A Maintenance Supervisor and two Mechanics report about trouble shooting the cause of a B757-200 aborting take off. The #1 engine throttle would only advance halfway. Maintenance Supervisor had failed to give a Maintenance Manual reference for the work that was performed. Second abort occurred later.

Narrative

Mar/XA/09 I was informed by company operations that Aircraft X was returning to the gate for an aborted takeoff attempt. Once I had heard that; I then contacted the Lead Mechanic for the area to let him know what was going on. He had said that he already was informed by the aircraft Controller at headquarters. The Lead then went on to say that the Controller had told him that the aircraft had been out of service at the hangar for the past day due to work on the #1 and #2 engine thrust reversers and had asked the Lead to look for any rig pins that might have been left in the aircraft. By the time I had gotten to the aircraft; there were 3 Mechanics inspecting the aircraft. 1 mechanic was in the flight deck; 1 mechanic was in the forward E&E compartment looking at the throttle quadrant; and the third mechanic had the #1 engine cowling open inspecting the reverser drive actuators. While on scene; I was told by the First Officer that the reason for the aborted takeoff was due to the #1 engine throttle would only advance 1/2 way then hit against a mechanical stop. He also said that they had difficulty deploying the #1 thrust reverser. I had asked him if there were any associated fault messages or lights and the First Officer claimed that there were none. The mechanic in the flight deck had activated the EECs for the aircraft which power the thrust reversers and was able to successfully deploy them with no issues. The Mechanic inspecting the engines found no obvious defects. The Mechanic in the forward E&E bay had found that the #1 engine interlock actuator had extended and the stops were what was preventing the throttle from moving. While myself and the mechanics were discussing what could have caused this issue; one of the mechanics had gone into the flight deck and reset the EEC circuit breakers based on the information provided in the description and operation section of the Aircraft Maintenance Manual for the thrust reverser interlock. Once that was done he heard a click come from the center pedestal. At that point; the #1 engine throttle stops had been released and there was full throttle movement on the #1 engine. At that point; I then asked the Lead Mechanic to operate the engine and the thrust reversers to see if the issue would return again. He operated the engines and thrust reversers and the issue did not return although there was still concern over what had caused the interlock to extend in the first place; we could not duplicate any of the issues. I had signed off the item along with the Lead Mechanic that operated the systems. The purpose for this report is to disclose that I had failed to give a Maintenance Manual reference for the work that was performed in order to support troubleshooting direction as I may be potentially investigated by a member of the FAA for failure to document my references. I was under the impression that the Mechanics and I had followed information given in Aircraft Maintenance Manual 76-11-00 and in Aircraft Maintenance Manual 78-34-00 in regards to the EEC giving commands to the interlock regarding thrust reverser position. The next manuals to follow were Aircraft Maintenance Manual 78-34-00 and Aircraft Maintenance Manual 76-11-00; however; due to the release of the interlock and proper engine and thrust reverser operation we did not continue with the troubleshooting; as I felt that we had a confirmed fix as we could not reproduce the problem. Later that day; the aircraft had flown 3 flights before the issue had resurfaced again in ZZZ2 where they replaced the #1 engine interlock actuator. I would like to state that I do not believe the rejected takeoff was attributed to anything that I had signed for. After speaking to the hangar manager; the aircraft had been towed from the hangar to the gate. At no point in any of the Aircraft Maintenance Manual references given for the thrust reverser work or on the relocation of the aft from the hangar to the terminal; did I see that the engines had been operated. The Aircraft Maintenance Manual doesn't require an engine run to verify operation; however; seeing as there were different shifts and several other mechanics working on the aircraft; this leads me to believe that the aircraft interlock system was tripped while maintenance was being performed at the hangar. My role in the rejected takeoff was purely reactionary to the root cause of the rejection. Supplemental information from ACN 828018: We attempted to determine what exactly the hangar had done to the reverser that may have affected the throttle. We cycled the reverser several times; and found the throttle interlock actuator was extended. We cycled #1 engine EEC circuit breakers. The throttle interlock actuator retracted. We were then able to advance the throttle. The engines were both run; and the reversers were cycled. We were unable to duplicate the fault or determine what caused the malfunction. Because there were no other faults or history of faults; I was not comfortable with letting the aircraft go without determining the cause but because we no longer had a fault; we had no procedures to follow. So; the Area Foreman signed the log off and returned the aircraft to service. Supplemental information from ACN 828017: The #1 throttle interlock actuator was blocking the movement. After pulling the circuit breakers for the #1 EEC; the interlock actuator was able to be moved and allowed full throttle movement. Callback conversation with Reporter revealed the following information: Reporter stated the #1 engine Thrust Lever Interlock Actuator was replaced after the second abort and later found to have an internal fault. The Actuator would cause intermittent failures and not always retract the mechanical lock; unless the circuit breakers for that specific engine EEC were reset.