The piece in question is the flame holder for the afterburner system. It creates a zone of turbulent air directly behind it to keep the flame near where the fuel is sprayed into the afterburner. It is only needed to help the engine function properly when there is indeed a great deal of flame in the exhaust.

Always good to hear from someone who has been there and done it !

Love your videos. I've learned so much and it helps that I work in aviation and can recognize what I'm looking at on the ramp. Keep em coming!

I'm 66 and Istarted to crye watching this video,,, my dad was a millright at Air Canada bassed in Montréal, many times we've spoke about his work on rebuilding engins landing gears and more of planes stuf, But, your vidéo, and only now it made me better understand how important his working skills as a millright was before he retired in the mid 80's, for some reason your video got me closer to my dads trend like never before! Thank you sooo much for posting this sir!! 🙏

Love these videos... truly one-of-a-kind!!!

Awesome video. Very informative and interesting!

Osm look and clearly shown the aftetburner component THANKU SO MUCH

Thanks for making this video, very impressive!

Fabulous explanation!

Very interesting! Thank you for posting!

thanks for showing the relationship between the spray bars and the flame holders! I'd still like to understand the variable geometry outlet operation and bits better... it's amazing to think of moving those parts into and out of the hot exhaust and 'burner flames. By chance, I had the privilege of seeing a QF-4 Phantom fly at the 2015 Airventure at Oshkosh. So nice to see a Phantom fly and hear the J79's roar! :-)

Fantastic video! I've been a aircraft mechanic for many...many years but never had the chance to get close to an afterburner. (although I did service the Concorde once)

lovely video i love with your explanation great thanks a lot

Good information and well explained

The guy who dropped a screw inside the rusty engine lol good video thank u

Had a curious thought..looked it up..found ur video!! Wish more things played out so smooth🤔😁 Honestly tho it was very informative..ty

@JetMech72 There are four hydraulic cylinders shown in the spark test video. They are connected to rods that move forward to increase nozzle area and backward to close it down. Whenever I call the nozzle segments turkey feathers I hear snickering, but it is my favorite term for them.

I think the ignitor works continuously in AB... but I am not sure on that. The metal liner with all the holes in it is... the jet pipe liner. It helps the outer flow of cooling air mix inwards through those holes to protect the jet pipe and the liner itself from contact with the actual flame of the afterburner. It is very similar in form and function to the combustor liners. Couple videos posted about those.

Ah, this is the vid I've been hoping for, TYVM. I also missed the howling sound. One thing, does the engine keep the AB igniter lit all the time? Anyone who has seen those Swedish AF clips of F-104s taxiing for takeoff, has also noted the presence of the AB torch inside the tailpipe. The title is F104G Volkel A/B for anyone interested. Some nice four part J79 harmony going on too.

Thanx. Really interesting 🏴󠁧󠁢󠁷󠁬󠁳󠁿🇨🇦

@beenselock The gases continue to expand through the remaining stages. The nozzle guide vanes between the stages redirect the flow for optimal power extraction.

@sharrynuk I don't mention it in the video, but there's a small hole on the upstream side of the housing, and that's to let air in. You can see it for a few seconds...

Thanx sir for all the comprehensive tutorials. l'm really curious on the detail of a variable nozzle mechanics. How its put together. Will u plz make a video on assembling or disassembling it during yo spare tym? Thanx in advance!

Thanks Jay ! :)

@indoorherbivore I've seen those clips and, to answer your question in a roundabout way, what really jumps out is the torch ignitor flaming away. It's malfunctioning, with a control relay stuck open.

The three stages of the LM1500 / J79 turbine are all attached to the same shaft.

@prandtl002 Causing the gases to accelerate backwards results in the nozzle and the rest of the engine being pushed forwards. If the nozzle was doing a perfect job, the pressure difference accross its outlet area would be zero. You get an indication of the residual pressure in the gases once they've left the engine by how much they expand once outside. This is indicated by the shape of the "cone" of hot gases visible escaping. The wider the cone, the more residual pressure.

@billymach4 We service the J79 for military aircraft, because GE no longer supports this engine. The power turbine used with industrial gas generators is optimized for a single temperature and mass flow. Afterburners are not used in industrial applications because power turbines are not adjustable. Interesting idea, though.

OK sir, I understand. maybe I just missed that topic. Thanx go yo response and time.

Thanks Sir.

What is the cheese grater looking texture in the afterburner pipe? Also, does the igniter run continuously or just to start the burner?

Another stunningly fascinating vid!! You are the best for showing us that which we cannot see. Can you tell us anything about the stippling inside the afterburner/reheat pipe? Some clever bugger must have figured out it needed it and prepared a pattern.... random? ordered?

Thanks!!

Was also wondering, do the four fuel lines to the AB spraybar manifolds allow for four levels of AB? Or is that for firing it up in a progressive manner?

@AgentJayZ I guess I was talking specifically about how the exhaust nozzle is actuated.

Hey AgentJay, when I see some vids of turbojets/fans in full AB sometimes you'll see a bright glowing 'something' exiting the back end. They persist for quite some time which makes me think that maybe parts of the AB section are melting and being ejected. What am I looking at when I see this effect? Could this be globs of unburned fuel slowly burning in the O2 poor exhaust?

Could you talk about how the nozzle works?

Always wondered how this engine is pulled in and out of the starfighter and then secured when you only see that the tail section has been removed?

@indoorherbivore Yes to both questions.

@AgentJayZ As always, thanks! :) Makes total sense. I would guess if you burn propane you don't get much coking either. Such such fun stuff. I don't know if I said it before, Oh yes I did. Thanks!

MiG 21 engine has quite a similar flame holder as that. And it had a special russian green enamel on it that could take the punishing enviroment. To compare it with some undisclosed more modern western design I've seen, that was buckling and cracking and even shedding pieces. If I remember right the flame cans were also covered with that same green enamel.

@JetMech72 Thanks JetMech72. So chances are that sometimes I am seeing flame holder erosion going on? Thanks.

AjentJayZ, Are the engines with AB used for industrial applications? Or do you rebuild the AB engines for aviation applications?

@TalksWithDirt I have an idea. If the engine seems to be functioning normally, and you see the odd bright orange "spark" get spit out the back at extremely high speed, it could be a dislodged and ignited soot deposit. Turbine engines that burn jet fuel do accumulate carbon deposits from incomplete combustion. At S&S, we never see these deposits because our engines are all clean and running for the first time. In an aircraft though...

how does a multistage turbine work? i understand exhaust from the combuster liners pushes the first stage....what happens after that?

@TalksWithDirt Can't really say what you've seen. But sometimes flames can be seen, and in those flames are shock waves that sometimes form diamond like shapes. There should not be any bits of metal.

When he stuck that camera into that afterburner, I swear to god I could smell kerosene.

Is there cooling air directed through the afterburner flame holder? Since the afterburner fuel rails are located in front of the flame holder, I'm surprised the flame holder does not melt. Or is the front of the afterburner flame located further rearward from the fuel rails and flame holder?

What materials the flame stabilizers are made of ? Sir

Does the torch igniter have an air input? In the rocket world, a torch igniter has high pressure fuel, high pressure oxygen, and a sonic choke (small output orifice) so the igniter doesn't get blown out. On a jet, I would expect it to use high-pressure bleed air, but I don't see anything like that.

How often do the fuel nozzles crack? Based on the coloring it looks like it gets pretty hot

The J79 on the F-4E Howled (AIRFORCE 431 5 LEVEL HAHN AFB)

@cheetawolf If I ever get to work on thrust-reversing equipment, I will definitely be filming everything. However we never deal with that stuff here. I'm an engine guy working on engines in an engine shop... Thrust reversers are more part of the airframe of a modern airliner. You need to find an AME who makes videos about the rest of the plane...

Nice

greetings from a frosty -10 deg F minnesota, USA --hey Agent Jay Z I have a question. I understand a gas turbine can be modified to operate on a number of different fuels. Then I wondered could LPG/ natural gas/ propane ever work in an afterburner or is jet A or that type of fuel the only suitable fuel for re-heat (afterburning). thanks in advance would love to hear your thoughts in a video

what is this one from Jay? F-4, Kifr?

At very high temperature why the turbine blades does not melt?

@AgentJayZ I wouldn't mind seeing a video that shows how the petals open and close.

nozzels ? To me that are just holes ...are fuel nozzels in modern engines any differen`t ? The ones you showed dont seem to atomise / spray the fuel very good

How does this metal not melt, or break off with all that air from behind the turbine?

GOOD👍❗️

@prandtl002 Here you are attempting to answer the question of just how the nozzle shape produces thrust. I don't believe that's what oissaa is asking, and even if he was, you've repeated here the classic misunderstanding. The thrust is not produced by pressure differential accross the area of the nozzle outlet. It seems to make sense, but that's not what's happening. The nozzle acts according Bernoulli s principles to accelerate the hot gases, converting their pressure into velocity.

Hmm, beginning around 0:45 in the background I see what looks to be a very small turbine wheel...it looks a lot like a power turbine section from a Garrett JFS100

@boygrego12 No I didn't notice the sound. Also I forgot that I must blink my eyes every so often as well when watching Jays videos or they dry out. ;-)

Fun fact, the afterburner duct weighs as much as a pallet of paper towels and toilet paper at Walmart.

Love your work, jet engines really are interesting to me. Can I come and work for you?

@oisiaa Hmmm, nozzles... There are fuel nozzles, which are fuel nozzles There are turbine nozzles, which are inlet stators There are afterburner nozzles, which are fuel spraybars There are jet thrust nozzles, which are jet thrust nozzles I'm guessing you mean the last one. And by "works" do you mean the theory of its function, or the mechanism by which it is actuated, or the variables and their influence on its control? No, please, not the last one...!

What plane does that engine go in to? 😊

@AgentJayZ It's not the mach diamonds. I understand those. Oh, for the love of my propulsion classes. Humm.... let me see.... Darn can't find an example. They look like sparks and sometimes there is a grav induced component to their trajectory which implies some mass. I see them maybe every 10 times I watch the F-16's here at TUS take off in full AB. They are single events, not systemic in the exhaust plume.

Hi again. Very interesting stuff about the aterburner and its special igniter. I had no idea, I assumed it just used sparks like the main combusters. (I know the SR-71 uses triethylborane chemical igniters, but that's a very special case.) If you look at this video watch?v=cayblOY0h00 , at around 2:30 you can see what I assume to be the torch igniter. Is it normal that it is firing so early before the AB is actually going to be used? Again ... thanks for making!

@boygrego12 In Jet City the skies are always full of gunships

👌👌👌👌👍👍👍👍👍👍

Sorry, I meant at 3:30, not 2:30.

Anyone notice the helicopter noise ?

i wish i could work with you

What's the purpose of 8 question marks, when one would do? Your second sentence fragment makes no sense at all.