How Jet Engine Works | Part 1 : Starting – YouTube Dictation Transcript & Vocabulary

1.the GE90   is the world's most powerful commercial jet engine in service the Boeing 777 the best-selling  wide-body aircraft of all time the combination of the engine and the airframe is nothing short of an engineering marvel in this comprehensive 777 engine series we will build up the engine from scratch and understand how all the components  function as we start and operate it the engine has two rotor shafts high  pressure shaft and the low pressure shaft a stator and a rotor combine to form  a single stage the N2 shaft has nine such stages of high pressure compressors and two stages of high pressure turbine the N1 shaft has six stages  of low pressure turbine four stages of low pressure compressors and ahead of them is the massive fan before we look at more engine components let's  do the aircraft configuration for engine start first the battery switch battery provides limited  power good enough to start the APU a small engine in the empennage of the aircraft rotate the  APU start switch hold for a second and release the APU is online now we can use the APU generator selecting the generator switch establishes  full electrical power of the aircraft during engine start electrical panels  will provide power to the electronic engine control installed on the engine fan case APU will also provide the  pneumatic power to start the engine   make sure the bleed switch is in auto position next the fuel panel selections we only  require fuel from the left main tank so select the two left tank pump switches two boost pumps inside the  fuel tank transfer fuel to the engine spar valve in the wing aft spar section aircraft configuration is complete let's attempt an engine start on the engine the pneumatic  pressure reaches the start valve 777 has an auto start feature when used the EEC  takes over the entire engine start operation now turn the engine start switch to start position EEC gets the start signal and power to operate EEC commands the start valve to open the  pneumatic pressure reaches the air starter the air starter drives the accessories gearbox several torque requiring components are mounted on the gearbox one of them is the horizontal  drive shaft that connects to the transfer gearbox the transfer gearbox changes the axis of rotation and with the help of a radial drive shaft rotates the N2 shaft as N2 rises airflow is established  through the core of the engine due to the airflow N1 shaft has positive rotation fan rotation in  turn leads to bypass airflow through the engine at 7 percent N2 a small alternator  installed on the gearbox supplies power to the EEC and the airplane power  supply goes into standby mode since we are doing an auto start we  can use the fuel control switch and need not wait for the engine to reach  21 percent N2 which is the case in manual start let's select the fuel control switch to run and see how the fuel travels within the engine the fuel control switch opens the spar valve and the fuel rushes to the main fuel pump the pump driven by the gearbox increases the  fuel pressure and transfers it to the fuel oil heat exchanger where fuel picks up heat and  cools down the engine oil from the heat exchanger fuel travels to the fuel filter filter screens the  fuel for debris and transfers it back to the pump from here the fuel is sent to the hydro  mechanical unit the HMU now controls the fuel to the engine for combustion and any excess  fuel is bypassed back to the pump HMU waits for the EEC command to open the fuel shut-off  valve and EEC waits for N2 to reach 21 percent as N2 reaches 21 percent rpm EEC sets  up the engine for combustion out of two ignition exciters EEC commands  one to activate keeping the other as backup the ignition exciter converts  the input power to high voltage pulse and transfers it to the igniter plug three seconds after ignition activation EEC  commands the HMU to open the fuel shutoff valve before heading to the combustion  chamber fuel travels through the fuel flow transmitter and back into the HMU fuel  flow transmitter sends signal to the EEC to determine engine fuel consumption which is  crucial for engine performance monitoring fuel is now sent for combustion through two  manifolds to which are connected 30 fuel nozzles each fuel nozzle has two sprayer tip and each tip goes into the swirler slots in the combustion chamber the swirlers  diffuse the core airflow slowing them down ensuring proper fuel air mixture and  buying enough time for efficient combustion combustion gas forces directly affect the turbines since they are mounted on the same shaft increase in high pressure turbine rotation drives the  high pressure compressor at a faster rate likewise increase in low pressure turbine rotation drives the low pressure compressor and the fan as a result the rate of airflow through the engine  increases leading to steady increase in thrust temperatures inside the combustion  chamber is adequate for sustained combustion therefore at 56 percent N2 the  EEC deactivates the ignition system at about 64 percent N2 the EEC commands the start  valve to close and the pneumatic pressure to the starter is cut out disengaging  the air starter from the gearbox rotation as the engine reaches and stabilizes at  the idle power EEC sends a signal to the airplane systems that the engine  start procedure is now complete this allows the airplane systems to  de-energize the start switch latching solenoid so that it could return to normal position ready for next start attempt when required join us in the next part of the 777 engine series as we continue to put the engine through its paces thanks for watching