A line technician reports that an airbus aircraft returned to gate after he had replaced hi-speed fa...

Narrative:

An airbus aircraft had vent blower extract fan circuit breaker popped. Circuit breaker that was popping was for hi-speed fan; troubleshot to fan blower. So we had one and removed and replaced (right/right) fan blower. Performed operational check and got all indications in cockpit which are flow bars that switch from inboard to overboard when you pull circuit breaker for flight/ground; which tells you which fan is working; hi or low speed. Since I got the flow bars I assumed both [fans] were working and I was done. Had I waited at least two minutes between checking the hi and low speed fan I would have got the warning. It takes a few minutes to get the warning. Maintenance manual tells you the fan will go to low-speed; but hard to hear in the cockpit so you look for flow bars. What happened is that I assumed that both fans were working because [of] the indications and I did not reversed the MEL process [procedure] and double check myself. We decided in our shop that a second person will check the reversal of the MEL. Avionics cooling. Gate turnback.

Original NASA ASRS Text

Title: A Line Technician reports that an Airbus aircraft returned to gate after he had replaced hi-speed fan blower for popping the vent blower extract fan circuit breaker. The vent blower fan had been on MEL deferral.

Narrative: An Airbus aircraft had Vent Blower Extract Fan Circuit Breaker popped. Circuit breaker that was popping was for Hi-Speed Fan; troubleshot to Fan Blower. So we had one and Removed and Replaced (R/R) Fan Blower. Performed Operational Check and got all indications in cockpit which are Flow Bars that switch from inboard to overboard when you pull circuit breaker for Flight/Ground; which tells you which fan is working; Hi or Low speed. Since I got the flow bars I assumed both [fans] were working and I was done. Had I waited at least two minutes between checking the Hi and Low Speed Fan I would have got the warning. It takes a few minutes to get the warning. Maintenance Manual tells you the fan will go to Low-speed; but hard to hear in the cockpit so you look for flow bars. What happened is that I assumed that both fans were working because [of] the indications and I did not reversed the MEL process [procedure] and double check myself. We decided in our Shop that a second person will check the reversal of the MEL. Avionics cooling. Gate turnback.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1009701
Time
Date	201205
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	Airbus Industrie Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Air Conditioning Distribution System
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant Maintenance Avionics
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy

A line technician reports that an airbus aircraft returned to gate after he had replaced hi-speed fan blower for popping the vent blower extract fan circuit breaker. The vent blower fan had been on MEL deferral.