delay in the delivery of the aircraft. On-time delivery is critical in maintaining our customer base. This is only possible if a clear set of guidelines is established and followed regarding what makes up the maintenance requirements for an aircraft. In this article we will cover inspection and maintenance requirements, where they come from, and the different weights that those requirements carry relative to severity.

To start with, the focus here is on Part 91, multi-turbine powered aircraft which are not subject to annual inspections but instead are to be inspected as outlined in the manufacturer’s recommended inspection and maintenance program or a program compiled by the owner or operator and submitted to the FAA for approval. Regardless, the inspection program consists of five major components:

• Look phase and special inspections
• Lubrication and servicing requirements
• Overhaul and replacement requirements
• Airworthiness limitations
• Service information and Airworthiness Directives

Let’s take a moment to examine each of these five components of an inspection and maintenance program.

Look phase and special inspections consist of any requirement in the recommended inspection and maintenance program that must be looked at to determine that the aircraft continues to be in airworthy condition. In order for the manufacturer to obtain a type certificate for the aircraft it must consider all stresses and strains that the aircraft will be subjected to when operated in accordance with its normal operating limitations. Considering these stresses and strains provides the engineers and technical writers with the data necessary to compile the list of required inspections and the corresponding frequency of inspection. In many cases the list is quite long, hundreds and sometimes over a thousand line items. The manufacturer provides both general instructions on what to look for and, in some cases, specific tooling and explicit instructions on what to look for to ensure that the aircraft continues to be safe to operate. Completion of these inspection items can generate a list of discrepancies that need to be handled prior to returning the aircraft to service. Once the discrepancies are listed and need to be worked, the inspection item itself can be bought off. Further inspection following the correction of the discrepancy provides an adequate method of coming full circle on the inspection.

Lubrication and servicing requirements are somewhat self-explanatory, obviously. These are the items or areas of the aircraft that carry some sort of fluid or are subject to wear due to friction or exposure to the elements. The manufacturing engineers have identified and set forth the time frequencies for these items as well. Great effort is put forth to ensure that the lubricant or other fluid used in the aircraft in these specific areas is the appropriate material for its specified use. Too often an unlikely substitute is used that can compromise the safety of the aircraft. As an inspector it is critical to verify if at all possible that the last person to touch the aircraft used the appropriate lubricant and or fluids. Many of these areas are also subject to inspection and must be thoroughly cleaned as part of the inspection process prior to applying the specified lubrication material.

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