Question about afterburner stages

[_Viper_]

Hello!

I have read that both GE F110 and PW F100 has afterburner stages. So what this "stage" system exactly means? For example F100-PW-220 has 5 stages and F100-PW-229 has even 11 afterburner stages according to http://www.f-15estrikeeagle.com/ . Does that mean that the pilot can choose by his throttle how many AB stages he/she is currently using or what? Although I have always seen afterburner fully light; not halfway on or something like that. Oh and is this "stage" system common in military afterburner engines and does it always works in the same way?

This video from youtube shows quite nice all the five stages when the pilot hit the throttle up to the max AB. And the engines even kicks out some smoke, probably because the engine speeds up?
http://www.youtube.com/watch?v=dzR1se9St1U

[Purplehaze]

First of all the GE does not have stages like the Pratt. It does have different power settings but not stages. In your last comment about the smoke and the engine speeding up, the engine does not speed up in augmentation. The RPM's are the same, the only change is you are dumping raw fuel into the exhaust creating augmentation or added thrust.

[ACMIguy]

The smoke is most likely from the raw fuel being dumped like Purplehaze said.
The most impressive AB I have seen came from the F-104 Star Fighter PW J-79, which produced a series of blue/green diamonds within the flame.

[_Viper_]

Many thanks to both of you. Actually I didn't know at all that GE engines doesn't have stages. But the first question waits some kind of answer from some one

[JoeSambor]

I had the opportunity once to watch an SR-71 engine start. Green flame about twenty feet long!

Best Regards,

[That_Engine_Guy]

I had the opportunity once to watch an SR-71 engine start. Green flame about twenty feet long!

Ah yes, the TEB (Triethylborane) ignition system. The JP-7 had too high of flash-point for electrical spark ignitors, so P&W used a chemical ignition system!

NAAAASTY STUFF.... This stuff would ignite on contact with very little oxygen. One "shot" would start each engine, and each AB light would require a shot. There was a counter for each engine showing how many ignition shots were remaining.

Back on topic...

As for staged augmentation, yes the throttle determines how many stages are used. For a given PLA (Power Lever Angle - the number of degrees the throttle is pushed forward) sensed by the engine's control system, you get specific augmentation.

The pilots can't actually tell what stage they are in, except for guessing at the fuel flow or the feeling of acceleration. There is no indicator for augmentation. During test-cell runs the zones can be "seen" by reading raw-data from the engine's computer on a test and diagnostic computer.

As for the smoke; the engines will smoke a bit (esp -220s) when at MIL power. This is more pronounced during a "snap" throttle movement. If you watch the video again, you'll notice the smoke starts as the engine "winds up to MIL" but when the augmentor lights, the smoke is eliminated. Watch more videos of the aircraft operating at MIL/MAX. (The easy way to tell is the nozzle will be closed in MIL and completely open at MAX.) The engines will NOT smoke in 'burner; that huge flame burns everything in the exhaust.

From another post of mine...

"Zone 5" would be for a F100-PW-200 and PW-220 engine models. Zone 1 through 5 represents the augmentor spray manifolds of the engine. The higher you go, the more manifolds are used. (1=1, 2=1+2, 3=1+2+3, etc) Get to five and you have full flow on the augmentor fuel system giving you MAX thrust.

PW-229 has 11 "zones" of augmentation, but only 7 Augmentor Spray Manifolds. The "zones" are achieved by lighting the manifolds in various combinations to get a "smoother" transition from zone to zone. This is not the same as the earlier F100s as the manifolds would were used progressively.

GE F110s (all models) have "spray bars" which are variable. They do not have "zones" to speak of. With a GE you wouldn't say "Zone 5 'burner" you'd just say "MAX 'burner."

Keep 'em burnin'

[That_Engine_Guy]

Although I have always seen afterburner fully light; not halfway on or something like that. Oh and is this "stage" system common in military afterburner engines and does it always works in the same way?

Sorry I missed this point in my first post.

There is Minimum Augmentation, Mid-Range Augmentation, and MAX Augmentation. It is achieved by the following.

MIN AUG - Just into the augmentor detent on the throttle.
MID AUG - Somewhere between the detent and the throttle stop.
MAX AUG - Thottle against the stop.

Other than throttle position (PLA) the only other indicator would be fuel-flow.

The basic engine does not accelerate or gain any power when augmentation is used. At MIL (Military Power) the RPM of the engine is at it's peak. Augmentation adds power downstream of the basic engine. It does add some back-pressure to the engine, and the engine will accommodate this, but it will not turn faster. The augmentor simply takes the exhaust gasses of the engine moving at a specific speed, add enormous amounts of fuel, and ignite said fuel for lots of added heat. This added heat translates into extreme velocity, which increases thrust.

On a PW-229 we're talking about going from about 17,000lbs of thrust to over 29,000lbs. (About a 40% increase)

The downfall to this power is fuel consumption. For your 40% gain in power, you'll loose fuel about 5X faster....

[_Viper_]

Sweet. This forum never fails to impress.

So when it comes to the GE engine you either has your burner on or off. I mean you can't select nothing between that. And you can't see these stages when watching PW-229 if I understood everything what was written. I also noticed that you can even count these stages when watching this clip which I linked.

Again, thanks to everyone.

[That_Engine_Guy]

So when it comes to the GE engine you either has your burner on or off. I mean you can't select nothing between that.

No. The GE F110s have "spray-bars" that are variable. They flow DOES change from MIN-MID-MAX Augmentation; you just can't discern the actual change.

The PW-229 is staged, but the stage increments are so much smaller now, they are almost impossible to see or feel.

Old afterburners on turbojets were often ON/OFF type arrangements.

It just depends on the design of the specific engine you're talking about.

[MechFromHell]

Hey TEG, something that is taught in the CC course here at Sheppard is that there are 7 total spray rings, in 5 segments. (engine portion of the course is built on PW-200's) I guess my question here is why is it that segment 4 consists of 3 rings where as the others are just the one?

[1machinist]

The smoke is most likely from the raw fuel being dumped like Purplehaze said.
The most impressive AB I have seen came from the F-104 Star Fighter PW J-79, which produced a series of blue/green diamonds within the flame.

I'm kinda dating myself here, I also saw J-79s on the test cell and saw the diamonds..

Another thing that was cool to see was the last flying F-101 Voodoo. It did several burner passes over the base. The J 57's used whats called a"wheel light" A/B. The burner was lit off of the turbine wheel and since the 2 engines never lit exactly at the same time, you saw then heard the characteristic BA_BOOM.

Old Guys Rule

[That_Engine_Guy]

Hey TEG, something that is taught in the CC course here at Sheppard is that there are 7 total spray rings, in 5 segments. (engine portion of the course is built on PW-200's) I guess my question here is why is it that segment 4 consists of 3 rings where as the others are just the one?

EDIT: To answer the question why? Lots of fuel flow! That and Seg-4 is the smallest rings at the center. Smaller rings smaller area; link multiple "small rings" to get flow like the larger ones with larger diameters.

On PW-100/-200/-220 engines Correct Seg-4 does have 3 rings, but...

All 3 of those rings are fed at the same time. They are all plumbed together as a single manifold. That manifold flows as a one unit or "Segment"

You count "Segments" or "Zones" but not the individual rings. They can't light individually.

To put it in prospective, on a PW-220 when you pull "Seg 4 Manifold" you pull an assembly with 3 rings, that operate as a single unit.

Now on the PW-229 there are 7 manifolds and 7 rings, that comprise 11 "Zones" of augmentation. They light in differing combinations to provide a smother transition from one zone to the next.

Here is where it gets tricky on the PW-229... There are 3 assemblies, that hold the 7 rings:

Core Sprayring Assembly (3-rings)
Mid-Core Sprayring Assembly (2-rings)
Fan Sprayring Assembly (2-Rings)

Pull the Fan Sprayring Assembly on a PW-229, you're removing Rings 6 and 7 that comprise zones 9, 10, and 11. (Remember the rings light in differing combinations for specific Zones.)

Clear as mud?:shrug:

For further reference see the 2J-F100-46-1 (for -220) or the 56-1 (for -229) or if you want to get the true nuts/bolts of engine operation ask an "Engine Guy" to see a copy of the "ENGINE MONITORING SYSTEM REFERENCE GUIDE" from P&W. The EMS Guide is not a T.O. but is an awesome reference guide for troubleshooting engine problems.

Keep 'em Flyin'

[_Viper_]

Many thanks to your very specific information but there is just one thing to ask. How often and when the pilot uses some of his engines stages? I have been on several air shows and always seen the Viper's PW burner fully light instead of 3/5 on. I hope you got the point and for me this should be the last detail to know.

[That_Engine_Guy]

At an airshow the engine is used at MAX for dramatic effect. (Cool fire, loud noise, vibration, top-performance etc.) When you're flying directly over a runway, one doesn't have to worry about the Fuel Flow, or Quantity...

Throttle settings are up to the pilot and his/her needs to fly the aircraft... Use as required for flight...

If you need a little boost to bring up your speed, you may only use MIN-AUG. It will give you a bit more thrust with say only a 2x increase of fuel consumption. If you don't need MAX-AUG for a particular situation, it's best not to use it to save fuel.

Side note: when the F100 is at MIN-AUG the nozzle only opens a slight bit from closed and shows no external flame. Other than the lack of some smoke, it is very hard to discern from MIL unless your hand is on the throttle, or can see the Nozzle Position or Fuel Flow Indicators. Standing on the ground or at the airport fence, most never know the difference!

It's like driving a car _Viper_. If you slam your foot down on the accelerator every time you come up to speed you're going to use a lot of fuel. Use your foot more softly and only accelerate as needed, it takes more time but you'll save fuel and money. You use the throttle as required to maintain the speed you want. Up hill needs more (climbing); down hill needs less (diving); put luggage (weapons) on the roof and you'll increase drag. When you pull out into traffic, you may want ALL your horsepower; it's there if and when you need it.

[SixerViper]

On the Pratt & Whitney J-75, which powered the F-105 & F-106, afterburner was either on or off, but you could vary engine rpm while in burner between 85% and mil power. Those engines had the real sharp KA-BOOM when the burners lit off. Gawd, what a sound!!!