MIL-STD-1798 Mechanical Equipment And Subsystems Integrity ProgramThe purpose of this standard is to describe the general process to achieve and maintain the physical and functional integrity of the mechanical elements of aircraft systems. The goal of this integrity program is to achieve the desired level of safety and aircraft availability at the most economic cost across the life cycle of the weapon system. This standard allows the process to be tailored in a competitive environment to meet specific equipment, subsystem, and/or system requirements. The Mechanical Equipment and Subsystems Integrity Program MECSIP is implemented in the planning process and continued until retirement of the system.

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MIL-STD-1798C

5.2.12.3.1 Uncontained failure control.

This refers to any failure which liberates parts which can do damage to flight-safety critical parts. Most commonly these are high-speed rotating parts, but it also can include pressure vessels

and tires. For parts such as these, containment is the most common design criteria to control the hazard. In some cases it may be more advantageous to provide shielding to safety-critical

components to prevent damage. For pressure vessels, a leak-before-burst or proof pressure

direct failure mode approach is most commonly used design criteria, but containment or shielding can also provide adequate control.

5.2.12.3.2 Components operating in a flammable zone.

For components operating in a flammable zone (e.g., inside a fuel tank), surface temperatures shall be maintained under all conditions (including failure conditions) to less than the auto- ignition temperature of the flammable fluid. If the part is electrically powered: verify power levels are within the intrinsically safe range and/or verify the electrical elements are contained within the part and any ignition within the part cannot propagate outside, igniting the flammable vapor.

5.2.12.3.3 Components operating in a flammable fluid leakage zone.

For components operating in a flammable fluid leakage zone (e.g., drybay next to a fuel tank), surface temperatures shall be maintained under all conditions (including failure conditions) to less than the auto ignition temperature of the flammable fluid. If the part is electrically powered: verify the part is compatible with operation in an explosive atmosphere.

5.2.12.3.4 Flammable fluid carrying line and wire harnesses.

Insure the line/wire harness does not chafe on aircraft structure or other components throughout the range of bending/movement experienced in service.

5.2.12.3.5 Electromagnetic compatibility.

Insure through component level and system level testing that equipment installed on the aircraft will not induce safety-critical failures of other equipment or systems due to electromagnetic interference.

5.2.13 Aerospace castings.

The USAF has experienced numerous problems when castings are utilized in lieu of forged or machined parts. When castings are used (either in the original design or as a replacement part), 5.2.13.1 and 5.2.13.2 apply.

5.2.13.1 Casting requirements.

Castings shall be classified and inspected in accordance with SAE AMS2175. Structural castings shall be procured to guaranteed property, premium quality specifications such as SAE AMS-A-21180, AMS5343E, or equivalent. Design criteria shall be governed by the Joint Service Specification Guide for Aircraft Structures, JSSG-2006.

5.2.13.2 Guidelines for digital radiography (DR) inspections of castings.

Digital radiography inspection systems are not "drop in" replacements for film radiography. Structures Bulletin EN-SB-12-001 identifies the procedure to follow to authorize use of DR inspections for castings.