1、Lessons Learned Entry: 1478Lesson Info:a71 Lesson Number: 1478a71 Lesson Date: 2004-06-06a71 Submitting Organization: LARCa71 Submitted by: Daniel YuchnoviczSubject: Use of Hardware Beyond its Qualification and Certification Limits Abstract: The Space Shuttle Orbiter Rudder/Speed Brake (R/SB) Actuat
2、ors on Orbiter OV-103 were disassembled for inspection after 23 years in service. The actuators had been in service for 23 years and had flown 27 missions; they had been certified for 10 years and 100 missions. The inspection revealed corrosion, pitting and wear to varying degrees, and the four R/SB
3、 actuators on OV-103 were replaced with the spares, which had themselves been in storage for 17 years. The use of actuators that had been in storage for a longer period than their certified life led to several concerns, which were duly addressed and the spare actuators were cleared for flight. The p
4、ossibility of other flight hardware being used beyond its certification limits, whether spares or components that had never been replaced, led to issuance of the Lesson Learned documented herein, which cautions against the use of hardware beyond its qualification and certification limits.Description
5、 of Driving Event: Disassembly inspection of the Space Shuttle Orbiter OV-103 Rudder/Speed Brake (R/SB) actuators revealed corrosion, pitting, and wear to varying degrees, along with degradation of the lubricant, Braycote 601. A program decision was made to replace the actuators in OV-103 with the e
6、xisting spares, a single ship set which had been in controlled storage for the past 17 years. An assessment was performed to address the following two issues, which had been raised within the Program Control Review Board process: Issue 1. Grease separation into its component oil and thickener is kno
7、wn to occur in storage. Its effect on lubricity is not known. Issue 2. Chemical reactions involving the grease and the gear/housing material, 9310 steel, could lead to formation of Lewis acids, resulting in corrosion, pitting, and cracking. Provided by IHSNot for ResaleNo reproduction or networking
8、permitted without license from IHS-,-,-Issue 1 was addressed directly by performing lubricity testing using aged and separated grease obtained from several sources, including grease that had been removed from the OV-103 actuators. Issue 2 was addressed by measuring the thermodynamic characteristics
9、of the corrosion process - the rate constants and activation energy - for the particular material/lubricant combination. Both issues were shown not relevant with respect to flight safety, and the spare R/SB actuators that had been installed on OV-103 were declared to be flight worthy. However, the e
10、xistence of hardware which had exceeded its service life, within the spares inventory, as well as the actuators that had just been replaced in OV-103, raised a concern with respect to maintenance and refurbishment practices within the aging Space Shuttle fleet. This concern is the subject of an ongo
11、ing study, and the Lesson Learned is documented herein. Lesson(s) Learned: “Programs should periodically review hardware components to ensure that they are operating within qualification and certification limits. Where hardware exceeds those limits, testing or analysis should be performed to properl
12、y envelop the actual operating environment.“Recommendation(s): The Office of the Chief Engineer, with the assistance of the Associate Administrator for Safety and Mission Assurance, should effect the following activities: 1. For the Space Shuttle and Space Station programs, review all hardware compo
13、nents that are not currently refurbished on a prescribed, certified maintenance schedule, with particular emphasis on hardware that is not readily accessible for inspection.2. The same Offices should order similar reviews for all other equipment that may be in use for a longer period than intended,
14、including facilities and ground support equipment, with special emphasis on those the failure of which might have adverse consequences with respect to personnel safety and loss of critical assets.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s):
15、 a71 Exploration SystemsProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Aeronautics ResearchAdditional Key Phrase(s): a71 Flight Equipmenta71 Hardwarea71 Parts Materials & Processesa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 2004-06-16a71 Approval Name: Leslie Johnsona71 Approval Organization: LARCa71 Approval Phone Number: 757-864-9409Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
