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Enthusiast Joined: Aug 02, 2006 Posts: 62 Status: Offline

This question is probably solved but I found one more interesting video Razz

Actually it could be familiar to you.
http://www.youtube.com/watch?v=mMVF5yzDVvc
Against all explanations explained here I can't see the engine smoking. [0:52, 5:10] Perhaps really sharp throttle movements might skip the "smoking" MIL section or... Two Cents

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Hard to tell since the video is clipped so much. The smoke's visibility is also effected by lighting and background. Being an evening demo, it is rather dark...

Enthusiast Joined: Aug 02, 2006 Posts: 62 Status: Offline

That_Engine_Guy wrote:

Hard to tell since the video is clipped so much. The smoke's visibility is also effected by lighting and background. Being an evening demo, it is rather dark...

Yeah. Darkness and editing might hide the evidences what I was looking for. I have also noticed that takeoffs without burner aren't so smoky at all. I also wonder is there a significant difference between GE or PW smoking. I mean I haven't found any specific data about MIL at takeoffs from my pdf procedures. Or probably pilots turn it off before I can see it. This might be the answer and my eyes were wrong again Doh

Anyway thanks for your patience.

I always see that smoke whenever the engine is going from aug to mil during takeoffs and demo runs. Never seen our GE's steadily smoking when atmil. Must be a Pratt thing!! LMAO

Just joking TEG...

Salute

Mush

Mushmouth wrote:

Must be a Pratt thing!! LMAO

Just joking TEG...

Salute

Mush

Yep

Smoke 'em if you got 'em Devil

http://www.youtube.com/watch?v=WQ1kCNoDfQA

F-104 Starfighter at 1:14 and 1:40 there's a fairly good smoke trail from the J79. I think (someone back me up) that all the QF-4s still flying have had the smoke kit that SixerViper mentioned installed. Looks like the F-104 is one of the last jets sitting in the smoking section...

http://www.youtube.com/watch?v=CB3Rq-bdqrs
4:58 = AV-8B Harrier. I'm not sure if the pilot was using water injection but the hover lasted a lot longer than 40 seconds (however there were no stores on the jet).

Enthusiast Joined: Jan 07, 2006 Posts: 22 Status: Offline

In an ideal jet engine, all the fuel would be burned. This is called stoichiometric combustion. However, it is a little tricky to make a fuel control unit that does a perfect job. The problem is that if the fuel air mixture is to lean, the engine quits. Therefore, especially on older engines, it was safer to design the fuel controller to schedule a rich mixture. That would keep the engine running, but you got some smoke...

DesignAndConquer wrote:

http://www.youtube.com/watch?v=WQ1kCNoDfQA

F-104 Starfighter at 1:14 and 1:40 there's a fairly good smoke trail from the J79. I think (someone back me up) that all the QF-4s still flying have had the smoke kit that SixerViper mentioned installed. Looks like the F-104 is one of the last jets sitting in the smoking section...

http://www.youtube.com/watch?v=CB3Rq-bdqrs
4:58 = AV-8B Harrier. I'm not sure if the pilot was using water injection but the hover lasted a lot longer than 40 seconds (however there were no stores on the jet).

The AV8 display shows why the engine is the primary flight control in VSTOL flight, good illustration of the hot gas recirculation plumes. The puff of smoke as he enters the break to the hover is caused by the nozzles going down and opening the bleed air ducts to combustion air. In VSTOL flight, when the plume is dark, water is flowing.

Smoke index is a measured parameter during engine certification and is primarily driven by turbulence within the combustor. Its a constant design battle to get both a low visible smoke index and low Nox emissions.

The "smoky joe" F-4's used by the USAF had an old design of combustor, the lower smoke engines used by the USN/USMC had a newer design of combustor fitted with a different design of swirler.

Here is a NASA report with a lot of information on this issue.

.

Enthusiast Joined: Aug 02, 2006 Posts: 62 Status: Offline

That_Engine_Guy wrote:

When the burner kicks in, the smoke goes away as the flame of the augmentor cleans up the exhaust of the engine. (The smoke still enters the augmentor duct, but it burns off before it can emerge.)

Sorry to get back this old and discussed thread but I can swear that I've seen a few videos where jets drag a faint smoke trail even at full afterburner. In some occasions It can only be seen from a specific angle. Especially twin engined jets like Eurofighter, F-15, Hornet, Super Hornet, Panavia Tornado and Raptor tend to do that. Hopefully I'm not seeing things or something Laughing

but there's definitely something action there. The quote probably means that the flame fades most of the someke away but not everything? I'd be pleased if I got some confirmation about that.

Elite 1K Joined: May 26, 2005 Posts: 1135

The smoke is unburned hydrocarbons. Read Dolby's response, that is exactly what is happening.

Newbie Joined: May 10, 2008 Posts: 6 Status: Offline

That_Engine_Guy wrote:

seat_dreamer wrote:

What model B-52 is that ??

The B-52H had TF33s with more thrust than that of the J57s with water.
(But you have to consider water injection on any engine only lasted a specific amount of time before it ran out... typically 1 minute or less.

Actually, water injection operation lasted for about two minutes on both the bomber and the tanker, with the J57 engine. The B-52G had a water tank with a 1280-gallon tank. For two minutes of operation, each engine had to consume 160 gallons of water, or 80 gallons a minute. However, only the even numbered engines (2, 4, 6, and Cool

had water pumps installed, so they pumped the water for both engines on that pylon. If I recall right, the limit for water operation was 120 plus/minus 10 seconds.

Elite 1K Joined: Apr 26, 2004 Posts: 1198 Status: Offline

Do we still have anything water injected?

Enthusiast Joined: Nov 04, 2007 Posts: 42 Status: Offline

Demineralized water was always fun on a SAC base. I worked around the B52D's and KC135A's. If no wind was a blowing, the heavy black smoke would stay around for a while. If you look at old pictures of B52's taking off from Guam, you will see what I mean. During excerises when all the jets took off, you could see for miles the heavy black smoke that stuck around in the air.

And then of course there was the water truck that came out and soaked a crew after a last flight Very Happy

The G & H's used demineralized water for the cameras on the nose. I don't know if they still use a truck for that anymore or not.

Another tradition at SAC for POL troops was on your last day there, you
got thrown under the fill stand and soaked at 600 gpm!

Purplehaze wrote:

Do we still have anything water injected?

I believe only the Rolls-Royce F402 of the USMC AV-8B Harrier II still has water injection.

Quote:

Hot weather takeoffs and landings are aided by a water injection system that increases thrust by 2,500 lb. (1,134 kg) for 1 1/2 minutes.

Enthusiast Joined: Jul 31, 2005 Posts: 93 Status: Offline

I remember them days of old SAC... love them water burners on old A frames, i do miss it a lot.

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Engine smoke. Where does the smoke come from?