B767 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 140; Flight Crew Total 7800; Flight Crew Type 200
Troubleshooting
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Aircraft
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport
Aircraft
The flight crew received our flight release indicating the MEL for the RH EEC. When the crew arrived on the aircraft maintenance was already on and working numerous issues on the aircraft. The flight crew was informed that a bite test showed no errors with the EEC and and at the time it was operating normally. It was believed a ground air start error was what caused the EEC to trip off. The MEL was signed off and the release amended to show its removal. A ground air start was conducted at the gate with no issues; and the aircraft was pushed back. After a cross bleed start and concurrent with the tug disconnecting the RH EEC tripped offline. The crew ran the appropriate EEC QRH checklist directing both EECs to be selected off. Since we had previously reviewed the MEL we elected to continue. During the takeoff it was noted that the auto throttles were not responding and takeoff thrust was set manually. During climb and initial cruise it was noted by both crew members that the left engine EGT was fluctuating 30-50 degrees but stabilized with cruise power set. After approximately an hour of cruise at FL390 and 0.78 Mach the aircraft passed a front causing the airspeed to increase above the assigned speed. Power was gradually reduced to allow the speed to decrease to the assigned value. As the power was increased back to maintain Mach speed it was noted that the left engine was stuck at flight idle and was not responding to thrust lever movements. The thrust lever was positioned to the firewall with no response. As the airspeed was deteriorating rapidly the aircraft offset from the airway and began a descent while a revised clearance was received from New York via HF to return to JFK. ATC issued a revised clearance to JFK and approved the initial descent to FL360. At approximately FL370 the engine again began responding to thrust lever movement. Further descent was not considered necessary at this point and we continued to JFK since we couldn't guarantee that the engine would not stop responding again. After getting the aircraft stabilized; [we] notified via phone patch and the flight attendants and passengers were briefed on the situation and decision to return to JFK. No emergency was declared nor any emergency services requested. The flight continued normally to JFK and accomplished a normal approach and landing to runway 31R with no further incidents. Upon shutdown the crew briefed on site maintenance along with [Operations and Maintenance Control]. The issues were also written up in the log book.
B767 First Officer reported electronic engine control and throttle malfunction resulted in a return to departure airport.