Mr Spaceman
Topic Author
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What Is Jet Engine "Inhibitor" Made Of?

Wed Apr 02, 2003 6:07 am

Hi guys.

After doing a search about what Engine Inhibitor is, I learned from a posting by VC-10 that (in his own words)......

A pickeled engine is one that has been soaked in inhibitor while it is in storage.

The fact that engine inhibitor is used to preserve an engine that's been in storage is also mentioned by the photographer of the 2 photos below. He says that the flames are caused by the inhibitor during the engine very first start.


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Photo © Will Lanting



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Photo © Will Lanting



My question is ..... What is jet engine "Inhibitor" made of?

It's obviously very combustable, so I'm wondering if it's simply a coating of oil to prevent the engine from rusting while in storage.

Chris  Smile
"Just a minute while I re-invent myself"
 
jim
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RE: What Is Jet Engine "Inhibitor" Made Of?

Thu Apr 03, 2003 2:56 pm

To the best of my understanding, the inhibitor is just a light-weight mineral based oil which is used to fill the Fuel Control Unit before the unit is placed in storage. This is to prevent the FCU from rusting while the unit sits around on the shelf. If the unit is placed on an engine which is already in service, the oil is usually drained out during the installation. But, if the ENGINE is stored with the fuel control installed, then the oil gets burned as it is forced out of the fuel control by fuel.
The results are very spectacular, as seen in the photos.
 
dc10hound
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RE: What Is Jet Engine "Inhibitor" Made Of?

Fri Apr 04, 2003 1:39 am

Whenever I've started an engine that has been "pickled", I've only seen lots and lots of dark gray smoke, but no flames.

The photos sure look like the engine might be experiencing a "hot start".
"Eagles soar. But weasels never get sucked into jet intakes.."
 
Mr Spaceman
Topic Author
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RE: What Is Jet Engine "Inhibitor" Made Of?

Sun Apr 06, 2003 7:01 am

Hi guys.

OK, Thank You for that info.

So the mineral based inhibitor is only used to protect the FCU while it's in storage and not the whole engine. I was imagining the whole engine being coated in a type of oil to prevent rusting, thus the term "pickeled", but I guess that would cause quite the mess and isn't nessesary anyway.

Here's a question.

Whether or not the flames in the photos are being caused by oil in the FCU burning off during the engine's first start since storage, or the fact that it might be experiencing a Hot Start (caused by an excessive fuel flow during initial fuel application which exceeds a pounds per hour limit), why is the flame only located at the bottom of the tailpipe, and why is it blowing aft in such a "straight" line.

Doesn't the column of hot exhaust gases and bypass air exit a jet engine's tailpipe in a turning, swirling, twisting pattern which is caused by the spinning compressor and turbine blades? I'm curious about this.

Also, how big is a FCU?


Chris  Smile
"Just a minute while I re-invent myself"
 
Staffan
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RE: What Is Jet Engine "Inhibitor" Made Of?

Sun Apr 06, 2003 7:38 am

The excess fuel in the engine will collect in the bottom part of the combustion chamber, and when ignited, that's where the flame will come from. Regarding the flame blowing in such a straight line, vanes are used to steer up the airflow before it exits the engine.

Hope that helps!

Staffan
 
rmm
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RE: What Is Jet Engine "Inhibitor" Made Of?

Sun Apr 06, 2003 1:23 pm

When we used to inhibit engines, including 737's, we actually motored the engine and turned the fuel lever on so that the inhibitor would flow thru all fuel circuits. When we saw "oil mist" coming out the tail pipe we would close the fuel lever. What you are seeing in the picture is the heavier oil sitting in the bottom tail pipe. Remember, you can inhibit a component, such as an FCU or an entire engine system.

We used a product called "Diala B" to inhibit engines. It's actually a transformer oil made by Shell. There was also an oil tank additive.

Rmm
 
DC-10Tech
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RE: What Is Jet Engine "Inhibitor" Made Of?

Mon Apr 14, 2003 4:24 am

I've never seen flames like that from a pickled engine. Usually just tons of dark gray smoke. But I have seen flames like that on a wet start on a new engine. Hell, I've even had them so bad that we couldn't put the flames out!
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jim
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RE: What Is Jet Engine "Inhibitor" Made Of?

Tue Apr 15, 2003 1:28 am

Folks,

I have personnally seen this happen only a couple of times. Here at DAL, there have been quite a few photos taken of it. It can happen after every CFM engine change. The maintenance crew normally will motor the engine with the ignition breakers pulled (to force the preservative out), abort the motoring, and then attempt to start the engine.

But, if the motoring is not done, and the first 'wet-spin' after an engine change is allowed to be a start, well, what you see is what you get.

Think about this: how did the photographer KNOW that there was going to be a hot start, so he could have his camera ready?

Of course, my experience may be due to Delta using a different preservative than other airlines, I don't know.

The first time I saw this was actually on a 727 APU start. We had changed the APU and as we were pulling the a/c out of the hangar, the A&P in the flightdeck started the APU. A flame about 7 or 8 feet shot out of the top of the right wing, at the APU exhaust. As I was a new hire, I naturally began to run for an extinguisher, much to the amusement of everyone else watching. It was over before I had taken my second step, but my explitive was loud enough for all to hear!

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