Narrative:

Working at the terminal in training status as assigned by ZZZ training coordinator. It was brought to my attention that aircraft XXXX on landing at ZZZ1 flight XXXX had no thrust reverser operation on #1 engine. The previous evening I worked log page xxxxxxx air engine 1 hp valve fault. I was assigned to pick up this job already in progress and started by afternoon shift on gate C20. My direction issued by my lead was that this job was previously in progress to MEL for a live flight but midnight shift was given a turnover to replace the hp and prv valves troubleshot by afternoon shift; and the aircraft flight was changed to ron status.when we arrived at gate C20 #1 engine was open and the lh T/right was open. The move crew was already at gate C20 prepping to move the aircraft to C26. There was some discussion in planning the logistics for the job and why it was necessary to move the airplane to a different gate while the job was already started and the engine was open. As a result; the engine had to be closed to move the aircraft. As the job progressed; we reopened the engine; replaced the hp and prv valves; completed operations checks and closed engine for run.it was discovered in ZZZ1 that the hcu for #1 engine was deactivated with a lockout pin. While I worked the aircraft I was unaware the hcu was locked out and I did not install the lockout pin in the hcu. No streamer associated with this lockout pin was visibly noted that is typically attached to the hcu lockout pin. And it should be noted that if the correct streamer associated with the lockout was used; it would have been easily discovered due to a very long length streamer. We locked out the entire aircraft in a powered down state; with flip chart placed in center pedestal noting do not flip any switch.an update to log page xxxxxxx stating locked out #1 engine T/right hdc for maintenance on hp valve was determined to only be the lockout for the hp valve as defined in the MEL 36-xx-X-X. It appears the shipset lockout pin was used to deactivate the hcu and was not removed upon job completion due to the confusion on job turnover from shift to shift; repositioning the airplane to a different gate; failure of no verbal turnover from the afternoon shift to midnight shift mechanics; and the impact of working in inclement weather.a separate log for each device locked out. The ship set lockout pin be replaced and maintained with a long enough steamer so it cannot be missed.

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Original NASA ASRS Text

Title: Technician reported that the #1 engine HCU was locked out by the previous shift and was not documented; subsequently the aircraft flew with the lockout pin still in place.

Narrative: Working at the terminal in training status as assigned by ZZZ training coordinator. It was brought to my attention that aircraft XXXX on landing at ZZZ1 flight XXXX had no thrust reverser operation on #1 engine. The previous evening I worked log page XXXXXXX air engine 1 hp valve fault. I was assigned to pick up this job already in progress and started by afternoon shift on gate C20. My direction issued by my lead was that this job was previously in progress to MEL for a live flight but midnight shift was given a turnover to replace the HP and PRV valves troubleshot by afternoon shift; and the aircraft flight was changed to RON status.When we arrived at gate C20 #1 Engine was open and the LH T/R was open. The move crew was already at gate C20 prepping to move the aircraft to C26. There was some discussion in planning the logistics for the job and why it was necessary to move the airplane to a different gate while the job was already started and the engine was open. As a result; the engine had to be closed to move the aircraft. As the job progressed; we reopened the engine; replaced the HP and PRV valves; completed operations checks and closed engine for run.It was discovered in ZZZ1 that the HCU for #1 engine was deactivated with a lockout pin. While I worked the aircraft I was unaware the HCU was locked out and I did not install the lockout pin in the HCU. No streamer associated with this lockout pin was visibly noted that is typically attached to the HCU lockout pin. And it should be noted that if the correct streamer associated with the lockout was used; it would have been easily discovered due to a very long length streamer. We locked out the entire aircraft in a powered down state; with flip chart placed in center pedestal noting do not flip any switch.An update to log page XXXXXXX stating locked out #1 engine T/R HDC for maintenance on HP valve was determined to only be the lockout for the HP valve as defined in the MEL 36-XX-X-X. It appears the shipset lockout pin was used to deactivate the HCU and was not removed upon job completion due to the confusion on job turnover from shift to shift; repositioning the airplane to a different gate; failure of no verbal turnover from the afternoon shift to midnight shift mechanics; and the impact of working in inclement weather.A separate log for each device locked out. The ship set lockout pin be replaced and maintained with a long enough steamer so it cannot be missed.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.