MIL-DTL-53077A
3.14.2 Failure definition. A failure is defined as any malfunction which causes or may
cause inability to commence mission, cessation of mission, degradation of performance
capability of the mounting kit by continued operation, or serious safety hazard. Simultaneous
related malfunctions are considered as one failure. Failure is also considered if there is a delay
or prevention of an operating cycle to the extent that specified performance requirements cannot
be met.
3.15 Maintainability.
3.15.1 Mean time to repair (MTTR). The mounting kit shall have a meant time to repair
at organizational level of 30 minutes or less (see 4.5.2.4).
3.15.2 Maintenance ratio (MR). The mounting kit shall have a MR not to exceed 0.1
man-hours per hour of operation. Maintenance ratio is defined as the ratio of the total active
scheduled and unscheduled maintenance man-hours required to the total operating time. Man-
hours for repair of replaced components and scheduled checks and services are not included.
The maintenance schedule shall be established prior to the start of any testing. Repair of blast
damage is not included in the maintenance ratio (see 4.5.2.4).
3.16 Workmanship. Each mounting kit component shall be clean and free from sand,
dirt, fins, pits, scale, corrosion, burrs, sharp edges, cracks, poor welds or welds not meeting
drawing requirements, or any other defects that could impair the function of the mounting kit.
3.16.1 Metal fabrication. Metal used in fabrication shall be free of kinks and sharp
bends. The straightening of material shall be done by methods that will not damage the material.
Corners shall be square and true. All bends shall be made with controlled means to ensure
uniformity of size and shape. Precaution shall be taken to avoid overheating. Heated aluminum
shall be allowed to cool by natural convection. External surfaces shall be free from burrs, sharp
edges, and corners, except when sharp edges or corners are required or where they are not
detrimental to safety.
3.16.2 Welding. The surface of parts to be welded shall be free from rust, corrosion,
scale, paint, and grease, and mill scale that can be removed by chipping and wire brushing, as
well as from other foreign matter. Welds shall withstand stress without permanent deformation
or failure when the parts connected by the welds are subjected to proof and service loading.
Parts to be joined by fillet welds shall be brought into as close contact as possible, and in no
event shall be separated by more than 3/16 inch unless appropriate bridging techniques are used.
The welding process used in fabrication of the mounting kit shall be as specified in applicable
drawings. No deviations from these requirements are permissible without prior approval from
the Government.
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