Hi everybody,

We are currently investigating whether contamination in the UAT may be affecting the low RPM operation of the turbine.

The turbine has control loops that are calibrated to the necessary voltage at idle. If something affects that "draw" too much, too fast, in some cases the turbine cannot recover fast enough and the turbine may quit, sometimes even on taxi out.

Here is what it looks like. We are researching with BVM right now and will keep everyone apprised.

thats what mine look like too, still seem to work though with no flame outs.

jason

Hi Matt,

I can just about guarantee that your looking at a good old fashion algae bloom; aka pond scum. Back prior to January, 2000 I had exclusively run Jet-A from the local airport FBO's fuel trucks. During this time frame, I started accumulating large amounts of dark green gooey slimy gunk in the filters that go from my ground based fuel supply to my planes.

Then, during several flights, I started loosing power and I had a couple of flame outs. Once on the ground, I discovered that the filters on board my airplane were clogged up with the same gooey stuff, thereby inhibiting fuel flow and power level. I then came home and closely examined my fuel supplies to discover the same gooey slimy gunk everywhere. ugh...

I did a bunch of research and learned that algae loves to grow in kerosene. Actually, it lives in water that accumulates within fuel tanks and the algae eats the kerosene for food. You most probably got the water/algae from an airport's Jet-A fuel truck or storage tank. Unsealed storage tanks such as the airport fuel truck tanks and underground fuel storage tanks are vented to the atmosphere and kerosene is anhydrous so it absorbs the water out of the air. Contrary to popular opinion, Jet-A (and any other fuel purchased from an unsealed tank) is the dirtiest source of fuel around.

In the beginning, I purchased Jet-A exclusively. However, I have since gone to the odorless K-1 kerosene that you can purchase in the hardware store in hermetically sealed 5 gallon containers which are re-sealable. I have been flying this stuff exclusively since January, 2000 and I have not had another algae episode yet. All of my UATs remain totally white (except for a little pink from the red dye in the kerosene). I check my filters often and they are always totally clean. While the hermetically sealed K-1 from the hardware store is more expensive than Jet-A it is more than worth the price. Its absolutely the cleanest stuff around. I have purchased both the Crown and the Parks brands of hermetically sealed Kerosene and have found them both to be equally free of any type of contamination.

So, anybody that is noticing your UATs turning dark green need to consider changing your fuel source. I would also recommend that you either replace the contaminated UAT or the UAT's bag. Otherwise, you definitely will eventually run the risk of a flame out due to the algae clogging up the UAT or your fuel filter.

Gordon Dickens
mailto:[email protected]
http://www.gajets.net

Hi Matt:
Is this the same pic from John Redman. Or did this happen to you?
I was not sure. I had a flame out when I was taxiing out for take of with my T-33. Hmmm better check this out.

Dave R

I don't know how old Matt's UAT is but it is my understanding that Mat has been burning Crown kerosene for quite some time. I hope that someone finds the exact cause of this....that stuff looks awfull!!! My local Home Depot has K-1 kerosene reduced to $14.95/5 gallons. I was going to buy some and try it but I'll wait until this is resolved. Mat didn't say whether or not this UAT came from one of his birds. Matt, can you please be more specific as to what fuel was used in conjunction with the affected UAT?!?

Kevin

When I started flying turbines 2 years ago I asked AMT USA what type KERO was it factory tested with, they told me the stuff out of the pump down at the local BP gas station. So I just buy my K1 at the local gas station for usually $1.50 gal. I have 50 gallons now thru my uat and MERCURY with a clean white filter.

I always leave the uat filled and capped off, even during winter storage, just my .02

Look for something like "Marine Diesel Power", which is an antimicrobial treatment.
Boaters use it in diesel tanks, for this very reason. There's probably a formulation for kero.


Off a quick Google... Pri-D:http://www.slpcorp.com/Products.htm

This is what John Redman wrote me

Well guys I had a couple of low rpm shut downs on my Bobcat the other day. What I noticed was the rpm falling to around 27,300 from a full throttle to idle transition and then on occassion when I taxied out for takeoff and hit the brakes the engine would shut down with a low rpm condition.

I talke dwith Gordon Dickens as he had encountered the same problem. I gave him the info and he directed me to the UAT. I had mentioned the UAT because of how dark it was. I had suspected it as well, but didn't want to go the $50 way.

Well I pulled the bag out and it was down right discuting. This UAT was in my last Bobcat and now the new one. The UAT has seen close to 300 flights. Now as we know the UAT sits full all of the time. There will be times where I don't fly for a couple of weeks. My guess is the algae groth occured during those times.

End prognosis is if you don't plan on flying for a while then it might behove us to drain the UAT. This is just a thought. I have ran exclusively JP-8 with mil spec 7808 engine oil. This could be a determining factor as well. Now that I am out of the Air Force game I will be running Jet-A. I will continue to monitor this for a while. Don't have a clue about kero as I haven't used it. I do believe if you fly at least once a week, then you have no worries. Fuel continues to transfer through hte system without a chance for growth on an expanded schedule.

I plan on calling BVM and seeing how much these bags are. My guess is they will be cheaper than a UAT tank and they are a snap to change.

Pics are attached to show the discoloration.

John

For those of you who heard from John Redman this is his UAT.

He used military fuel, not Crowne. We are still investigating.

Matt- I agree with Gordon that you are looking at good old algae bloom.

You might consider using the Jet Model Products accumulator in place of the UAT.
The advantage other than impact resistance of the aluminum construction is that no sunlight or UAV rays can penetrate the canister.
RESULT- NO ALGAE BLOOM
Those of us that have been using their system for over two years have had none of the problems that you are experiencing.

Clean fuel to the engine every time.
Think about it.

Marty O

The JMP filter is a nice item but won't prevent bloom due to it's metal opaque housing. The kerosene algae grows fine in underground tanks at airports, in jet fuel tanks, and in my dark blue opaque fuel containers.
All you need is a good dose of contaminated fuel, lots of air interface, like with 1/2 filled fuel cans, and heat.
I have never witnessed algae blooming in the UAT itself. It formed in my blue opaque fuel containers, and then was trapped by the UAT.

Tom

Algae-


My old biology prof still says that if you have light present it will aggravate the situation of algae, ask any aquarium hobbyist.
It may be that these folks are leaving a little fuel in the UAT and with the hatch off it starts the cycle for the algae to grow. It would be interesting to know if they have it in their fuel cans.

All I know is that we don't purchase special Jet fuel and we keep it out of the suns rays as much as possible and we don't have the problems.
Nuff said.
Marty O

We have never seen this problem at all with Crowne

We are trying to understand what process is at work, as well as a way to diagnose this via the ecu and the behaavior of the turbine.


More to follow.

Well guys I am a little late but here I am. The pics of the UAT are from my Bobcat. I sent the pics out to a few people who I know run jet cats. I went to Matt as well as Bob Wilcox because I know they won't let this thing die until we are exactly sure what to check for and prevent in the long run. I have come to the conclusion that it is algae inside the UAT bag. I run JP-8 exclusively, as well as Mil spec 7808 oil (I believe this is the same as aeroshell 500, but not sure).

The UAT in my Mig looks very similar. Since installing the new bag I have noticed that the RPM's don't seem to fall off as much as before. I have been running the engine on both Jet-A, JP-8, and Kero K-1 from Crown. I haven't flown much at all in the last month due to preparing to make a family move and such.

Don't sweat anything yet. It is apperantly obvious that there was a large amount of algae growing inside the UAT bag. But here is the good news. This bag is also an unbelievable filter in that the max pump voltage never went up at all for the simple reason that none of the algae left the UAT. The UAT bag is large enough to handle this without a problem in the air.

Being as large as it is did not affect the medium to high output of the engine, as well as the filter in the fuel line from the pump to the fuel valve is clean. There is absolutely no evidecne of algae anywhere inside the fuel system except the UAT. So the end result is the UAT did more than its job in this case.

John Redman
Team BVM, Jet Cat USA, Shultze Chargers

And, now that we've come full circle about the algae --------bag is terrific filter not allowing algae to get out of it ----- what about the idle shutdown occurrence/syndrome? Unexplained idle shutdown has only happened three or four times in my Jet Cat experience, but those three or four times really puzzles me. Damn, the Jet Cats operation is otherwise so perfect, these unexplained shutdowns really bug me. Jet Cats are so close to perfect when something is slightly screwy it really sticks out like a sore thumb----.

Nat says I should idle up to about 35,000 for cooler operating temps, possible elimination of the shutdown syndrome, and better throttle response times. Well, I tried it and noticed I needed slight braking during taxing, and it seemed like I was being pushed a little during landing. Nat claims that the idle up RPM's don't increase idle thrust noticeably, but I thought I noticed a slight more push on idle. Bottom line I re-set my idle to factory default of 33,000, I'm stubborn!

Fact is I had Bob change limits so I could idle down to 31,000 RPM's. I've only tried that once or twice, with no idle shutdowns but have basically stuck with the factory default 33,000 ---------- Also, a note here out of the four idle shutdowns I have experienced one of them was my P-80 in my MIG, and the three others were in my P-120 powered Bob Cat!
Lee H. DeMary
AMA 36099
Not complaining a bit Bob just puzzled, why does it happen? Seems like to me a slight software change with a built in time delay of sorts could eliminate any unwanted shutdowns -------

I have had about 5 or 6 low rpm shutdowns. I have checked and rechecked everything and UAT is clean. Motor runs perfect but sometimes after a snap or tailslide it will low rpm shutdown. Never happened on ground. This motor is on my Bobcat and its a 120. It reads 126300 low rpm shutdown. Maybe we can establish a pattern.
This motor just received new combustion chamber and compressor wheel and I replaced all line and filters all the way to tanks. I also pulled tanks out and checked them. About the fifth flight from work being done it low rpm shutoff after a snap.
Scott

Well, I have never had a low RPM (idle shutdown while airborne) mine have always been while taxiing! The airborne type would have gotten my attention much sooner than my mentioning it now --------- maybe Bob can comment, and or has a solution to this possible problem. I totally rely on these turbines when I'm airborne, and so far have never been bitten ----- dumb luck I guess ------- have done snap rolls entered vertically with power reduced to idle at snap, also hammer-head-stall turns, they don't work well with zero blast on the rudders -----although I thought I notice some blast effect with my Bob Cat -- bottom line the motor has always been there ------ and I will assume it will be until I get bitten --------

Lee -----

I am not sure if this helps. This a pic of my UAT from a 50 flights Hot spot. I used JetA, Gas station Kero, Ace hardware kero and a friend's kero. It looks perfectly clean to me. Just FYI!!!
Now I hope I will not get a flame out due to air bubbles in the UAT after inspection for this shot

Just checked the bag in the UAT from my BobCat which was installed when I had the RAM 500 flame out at low rpm. The bag is discoloured but seems to have very little or no resistance when blown through.

The bottom line is I have NEVER had a flame out using centered pickups in header tanks. Is the UAT really as good as is claimed and is it an overcomplication with the potential to cause the very problems it was designed to eliminate ?

After almost three years there is no sign of algae growth in my F4 tanks or tubing, the filter is almost clinically clean and after 4 years of use the F15 tanks etc are the same and neither has suffered a single flameout on the AMT Peg or JetCat 80, 120 or 160. I have used almost exclusively Jet A1 and the cleanliness , as proven by the refuelling line and airborne filters has been near perfect. Nothwithstanding Gordon Dickens pst, if you get dirty Jet A1 fro am Aviation source that is unacceptable. and very worrying and should be brought to the attention of the fuelling company.
BRG, David Gladwin.

It has been my belief that the UAT is really NOT needed. I too have used a 2oz header tank with a center pick up in my "for sale Bandit" and never had a flameout or else it would not be here for sale.

I use THREE kero filters in my 5 gallon jug. An Auto filter with a glass body, a paper filter and a FESTO large filter. I keep my kero sealed the best I can and out of the sun or humidity. I take it out of my van if I do not fly for more than a weekend or two. Although I had kero sitting in my garage for three months and I just finished flying with it, no problems. I use Exxon oil in case some one wants to know. Hope this adds to the confusion

Well guys the UAT bag went to my Boy's High School to be looked at under a microscope to see exactly what it was. Mike Danchak made this suggestion just to make sure we knew what we were dealing with.

Well it turns out that most of it was dirt. The Biology teacher who looked at the contents of the "gunk" under a microscope said while there was some algae, most of it was dirt. His descrition came to be that he felt the algae content was no more than 20% on hte stuff in the gunk.

I found this definitely interesting. the end result is it wasn't a large algae bloom as some of us suspected. What does this mean, well nothing really, it is just more information for the puzzle. I will continue to work this issue until I am sure what is going on.

I will keep you informed.

John Redman

John, just out of curiousity, how much filtering did the fuel get before it reaches your UAT? Just trying to make the best use of your experience in this situation....

Thanks,

I have two car filters on my fuel jug as well as a clunk fliter inside the fuel jug. When I pour the fuel into the main jug it is filters through a fine mesh screen, around 15 microns, so it should be pretty clean. I am guessing the dirt come from our desert environment here. No matter what you do to keep it out it still finds a way in.

Don't know what else to say on it. I am still a little baffled.

John

Thanks, I know most of us rely on a filter AFTER the pump, and perhaps one or two in the fueling station.......

so, and I am just speculating here, is it possible for dirt/dust to enter through the main tank vent on the jet..? Should modelers be thinking of some sort of filter for the vent line? This could raise a whole new set of concerns about getting clean air in the tank without causing a vacuum, and fuel starvation... Again, I am only speculating....I am just about to lay the plumbing for my first jet, so this comes at a very appropriate time.....

Thanks....

Wayne B.

Hi David,

I believe that full scale turbine engines are capable of handling dirty fuel a bit better than our miniature turbine engines. I am not an expert here, however, I believe that is the case. In any event, the Jet-A that I have purchased over the years has not been very clean. For example, the Jet-A that came out of the fuel truck at the Lakeland, FL airport this year at Top Gun was very suspect. Joe Rafalowski has a water trap that he pours his fuel through into his 5 gallon storage tank. He put about 3 gallons of Jet-A in his storage tank at Top Gun from the Lakeland fuel truck and ended up with several ounces of water in the trap. The mere existance of water in the fuel virtually guarantees that algae was also present.

I don't think that our miniature turbines would care about this much either if it were not for the very fine mesh filters that some of us use as well as the UAT which also has a very fine mesh. Algae will go right through a coarse mesh filter such as a Sullivan Crap Trap. I have even seen it get by the fine mesh filters such as those used and recommended for JetCats. That is why I double filter my fuel going from my ground supply to my airplane tanks. So, if you don't use a UAT or fine mesh filters then the algae probably doesn't matter very much and may not clog your fuel filters.

While I am not a full scale pilot, I am a fractional owner of a Learjet 60 and I have often overheard pilots talking about not wanting to take fuel from a truck that is getting low on fuel because of the algae, dirt and water that they believe accumulates there.

FYI,

Gordon Dickens
http://www.gajets.net