1、Lessons Learned Entry: 0290Lesson Info:a71 Lesson Number: 0290a71 Lesson Date: 1993-07-14a71 Submitting Organization: JSCa71 Submitted by: Larry GreggSubject: Training/Certification for Personnel Installing Hardware Description of Driving Event: During burn-in testing of an orbiter General Purpose (
2、Flight) Computer (GPC) in the JSC avionics engineering laboratory, a “fail to synchronize“ error was detected. This error indicates that the computer is out of synch with other GPCs involved in the test, and may be the result of a computer hardware problem. The GPC in question was discovered to be v
3、ery hot to the touch, and inspection of internal sensors indicated the GPC had been overheated beyond design limits. An ensuing investigation showed that the unit had operated without cooling for 11.5 hours due to failure to remove the ventilation system air duct cover prior to installation of the G
4、PC in the test bed. This event was a direct result of not following installation procedures described in the Test Preparation Sheet (TPS). Additional factors contributing to this event included:A. The design of the cover plate for the GPC cooling duct did not prevent installation of the GPC with the
5、 cover in place. Most of the cover plates used in the laboratory were modified with additional foam to preclude installation of the GPC without removing the cover.B. The alarm system used to monitor GPC cooling depended on vacuum sensing instead of positive airflow indications. With the air duct cov
6、er in place, the vacuum sensor on the GPC in question showed a normal range reading even though there was no air flowing through the computer. The monitoring of an indirect parameter (vacuum) rather than a direct indication of absence of a critical parameter (cooling air flow) or the existence of th
7、e hazardous condition of concern (temperature of the GPC) did not guarantee that proper cooling was provided.C. Only one junior technician was assigned to install the GPC. This was a violation of instructions on the TPS, which required two technicians to perform this task. As a result, the quality a
8、ssurance assignee for the task helped to perform the installation procedure rather than performing his intended monitoring function.D. There was no formal program of training or certification in place for technicians in the laboratory. The training received was principally an undetermined amount of
9、on-the-job training.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHSFactory evaluation of the GPC involved in this event determined that it was fit for use only as a test or prototype unit and not as a flight unit. The difference in cost between a flight
10、GPC and a test GPC is approximately $700,000.Lesson(s) Learned: Lack of a formal training/certification program can result in an improper installation of hardware, which may contribute to significant damage or loss.Recommendation(s): Mishap board recommendations: Use only certified technicians for c
11、ritical installations and document training/certification. Use written procedures that include cautions, warnings, and operational (cooling) verification.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Test Art
12、iclea71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHSApproval Info: a71 Approval Date: 1993-09-13a71 Approval Name: Ron Montaguea71 Approval Organization: JSC/NS3a71 Approval Phone Number: 281-483-8576Provided by IHSNot for Resale-,-,-
