Very nice. I love AgentJZs videos but they can be too in-depth sometimes. This is nice to just see everything in one short video. It's a great overview thanks
Thank you sir. This is something Im adding to my study tools for my O & P,s . Great explanation very thorough. Again thanks for taking the time to make this video. Extremely helpful. I’m taking my tests next month ! Mike.
This is awesome! Was looking at a jet ranger at the local FBO, wuth the beautiful Allison 250 sitting up top. Can't wait to start flying and get the turbine rating!
Nicely demonstrated. Getting slowly ( not an engineer ! ) at understanding how a turbine engine works. Fabulous piece of engineering. Thanks a lot for all the detailed explanation. Now I just need to understand the N1, N2, etc,...
I found it easier to understand using Ng and Np. The Gas Producer, Ng/N1 is compressing gasses (air) in the compressor section. The Power Turbine, Np/N2 is taking the energy created in the combustion chamber and generating power, horse"power" or torque.
@@weswood151 that helps give it a little more tangibility. . N1 is the beginning like "pitcher" initiates a play sequence in baseball..no hits without a pitch..it just clicks when you become involved with it!
That's simple. N1, means the main fuel producing turbine, which is directly connected to the compressors. The heart ❤️ of the engine. N2, is the power turbine, or, power takeoff, which is connected through the N1 shaft, driving the main gearbox.
Great video thanks am watching an Allison 250 being overhauled and made ready for a jet boat with AgentJayZ I enjoy learning about the Jet Ranger engine and OH6/md500
short "i" sound in diffuser, like in "different"... Also the explanation of why compressor bleed is required isn't correct. Simply, for a fixed-geometry. multi-stage axial compressor at low speed the flow would be so low that the angle of attack on the blades would be high leading to stall/surge. By having bleed the flow at a given speed is increased reducing the angle of attack and preventing stall. This is true whether the compressor involves a centrifugal compressor or not.
El aire entra a través de las paletas de guía(frontal) de tras de eso está el compresor lo cual genera un movimiento a los rotores y luego paso por los alabes de estator (es de compresión axial) después va al compresor centrifugo lo cual importa energía al girar. DIFUSOR= cuál el aire sale del compresor centrifugo los conductos divergentes intercambian velocidad
Now my question is. If the labyrinth seal on the No2 bearing is deficient, can you have air from the scroll diffuser getting into the oil system therefor having an High ITT and a variation of the oil pressure while the motor is running ? if yes how often are you supposed to check those labyrinth seal ?
Generally that can be adjusted externally by changing out the vent orifice fitting that sticks up on the back of the compressor scroll case at the diffuser. That orifice regulates how much air from the diffuser will be allowed to pressurize the cavity leading to the lab seal. The excess air will escape the orifice. Those vent orifice caps are different sizes by part number and you have to change them in and out to achieve a proper balance. Density altitude and drastic temperature changes can also effect its characteristics. If the orifice is too big: it wont pressurize the cavity enough and oil will bleed past the air side of the seal and blow oil back up through the diffuser vent. If the orifice is too small: too much air will push through to the accessory gearbox. It will cavitate the oil and will cause the air/oil separator gear to work inefficiently, thus instead of venting air it will be blowing oil out through the oil vent of the accessory. In the case of a Bell 206 you will see it blow out the r/h exhaust stack and back over the tailboom.
Thanks for correcting my mistake. I looked at another video and realized that it's the round blank w/ 6 studs and nuts. Also noticed that both front and rear are used on helicopter application. Front for main rotor drive and rear for anti-torque tail rotor drive. Great Video ! 😎
I’m seeing a term NL and NH on Wikipedia. I’m assuming it’s the Low Pressure turbine and High pressure turbine? As I understand it the first turbine stage Gas Producer Ng is also known as N1? And the second the Power Turbine Np is also known as N2. Which one is the High and Low pressure turbine? In turbofan engine diagrams they all seems to have Combustion, then HP turbine (labeled N2) then LP turbine (labeled N1). Are turboshaft engines different?
It’s confusing but… I’ll do my best to explain. This RR250 compressor is a combination compressor meaning it combines an axial and centrifugal compressor. Both those two compressors are on one shaft operating at the same speed. This RPM (N) is known as N1 (first rotor air hits) or Ng (gas producer). The N2 on the RR250 is the power turbine, which drives the output shaft, sometimes called Np. Or when it’s running with the rotor system on a helicopter it’s Nr (Rotor). To confuse that even more… put that engine’s output shaft to a propeller and it becomes Np (prop RPM). When you see NL and NH those are dual spool or triple spool engines. NL is sometimes a combination of the Fan and the first couple stages of axial compression. Also, since this is the first thing the air hits it’s also sometimes called N1. Then the NH sometimes called N2 is the high pressure compressor which is next in the pathway of air, just before it hits the combustion chamber. They both have their own turbine(s) and operate at their own proffered RPM. Spinning a shaft inside a shaft. The increased complexity is offset by the efficiency gain. The newest turbofans are triple spool N1= fan, N2 or NL=first stages of compressor, N3 or NH= high pressure turbine. See simple lol
Hello sir. I have this engine to overhaul. It is my senior project. May I ask you some questions. How can I connect starter generator to battery? I don’t have any ideas to do that.
Yikes. That’s a great question. The starter generator is an airframe part. You need to connect it to the battery through some starter/generator control relays. Check the bell maintenance manual for details.
Probably, you're asking about the impeller. On C18 and C20, which were in this video, they are made of steel. C20R and Series III and Series IV (C28, C30, C47, C40) - titanium.
Hal, my Allison 250 B17F is starting to leave small amounts of oil at the leading or entry of the axial compressor. Is there a way to send you photos ? Do you have a video showing how to fix that oil leek ? I am sure it’s only one -0- ring
Hey Kevin, The number one bearing utilizes a carbon seal. It’s a bit of a job to change it. You need a couple special tools to remove it. Also you sometimes have to remove the compressor from the accessory case to hold it vertical during the replacement process. Best to have someone from an MRO come replace it for you. If that’s possible.
@@halhobenshield5931 It is, actually, doable in situ as long as there is access. I've done #1 carbon seal change a few times on a jet ranger. Of course, it's easier in vertical position.
Helicopter engine. Originally built by General motors. Bought by Rolls Royce , Alison is the inventor of the reduction gearbox for turbin engines. Alison transmissions like in GM trucks and the Abrams 1 tank and transmissions in comercial trucks .
Yes, true. However, you do want to start it as quickly as possible so when we adjust fuels controls, or the newer FADEC units, we use the maximum starting temp as a guide. With very little cooling air during the start we want them to get them up to idle speed as quickly as possible. Hot and fast start is best. The burn marks can also come from a nozzle that’s not flowing correctly. So, doing follow checks at their recommended time and us essential. A streaking fuel nozzle can lead to very expensive for section.
@@halhobenshield5931 Wow! Thanks for clarifying that. I have always loved the Bell 206 Jet Ranger and the Hughs 500 that both have used this awesome little gas turbine for well over 50-years now and with an excellent reliability and safety record. Your explanation on that unit was exemplary. You really know your stuff! Bravo, Sir!
Best material I have seen in 30 years of flying. Congratulations and thank you very much.
Hal, that is a fantastic explanation of how the 250 works. Definitely adding this one to the Instructor playlist.
Very nice tour! I especially enjoyed some of the pauses and explanations of the details.
Great and easy explanation! Super Job. Thanks a lot!
Thank you! In school now for my A and P this helps a lot
THIS WAS SUPER HELPFUL , JUST PULLED A c30 TURBINE AND IS VERY SIMILAR TO THE C20 SERIES .
Great explanation maybe people would like to know this engine was developed by the Allison division of General Motors in Indianapolis Indiana.
Very nice. I love AgentJZs videos but they can be too in-depth sometimes. This is nice to just see everything in one short video. It's a great overview thanks
Good video. Pretty good short and sweet. Working on these on Bell 206 .
Thank you sir. This is something Im adding to my study tools for my O & P,s . Great explanation very thorough. Again thanks for taking the time to make this video. Extremely helpful. I’m taking my tests next month !
Mike.
Nice video and explantation. !!!!!
Awesome video. Thank you
This is awesome! Was looking at a jet ranger at the local FBO, wuth the beautiful Allison 250 sitting up top. Can't wait to start flying and get the turbine rating!
This is amazing THANK YOU
Nicely demonstrated. Getting slowly ( not an engineer ! ) at understanding how a turbine engine works. Fabulous piece of engineering. Thanks a lot for all the detailed explanation. Now I just need to understand the N1, N2, etc,...
I found it easier to understand using Ng and Np. The Gas Producer, Ng/N1 is compressing gasses (air) in the compressor section. The Power Turbine, Np/N2 is taking the energy created in the combustion chamber and generating power, horse"power" or torque.
@@weswood151 that helps give it a little more tangibility. . N1 is the beginning like "pitcher" initiates a play sequence in baseball..no hits without a pitch..it just clicks when you become involved with it!
That's simple. N1, means the main fuel producing turbine, which is directly connected to the compressors. The heart ❤️ of the engine. N2, is the power turbine, or, power takeoff, which is connected through the N1 shaft, driving the main gearbox.
@@ronaldgreen5292 Thank you for the reply! Have a good day. Alex
Nicely done Hal !
Well done.
Excellent video and explanation of how this engine works and all the parts but you forgot about the gearbox.
wonderful engine
Very helpful. Thank you
Great video thanks
am watching an Allison 250 being overhauled
and made ready for a jet boat with AgentJayZ
I enjoy learning about the Jet Ranger engine and OH6/md500
where are you watching that
@@montiac1333 England
@@micstonemic696stone do you have a link?
@@montiac1333 I have seen link before, cannot find it now though
@@montiac1333 know I trying on my tablet, I've seen it lots of times but cannot find it know
Not sure what to do now
Mic Stone
thanks very much, clear info
Amazing.
Thank you, sir. I especially enjoyed some of the pauses and explanations of the details. sir, t want to know the fuel system of M250-C30P engine.
Certainly answered a question I had about whether these could be used in a pressurized aircraft.
THANK YOU VERY MUCH :)
Nice video
Can you please do a video on the disassembly of the combustion and turbine sections ???
Good job
God id love to get my hands on one thats warped or just generally cant be rebuilt for airworthiness and put it in something.
Thanks!!!!
👍 очень хороший фильм
short "i" sound in diffuser, like in "different"...
Also the explanation of why compressor bleed is required isn't correct. Simply, for a fixed-geometry. multi-stage axial compressor at low speed the flow would be so low that the angle of attack on the blades would be high leading to stall/surge. By having bleed the flow at a given speed is increased reducing the angle of attack and preventing stall. This is true whether the compressor involves a centrifugal compressor or not.
Great video!! Love seeing the inter workings of these engines!! Any idea what material the compressor case is?
it is made of stainless steel per the Rolls Royce Model 250 Series II Engine Training Manual page 41 :)
most are made of titanium depending on where its place and some are stainless steel ( high temp )
I'm also presuming a titanium impeller..
Worked on those years ago
El aire entra a través de las paletas de guía(frontal) de tras de eso está el compresor lo cual genera un movimiento a los rotores y luego paso por los alabes de estator (es de compresión axial) después va al compresor centrifugo lo cual importa energía al girar. DIFUSOR= cuál el aire sale del compresor centrifugo los conductos divergentes intercambian velocidad
Now my question is. If the labyrinth seal on the No2 bearing is deficient, can you have air from the scroll diffuser getting into the oil system therefor having an High ITT and a variation of the oil pressure while the motor is running ? if yes how often are you supposed to check those labyrinth seal ?
Generally that can be adjusted externally by changing out the vent orifice fitting that sticks up on the back of the compressor scroll case at the diffuser. That orifice regulates how much air from the diffuser will be allowed to pressurize the cavity leading to the lab seal. The excess air will escape the orifice. Those vent orifice caps are different sizes by part number and you have to change them in and out to achieve a proper balance. Density altitude and drastic temperature changes can also effect its characteristics.
If the orifice is too big: it wont pressurize the cavity enough and oil will bleed past the air side of the seal and blow oil back up through the diffuser vent.
If the orifice is too small: too much air will push through to the accessory gearbox. It will cavitate the oil and will cause the air/oil separator gear to work inefficiently, thus instead of venting air it will be blowing oil out through the oil vent of the accessory. In the case of a Bell 206 you will see it blow out the r/h exhaust stack and back over the tailboom.
It’s actually the silver round cover at 5:37. There’s one on the compressor side and one on the opposite side.
Thanks for correcting my mistake. I looked at another video and realized that it's the round blank w/ 6 studs and nuts. Also noticed that both front and rear are used on helicopter application. Front for main rotor drive and rear for anti-torque tail rotor drive.
Great Video ! 😎
Also I found that the diffuser scroll is radioactive
How is power transferred to a shaft? I assume this jet engine must be for a small helicopter or fixed wing aircraft?
It uses a turbine driven by the exhaust that is connected to a gearbox
I’m seeing a term NL and NH on Wikipedia. I’m assuming it’s the Low Pressure turbine and High pressure turbine? As I understand it the first turbine stage Gas Producer Ng is also known as N1? And the second the Power Turbine Np is also known as N2. Which one is the High and Low pressure turbine?
In turbofan engine diagrams they all seems to have Combustion, then HP turbine (labeled N2) then LP turbine (labeled N1).
Are turboshaft engines different?
It’s confusing but… I’ll do my best to explain. This RR250 compressor is a combination compressor meaning it combines an axial and centrifugal compressor. Both those two compressors are on one shaft operating at the same speed. This RPM (N) is known as N1 (first rotor air hits) or Ng (gas producer). The N2 on the RR250 is the power turbine, which drives the output shaft, sometimes called Np. Or when it’s running with the rotor system on a helicopter it’s Nr (Rotor). To confuse that even more… put that engine’s output shaft to a propeller and it becomes Np (prop RPM).
When you see NL and NH those are dual spool or triple spool engines. NL is sometimes a combination of the Fan and the first couple stages of axial compression. Also, since this is the first thing the air hits it’s also sometimes called N1. Then the NH sometimes called N2 is the high pressure compressor which is next in the pathway of air, just before it hits the combustion chamber. They both have their own turbine(s) and operate at their own proffered RPM. Spinning a shaft inside a shaft. The increased complexity is offset by the efficiency gain.
The newest turbofans are triple spool N1= fan, N2 or NL=first stages of compressor, N3 or NH= high pressure turbine.
See simple lol
Hello sir. I have this engine to overhaul. It is my senior project. May I ask you some questions. How can I connect starter generator to battery? I don’t have any ideas to do that.
Yikes. That’s a great question. The starter generator is an airframe part. You need to connect it to the battery through some starter/generator control relays. Check the bell maintenance manual for details.
Hey thanks! Do you know what material the compressor is made of? Is it stainless steel? Or perhaps titanium?
Probably, you're asking about the impeller. On C18 and C20, which were in this video, they are made of steel. C20R and Series III and Series IV (C28, C30, C47, C40) - titanium.
@@yurivorontsov8925 yeah the impeller! Thanks!
The way you are touching the engine parts with bare hand they may get damaged due to static charges
Hal, my Allison 250 B17F is starting to leave small amounts of oil at the leading or entry of the axial compressor. Is there a way to send you photos ?
Do you have a video showing how to fix that oil leek ?
I am sure it’s only one -0- ring
Leak
Hey Kevin,
The number one bearing utilizes a carbon seal. It’s a bit of a job to change it. You need a couple special tools to remove it. Also you sometimes have to remove the compressor from the accessory case to hold it vertical during the replacement process. Best to have someone from an MRO come replace it for you. If that’s possible.
@@halhobenshield5931
Ok, thank you
K
@@halhobenshield5931
You interested ??
@@halhobenshield5931 It is, actually, doable in situ as long as there is access. I've done #1 carbon seal change a few times on a jet ranger. Of course, it's easier in vertical position.
Wait, there are people that spell diffuser as die-fuser?
Two Fusers?
@@allancopland1768 To kill the fuser
Thx for share ,Is this an APU ?
No.
Helicopter engine. Originally built by General motors. Bought by Rolls Royce , Alison is the inventor of the reduction gearbox for turbin engines. Alison transmissions like in GM trucks and the Abrams 1 tank and transmissions in comercial trucks .
where is the PTO to the transmission
Ralph Morgan Good catch, it’s on the accessory section near the bottom. I’ll see if I can figure out how to add an amendment in the AM. .
@@halhobenshield5931 I believe it is the square yellow plate with 4 studs & lock nuts.
Please correct me if I'm wrong. 😎
Seven stages...
Thought the 250's were centrifugal only?
No, it uses axial + centrifugal.
@@allancopland1768 They were both axial and centrifugal, but later models they dropped the axial sections of the compressor
Why your videos hide i can’t see it
Burn marks on the inside of the combustion chamber shows why you never want a "hot start" on the engine. Am I correct?
Yes, true. However, you do want to start it as quickly as possible so when we adjust fuels controls, or the newer FADEC units, we use the maximum starting temp as a guide. With very little cooling air during the start we want them to get them up to idle speed as quickly as possible. Hot and fast start is best. The burn marks can also come from a nozzle that’s not flowing correctly. So, doing follow checks at their recommended time and us essential. A streaking fuel nozzle can lead to very expensive for section.
@@halhobenshield5931 Wow! Thanks for clarifying that. I have always loved the Bell 206 Jet Ranger and the Hughs 500 that both have used this awesome little gas turbine for well over 50-years now and with an excellent reliability and safety record. Your explanation on that unit was exemplary. You really know your stuff! Bravo, Sir!
explain cooling on the rotating turbine blades