A Line Mechanic reported he forgot to reattach an electrical connector to the Leading Edge Standby Drive Shut-off Valve after completing the # 2 Engine Bleed System Health Check to clear a deferred item. Flight crew was unable to lower their Leading Edge Devices.
Synopsis
A Line Mechanic reported he forgot to reattach an electrical connector to the Leading Edge Standby Drive Shut-off Valve after completing the # 2 Engine Bleed System Health Check to clear a deferred item. Flight crew was unable to lower their Leading Edge Devices.
Narrative
In order to safely comply with a Bleed System Health Check on the Number 2 engine of a B737-800 aircraft; I locked out the Leading Edge Devices in accordance with B737 Aircraft Maintenance Manual (AMM) 27-81-00. One step in the Deactivation of the leading edge devices is to remove the electrical connector from the Leading Edge Standby Drive Shutoff Valve. I had not performed a Bleed System Health Check on a B737-800 before. Since the accomplishment of this Check was required per our deferral program; Quality Control (Q/C) was required to observe its accomplishment. One other Technician was working the Bleed System Health Check with me; however he too had never accomplished this Task [Jobcard] before. After the completion of the Bleed System Health Check; I restored the aircraft to normal by reactivating the leading edge devices but unfortunately; I failed to reconnect the electrical connector to the Leading Edge Standby Drive Shutoff Valve. The next day when the flight crew tried to lower their leading edge devices they failed to deploy. This caused the aircraft to return to the gate where Maintenance discovered the disconnected electrical connector.In order to have better documentation for the tracking of Deactivating and Reactivating the leading edge devices on aircraft; I have submitted a company documentation feedback requesting that the Leading Edge Deactivation and Reactivation Jobcards be attached to all engine bleed system health check cards for all fleets in the future. This will give technicians more visibility of the deactivation and reactivation of the leading edge devices and is more user friendly than referencing all of the sources in the Maintenance Manual (M/M) to complete the task.The Jobcard for Leading Edge Deactivation should have been included in the package since the Task of engine bleed system health check requires opening the Thrust Reverser [cowls]. Using the Maintenance Manual (M/M) alone for leading edge deactivation is confusion and time consuming. It also does not give the Task specific visibility of the jobcard.Because I communicated with my Lead; that neither myself nor the other Technician working with me had accomplished this task before; he sent several other technicians over to my aircraft to monitor my progress and this was distracting.
NASA callback
Reporter stated the Corrective Action to clear the engine bleed deferral was to perform an Engine Bleed System Health Check; which also required that an Inspector verify the results. If the Number 2 engine passed the Health Check; they could sign-off the engine deferral. Only one item at the beginning of the Engine Health Check Card made reference to opening the Thrust Reversers using the Maintenance Manual (M/M).Reporter stated he was part of his company's internal audit of what contributed to the Leading Edge Standby Drive Shut-off Valve electrical connector not being reattached after completion of the Bleed Health Check card and Thrust Reverser cowl close-up. Working with their Engineering and Jobcard Writers; they developed a condensed four-page Jobcard for the opening and closing of Thrust Reverser cowls. When that Jobcard is issued; their Maintenance program will also issue and include the Leading Edge Deactivation and Reactivation Jobcards.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.