1、Lessons Learned Entry: 1841Lesson Info:a71 Lesson Number: 1841a71 Submitting Organization: KSCa71 Submitted by: Gregory RawlSubject: Discovery Main Landing Gear Dynamic Seal Installed Incorrectly Abstract: Lack of adequate detail on the landing gear installation drawings contributed to the incorrect
2、 installation of the Orbiter right Main Landing Gear (MLG) hydraulic seal. The installation drawing that showed the detail for the dynamic seal was owned by the seal manufacturer, not the landing gear manufacturer. To reduce human errors during parts installation, parts should be marked to show inst
3、allation order and proper orientation. Update engineering drawings to show sufficient detail of piece part installations.Description of Driving Event: During final OPF preparations for STS-120 flight, technicians discovered the right Main Landing Gear (MLG) of Orbiter Discovery (OV-103) had a hydrau
4、lic leak rate which exceeded specifications. As a result, the MLG strut was removed and engineers determined that hydraulic seals needed to be replaced. Representatives from the landing gear original equipment manufacturer (OEM) were contacted to help assist KSC technicians with the seal replacement
5、. The seals were replaced and a successful retest of the MLG strut showed no signs of leakage. Normal OPF processing progressed with the MLG being raised for flight configuration and Discovery was cleared for mate with external tank. One week after the seal replacements, the landing gear OEM was rev
6、iewing their paperwork and realized the installation of the dynamic seal was incorrect. They contacted KSC representatives and stated the dynamic seal had been installed improperly, according to new information from the seal manufacturer. The OEM stated their technicians had installed the replacemen
7、t seal in the same configuration as the discrepant seal, assuming the old seal was installed in the proper location and orientation. Unfortunately the discrepant seal had been installed incorrectly during a previous seal replacement 20+ years earlier. Later investigations revealed that the left MLG
8、seal had also been installed incorrectly. Based on the low risk that an out of tolerance leak would develop in orbit, Discovery was cleared for one flight with the seals in the incorrect configuration. Once the STS-120 mission had ended, the seals on both landing gears were replaced and restored to
9、the correct configuration.Lesson(s) Learned: One of the contributing factors that led to the incorrect installation of the dynamic seal was a lack of adequate detail on the landing gear installation drawings. The installation drawing that showed the detail for the dynamic seal was owned by the seal
10、manufacturer, not the landing gear manufacturer. The landing gear manufacturer did not show this detail on their drawings, therefore any recorded knowledge of this design was effectively lost over the course of the shuttle program. This caused vendor technicians to rely on the previous seal installa
11、tion to guide them in the new installation, instead of an approved design. Another factor leading to the mistake was a lack of training. The vendor technicians that performed the seal change-out had little or no experience with space shuttle landing gear. The landing gear designs are specific to the
12、 shuttle program, and the hardware is rarely rebuilt, offering little opportunity for hands-on training. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Recommendation(s): Update engineering drawings to show sufficient detail of piece part installati
13、ons. Update old, hand-drawn, electronically scanned drawings with modern CAD drawings. To reduce human errors during parts installation, design piece parts such that the installations are fool proof and intuitive. Parts can be marked to show installation order and proper orientation. Also, provide t
14、raining in complex installations that are rarely performed.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: Orbiter Project Office Technical Tag-Up (OPOTT) Presentation: MLG_Seal_Plan_OPOTT_11_16_07A Located in the Orbiter Project Office Technical Tag-Up Archive: https:/
15、sspweb.jsc.nasa.gov/meeting/OPOTT/presentation.cfm?date=11162007&special=Y&Archive=2007Mission Directorate(s): a71 Space OperationsAdditional Key Phrase(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Manufacturing and Assemblya71 Mission Ope
16、rations and Ground Support Systems.Ground processing and manifestinga71 Safety and Mission Assurance.MaintenanceAdditional Info: a71 Project: Space Shuttle ProgramApproval Info: a71 Approval Date: 2008-06-13a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
