A Contract Repair Station Lead Mechanic reports an EMB-145 flight crew declared an emergency and returned to field because flaps could not be raised after take off. EICAS 'Flaps Failed' message had appeared. Aircraft had just been released with a Flaps Electronic Control Unit (FECU) MEL deferral after a previous return to the gate.

Narrative

Aircraft returned to gate due to 'flaps half speed' message on EICAS. I and four other people met the plane to isolate and defer the problem. We had a copy of the MEL procedure in hand. As me and a co-worker were in the cockpit isolating which flap channel had failed; the other people were under the plane removing the Flaps Electronic Control Unit (FECU) panel; once the faulty channel was Maintenance Controlled for an MEL Authorization number. The person that was in the cockpit with me exited the cockpit to instruct the people under the plane which Cannon plug to disconnect from the Flap Electronic Control Unit [for the MEL deferral]. I completed and signed-off the logbook entry when I learned that the Cannon plug was disconnected and insulated per the MEL. I placed the MEL sticker in their respective places; briefed the crew and exited the aircraft. When I met my co-workers on the jet bridge I was told the FECU panel had been reinstalled and the plane was good. We left the plane and went back to our shop. After about 10 or 15-minutes had passed; I was informed that the plane was returning to field and declared an emergency due to flaps stuck at nine-degrees. The plane landed without incident and we; once again; met the aircraft at the gate. Upon the planes arrival and after the passengers de-planed; I checked all circuit breakers and found everything to be in order. I noticed the 'Flaps Fail' message on EICAS. After the FECU panel was removed it was discovered that the person that disconnected the cannon plug had disconnected the cannon plug from the right-hand (R/H) Flap Drive Unit (FDU) instead of the P1102 (J2) plug from the Flap Electronic Control Unit. We then reconnected the flap drive Unit [connector] and disconnected and insulated the correct plug from the FECU. The FECU panel was reinstalled. I and two others were then taken off the ramp to report to Supervision and for drug testing. I do not know who signed-off the Logbook the second time; or who was on the aircraft after that. I believe that there were a few factors that caused this event: 1) The person that physically disconnected the flap drive unit cannon plug was not familiar with the aircraft and said he 'disconnected the plug that someone else pointed at'. He does not recall who 'pointed' at the plug. 2) Noise outside the aircraft; due to the aircraft's APU and air conditioning packs running. 3) Pressure from getting the aircraft back out; since it was a return to the gate and had passengers on board. 4) I should have inspected the work before signing-off the logbook; which I believe is the biggest contributing factor.