1、Lessons Learned Entry: 0449Lesson Info:a71 Lesson Number: 0449a71 Lesson Date: 1990-12-15a71 Submitting Organization: JSCa71 Submitted by: L. UnderwoodSubject: Migration of Conductive Contaminates in an Electrical Switch in Zero “G“ Description of Driving Event: APU 2 Fuel Pump Heater was cycling hi
2、gh during flight. Detailed analysis of the thermal switch showed extreme wear from the switch bi-metal disc and case. Large amounts of conductive contaminates were found. Analysis showed that they came from the disc and case. It is concluded that excessive vibration caused the wear and in zero gravi
3、ty particles were free to migrate into the electrical contacts, resulting in a higher disc deflection to open the thermostat contacts. The result is a higher heater turn off temperature.Lesson(s) Learned: Excess wear led to migration of conductive contaminates into electrical contacts. High (off lim
4、its) temperatures were required to open contacts.Recommendation(s): Test electrical components at expected vibration levels to establish usable life limits.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AProvided by IHSNot for ResaleNo reproduction or networking perm
5、itted without license from IHS-,-,-Mission Directorate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Parts Materials & Processesa71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1996-09-30a71 Approval Name: Ron Montaguea71 Approval Organization: JSC/NA3a71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
