1、Lessons Learned Entry: 1212Lesson Info:a71 Lesson Number: 1212a71 Lesson Date: 1998-12-07a71 Submitting Organization: JSCa71 Submitted by: N. O. Gaspar/ Ronald A. MontagueSubject: Contingency Planning for Control of Test Hardware During Anomalous Episodes Description of Driving Event: During functio
2、nal test of the Qualification Model of the Mobile Transporter (MT) Linear Drive Unit (LDU), mounted on the Functional Test Fixture (FTF) a power surge followed by a facility power outage occurred. A sequence of events began that resulted in two incidents.Incident #1: When power was restored, the Spe
3、cial Test Equipment (STE) console and data acquisition systems (computers) were restarted. For the STE, the operator selected the appropriate program to power up the fixture motors to warm them up, in preparation for the start of the Fixture Characterization Procedure. Unexpectedly the X-axis motor
4、started, raising the carriage until the screw securing the load cell contacted the lower end of the motor ball screw, causing the flexible coupling to be sheared off. Investigating of the uncommanded movement revealed that several Test Console electrical/electronic components were defective, most li
5、kely as a result of the power surge. The fixture motor controller PMAC card, the X-axis motor servo amplifier and the Y-axis motor relay were removed and replaced. The flexible coupling was also removed and replaced.Incident #2: Under the assumption that the motor was still disconnected from the X-a
6、xis ball screw, the system check-out was started. The motor drove the X-axis to the lower end of travel at which point the kill switch was activated to disable the unit. During the uncontrolled motion the LDU qualification unit bogie wheels contacted the lower flange of the test rail and became load
7、ed (no damage found, only superficial scratch) but damage was incurred by the STE X-axis load cell and related hardware. Root cause: Incident #1: Primary Cause: Failure to properly check out the electronic equipment following a known power surge/power outage. Contributing Causes: Provided by IHSNot
8、for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. The ball screw mechanism was not disconnected from the actuator (motor) to guard against inadvertent/unintended motion.2. An Uninterruptible Power Supply was not installed.Incident #2: Primary Cause: The safety of pers
9、onnel and hardware was jeopardized when two different groups worked on the hardware simultaneously and without proper coordination. Contributing Factor: It should have been confirmed first that the motor was still disconnected from the test fixture before the motor system checkout was performed . Le
10、sson(s) Learned: The safe back-out of a test when anomalous conditions occur must be built into the test design and operations to ensure the safety of costly test equipment and hardwareRecommendation(s): 1. Management needs to clearly delineate responsibilities and appoint one individual to be in ch
11、arge. This individual must plan and coordinate all activities between personnel involved to ensure no conflicts or hazards arise. Before commencing testing, the software and hardware functions must be checked-out in a manner that does not endanger the test article. In the above case, the test fixtur
12、e motor(s) should have been physically disconnected (flex coupling removed) prior to check-out of the system functionality.2. An Uninterruptible Power Supply with proper surge protection is a preferred practice to protect expensive and delicate electronic test equipment from electrical power surge d
13、amage.3. All personnel involved in designing, assembling, handling and testing ISS hardware should know how to “Murphy“ proof the process. A “Can Not Fail“ briefing was developed by Boeing-Huntington Beach which addresses two different approaches to maintaining a safe environment during Production a
14、nd Test.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AAdditional Key Phrase(s): a71 Computer-Aided Design/Manufacturing/Engineeringa71 Confi
15、guration Managementa71 Flight Equipmenta71 Flight Operationsa71 Ground Equipmenta71 Ground Operationsa71 Hardwarea71 Independent Verification and Validationa71 Parts Materials & Processesa71 Policy & Planninga71 Risk Management/Assessmenta71 Safety & Mission Assurancea71 Test & Verificationa71 Test Articlea71 Test FacilityAdditional Info: Approval Info: a71 Approval Date: 2002-06-17a71 Approval Name: Ronald A. Montaguea71 Approval Organization: JSCa71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
