Understanding How an Aircraft's Jet Engine Starts! A look at the Start Sequence of a Turbofan Engine
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- Опубліковано 29 чер 2020
- Hello. In this video we consider a turbofan engine on a commercial aircraft. These engines are started through a set of switches in the cockpit. The start sequence of the engine, gets initiated when the air from a high pressure air source enters the starter unit in the accessory gear box.
In this video we see and understand what is start sequence by looking at the different components on the engine and how each component contributes to the engine start.
hope you enjoy. thank you.
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One important correction, N1 rotation begins before fuel is introduced. When the N2 shaft is spun by the starter, it will suck air through the engine, which will turn the N1 shaft at a low speed. This rotation must be confirmed before fuel is introduced, as lack of N1 rotation could indicate a seized engine.
Thank you for the information!
@@JxJAVIATION Thank you for jet engine start steps.
thank you very much
Thank you, I have always wondered about that. Thanks for explaining.
Good explanation, I was wondering how N1 starts, now I know...
I’m an A+P who no longer works in the industry so I really appreciated that you did not call this a jet engine but a turbo fan. Most high bypass engines have a twisted arrow on the inlet so the crew can verify the correct rotation before initiating ignition and fuel. Thanks again!
You are Welcome! Check out my other videos as well!
I am confused. This isnt a jet engine?
@@majestikstyle It’s not a true jet engine It’s a turbine which uses a series of compressor blades mounted on wheels in the convergent duct thus compressing the air. After which fuel and ignition are introduced in the hot section driving another series of blades in the divergent duct mounted to a common shaft that also drives the compressor section. A high by pass fan is also used for thrust around engine case .
A true jet is much simpler in design.
You nailed it! This is so good I chose to use it in my classroom of aircraft mechanics students.
WOW! Thank You. A PLEASURE!
Where has this video been my whole life? I've watched so many videos just to understand this but they all deviated. Thanks a lot. Good video.
You're very welcome! Please do Watch other videos on my channel as well.
You should also watch this one. It is also
as good ua-cam.com/video/GzhdxSsoT0g/v-deo.html
Thank you. As a flight sim enthusiast I really wanted to understand the N2 importance initially and why N1 is important later for most of the flight. You nailed it.
Thank you mate!
Think of it this way: N1 is your thrust, and N2 powers your systems. The N1 shaft has many more turbine stages, in order to extract as much energy as possible from the jet exhaust and use it to run the fan. That's where most of your thrust comes from. The N2 compressor gives you bleed air, which runs your AC, anti-ice, and engine starters. The gearbox linked to the N2 shaft runs a generator and a hydraulic pump.
Thanks so much for the info, nobody out there explaining “how a turbine works” shows how the turbine starts or accelerate. Thanks again ❤️
You are Welcome! Check out my other videos as well!
One of the things I did on pushbacks, before I give the pilots permission to start. I notice the wind. A strong rear wind would turn the fan blades in the opposite direction. If the wind is really strong from the rear, I would alter the angle in order to prevent a hot start.
That's very interesting information! thank you! :)
I want to learn this
What is a hot start? Very interesting!
It’s always refreshing to work with push back crews who have that kind of situational awareness
@@hugolafhugolaf in order to make more power, engines must get hotter. We measure this heat by the temperature of the gasses that are exhausted out of the engine, known as exhaust gas temperature or EGT. During an engine start, the EGT is monitored to not exceed a certain value before the engine is started and stabilized. If it does exceed this value, that is known as a hot start.
Thanks, I dont know why so many videos skip how to initially get the turbine spinning, that's what I needed to know.
You are Welcome!
This is the most crisp and on the point explanation of turbofan engine start i have ever watched. Thanks a ton for your work. Liked and subscribed.
Thank you so much! :)
With a shit computer generated voice ? WOW
This Video would be WAY BETTER with out the robot voice
Very true. That robot voice sucks.
True
False
Forreal, if you take pride in what you do you should be confident in speaking your knowledge
He doesn’t give a $hit because he’s too lazy to bother.
Thank you very much for sharing this information, you took away the darkness of my ignorance.
Glad it was helpful!
2:59 finally a video explaining what started the engine! Most videos just start with "air is sucked in" lol
Cool! :)
Really great explanantion. Thank you. My lecturer insist us to watch this vid, does not have any regret at all. 🔥🔥🔥
You are welcome! This has definitely made my day today. Thank you. Do watch my other videos as well and please share. :)
You're videos are so educational thank you for sharing!
thank you for watching!
This video just solved one of the biggest doubts i had as aplane enthusiats. Thank you very much, and you've gained a new subscriber :)
Thank You so much and WELCOME! Check out some of my other videos as well!
What were you doubting if I may ask
@@lewismuange3786 Well I understand why many people are wondering what is right, as I've seen multiple TV shows telling it wrong. I even remember the startup sequence being described as "compressed air pushing down the pistons" in "Ultimate Airport Dubai". Which is of course laughable.
Thanks, Stephen Hawking, that was super education!
Thank you so much man! Made my day!
@@JxJAVIATION ... al. EducationAL. But also a super _free_ education, so I guess it kinda fits!
I just had to replace a torque converter on a car and there are similarities, that's how I arrived at your video.
Plus TheFlightChannel is like super addicting, and also super sad and frustrating
Thanks again! I'm all about making days!
@@egregiousqueef7781 Great to have you onboard! Check out my other videos as well. As you mentioned its free aviation education! :)
AWESOME video
The diagrams are very easy to understand and the slow-rate voice really helps to follow the explanation. Thank you
You are Welcome!
very neat, concise and clear presentation
Thank You!!
Beautifully explained... Looking forward for more videos!!! 💯
Thank You so much! Please do share the videos! and Watch my other videos as well!
I have to agree. Your clear and easy-to-understand explanations together with the fantastic animations are first rate! Well done and thank you.
absolutey FANTASTIC! thank you!!
You are welcome. Check out my other videos as well
Superb demonstration
Thank you so much!
Some jet engines now start electrically. On the 787 they have what are called VFSG for Variable Frequency Starter/Generators. The starters are also the generators once the engine runs on it's own.
Yes, just focused on the Pneumatic Starter
@@JxJAVIATION Love the video.
And each engine has two VFSG's (as does the APU).
Good point. And most business jets.
The accessory gearbox is like a drive belt on the cars. It drives the fuel pump and the oil pump and the hyrdaulics. It is driven by the Hp turbine. So to drive the Hp turbine itself we can drive this gearbox itself.
That is a good explanation!
Most find qn answer how jet engine starts.....thanks man
No problem!
Nice work! Very helpful!
GREAT PRESENTION. I enjoyed the video fully. Thanks for sharing ✈️🛫
Thanks for watching! Do Check out my other videos as well!
Of course
Its 2020 and flight schools still teaching trash. Best way to teach airplane systems is either with real airplane opened or watching videos like this from someone that really knows his stuff.
Thank You! It really means a lot!!
As an important point with regards starting a turbo fan engine. The air starter for the engine is fed low pressure high volume air. A popular understandable mistake is that the starter is fed high pressure air.
The air pressure is generally around 45 psi. The volume of air supplied is what provides the energy to drive the air starter.
Yes that is a very good point! Thank you for sharing!
I'm fascinated with aviation and always learn something new everyday. Thanks 👍
Thank you! Check out my other videos as well!
You are the MAN!! This video is the best ever!
Thank you so much!!
Great explanation sir ! It's just mind-blowing awesome...
Thanks a ton! :)
There’s always a portion of magic in the procedure nobody has ever fathomed
That is the beauty of it!
Very straight forward, excellent explanation, thank you! /ATPL student
Thank you! Check out my other videos as well! Could be useful!
This was a huge help, best one I've seen. Well done!
Thank you so much. Do check out my other videos as well!
thanks a lot for this video....crystal clear
You are welcome!
Thanks good explanation.
Thanks for watching!
Oh thank you so much for this info.
The _shaft_ from the accessory gearbox does not disengage from the N2. The gears in the starter unit disengage from the shaft. The shaft is still required to drive the accessories.
Did some research: The shaft which drives the accessories is separate from the shaft that is used to start the engine.
@@JxJAVIATION Engine type? The N2 (or N3) shaft drives the accessory gearbox (permanently attached) on most engines. There are various components attached to the gearbox: Hydraulic pump, EEC power generators, fuel pump, electrical generator and starter motor. i.e. The starter motor is mounted on the gearbox (CF6, RB211, CFM56, etc). You said that "the shaft from the N2 starter unit disengages from the N2 shaft" and the graphic in the video shows the accessory gearbox shaft disengaging from the N2 rotor. What actually happens is that the starter disengages from the gearbox. According to your graphic, all the accessories would stop working.
Sir this video, i like most. Marvelous video. Thank you sir.
thank you and welcome!
Very good explanation 🙏🙏🙏
Great explanation, very helpful
Glad it was helpful! Check out my other videos as well!
I m in love with this channel
Thank you!
Just loved it, so easy now.
That's great!
I am exciting this video. This is so good I chose to use it in my classroom of aircraft mechanics students
Thank you so much! Do check out some of my other videos as well!
Really great and to the point explanation
Thank you! Do check out my other videos as well!
Impressive, easily understandable
Do watch my other videos as well!
Very clear explanation 👍
Thank You!
Excellent. Complete & concept educate. Thanks 😊
Most welcome 😊
Super informative and im looking forward to more videos 🙂
Thank You!!
Can you tell me
N1 shaft & N 2 shaft are two independent module which are disengaged during start up
or N 1 shaft & N 2 shaft are coupled permanently (single shaft)
N1 and N2 shaft are 2 separate shafts and are not coupled mechanically. The aerodynamic forces cause these shafts to rotate. So basically they are always disengaged mechanically.
great video, thanks
You are Welcome!
Great explanation. Thank you.
You are Welcome!
The video is so much useful an understandable then others, the voice is robotic or not, it is more important that talks slowly and gives the listener some gap to digest the information, thank you so much for the video
Glad it was helpful!
Very nice explanation, it is easy to understand it. Thanks!
Glad it was helpful!
VERY NICE WAY TO TEACH, IMPRESSIVE THANK YOU SIR FROM PAKISTAN
Welcome!! :)
Thank you so much the detailed explanation but can you please provide more information about accessory gear box and its way of operating and stopping mechanism .
You are Welcome! Noted and will do a video on the AGB soon!
Thank you.Help me a lot
You are welcome! Please Share and Watch my other videos as well
Great video ! I’m wondering what happen to the airstarter after the starting cycle is complete ? Do the ground crew take it off ? Isn’t it tricky since the turbine of the airstarter still has a lot of inertia even thaugh it has been disconnected to the N2 shaft ?
The air starter unit is not removed by the ground crew.
This is because, when the aircraft is in flight and the engines were shut down and need to be restarted, the air starter may be required to restart the engine.
JxJ AVIATION oh so the pressure that flows in the airstarter during flight is enough to start back the engine !? Waw
Thanks a lot for your accuracy in your videos and for taking time to share this knowledge with simple terms ! Hope to see you doing well on youtube it is really well deserved !
@@Binette96 Thank you, and Welcome! Please do Watch my other videos and Share the videos as well
The starter attached to the engine gearbox (about 6" in diameter and about as long) has an overrunning clutch like your car. At some point during the start sequence, the clutch disengages, the starter valve is shut off.
@@Greatdome99 You are right Sir.. maybe you are acft engineer or A&P instructor.
Very informative n Interesting..🛫🛫
Thank You. Check out my other videos as well! and please share!
@@JxJAVIATION Sure..Regards..🛫🛫
Splendid job!
Thanks Mate!
Your videos are so educational thank you for sharing.....
Welcome & Glad you like them! :)
Good stuff. Thanks 👌
Thanks for watching!
Thanks for the details 🙏
No problem 👍
Did you miss the sequence of the 3 rubber bands ? Thanks , simple and we'll put. It sure beats 24 volt starting motors and ring gears.
I was expecting..
"Next press the switch to release the Hamsters in to the rotating wheel"
Thanks a lot ... more informative Vedio
Thank you! Please check out my other videos as well!
perfect animation :) love from Pakistan
Thanks man! Love from India! :)
So when the engine starts, is that the rumble noises u hear when ur being pushed back?
Usually one of the engines is started during pushback!
@@JxJAVIATION oh ok
Thanks, very interesting!
How does the APU start? electric?
What is the pressure of the air needed for starting? Something like 10 bar or more to 100 bar?
You are Welcome!
The APU uses an electric motor for starting.
The air pressure required for starting the engine would be less than 5 bar.
@@JxJAVIATION thanks!
@@JxJAVIATIONindeed, I cannot imagine a electric starter to a GE90, I just cannot conceive it
@@JxJAVIATION 5 bar is enough for making the HP shaft turn ?
@@bobelaviador The 787 has starter-generators
Hai i just want to clarify that the HP air opens HP valve then it passes through air stater unit before entering to AGB. From AGB it is coupled to N2??
the HP valve opens and this allows hp air to flow to the air starter unit. the air starter is housed inside the AGB. the coupling is from air starter/agb to N2
Starter Valve (electrically activated)->Starter->Overrunning clutch->Gearbox->driveshaft to HP spool (via bevel gear). The engine control unit (EEC) controls start sequence of the engine fuel and ignition.
@@JxJAVIATION Starter is not housed inside the AGB, it is connected via shaft to gearing inside the AGB.
What a video thank you so much. I just want to request from you, can you describe accessory gearbox duty basically?
You are welcome! Will make a video on it soon!
Thank you so much for this video
You are so welcome!
Great video thanks man
Glad you enjoyed it
Very good explanation...thanks
Welcome!
Thank you so much! , so informative and short
You're welcome! Check out my other videos as well!
Super explained , sir aabout N1. And N 2 shaft because of I knows one main shaft and one another and well explained about N1 and N2 shaft connections ,
Thanks and welcome! :)
On the C-17 (pw2000 engine) the ignition is left on. It’s turned off as part of the cruise checklist and then turned back on in the descent checklist. This is so that the engine has less chance of flameout at critical stages of flight.
That's right. A very good point!
I think that is quite normal for almost all turbofan or jet engined aircraft. Boeing aircraft definitely have it and I think Airbus too.
Very well explained!
Thank you!! Do check out my other videos as well!
Very. Informative
Glad it was helpful!
Thank you for sharing 🤝🏻
You are Welcome 👍
Great video.☺️ I just subscribed to ur UA-cam channel.☺️
Personally, I Think The Robotic Voice ADDS To Value Of This Long Overdue Explanation.
WOW! Thank You!
Very well explained Sir
Thank you! Check out my other videos as well!
Thank you,information.
You are welcome
very educative. Thank you Rgards
Glad you enjoyed it
Superb well explained
Thank you! Do watch my other videos as well
The graphic appears to be a 787. I worked on the 787 Common Motor/Starter Controller, which was the 1st all electric start of an engine of its size; otherwise the information is mostly consistent with other turbine engines I've worked on.
On the 787 there is an electric starter, but I was giving an idea about the air starter unit!
Good explanation!!
Thanks!
Great vid and very informative.
Thank you!
Awesome!!!!! :D!
Where does the high pressure air in the first place come from? Is it some pump working sucking air from the atmosphere?
It is a compressor that takes air from the atmosphere and compresses it.
@@JxJAVIATION thank you for the clarification
Nice I understand the others I never got it ,
that''s great
We don't know exactly where, when airplanes begin but i believe there is a wire to connect the engine to start.
Some engines need wire, pipes, tubes etc
what is the rate of the n2 for the start n1 shaft? I mean n1 shaft starts at what percent of n2 shafts
At approx 20 to 30% N2 the N1 shaft should start rotating.
Thank you for jet engine start steps.
I have a question, burning chamber is at high pressure as compared to compressed air entering it - in flow line and due to generation of product gases. What is the scientific answer? Is it high velocity? Engr. Muzzafar Iqbal.
Because of the fuel air mixture being burnt in the combustion chamber the pressure increases.
very GOOD
Thank You!
Thank you
You're welcome! Check out my other videos as well!
wow u are amazing, god bless you mr😻
Thank you so much 😀
easy to under stand tq
Thank you! Check out my other videos as well!
Thanks
Welcome!
Awesome 🙏💎 work
Thank you!