Forum: F-16 Design & Construction

I been wondering what sort of system is used in the F110 & F101 to ignite the afterburner fuel.

The PW-229 looks like it uses two spark igniters, low down in the main gutter at about 4:30 and 6:30.

The F101 & F110 have a single large igniter in the mid circular v-gutter. I think its a pilot torch igniter, but part of me also thinks it could be a catalytic system. Could anyone shed some light on this please Question

Cheers
Obi

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Obi_Offiah wrote:

The PW-229 looks like it uses two spark igniters...

Correct, there are two igniters in the PW-229's Augmentor Flame-holder. "Pilot holes" in the augmentor's core fuel manifold fill the flame-holder with fuel vapor that is ignited, this ignition then lights the full fuel spray that follows.

Obi_Offiah wrote:

The F101 & F110 have a single large igniter in the mid circular v-gutter. I think its a pilot torch igniter, but part of me also thinks it could be a catalytic system. Could anyone shed some light on this please Question

The F110 uses an single igniter, similar in design/function to others, but it lights fuel sprayed into the torch. (Not a catalytic system) The torch then ignites the fuel flow that follows from the spray bars.

Keep 'em flyin' Thumb

TEG

Thanks TEG

So with the PW system after the main gutter has ignited, the AB ignition system is switched off and the circular gutter sort of becomes the pilot for the burner.
With the GE system the igniter lights the small torch pilot and the torch remains active throughout AB operation. Is this basically how they function Question

In the above image between the inner and middle v-gutter, both above and below the the engine centreline is an additional part of the flameholder structure. If only the bottom structure was shown I would have taken it to be the torch igniter, but the the fact that there is also one above the centreline has me stumped.

Obi

Obi_Offiah wrote:

So with the PW system after the main gutter has ignited, the AB ignition system is switched off and the circular gutter sort of becomes the pilot for the burner.

Yes; the PW's augmentor ignition system stops functioning when the LOD (Light-Off Detector) senses UV light being produced by the flame inside the augmentor. Segment I lies directly forward of the main gutter of the flame-holder, so yes it would act as the 'pilot'; since it's the first/last Segment to light/cancel. It's adding thrust whenever it's lit, so being the 'pilot' for the rest of the system isn't SEG-I's primary function.

Obi_Offiah wrote:

With the GE system the igniter lights the small torch pilot and the torch remains active throughout AB operation.

Someone else may have to help with this one; I know the GE has a "Flame Detector" that serves the same function of the LOD on the PW. I would think the ignition system/pilot would stop after picking up the presence of a positive 'light' inside the augmentor; but can't be certain until a "GE Engine Guy" chimes in...

Obi_Offiah wrote:

In the above image between the inner and middle v-gutter, both above and below the the engine centreline is an additional part of the flameholder structure. If only the bottom structure was shown I would have taken it to be the torch igniter, but the the fact that there is also one above the centreline has me stumped.

The flame-holder in the GE has two main concentric gutters that are interconnect by radial gutters. (An O inside another larger O connected by spokes)
http://www.airliners.net/photo/USA---Ai ... 8414ec5cac
The flame-holder in the PW as one main concentric gutter with radial gutters that extend inwards and outwards. (One O with spokes sticking in towards the center and outwards towards the wall)
http://www.airliners.net/photo/USA---Ai ... 8414ec5cac
(Note: In the PW exhaust about the 5:30 position is the ASEP (Augmentor Signature Elimination Probe) which empties the manifolds when the augmentor is canceled, keeping the smoke/vapor to a minimum during this time)
Keep 'em flyin' Thumb

TEG

GE do have a "flamesensor" that detects augmentor lightoff. im not certain if it shuts off the aug ignitor if it doesnt detect but the resulting "AB NO LIGHT" MFL, will tell you theres a problem and bring it back to MIL. let your gauges stabilize and try again.

GE flame sensors are cleaned and inspected every 10hrs … if dirty will spit out PFL and appropriate EMS code for no lite, however pilot normally does not report any augmenter anomaly. If he does along with the PFL, then something is broke!

That_Engine_Guy wrote:

Someone else may have to help with this one; I know the GE has a "Flame Detector" that serves the same function of the LOD on the PW. I would think the ignition system/pilot would stop after picking up the presence of a positive 'light' inside the augmentor; but can't be certain until a "GE Engine Guy" chimes in...

A couple of reasons why I think the F101/F110 system is continuously alight when in burner, is because this is how the torch system of the GE equipped Phantom's worked and you can see the pilot igniters still alight in the following pictures:
http://www.airliners.net/photo/USA---Air/Rockwell-B-1B-Lancer/0982455/L/&sid=b5d544bfacf0359fbcfba3dd070f6e9d
http://www.airliners.net/photo/USA---Air/Rockwell-B-1B-Lancer/0710905/L/&sid=b5d544bfacf0359fbcfba3dd070f6e9d
There's also a video of a F110 powered F-15K that shows the same.

That_Engine_Guy wrote:

The flame-holder in the GE has two main concentric gutters that are interconnect by radial gutters. (An O inside another larger O connected by spokes)
http://www.airliners.net/photo/USA---Ai ... 8414ec5cac
The flame-holder in the PW as one main concentric gutter with radial gutters that extend inwards and outwards. (One O with spokes sticking in towards the center and outwards towards the wall)
http://www.airliners.net/photo/USA---Ai ... 8414ec5cac
(Note: In the PW exhaust about the 5:30 position is the ASEP (Augmentor Signature Elimination Probe) which empties the manifolds when the augmentor is canceled, keeping the smoke/vapor to a minimum during this time)
Keep 'em flyin' Thumb

TEG

Thanks for the ASEP info TEG Thumb

The F110 has three v-gutter rings. An outer and middle ring, that are linked together by radial gutters/spokes and an inner central ring (of roughly equal diameter to the diffuser cone).

The object I'm looking at is positioned between the inner and middle v-gutter rings as shown in the cutaway schematic, so it can't be the radial spokes. The inner v-gutter ring protrudes further (is further from the turbine) than the middle ring.

Looking at the cutaway this object also protrudes further from the turbine than the middle v-gutter ring. In fact when focusing on the rear end of this object (the end furthest from the turbine) in the cutaway, it can be seen that it slopes, with the end closest to the engine wall inline with the middle v-gutter ring and the end closest to the engine centreline protruding rearwards (further from the turbine) and inline with the inner v-gutter ring.

Looking at the following rear pictures of an F101 and F110:
http://www.flickr.com/photos/52529591@N00/244992676/sizes/l/
http://farm4.static.flickr.com/3583/3692821045_6faab854c3_b.jpg
http://www.airliners.net/photo/USA---Air/General-Dynamics-F-16CJ/1482963/L/&sid=fa6a8308d8cce574d96fad173c2b603c
The only structure that appears between the inner and middle v-gutter rings seems to be the pilot swirler igniter. In the pictures it can be seen that the pilot igniter has a sloped end http://www.flickr.com/photos/52529591@N00/244992676/sizes/l/ a bit like the following picture of an exhaust muffler http://www.mufflermall.com/images/medium/62_1807D.jpg. The lower end is inline with the middle v-gutter ring and the taller end sticks out futher and is inline with the inner v-gutter ring.

If it wasn't for the fact that the cutaway schematic displays two of these objects (upper and lower in the cutaway), I'd have be pretty sure the device was the AB pilot igniter.

BTW, the comparison of the F110 and the -229 is quite interesting because the -229 appears to have less structures/blockage in the AB section, as the following image of an almost pristine F100-PW-229 shows: http://www.airliners.net/photo/Poland---Air/Lockheed-Martin-F-16CJ/1499447/L/&sid=6ebe47447c09eabca42051376b14fb2e. You can clearly see the turbine blades compared to the obstructed view in the F110.

Obi

The following link is from a page of the F-14D NATOPS that shows the F110 Afterburner sequencing I've labelled the parts of interest: http://www.4shared.com/file/127689332/1858e640/F110_Ignition_Pilot__Flameholder_Diagram.html

Obi

The following link shows a cutaway diagram of the J79-GE-7 turbojet afterburner, with a single pilot burner/igniter positioned how I would have expected the F110 igniter to be: http://www.4shared.com/file/127956086/af2223f9/J79-GE-7_Pilot_Burner.html

Cheers
Obi

Yup … the motors nowadays are really good and no fun.

In a way, I miss the days of duping compressor stalls and AB blowouts in the hush house!

That sh*t just doesn’t happen anymore Laughing

That_Engine_Guy wrote:

Obi_Offiah wrote:

With the GE system the igniter lights the small torch pilot and the torch remains active throughout AB operation.

Someone else may have to help with this one; I know the GE has a "Flame Detector" that serves the same function of the LOD on the PW. I would think the ignition system/pilot would stop after picking up the presence of a positive 'light' inside the augmentor; but can't be certain until a "GE Engine Guy" chimes in....

Correct, the flame sensor on the augmentor detects presence of a light successful light-off. Once the flame is detected, the igniter cuts off and the augmentor fuel control keeps scheduling fuel until aug is no longer needed. If the flame sensor does not detect a flame after so many milli-seconds, the fuel scheduling is terminated and the Ab No Light MFL is generated.

That_Engine_Guy wrote:

Obi_Offiah wrote:

In the above image between the inner and middle v-gutter, both above and below the the engine centreline is an additional part of the flameholder structure. If only the bottom structure was shown I would have taken it to be the torch igniter, but the the fact that there is also one above the centreline has me stumped.

The flame-holder in the GE has two main concentric gutters that are interconnect by radial gutters. (An O inside another larger O connected by spokes)
Keep '[/i]em flyin' Thumb

TEG

We usually refer to the inner gutter as that 3rd main gutter. Therefore given you the outter gutter, mid gutter and the inner gutter. The mid gutter and outer gutter are connected by the radial gutter. The inner gutter is connected to the mid gutter by links. Merged into the mid gutter at the 4 o'clock position is the pilot burner or "swirl cup" which houses the aug igniter and a pilot fuel tube.

The old F101 and F110 has the same aug concept with similar characteristics like the way the outter, mid, radial, and inner are set up on the flameholder. Where they differ is in fuel nozzle placement. F110's have their local, core and fuel spary bars as individual bars. With the fan/core bars behind the flameholder just above the aft centerbody and the locals attached to the flameholdrs mid gutter with thermal barrier coating and the spot when the 20th sparybar is removed due to the temp difference in that spot.

One the 101's all three spraybars are on one unit and they are arranged over the aft centerbody as well. However, the exception of the pilot fuel tube in the burner can, there are no spraybars attached to the flameholder, there fore, that is the reason why there is a themal coating on the mid gutters. Since there is no actual fuel spraying in the mid gutter like the 110's, the mid gutter tends to get hotter in that area.

Mushmouth wrote:

Correct, the flame sensor on the augmentor detects presence of a light successful light-off. Once the flame is detected, the igniter cuts off and the augmentor fuel control keeps scheduling fuel until aug is no longer needed. If the flame sensor does not detect a flame after so many milli-seconds, the fuel scheduling is terminated and the Ab No Light MFL is generated.

When AB light off is detected and spark ignition within the swirler cup is terminated, does the fuel system continue to supply fuel to the pilot fuel tube and thus the swirler cup?

Mushmouth wrote:

The inner gutter is connected to the mid gutter by links.

I initially thought those links could be the object causing my confusion, however they are situated behind the gutters so that can't be it.

Mushmouth wrote:

F110's have their local, core and fuel spary bars as individual bars. With the fan/core bars behind the flameholder just above the aft centerbody and the locals attached to the flameholdrs mid gutter with thermal barrier coating and the spot when the 20th sparybar is removed due to the temp difference in that spot.

I have always wondered about the TBC on the upper left of the mid gutter. Thumb

Cheers
Obi

Mushmouth wrote:

F110's have their local, core and fuel spary bars as individual bars. With the fan/core bars behind the flameholder just above the aft centerbody and the locals attached to the flameholdrs mid gutter with thermal barrier coating and the spot when the 20th sparybar is removed due to the temp difference in that spot.

I have always wondered about the TBC on the upper left of the mid gutter. Thumb

Cheers
Obi[/quote]

Makes sense?
We had a loaner jet ( with GE 129) that spit that section of the flame holder out twice!
Must be the fix … you always learn something here!

VarkVet wrote:

We had a loaner jet ( with GE 129) that spit that section of the flame holder out twice!
Must be the fix …

This one is similar, no TBC: http://www.davidpride.com/Aviation/MAPS/images/MAPS_05_105.jpg
Its also interesting to note that some F110s have a small crossfire gutter between the inner and middle gutters, while others don't.

VarkVet wrote:

you always learn something here!

Definately and quoted for truth Very Happy

Obi

VarkVet wrote:

We had a loaner jet ( with GE 129) that spit that section of the flame holder out twice!

We had the same thing happen when we were in Saudi. Changed one for cracking in that same spot, changed it, and when we took it to that trim pad, burned through on the post install run!

Obi_Offiah wrote:

Its also interesting to note that some F110s have a small crossfire gutter between the inner and middle gutters, while others don't.

There was a change that came out after they tested it on the S.L.E.P. motors that no longer required the link with the scoop on it. It was replaced by the same link that is on the rest of the inner gutter ring. Also, when that change came out, the inner gutter ring was modified. There used to be a notch on it right under that scoop. The that notice is no longer there on the new inner gutter rings.

That TBC on the flameholder in the picture it most likely there, just really dirty. That flameholder looks like it has been there for a while. Just a little backgorund on the TBC if you were wondering. The coating is there due to placement of the local fuel spraybars. There are 20 slots for the locals and 1 spot for local in the swirl cup (which has to be there for initial light off). That would make 21 sparbars total if they were installed. But during G.E.'s test phase, they determined that they want the fuel to be distributed from 5 points. So to keep it equal and even, they dropped on spraybar and now there are 4 spraybars per local distribitor.

Now the way the spray bars are mounted and spray, the fuel from the spray bar actually keeps the mid gutter ring cool in that area. Now that the spraybar is removed from the 11 o'clock position it gets alot hotter there than the rest of the gutter. The solution for that, the TBC. That is why we refer to it as the hot spot.

Just a little extra info.

Forum: F-16 Design & Construction

F110 AB Igniter System?