1、Public Lessons Learned Entry: 2916 Lesson Info: Lesson Number: 2916 Lesson Date: 2010-05-10 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Avionics Line Replaceable Unit Built in Tests Abstract: The Space Shuttle Program Orbiter Avionics Line Replaceable Units (LRU) were designed w
2、ith limited or no diagnostic capability. The lack of fault isolation capability resulted in flight processing schedule impacts and collateral damage to flight hardware. New LRU designs need to provide an Integrated Built In Test that will verify the LRU internal components and external outputs of th
3、e LRU are functioning nominally. Description of Driving Event: There were several major implications as the result of not providing better diagnostic test capability internal and external to the LRU such as: 1. A failure during system functional testing normally required personnel and equipment to e
4、nter the orbiter to isolate the failure. The inability of the LRU to provide fault isolation capability had several consequences: a. Major impact to flight processing schedule to access the LRU for fault isolation. There were areas that were not accessible while fully integrated to the external tank
5、 (vertically stacked) and required the orbiter to be de-stacked to isolate the cause of the failure. b. Minor impacts to flight processing schedules to access an area closed out for flight to perform LRU fault isolation. c. Limited or no option to accept a failure for flight (Accepted Risk) without
6、performing on vehicle testing. d. Intrusive on vehicle fault isolation resulted in many instances of collateral damage to flight hardware. 2. Functional testing of internal LRU circuitry required connection of Ground Support Equipment (GSE). The following issues resulted from this method: a. Install
7、ation of GSE resulted in many instances of collateral damage to GSE and flight hardware. b. GSE adds a potential failure mode for the LRU testing. GSE was the cause of many LRU testing failures and resulted in extensive troubleshooting to isolate the failure to the GSE. Provided by IHSNot for Resale
8、No reproduction or networking permitted without license from IHS-,-,-Lesson(s) Learned: 3. Internal Diagnostic Capability - LRU internal components: Avionics LRUs should be designed to have the capability of remotely performing internal diagnostic checks (built in tests) and reporting system health
9、status. GSE should not have to be mated to the LRU to perform this test. 4. External Diagnostic Capability - hardware electrical connected to LRU connector interfaces (inputs and outputs): Avionics LRUs should also be designed to remotely perform diagnostic checks external health checks of the compo
10、nents connected to the LRU. This could include proper valve operations, electrical short or open, etc, . Recommendation(s): New LRU designs need to provide an Integrated Built In Test that will verify the LRU internal components and external outputs of the LRU are functioning nominally. The IBIT tes
11、t should able to be initiated and pass/fail results reported by ground or flight software. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: N/A Mission Directorate(s): o Space Operations Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
12、e from IHS-,-,-o Exploration Systems Additional Key Phrase(s): o Ground processing and manifesting o Launch support systems o Acquisition / procurement strategy and planning o Ground support systems o Human factors planning o Engineering design and project processes and standards Additional Info: o Project: Space Shuttle Program Approval Info: Approval Date: 2010-07-29 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
