Hi there,

I am new to turbines and am in need of some help and advice from some fellow turbine fliers. I have a JJ 1400, and the thing runs superbly. I had it mounted on a test stand before installing it in my stingray, and all the test runs went just fine. I had to tinker around with the acceleration, deceleration and stability delay just a bit, but I eventually had it so that I could "slam" the stick to full power, and the engine wouldn't flame out.

So, I pulled it off the test stand like I said, and installed all of the gear in my stingray. I then tested the engine several more times just to verify that every thing was still working properly. Up to this point, I was using a 5 channel FM radio system, and I had ordered a 7 channel radio system with PCM capabilities.

I swapped out the FM receiver and installed the PCM receiver and got all the channels sorted out and also reprogrammed the FADEC to the new radio. I went out to once again test and check everything to make sure things were still in working order. However this is when despair came knocking on my front door!

I initiated the start sequence, and the engine started just like normal. I let it idle for about a minute and just watched the HDT to make sure things were "cool." I then slowly advanced the throttle all the way to full power and then slowly back again. Everything was fine, so I once again advanced the throttle slowly to full power and then quickly pulled the throttle to idle to make sure the Deceleration delay values were still suitable. Deceleration went without a hitch.

Now, the third time I "slammed" the throttle to full power, and seemingly at about 75% power the engine faltered and began losing rpm and eventually there was a torch like flame suspended in the air just behind the exhaust nozzle and the engine spooled down. Of course I immediately shut down the engine with my controls and turned the fuel shut off valve to the off position.

After contemplating what had just happened, I started the engine again, and after letting it idle for just a little, I slowly advanced the throttle and was able to obtain full power and hold it indefinitely. Also, I could chop the throttle from full power and no problems there either. It is only when I "slam" the throttle to full from idle that the engine will quit.

Anyway, to make a long story of, start after start after start and test after test after test, short I eventually had a value of 150 on the acceleration delay, and still it would falter, lose rpms, and flames will be suspended in the air just behind the tail cone.

It is very frustrating to me when I had it running just fine, and now all of a sudden when I am ready to go test fly it the acceleration is giving me problems.

Anyone have advice or know what cold be wrong?? The only thing that changed what the radio system. I just thought that somebody here might be able to help me with this problem.
If you have any questions that need answering for you to determine what might be wrong, please ask and I will answer. I just want to go flying!

Thanks for your time,
Brandon

I don't think changing the radio would have that effect but for trouble shooting switch it back to the configuration that last worked and see how it behaves.

Marc

Hi Brandon,

Sorry to hear about your problem, but unfortunately not surprised, you are me a year ago. http://www.rcuniverse.com/forum/fb.asp?m=3109179

I tried all kinds of things and eventually sent my engine back to Joe and he sent me a different one that has run well but not without its own minor issues to be worked through. Joe later told me that the problem with the first engine involved binding in the rear bearing.

My suggestion is don't waste your time trying to fix it with the settings, send it back to Joe.

Mike

Thanks for the replies. I took a look at the thread Mike posted, and what he describes is exactly what is happening to me!

Mike, did you ever have the engine running just fine, or was it messed up from the beginning?


Brandon

Well, here is what I am going to do. I am going to switch back to the configuration that it was working in last. If it still does the same thing, then I think it would be safe to say that something is deteriorating very rapidly inside the engine causing poor mixture of the fuel.... like the fuel sticks. I have seen several pictures now where they have basically melted away. I am pretty sure I have the SS CC because the sticks are not straight but curved.

If I still can't get it to run like it was before, then I will take it to work were I can scope it out through the glow plug hole and maybe find out what is going on in the inside. If I can take pictures I will and post them.

Brandon

Brandon,

Mine would run great sometimes and then blow flames the next time. At one point I thought I had it fixed and had about 4 runs in a row where I tried to make it flame with quick throttle changes etc. and it worked perfect. I was ready to put it in the plane but decided to run it one more time on the stand about a week later and it was back to its old trick of losing RPM and flaming around 100k. My current 1400 has never done this (Knock wood), but it was poorly balanced and the pre-load was sticking and the SS fuel sticks burned away after 25 flights, all fixed and running great now.

Mike

Well,

I took the engine to work and removed the glow plug so that I could get the scope inside to check things out, and felt a little relieved. The ends of the fuel sticks are still in tack, and in general everything looks to be in place. Just a few things caught my eye while I was looking around.

There seamed to be a lot of "soot" and "flaky stuff" collected especially on the ends of the fuel sticks. The best way I can describe it would be to relate it to very very dry skin or even a bad sun burn when the skin begins to peal. Is this normal?

The thing that concerned me the most I suppose would be the swirl jets and their relationship to the ends of the fuel sticks. I believe it is normal that there are half as many swirl jets and fuel sticks, and they alternate every other stick right? However, the relationship of the swirl jets to the fuel sticks was not consistent from one to another. They were close, but not in the exact same position. I am sure this is not ideal, but is it enough of a problem that is could be the cause of my troubles?

Something else that came to mind was case pressure. I started the engine and while it was idling, I put several drops of water right on the seam where the front cover and the outer case meet. When I did this, I did get some air bubbles. So, I took some electrical tape and tried sealing the area up, and still had no success. It would still do the torch thing on spool up. I then started it again and put some water drops on the electrical tape seams, and I still had air bubbles form, so I guess I didn't really seal it up very well after all.

The best thing I can think of right now is that the mixture is becoming to rich (excess fuel) on a fast spool up, and this is why is begins to burn on the outside of the engine. But, if it is powered up slowly, I am in a way babying it along until it reaches full power. Does this make sense? I wonder if this could be my problem.

Thanks in advance for any advice or help,
Brandon

I'm not familiar with the JJ-1400 but no micro-turbine should leak air at the diffuser.
You probably need to replace an o-ring on the intake assembly.
If you're not comfortable with over-haul work (or if it is under warranty) then send it in for service.

ROB

I did notice that the outer case doesn't fit very nicely on the diffuser cover. The screws obviously line up, but in between some screws the cover is "bunched up" causing it to lift away from the diffuser cover. I am sure the O-ring is "trying", but if the cover isn't a nice fit, then it is a lost cause.

A friend of mine looked at the outer case as well as the exhaust cone, and he mentioned to me that he thought they were water formed or something like that. For example, I think I am correct in saying that Wren Turbines turn their outer cases down from solid stock. I am sure this makes for a perfect fit. To bad the same isn't true for the JJ's

Brandon