B777-200
Maintenance Airframe; Maintenance Powerplant
Maintenance Technician 38
Communication Breakdown; Situational Awareness; Troubleshooting
Aircraft Equipment Problem Critical; Ground Event / Encounter Other / Unknown
Aircraft Aircraft Damaged; General Flight Cancelled / Delayed; General Maintenance Action
Manuals; Procedure; Human Factors; Chart Or Publication; Aircraft
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.
Reporter stated he has been working on the B777 aircraft since the mid 1990's and Line Maintenance for 38-years. He has been involved with over 100 B777 engine changes and has never had an engine fireball /tailpipe fire occur during engine runs after their engine changes.  He has experienced five such booming fireball; tailpipe fires; three while in the left seat and two while on the ground with a communication headset on. Each of those incidences were after heavy maintenance had been accomplished on the engine.  By that he means; whenever engine fuel lines; a fuel pump or a Fuel Control Unit (FCU); also known as Fuel Metering Unit (FMU); had been replaced. The FCU had been replaced on the Off-shift before he returned the next day. Reporter stated during the initial Dry Motor run no fuel mist (fog) was noted; but as soon as he moved the 'Cutoff' switch to 'RUN'; a booming fire shot a flame over 40-feet long out of the PW-4000 engine tailpipe; splattering excess unburned fuel on the engine aft pylon and lower wing that caught fire.  Numerous composite panels and the left Flaperon had to be replaced due to serious damage from the fire and heat. Sometimes; during Engine Runs; the Engine Fire handle has to be used to stop the fuel flow because the 'Cutoff' switches on the cockpit control stand do not always shut-off the fuel flow.Reporter stated that after weeks of no one responding to his concerns and because he felt there was some malfunction occurring on the B777s; company Engineering asked him to help them pull pages of data from the Maintenance Access Terminal (MAT) in the B777 cockpit where the Second Officer's position would be on other fleets.  The information from the MAT indicated the # 1 engine had the equivalent of 32;000 # lbs of fuel per hour (Full Throttle Takeoff Power) being pumped into the engine; or 6-7 gallons of fuel per second; when he moved the Fuel Control Switch from 'Cutoff' to the 'Run' position. The fireball was immediate. Normally the engine takes 25-30-seconds to reach Idle speed.Reporter stated Engineering noted that the Engine Manufacturer had a problem with the software in the EEC that controls the fuel demand placed on the FCU and also had a problem with incorrect Fuel Control Unit assembly build-up. The 'Cutoff' switches and micro-switches are also a concern.  When they Dry Motor the engine for a length of time; the EEC software seems to believe fuel should be flowing and keeps telling the FCU to increase the fuel supply; which results in excess fuel at engine start. There is also a concern that some Maintenance procedures are being accomplished out of sequence; where Maintenance static test procedures are occurring with fuel pumps on; allowing for fuel to be dumped into the engine; or air gets trapped in fuel lines when engine fuel systems are disturbed. Reporter also stated there is a lot of training for Engine Tailpipe fires; but mechanics have to be reminded that on the B777; the fuel supply must be Shut-off; that continuing to run the engine; to burn-out the fuel is not the correct procedure.
Pushed a B777-200 airplane outside for engine run. Motored engine for five minutes or so; told cockpit [Mechanic] clear for engine start.  Immediately noticed ball of fire and smoke.  Relayed message to cockpit via headset.  Cockpit responded and kept motoring engine till flame and smoke had cleared.
A Line Mechanic reported his concerns regarding B777 aircraft engines experiencing booming fireball; hot engine starts with flames shooting out the tailpipe.