MD-11
Flight Crew Air Transport Pilot (ATP)
Troubleshooting; Workload
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action
Aircraft
During climbout after a standard power takeoff; at or about 6;000 FT; I noticed Number 3 engine EVM Comp amber box; with a value of 5.0. All other engine parameters were normal. The Captain moved the throttle to idle; and the EVM value went back to normal. We also noticed that a low 'background' vibration went away as the throttle was retarded. The Captain then advanced the throttle slowly; noting that the vibration started to return around 40% N1; and the EVM value started to climb at the same time. At 60% N1; the EVM value rose above 4.0 and the amber box returned. He then retarded the throttle back to idle and left it there. Meanwhile; I had looked at the QRH procedure for EVM high; noting that all other engine indications were normal. After consulting with Maintenance; we decided that as long as all other indications remained normal; we would leave the engine running at idle. We were advised by ATC to expect a visual approach. Weather was VFR; with no conflicting traffic in the terminal area; so we anticipated no undue delays in our approach. After landing; the Captain shut down Number 3 engine; and we continued to the ramp.
A MD-11 number three engine vibration indicated 5.0 with an Amber Box after takeoff so following trouble shooting the crew returned to the departure airport for maintenance with the engine at idle.