Original Date: 04/20/1998
Revision Date: 01/18/2007
Information : Production Reliability Acceptance Testing
ITT Aerospace/Communications Division (A/CD) uses Production Reliability Acceptance Testing (PRAT) to demonstrate successful subsystem operation in simulated field environments, and to verify compliance with contractual reliability requirements. This aggressive testing also confirms consistency in the product’s manufacturing processes, and identifies changes in the component’s quality or supplier’s manufacturing processes.
Sample functional testing is performed quarterly on 12 vehicular long-range configurations for a total of 15,560 test hours under controlled environments (e.g., thermal excursions, vibration, power cycling, voltage cycling, moisture injection). Over a nine-year period, ITT A/CD conducted 49 PRATs, accumulating more than 766,255 total test hours. For its latest equipment design iteration, ITT A/CD determined the product’s mean time between failures (MTBF) at 5,399 hours. This result is four times better than the failure rate (1,250 hours MTBF) required by the program. PRAT’s aggressive approach was a predominant factor in the company winning two production year (PY11 and PY12), sole-source contracts.
In conjunction with this test philosophy, ITT A/CD also uses accelerated Test, Analyze, and Fix (TAAF) product analysis. Although performed at an accelerated rate, TAAF is a mirror image of the testing profiles used for PRAT, and its associated failure rates are based on the PRAT profiles observed. ITT A/CD conducts TAAF on equipment to promote reliability growth and identify areas for improvement within the current design. TAAF also identifies the operational limitations under which the equipment will work, which provides the company with a better assessment of design margins and a timely feedback of design, manufacturing process, test, and/or supplier shortcomings.
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