Downloaded from https://www.everyspec.com AMCP 70&196 attribute classification is standardized from Generally, the standard sequential plans project to project, from item to item, and (I through VI) offer acceptable risk levels from test program to test program, within a at minimum test time for development tests, project.
The use of a standard classification The high-risk sequential tests (plans VII, VIII, system simpli~fs failure diagnosis, corrective IX) should be used only if test resources are action, inspection, and design-change control, very limited and the high risks of incorrect .and provides baseline definitions for the reli- decision are acceptable, The fixed-length ability incentive in incentive contracts.
The testi (X through XXV) are generally used most direct benefit of' test planning is that for production sampling since the accept test subjective selection of attributes is replaced time is fixed, leading to easier эcheduiing, - by objective application of an agreed-upon and since, generally, more test equipment is set of 1pound rules. available for production testing than for developmental testing. Plan XXVI (develop- 4-3.2 TEST CRITERIA FOR RELIABILITY ment) and XXVII (production) specify a DEMONSTRATION PER MIL-STD. maxlmhtm test time of 500.hr on each 781" (REF.
8) sample equipment, Decisions can be made after a period equal to 3 times the specified 4-3.2.1 Test Levis MTBF (if such a period is less than 500 hr). MIL-STD-781 has 10 different test levels The longevity test is used for testing the that specify conditions of temperature arid total operational life of the equipment, At temperature cycling, input voltage cycling, least two equipments must be tested for a on-off cycling, and vibration. Table 4-7 time equal to the specified longevity. Time summarizes the test levels. These levels accumulated on the demonstration test may should be considered minimum requirements, be applied to the longevity test.
If there is and appropriate modifications should be no longevity reqiuirement, each equipment Is made to meet more stringent conditions, tested for 2000 hr. No accept criteria are The following considerations should apply: given, but all failures and patterns are ana- lyzed to determine if the longevity goal is 1. The test level should be severe -nough satisfied. to equal the anticipated operational stress. 2. The test level must be severe enough 4-3.2.3 Test Performanoe and Evaluation to uncover defective parts or workmanship. The fotlowing items are important: 3. The test level should approach or equal 1. Sample Size.
Generally at least 3 design extremes but should not exceed basic i, a re te , bute the at ul 3 rn. design specifications to such an extent that equipments are tested, but the actual num- bber depends on the purpose of the test and non-relevant failure modes become important. the lot size. See Raf. 6,.!• 4-3.2.2 Test Critela 2, Evaluation Criteria. MIL-STD-781 pre- sents the complete accept-reject criteria for MI)standard pequentialdtesfvetys; (2 tsort- : each of its 29 test plans (i.e., the ones shown () standard sequential tests; (2) short-run, in Table 4-8). high-risk sequential tws6, (3) fixed-length tests; (4) longevity tests; and (5) all equip- 3r ment Acreening test.
There are 29 individual . I pre- test plans. Their risk characteristics are *AU references to MIL.STD-781 are to version 3, China summarized in 'rable 4-8. 1, July 1969 revmlion. .,9I r - - .. I. -. i