WS-133A STP III SPECIAL TEST REPORTS ELECTRICAL AND ELECTRONIC SYSTEMS.
BOEING CO SEATTLE WASH
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This test investigated a design change DCV 97 proposed to minimize the failures of operational power supply drawers PN 25-22622-35 that have occurred at Wing I operational sites. These drawers are believed to have failed as a result of environmental control system andor standby diesel generator malfunctions which caused the LF batteries to completely run down. In running down it is probable that LF Battery Set No. 1, which supplies power to ECS emergency fan, discharges before LF Battery Set No. 2, which supplies power to the LF Motor Generator Set. Under these conditions the power supply drawers are operated without cooling air and if this condition exists for several minutes the power supply drawers will overheat and fail. Author