Jet Tech: Compressor Stall 

It's people like this who make the internet a good place

I can honestly say, I knew nothing about jet engines and only had a passing interest in their construction and functionality, However your videos have been an inspiration to learn more and take a more active interest in smaller model turbines. Thanks for sharing your knowledge with us.

I'm a student interested in rocket propulsion, but I know enough about ducted propulsion to know you are explaining very advanced things at a beginner level and that is the mark of an excellent teacher. I am very quickly falling in love with this channel! Well done, sir!

Your videos are amazing, inspirational, and very informative! Admittedly I am a bit jaded being an airline captain flying a turboprop, but the fact that I have learned more about the engines I use from you that any manual or user guide has ever offered remains unaffected. It took me a while to wrap my head around compressor stall and I must say that you did a wonderful job in providing an introductory nontechnical explanation of what it is. Excellent as always and thank you for all your hard work!

I was once standing in front of a cutaway jet engine at the Smithsonian National Air and Space Museum in Washington, DC saying to myself "How can this thing keep the pressure going only in one direction?" Thanks to AgentJayZ, I now know that it is due to many complex systems and procedures, including starting the engine at a high RPM, stators, combustor design, fuel control, bypass valves, etc. The aspect of balance, from the mechanical dimension, to the control of the speed, pressure, temperature, and angle of the air, is quite beautiful. AgentJayZ has the amazing ability to teach, as well as to do. A very rare and very valuable quality. These videos should be mandatory viewing for anyone that has anything to do with jet engines, including pilots.

Thanks! All these years of hearing about compressor stalls and it turns out it's nothing more about a little wing...stalling.

Makes total sense! My vision of what a compressor stall is, fortunately, matched your description. From a very basic aerodynamic standpoint, it's a fairly easy concept to grasp...if explained correctly! Your 'not a graph' graph is what helped me envision the relation between air velocity and blade angle. I was very excited to see this video in the lineup, and was not disappointed in your attempt to explain it. This, along with your previous videos regarding IGV's and Bleed Air Valves, compliment this topic nicely. Thanks again for another excellent video!

As a retired US Navy Man... with half my career as a Boiler Tech, (steam turbines... similar in a lot of ways!), then a Gas Turbine tech (M)... I Love how ya dumbed this down... and simplified the process! I shared it with my still active Navy friends... who I Hope will use this as a Training video! I Hope you dont mind! You did share it online... so... Anywho! Thanks! I'm sure itll make things Much clearer for alot of junior Gas Turbine techs!!!

That was a fantastic video. My son is being trained for aviattion maintenance with the USAF, and because of your channel, I will be able to understand what he is, and will be, talking about. As a father, I can't thank you enough for videos like these.

You're so much cooler than that other Jay Z guy.

I had a compressor stall on takeoff in flight school at Rucker. Landed and we went to the stage house to wait to be picked up. Happened around the time Challenger blew up, so getting a ride took a while. I had a really good instructor in that phase and had a good grasp on what happened. Your presentation here was great too.

'Paddles that stir the air versus air foils that move the air' - good explanation.

The part that finally clicked for me was understanding the compressor is always trying to produce 100%, even if the airflow won't support it. Variable geometry serves only to decrease compressor performance until everything is up to speed. Click!

"Answer some of them" - 6 years later still responding like a legend.

That's really a neat lesson of how a compressor stall can occur. As a private pilot, I know how to correlate the angle of attack of an aircraft's wing to it's behavior in the air but I was never considering that the same applies to a propeller blade (or turbine). Thanks and appreciate your time making this vid and explanation.

I watched this 5 years ago when you put up this video. @blancolirio just pointed us back to you because of the Delta engine failure on Sep 2, 2023. Just as good second time around.

Sail for a couple of years - and all this stuff makes perfect sense. Apparent Vs Ambient wind is a huge deal in sailing, especially if you're sailing something fast, like a Kite Board, or a High Speed Racing Catamaran - you can literally feel the power change depending on the angle of attack - but what's really strange - is you feel a sudden drop in power, the moment the air-flow detaches from the rear face, and you stall out. The key is that BOTH surfaces of the wing ( sail ) - front and back - contribute to the power, not the front facing surface.

The Light Bulb did go on, thank you for taking the trouble to put this together for us. I was in a B737 300 that after takeoff from Heathrow had Compressor Stall in the No 1 engine. This happened 3 times and then it settled down. I did not know at the time what this. But I do now. Kind regards and greetings from Africa.

To draw a picture in people's minds with only words is rare ability. Kudos to you, sir.

With the authority of an engineering degree and several gas turbine textbooks, I can say that this info is all exactly on point. Excellent job!

Annnnd my lunch just turned into a learning lunch - that was excellent - thank you so much!!!

Blancolirio sent me back to watch this again, you guys are GREAT! I love the stuff you do.

my brain stalled, but i backed off a little and recovered thrust allowing me to land safely, thanks, subbed

Thank you very much for the explanation. It clicked for me as soon as you described the angle of attack of the "wing" and the air separating from the "wing" as the stall. It makes perfect sense now.

I'm an old piston engine guy and had trouble understanding compressor stall. Near the beginning of the video, your pointing out that a compressor blade is just a wing and it can stall for the same reason a wing does turned on the light bulb for me. I got it! I watched the entire video to make sure everything you said stayed consistent with what I thought I got and it did. At last I understand. Thank you very much.

This guy is the Jayztwocents of jet engines.

As a 40 year career aerospace engineer I found myself back in class recounting the concepts you described - applaud your efforts to filter the information to be what is truly essential for grasping the subject. 💡 💡 💡 💡 💡 💡. Well done sir!

This is here ladies and gentleman is what you call Internet gold bullion and this man here is the gold mine..

I love this guys dead pan sense of humor..

I like how I started about an hour ago on a completely different channel curious about the bare basics of how jet engines work, and now I'm learning a lot more technical information than I ever expected to. God, I love the internet. . .

I really like your videos My profession is a Chemical Engineer and learning English is my great interest and watching your videos in such an interesting topic helps me to have the excitement of continuing to learn greetings from Mexico City.

Thank you very much for this video, I'm sure I speak for a lot of people when I say I've been waiting patiently for this video for a long time. I've been watching your videos for years, and they were what convinced to me to get involved in the industry. I have read a lot of books on gas turbines, and every single one spends one of the early chapters discussing compressor stall, however, your explanation manages to be much clearer than anything I have found thus far. You are an excellent teacher, please keep doing what you have been doing!

This probably the best explanation of compressor stall for the layman I’ve seen yet. Not everybody is going to get it, however; people learn in different ways and there are several ways to approach this visually. I love this channel. I also enjoy AgentJayZ’s dry humor - all of this is right up my alley.

Blancolirio sent us over here . Thanks !

You did an amazing job covering a complicated subject-matter. Looking forward to hearing more on this. The linear actuator for the IGV was very well explained. They should know that the ring - sets used on modern engines have rig pins used for setting a default angle of attack,along with the fact that the linear actuator is fuel driven to ensure the fuel schedule change happens when the PLA is advanced or pulled back. The other aspects of modern engines is the use of Blisk rotors and Integrated Bladed Rotor...both are Trademark terms used by GE and Pratt&Whitney.

Great explanation! I used to fly gliders when I was 16, so I know what a stall is. I also sailed, so I know what happens when you sail very close to the wind (right, your sails stall). Later on I worked as a control engineer, when controlling axial compressors we had to guard against "surge", which is a condition where the flow reverses quickly and creates pressure variations that can result in the destruction of the compressor. We were given a graph of delta pressure vs flow where a "surge curve" was drawn. Our job was to keep the operation to the right of the curve (often simplified as a line). We did this by measuring the flow and the difference between the inlet and outlet pressure, and see where it fell on the graph. If it went near the line, we would open a bypass valve connecting the outlet to the inlet so the flow through the compressor increased and the operation point moved away from the surge line. I guess that is what bleed valves are for in jet engines. We used a bypass because the gas being compressed was hydrogen or natural gas, venting is not a good idea. What I never realized was that surge was a consequence of the blades stalling (light bulb goes on), which makes sense. Blades stall, stop pushing air to the outlet, pressure drives flow back and the process repeats: surge. Thank you again.

this is honest the most useful, interesting topic i've learned and i'm still in high school. goes to show how vastly superior the internet is as a learning tool, yet no one can seem to remember that.

It makes me smile watching this video. I worked for GE and had applied for a field rep job and during the interview I was asked what a stall was. I tried to explain it like what I had learned in tech school as my instructor explained it, which is what you were explaining in your video. The interviewer wasn't looking for that answer. He wanted the interruption in airflow answer and fire will come out the front. Needless to say I didn't get the job. In retrospect it worked out well for me. I'm now retired where as most that got ghe field rep jobs found themselves looking for new jobs 2 years later.

This was excellent as I have always been a big fan of AOA as one of the major issues not well known by pilots and important to know in every aspect of flying. Your explanation brings it to another level. The LIGHT HAS DEFINITELY GONE ON in terms of the understanding about how AOA affects compressor operations. The really cool thing you explained, that I had never thought of, is the impact that the rotating compressor has on angle of attack and why the blades always looked like they were WAY too much pitched relative to the axial direction of flow. That picture (NOT GRAPH) was wayyyyyy Coool. I can now be a real GEEK and explain this to all of my Av Friends..Thank you so much

Great explanation AgentJayZ. The comparison of the compressor blade to a plain old wing and your description of the angle of attack and angle of incidence really cleared up my understanding of compressor stall. I'm glad you talked about the anti-stall features on the engines too because it reinforces how all those angles interact with the blades.

The principals of aerodynamics that you explain in this video, should explain to most people that a miniature version of a specific gas turbine design won’t work in the mini world. I have commented to people in videos that if a full size engine was shrunk to the size of a hand held toy that it wouldn’t work at all. I hope you understand what I just said. Please comment back if you would.

Found this video at midnight, trying to fall asleep.. Ended up watching it, very interesting and informative..

This was a great video, and you did an excellent job both with explaining compressor stall AND the myriad meanings of “bleed air”.

Hi JayZ, years ago, I and a few others went up to Michigan to repair one of our F-100's that was having an afterburner fuel control problem and I just happened to be the one in the cockpit running the aircraft, when I was given the signal to accelerate the engine to full throttle and select afterburner. When I did that, I experienced the worst compressor stall of my life. It was just getting dusk and all I saw was a giant ball of fire come out the intake. I immediately pulled the throttle back to idle and the fire crew that was standing by backed off about a couple of hundred feet and that was the last time I was able to select afterburner for several other runs. We finally ended up changing the afterburner fuel control while still in the aircraft which was normally not possible. We had an engineman that was able to do the normally impossible with us.

I am a little late getting here, but Mr. Browne of the "Blancolirio" channel fame sent me/us over to you for an in depth explanation of compressor stall, in light of the recent fuel dumping incident at LAX. And I might ad that I am pretty thick headed, and because of your excellent explanation, even I understand it now... Thank you sir...

That's an... interesting progression of flag sizes on the wall.

And thanks to your diagrams (not graphs!) and the velocity vectors, now I understand why the compressor blades have so much twist. Near the root, the tangential velocity is lower so the angle of attack is close to the axis of the engine, therefore the root of the blades are nearly parallel to the engine axis. "Click".

That was an absolute great learning. People like you make aircraft engine studies more interesting with ease.

Straight and to- the -point crystal-clear explanation by this maintenance engineer!!

If Robin Williams was a compressor expert rather than a comedian.

Jay, thank you so much for this video. I'm over 30 years in the aircraft industry and I found this to be a brilliant revelation on the subject.

Having known of the nature of aircraft wing and helicopter rotor stalls, this very rapidly made sense. Neat introduction to the technological solutions to this problem in a turbine engine, though.

As a broad brush explanation without diagrams, I basically came to grips with that. However, as a lad, I now realize the unknown problems Sir Frank Whittle had with his early development of the jet engine. His thrust I recall was measured in early days of mere several pounds or so. Eventually it got to fly as did our opposition, but what a way it had to go to now. Thanks.

Hello. I passed my European Atpl today. I wanted to thank you for helping me with understanding the compressor stall and other stuff.

The book "stick and rudder" hammers home a similar message about air stalling over a wing. What is also interesting is that one can read it as a book about how to live life as well.

Inside my head : *click* Got it. Now I can move forward. Thanks for the simplified theory. Why can't everyone explain things this way? No numbers, no jargon, just make it make sense.

AgentJayZ this has gotta be the most sensible manifestation of the friggin internet better than news, facebook, twitter, and google combined given the density of quality true info in one place also better than 4 years treading water at university any and every 4 minutes of this beats about ten years of reading books and listening to bearded boring lecturers

Only 17 stages ! Compressor Stall is analogous to Cavitation with a boat propeller. Not exactly, but easier to imagine. At least it is for me. Mr Newman sure knew his stuff. The history and science behind the Shape of the Blades and Stators is very interesting also. Great lecture, thank you. "This Not a Graph" 👍

I was an aircraft mechanic in the Navy. I had forgotten how much I enjoy this stuff!

Love watching your stuff, "natural born" teacher - A+. (I LOST our previous conversation about space taken up by 4,000 hp piston engine vs a turbine. I'm red faced) And, of course, you are correct, there is NO comparison. I'm a very retired, old truck/bus mechanic: big gas engines and Detroits. I used to own the largest production gas V8 ever made for highway trucks: '68 GMC 637ci V8. She was in a fire truck that had 30,000 miles on it. I miss my fire truck!! Got too old to take care of her. I'm off to a dark corner now.

I read a book by Pratt and Whitney that is much like the General Electric book you mentioned, and it said pretty much what your GE book said. No explanation. Thanks for making this video, I'm really glad I know at least the basics now.

WoW. Fantastic. Finally get it. At 13:30 I had my revelation. Thank you!!!!

This is quite literally the nicest comment section I've ever seen! You must be doing something right. Great videos, especially the J58.

Excellent overview of compressor stall - next step explaining what compressor surge is :)

don't know why youtube suggested this to me but you're a great explainer, it clicked for me at 12:15 before you had even said it

You just explained compressor Stall better than my Professor. Many thanks for your Videos !

You have a very engaging way of explaining things. Entertaining and illuminating at the same time.

I'm in my second year of A&P college. We are doing Turbines this semester and what you are explaining is just like in the book. VIGV, Variable stators, variable bleed values all remove the excess air at start to limit compressor stall. Our class projects are to do partial disassembly of the P&W PT-6 and the Allison 250. They only have Variable bleed valves. The PT-6 is a very clever design. It uses both multiple axial and a final centrifugal compressor in a reverse flow design.

I finally got hat 29:07. The penny dropped and I actually understand it. The documentaries I’ve watched all through my years could not convey an understanding of mechanical engine function, because they weren’t able to communicate at a - regular-man level of understanding. I gave you the benefit of the doubt and listened all the way through. I was beginning to get impatient just prior to the moment of understanding, and then - SHAZAM! Thanks mate.

I knew a compressor could stall, but for some reason (I only fly light aircraft with piston-powered props) I never considered the fact the actual blades were experiencing an aerodynamic stall like that. Really cool information!

This actually makes a lot of sense. I'd been struggling a bit getting my head around compressor stalls and how jet engines can be designed to stop them (particularly the how to stop compressor stalls), but this video has helped a lot to get my head around it.

Due to the absorption of such semi-exhaustible wisdoms over time, our individual careers as _Aerodynamic Design Scientist Engineers_ (based on collective understandings,) are ever-increasingly understood and well underway. We will continue to do the Matrix proud.

Very interesting. I'm sure there is a buttload of trig and differential equations to fully explain this. I think you did as good a job as is possible to simplify it . Thank you.

“So honey, what’s the plan for Saturday night?” [sees AgentJayZ Compressor Stall Video notification] “Woo hoo, order a pizza and get some beer, it’s true, it’s really true!”

Thank you so much for taking the time to explain this. For one the light bulb did go off! Also I liked your display of the Mobil Jet II and 2380, made me feel right it home.

Jet engines are amazing, I’ve learned a lot about them but I don’t know what compressor stall was even though I’ve heard of it many times. Thank you very much for explaining it, makes perfect sense now!

Well this is going to be the most viewed cause im going to look on over and over till i get it. Thanks.

Shit, all I know about is about machining these things and none of that engineering airflow volumetric efficiency stuff . I used to grind the blade tips of blade-loaded axial compressor spools, at 5000 rpm at G.E. Evendale... 5000 rpm was to hold the blades tight, slung out against the dovetails for grinding. Each stage was ground at a slightly different angle to match the curvature in the stator case. The noise was deafening even with ear muffs and sounded like you were standing next to a running jet engine. No wonder my hearing is shot to hell! The 4 to 9 stage compressor spools for the CFM-56 and CF-6 at Evendale, Ohio. 1979 to 1985 thereabouts. We also did stuff for the US military DFE-101 program engine, and SNECMA. It took about 8 hours to setup a complete bladed spool for grinding. Then another 8 hours to plunge grind all the stages. It was all manually done , none of that CNC stuff back then.

I've got to say your vids are pretty spot on. Sure, the explanation is more aimed at the layman than the engineer or researcher. But even some of these folks, who are perfectly able to handle numbers and equations, aren't arsed to explain fundamental notions to a kid. Your crash course gives an intuitive and easy-to-grasp understanding about compressor stall. Kudos to your patience and don't let neighsayers have the last word

Great explanation of why anti-stall technology is needed in the compressor part of a jet engine. I never realized it was just a matter of stall, due to opposing forces and a too high angle of attack.

I know this an old video but I really like the fact that you not only educate your viewers but I also like the fact that you can point out things like "Compressor stall" and how here in GENERAL Electric; who makes all sorts of engines. Have technical writers, who can't even properly explain what "Compressor stall" is and why or how it actually happens??? SO SAD!!!!

Thank you for sharing your time and knowledge. Greatly appreciated!!!!

Fantastic!! please make a part two where you go deeper in this topic, very useful.

...and the blades are twisted because the incidental speed is lower nearer the hub! Thanks for ALL the videos!

I wish you could have been my aviation mechanics instructor! I love your videos. Thank you for the time you dedicate making them. You are able to convey intricacies in a clear, concise manner. 👏

67 people wanted graphs and equations

And THATS how you explain an average Joe like me how a compressor stall works. Or not works for that matter hehe. Thanks a lot for taking the efforts to explain all these things.

Great illustration here, and I certainly brightened my dim bulb regarding this subject! Thanks! DD

Thanks for the video. I've learned so much that I use in my classes, and I'm a big fan of your channel. Please don't regret making a video because someone who sees it might think it's an invitation to parade their own ignorance. Haters gonna hate.

I hope Herman would be smiling at your great explanation.

Love the discriptions of how jet engines, afterburner, compressor stall, variable stator etc. videos. Before I started watching your youtube videos I never knew how any of these worked. Keep up the good work. Steven H. Ararat, Australia

AgentJayZ, awesome thanks, finally Compressor Stall declassified and unredacted. Good video, great explanation.

Juan Browne sent me! But I have to report back my findings.....

you are amazing to learn from. currently i am a mechanic for the blackhawk helicopter but am studying more on the other parts of my a&p and your videos are helping tremendously.

Very nice Jay, difficult subject that you handled well. Thanks for waiting until you were ready, it was worth the wait. Much easier to understand your methods than what others use, thank you.

Thanks as always for another excellent video. Truly a step above to translate from such a depth of technical theory and working knowledge to a "common sense" understanding and explanation. I know there's a lot of discussion on this video about terminology, theory, etc. After a huge bang at a test site, my father told me -- it just "sneezed" a lot of parts out of the front end. :-)

Good explanation, I understand much more now. Thanks.

A few years ago a plane I was on experienced a *bang* during takeoff. Pilot said “sorry laddies and gentleman, we just experienced a compressor stall”. Now I know wtf that was. (It was very windy out).

Brilliant explanation - I've now begun to understand something I've never got my head around before, thank you for your efforts!

Well done. The physics is complex. The engineering is very sophisticated. Some who have responded didn't learn much. I did. Keep up the good work!