scope:

Description of Driving Event:

During the performance of OMI V1103.002 (EMU Functional), a significant amount of water was found in the EMU 2 upper torso in the Primary Life Support System (PLSS) sublimator. After troubleshooting and data retrieval, it was found that the Orbiter airlock power supply had caused a voltage spike, which in turn opened the EMU feed water valve and caused the PLSS sublimator to be flooded with water. This condition forced the removal of EMU 2 from the airlock starboard wall so it could be sent back to JSC for repair while another replacement EMU was being prepared to be shipped to KSC. When EMU 2 was removed, it was discovered that the CCC was installed backward in the EMU. The error was then documented on PR FCS-5-11-0265. Then the CCC in EMU 1 was found to have been installed backward as well. This error was then documented on PR FCS- 5-11-0266. This raised concern that LiOH from the CCCs might have entered the EMU vent loop and that some mechanical damage might also have occurred (it takes slightly more force to latch the CCCs in place if they are installed backward). After the PR disposition was complete and the work steps were performed, it was determined that no LiOH had entered either of the EMUs and that no collateral mechanical damage had occurred. The CCCs were reinstalled in their correct configuration in the two EMUs and were flown successfully on STS-77.

A review of the KSC installation procedure and JSC installation drawing revealed work steps and drawing notes that stated "Correctly orient flight CCC, such that the identification tag is visible when installed" for both the EMUs. Obviously, these work steps were not performed correctly when these two CCCs were installed, and some later questioned whether the identification tag could be installed on the wrong side of the CCC, which could then lead to a similar installation error. Further research indicated that the original CCC design (P/N SV767790-05) had two cooling water ports on the left top, which would only allow a one-way installation. The newer design (P/N SV792600-00) did not have these two ports and the CCCs used for this installation were of the newer design. This problem was presented to the Shuttle Operational Action Group (SOAG #96-032, see attached backup material). FCS Engineering suggested to the SOAG that another check be added to the installation procedure and to the JSC drawing, as well as a Caution note to the installation procedure. The added check stated "Verify that the back of the CCC is flush with the PLSS" prior to zipping up the thermal cover flap covering the PLSS and CCC. The added Caution note stated "Due to the design, the CCC can be installed backwards. The CCC should be installed with little resistance and should sit flush with the back of the PLSS when the flap is closed." These actions were approved by the SOAG members. Since these actions, the CCCs have been installed correctly on all subsequent Shuttle flights.