and after ESS. Qualification ESS The testing of a production-representative unit to demonstrate that the design, manufacturing, assembly, and repair processes have resulted in hardware that conforms to the specification. Satisfactory completion of Qualification Testing denotes readiness for further stages of testing. Limited flight testing may be acceptable before completion of all phases of Qualification Testing. Production Unit Qualification Testing Purpose: Done for qualification of a new manufacturer, design, process, or facility to ensure the adequacy and suitability of the design to reliably operate during and after exposure to environmental stresses that exceed operational environment predictions by a prescribed margin. Method: Per Mil-Std-810G for LRUs and SRUs, per Mil-Std-202G for electronic piece parts, per Mil-Std-1540 for space systems, and per Mil-Std-883H for microelectronic devices. EMI/RFI Testing is usually included in ESS Qualification Testing and requires application of MIL-STD 461E. These Military Standards require tailoring. Mil-HDBKs-340, 343, 344 and 2164 provide detailed guidance. Sequence of First Production Article testing: Visual Inspection and Functional – Preconditioning – Acceptance ESS – Acceptance Reliability – Visual Inspection & Functional – Qualification ESS – Visual Inspection & Functional –Qualification Reliability – Visual Inspection & Functional. Note: Qualification Testing usually includes ‘aggravated’ ESS testing, i.e. test to actual environmental levels and duration plus a margin (typically 10 °C, 6 dB). Adding margin is required due to the statistically small sample size and uncertainties in actual environmental levels. Since this is a destructive test, the UUT shall never be fielded in operational systems. Note: Must do Acceptance Testing including Pre-Conditioning first. This is because these tests are done on all production units and so become parts of the environmental stress profile. Note: Another manufacturer (second-source) building the same unit or a replacement unit that is intended as a form-fit-and-function replacement for the original unit or unit sub-assembly must be qualified to specifications equivalent to those used for the original source. Repaired Unit Qualification Testing Purpose: Performed on First Repaired Article or Pre-Qualification Repaired Article units to qualify a new repair source or repair method. It is also performed to evaluate substitute piece parts. Method: If the repair parts and processes are equivalent to the original manufacturing parts and processes, then use the Repaired Unit Acceptance Test performed by the contractor, followed by Government inspection and operation in the next higher assembly. If the parts and processes are not known to be equivalent, then use applicable areas of