George62

Me and my Rc friend bought together two KingTech turbines K-45G for two small L-39 Albatros models (Black Horse) which we planned to convert for jet engine power. This month we started flying with the first completed Albatros.
First, we did several trial runs with the engine on stand and on the ground before maiden flight (10 runs in total) without any problem. Then we successfuly did the maiden flight and 3 following flights.
However during the 5th flight (15th run of the turbine in total) the engine suddenly shut down in about 4 min after starting it: it happened during a normal straight flight and at about half the throttle, the fuel tank was 3/4 full and clean, hopper tank showed no bubles, both Rx LiPo batteries as well as the ECU 3s LiFe pack battery were duly charged. The model suffered some nose and wing damage on landing off the runway, however fuselage stayed intact. So we did a test run of the turbine on the ground and it operated smoothly at idle,half&full throttle until the tank ran out of fuel in about 11min.
As this is our first jet engine experience we still wonder about the cause – can anybody give us some advice ?

gunradd

My Feedback: (9)

The data terminal will tell you why the engine shut down. This will help allot. Also what are your PW readings at idle and full throttle? Most turbine shutdowns are due to fuel system.

George62

Thank you for the advice - we´ll try to check the data terminal, however as I wrote we did another test run after the sudden shutdown to see if it happens again till we ran out of fuel thus we let it shut down again because the tank went dry. The manual says that the data terminal show only the last engine shutdown´s data. It also says that we can get the data for the last 51min thru an USB inteface cable - if we get it do we need any software to be able to read it on on a regular PC w/ Windows10 ? More, if that´s of any help we recorder the PW readings during the initial test runs of the engine on the stand: 103 on idle / 207 on half / 408 on full throttle

gunradd

My Feedback: (9)

Ok for the data record yes it works with windows 10 and yes you need software and that is available on the Xicoy website.

That PW is good but you need to get the PW while its running in the aircraft. This is what helps tell us whats wrong. Also make sure if it happens again you look at the data terminal and see why it shut down this is the most important thing.

Also what UAT you you using? Do you have any pics of the install?

George62

I have downloaded the software from Xicoy and ordered the USB interface cable, so now I am waiting for its delivery to check the data as you suggest - I will let you know more as soon as I get the USB cable. We use the Intairco UAT. For UAT and installation you can check two pix below.
George

mauryr

That looks like tygon hoses used in festo QS connectors. While that may or may not be the cause of your unexpected shutdown, qs fittings are secure only when used with polyurethane tubes. You also do not want sharp turns such as the one you have between the uat and the fuel tank, make a big loop instead.
I am not sure I understand your fueling connection so I won't comment on that, save reminding you that you cannot use a one way check valve because the vacuum caused by the pump would open it and let air in.
Good luck fixing your issue!

George62

Thanks for your advice and we will consider using the polyurethane hoses instead of tygon as well as avoiding hose´s sharp turns installation, however we are now waiting for the USB interface cable delivery to try learning more from the recorded data and conclude the actual cause of the shut down prior any action as advised by gunradd above. Anyway, thanks again for your advice.
George

George62

We got the USB interface cable and got the data for the last 51min as the manual claims. It seems there was no problem with temperature or PW - everything just went down suddenly. I used the software to make a graph and enclose it for your evaluation along with the data in numbers.

mauryr

This log looks to me like the result of a typical flameout caused by a bubble.
As the flame dies the rpm plunges while the ecu tries to keep it up by pumping more fuel. Once the rpm reaches the minimum limit, the ecu gives up and shuts off the fuel supply.
As said before, I think you need to take a hard look at your fuel system and check for leaks.

gunradd

My Feedback: (9)

I agree 100% with Mauryr. Looks like air in fuel system.

George62

Thank you gunradd and mauryr for your analyse and advice.

We ruled out the bubble could be the cause because we deliberately tested the engine on the stand to see what happens when we send few bubbles down the pipe from the UAT and all we saw and heard was some puffing, but no fameouts. Therefore, we rather tended to blame either mulfunction of the ECU or some problem with electric supply as we experienced some fast flashing and then no light at all on ECU´s violet control LED prior starting the turbine 4 cycles back from the unexpected shutdown. The ECU battery we use is LiFe ZIPPY Flightmax 2100mAh 30C and its testing yesterday showed it is capable of max continuous burst of 10A and max limited burst of up to 20A
- Is that enough ?
- Does the ECU/FADEC records battery related problems and data and if so how we can get them ?
- What average amps or Watts takes 1)the pump, 2)starter motor and 3)ingnition/glowing process ?
- What tell us the numbers apprearing under "Aux" in FADEC ?

Based on the findings, your advice and other information we plan:
- to remove the filter from the line between the pump and turbine, seeing it as a potential source of bubbles and an obsolete part as the UAT filter should do the job
- to replace all tygon hoses and sharp turns by loops
- to replace the ECU battery if you advise to do so

Kind Regards,
George


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gunradd

My Feedback: (9)

George in my opinion the entire electrical system is working perfect. The 2 things that could cause your engine to shut down in flight would be the temp probe or RPM sensor. The info you posted show both where working perfect.

I also would not suspect the battery. If your turbine can start fine then the the battery does very little after its running. Battery only runs the pump after start. So I would say your ECU Battery and turbine are all fine.

Really feel like you have have a fuel problem prior to the turbine.

luge_racer

I had a similar flame out on my K-60. Did you notice a puff of smoke when the engine shut down?

George62

Yes, there was a greyish smoke coming out of the exhaust pipe for a short time after the shutdown ...

George62

Thanks for your evaluation, Kris. We will continue flying with the repaired model and adjusted fuel system and will let you know about our further experience.

Best Regards
George

gunradd

My Feedback: (9)

The puff of smoke is what happens after an air bubble flames the engine out. The ECU pumps more fuel into the engine but the flame is gone so it just smokes out the back.

If the engine does not smoke then you know the ECU shut the engine down due to a different problem like temp probe or rpm sensor error.

mauryr

The tygon in the festos, really

George62

I understand - as I wrote "we will replace all tygon hoses ..." meaning ... replace for the polyurethanes as you suggested

extra 300

My Feedback: (3)

Maybe a dumb thought, but while running your turbine on the ground for the first runs did you shake your filter to make sure no bubbles remained trapped inside it? is your filter mounted horizontal or vertical and do you have it installed fixed or loose?
It should be installed vertical and loose.
My guess would be that at some point your filter had built a bubble which was released in flight thus producing a flame out. This would also explain why turbine ran without issues after this incident.
One more thing to look into, check your UAT after flight and make sure that it is still full (unless you have burned all the fuel in your main tank). If you notice that level has come down this would mean that your fuel system is not air tight and you should inspect same for leakage, usually at the Festo joints...

Hope this helps
Regards,

extra 300

My Feedback: (3)

On another note, as per your above plan, you intended to remove the filter between pump and turbine. Would strongly suggest to avoid this step as pump could still produce very smal particles that would clog your turbine and filter at this stage is meant exactly to avoid this risk.

Best regards,

George62

Thank you for your hints and we will consider adjusting our filter installation accordingly.
Best Reagrds,
George

George62

So we went for another flight after the sudden shutdown and alterations made as per the advice given here, i.e. replacing tygon tubes for PU & making loops to avoid sharp turns, but we could not start the turbine this time at all - when we triggered off the starting process, the connected terminal showed "zero" values for T/RPM/PW all the time of the initial stages while the reading said: "Ready - BurnerOn - StartOn" and then it ended up with reading "StartBad". After we repeated the process for several times without success we tried to adjust some of the starting parametres as suggested elsewhere on this forum, but the result was the same.
We assume the reason is that either the turbine is not able to send the information to the ECU or the ECU is not able to receive it, we tend to think the latter option is more likely as we are suspicious about the ECU since the sudden shutdown.
We would appreciate your suggestion on what to do to get the turbine working again ?
George

mauryr

Probably too obvious to be of any use, but: have you checked your connections?
These signals come from the flat black cable that plugs on the right side of the ecu

George62

Yes - all the ECU cables were among our list of possible causes and we duly checked them all and found no problem, imperfection or breakage ...

George62

You were absolutely right - the turbine´s running again Many thanks for your "obvious" advice we did not paid too much attention at first and which turned out to be the right clue to our problem. So here´s what happened :

When we re-connected all the cables back to ECU after finished repair of the fuselage and wing we did not notice one "small" difference we made in the ECU´s sockets labeled as "Thermocouple/RPM sensor/AUX Rx input/Throttle input" - while we were making sure to have the black cube connector correctly oriented with the white dot toward the LED light we completely overlooked we connected it into the RPM sensor&AUX Rx input sockets instead of the Thermocouple&RPM sensor sockets ! I enclose the pictures of wrong and right connection to illustrate our mistake that can be done by any beginner like us :
WRONG CONNECTION RIGHT CONNECTION


When we re-connected correctly the engine started and ran without any problem.
Now we are able to go to fly soon again hoping we eliminated flame out repeating by replacing all the tygon tubes for the PU ones because of the FESTO coneections and by making loops to avoid any sharp turns.
We will keep posted on our further experiences and we wish to thank to

mauryr, extra 300 & gunradd

for their valuable information so far

George