As may be expected, the Navy has extensive computerized systems that document equipment failure history, maintenance manhours, parts usage, etc. In general, the causes of failures are not documented in a manner that is useful to a design engineer. Quantitative comparative and trend reliability and maintainability information is useful, since any bias on the input data is reasonably constant with time. Thus, fleet reported data can identify "where" there is a problem compared to similar equipment or when an adverse trend is occurring. Such quantitative data, however, does not identify the "why" or "how to prevent" the condition.
The documentation system that includes fleet failure data is the U.S. Navy MDS (Maintenance Data System). The MDS data, when properly used, can be very useful to the design engineer because it is a historical baseline against which later reliability and/or maintenance requirements can be based after a design or maintenance procedure change has taken place on an avionic equipment. The MDS can also serve to raise "red flags" which trigger the more detailed engineering investigations necessary to provide the basis for corrective actions.
Maintenance actions at the OMA (Organizational Maintenance Activity) and IMA (Intermediate Maintenance Activity) are routinely documented and reported by MAF (Maintenance Action Form) on an avionic equipment and component identified by a special code called a WUC (Work Unit Code). The detailed procedures for requesting MDS data are contained in the "Catalog of Aviation 3-M Information Reports" promulgated per Navy Maintenance Support Office Instruction 4790.18 Requests are the sponsoring Naval activity to the Navy Maintenance Support Office, Mechanicsburg, PA 17055. Information on the particulars of the MDS are explained in Chief of Naval Operations Instruction 4790.2, "Naval Aviation Maintenance Program".9
ENGINEERING INVESTIGATION DOCUMENTATION
Another important form of failure documentation involves the EI (Engineering Investigation). Normally this is performed by an equipment CFA (Cognizant Field Activity) or, at his request, by a contractor. Completion of an EI does not necessarily mean that corrective action has been taken on the problem involved. Thus, on a particular piece of equipment the CFA may have a file of the various EIs previously performed. Access to these should be obtained by a request to the CFA of the equipment involved, submitted via the sponsoring Naval activity. Naval Air Systems Command Instruction 5400.15, "Master List of Engineering Cognizant Assignments",10 contains a list identifying the CFA for each type of avionic equipment. EIs are especially useful because they are performed by engineering personnel with the specific purpose of providing the engineering data in a form that can be directly applied in the process of developing a corrective design.
SPECIALIZED DOCUMENTATION SOURCES
There are other specialized data sources serving activities such as the Naval Aviation Safety Center and NAVAIR (Naval Air Systems Command). With these data sources the sponsoring naval activity of a procurement or engineering action normally withdraws the necessary information from the data sources and then provides the data to a contractor, as appropriate. These specialized data sources are:
a. Computerized Unsatisfactory Report Engineering System (CURES)
b. Analytical Maintenance Program Analysis System (AMPAS)
c. Depot Maintenance Data Collection System (DMDCS)
d. Navy Safety Center Failure Data