Narrative:

March 2012; I was assigned to pick up a B777-200 aircraft at a terminal gate. I was at the gate when aircraft arrived and helped park it. After aircraft was chocked; the # 1 engine continued running for about four minutes. I was going to connect a headset to the aircraft to find out why; [when] just at that moment I heard and saw # 1 engine spool down. Did walk around on aircraft and noticed smoke coming from # 1 engine for about three or four minutes. Went up to cockpit to get ready for taxi off gate and saw pilot; he made no comment to me about the aircraft. Looked at the flight displays and noticed message: left engine fuel valve. Checked chapter-31 in maintenance page and saw it was an erasable message. We see this message often after maintenance has been done; or when somebody moves the 'cutoff' switch [fuel control switch] out of sequence. We were delayed on gate for about one hour. After pushback; we had two normal starts; nothing unusual noted. Taxied aircraft to large hangar inbound a-check. Left seat; moved 'cutoff' switch to 'off' and engine did not respond. Moved cutoff lever [switch] back to 'on' [run] and then back to 'off'; engine still did not respond; removed fuel pump pressure and proceeded to lift fire handle to force pylon fuel shutoff valve to close. Engine continued to run for approximately 30-seconds. Conferred with taxi partner to interrogate [B777] maintenance access terminal (mat) to see if there is a fault. Fault message was present and printed copy to give to swing shift lead and supervisor; which was 15-minutes after our shift had ended. Made an electronic maintenance write up and notified swing shift lead and supervisor. Went home.next day; was assigned fuel control unit (FCU) [fuel metering unit (fmu)] change on same aircraft. Checked maintenance computer to see what had been done to aircraft since my [shift] turnover from previous day. There was an engineering order to test fuel metering unit (fmu) and then run engine. The test portion had been completed and all that was left was to run engine # 1 two times; to see if engine would repeat the previous day's results; or if it would operate normally. But decision was made to replace FCU. Fuel control unit [fuel metering unit (fmu)] was replaced and aircraft was pushed out for test and leak check and dry motor [operations]. Knowing that there was a possibility of extra fuel being left over in engine because of aborted shutdowns and possible checks being done on the off-shifts; care was taken to dry motor engine longer than normal. I and other mechanics have had experiences with B777 engines after heavy maintenance that have had booming starts with flames shooting out the tail pipe before. Even dry motoring the affected engine for longer than five minutes does not help; the booming and flaming starts. I motored engine to 25% N2; or max motor; engine was ready to light-off. Upon moving 'cutoff' switch to 'run'; immediately heard a loud boom; looked out of cockpit window which was open and saw a large fire cloud. Ground mechanic immediately responded and yelled 'fire' into headset. I had a millisecond to respond and knowing that this engine has had some problems shutting down I instantly moved 'cutoff' [switch] to 'off' and continued motoring engine [with starter]. Again looked out cockpit window and saw flame was gone but still had large amount of smoke; continued with motoring until ground mechanic had cleared me for shutdown. Twenty minutes later; restarted same engine with normal start and one hour later started two more times and engine started normally. ETOPS aircraft.

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Original NASA ASRS Text

Title: A Line Mechanic reported his concerns regarding B777 aircraft engines experiencing booming fireball; hot engine starts with flames shooting out the tailpipe.

Narrative: March 2012; I was assigned to pick up a B777-200 aircraft at a Terminal Gate. I was at the gate when aircraft arrived and helped park it. After aircraft was chocked; the # 1 Engine continued running for about four minutes. I was going to connect a headset to the aircraft to find out why; [when] just at that moment I heard and saw # 1 Engine spool down. Did walk around on aircraft and noticed smoke coming from # 1 Engine for about three or four minutes. Went up to cockpit to get ready for taxi off gate and saw Pilot; he made no comment to me about the aircraft. Looked at the Flight Displays and noticed message: Left Engine Fuel Valve. Checked Chapter-31 in Maintenance Page and saw it was an erasable message. We see this message often after maintenance has been done; or when somebody moves the 'Cutoff' switch [Fuel Control Switch] out of sequence. We were delayed on gate for about one hour. After pushback; we had two normal starts; nothing unusual noted. Taxied aircraft to large hangar inbound A-Check. Left seat; moved 'Cutoff' switch to 'OFF' and engine did not respond. Moved Cutoff lever [switch] back to 'ON' [Run] and then back to 'Off'; engine still did not respond; removed fuel pump pressure and proceeded to lift Fire handle to force pylon fuel shutoff valve to close. Engine continued to run for approximately 30-seconds. Conferred with taxi partner to interrogate [B777] Maintenance Access Terminal (MAT) to see if there is a fault. Fault message was present and printed copy to give to Swing Shift Lead and Supervisor; which was 15-minutes after our shift had ended. Made an electronic maintenance write up and notified Swing Shift Lead and Supervisor. Went home.Next day; was assigned Fuel Control Unit (FCU) [Fuel Metering Unit (FMU)] change on same aircraft. Checked Maintenance computer to see what had been done to aircraft since my [Shift] turnover from previous day. There was an Engineering Order to test Fuel Metering Unit (FMU) and then run engine. The Test portion had been completed and all that was left was to run Engine # 1 two times; to see if engine would repeat the previous day's results; or if it would operate normally. But decision was made to replace FCU. Fuel Control Unit [Fuel Metering Unit (FMU)] was replaced and aircraft was pushed out for test and leak check and dry motor [operations]. Knowing that there was a possibility of extra fuel being left over in engine because of aborted shutdowns and possible checks being done on the off-shifts; care was taken to dry motor engine longer than normal. I and other mechanics have had experiences with B777 engines after heavy maintenance that have had booming starts with flames shooting out the tail pipe before. Even dry motoring the affected engine for longer than five minutes does not help; the booming and flaming starts. I motored engine to 25% N2; or Max Motor; engine was ready to light-off. Upon moving 'Cutoff' switch to 'Run'; immediately heard a loud boom; looked out of cockpit window which was open and saw a large fire cloud. Ground Mechanic immediately responded and yelled 'Fire' into headset. I had a millisecond to respond and knowing that this engine has had some problems shutting down I instantly moved 'Cutoff' [switch] to 'Off' and continued motoring engine [with Starter]. Again looked out cockpit window and saw flame was gone but still had large amount of smoke; continued with motoring until Ground Mechanic had cleared me for Shutdown. Twenty minutes later; restarted same engine with normal start and one hour later started two more times and engine started normally. ETOPS aircraft.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.