B757-200
Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft
Our normal climb was stopped at 17;000 due to traffic. Upon clearance to climb; the Captain advanced power and selected VNAV. The autopilot responded so slowly that VMO was quickly reached and an overspeed warning sounded. Climbing through about FL260 the Captain brought to my attention the right engine EGT; which was in the caution band and climbing. He reduced power to get the EGT out of the caution range. At the reduced setting the EGT again climbed into the caution band. Further reductions were made until the right N1 was 15- 20% below the left engine to keep EGT in limits. No other abnormal indications were noted. We then noticed the speed decaying and the Captain initially made inputs on the MCP to correct the problem; but the autopilot did not respond. The Captain then disconnected the autopilot and recovered manually. Minimum speed reached was about 185 KIAS. After a brief discussion of the situation the Captain and I agreed we should divert back to our departure airport. The Captain took over ATC communication while I coordinated with dispatch and sent an ACARS diversion message. We declared an emergency with ATC and were cleared direct to the airport. The right engine EGT remained significantly higher than the left for the remainder of the flight but otherwise operated normally until touchdown. After touchdown the right reverser would not deploy.
When the EGT of the right engine of their B757-200 moved into the caution range during climb and required excessive thrust reduction to reduce EGT to the green band the flight crew elected to declare and emergency and return to their departure airport. They chose not to shut down the engine while doing so.