Narrative:

Aircraft returned to gate with the right engine anti-ice valve inoperative; with a history. Performed deferral procedures per MEL (minimum equipment list) 30-00-xx. MEL requires valve to be locked open and pressure switch connector removed. I inadvertently removed the tai (thermal anti-ice) valve connector instead of the pressure switch connector when I misinterpreted the figure in the MEL procedure. Partly due to a distraction from rain and hearing radio communication that a light extinguished when the connector was removed. Adding to the distraction and pressure to return the aircraft to service; was the requirement under this MEL 30-00-xx that an MEL and lockout of the engine hp (high pressure) valve is necessary per MEL 36-00-xy. While performing the hp MEL; the lockout collar was stuck and took added time to resolve. The aircraft was then dispatched after maintenance was complete. After takeoff; the crew reported the right engine tai over pressure indicator illuminated due to the pressure switch still connected. Flight dispatch requested the aircraft divert to ZZZ to have the situation inspected by maintenance. The proper MEL procedure was performed and corrected the mistake. The flight continued to ZZZ1. The MEL has this switch deactivated so as to not experience a nuisance light indicting an over pressure indication which is going to happen since the valve is locked open per the MEL. Having the valve connector off removed the valve position and control signal but also since the valve is locked open this did not pose an issue. I regret not taking the extra time to review the MEL to be sure I understood the procedure. Also taking extra time to discuss the situation with a colleague so we both agree with the MEL procedures. I would like to note that the MEL figure showing the anti-ice valve and pressure switch did not have a marker for the connector with a label number or reference.

Related reports:

Google
 

Original NASA ASRS Text

Title: Maintenance Technician performed incorrect Minimum Equipment List deferral procedure.

Narrative: Aircraft returned to gate with the right engine anti-ice valve INOP; with a history. Performed deferral procedures per MEL (Minimum Equipment List) 30-00-XX. MEL requires valve to be locked open and pressure switch connector removed. I inadvertently removed the TAI (Thermal Anti-Ice) valve connector instead of the pressure switch connector when I misinterpreted the figure in the MEL procedure. Partly due to a distraction from rain and hearing radio communication that a light extinguished when the connector was removed. Adding to the distraction and pressure to return the aircraft to service; was the requirement under this MEL 30-00-XX that an MEL and lockout of the engine HP (High Pressure) valve is necessary per MEL 36-00-XY. While performing the HP MEL; the lockout collar was stuck and took added time to resolve. The aircraft was then dispatched after maintenance was complete. After takeoff; the crew reported the right engine TAI over pressure indicator illuminated due to the pressure switch still connected. Flight Dispatch requested the aircraft divert to ZZZ to have the situation inspected by Maintenance. The proper MEL procedure was performed and corrected the mistake. The flight continued to ZZZ1. The MEL has this switch deactivated so as to not experience a nuisance light indicting an over pressure indication which is going to happen since the valve is locked open per the MEL. Having the valve connector off removed the valve position and control signal but also since the valve is locked open this did not pose an issue. I regret not taking the extra time to review the MEL to be sure I understood the procedure. Also taking extra time to discuss the situation with a colleague so we both agree with the MEL procedures. I would like to note that the MEL figure showing the anti-ice valve and pressure switch did not have a marker for the connector with a label number or reference.

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.