Hello
I have now logged four flights on my new Bobcat. All have resulted in a dead stick landing. The motor is a new P80 +(L version) Myself and my buddies with Jet Cat's are out of ideas. Every thing is plummed as Violets specs except I used Tygon on the vent lines. The funny thing is I can run it on the ground for 8 minutes, no problem. In the air it has been dying at almost routinely at 3 1/2 minutes(about 4 1/2 run time). The wing tanks still have fuel, the center tanks and UAT are completly full. After the first two flights I replummed all the tubing. I see no leaks and no air bubbles. Even the hose going directly into the turbine is full of fuel. The GSU shows all parameters to be in the normal operating zone. On the last flight we disconnected the vent tube and were able to get about an extra minute.
Thanks
Scott

What does the ECU show for the last shut down. Maybe you are over-speeding it or it thinks it is. Try 1/2 throttle for a whole flight and fly a big racetrack pattern to see if sunlight is the cause, it should turn off in the same place if sunlight.
Darryl Usher

The last shut down showed about 90,000 rpm. Since I only have four flights I've been around 5/8-3/4 throttle. What would Sunlight do?
Scott

i don't know if sunlight affects the jetcats. But if it did, it could give the motor a FAKE RPM READING. Is the jetcat ecu capable of recording highest and lowest rpm in flight? If so i would check that ...to see if it spiked up or down because of sunlight.

I WOULD DEFINITLY ASK MATT in the JETCAT TURBINE SUPPORT FORUM. HE IS VERY GOOD AT SUPPORTING JETCATS PRODUCTS.....AND IF HE CAN'T....HE HAS ACCESS TO MR WILCOX WHO CAN.

The Jet Cat is capable of recording that information and was checked. All rpm's appeared normal. The ECU should not see sunlight. I do have the clear canopy but it is under the tub deck. Again why would this only be effecting in the air and not on the ground? Seems like a pressure or vacume problem to me.
Scott

The front of the turbine is where the sunlight can cause problems.
The starter nut has hole in it and light passes through to give RPM. There are two basic types of sensors, light and magnetic.
What the new JetCat use I don't know.
Darryl Usher

Flameouts occur, generally, for one of 3 reasons, lack of fuel, air in the line, or the ECU shuts it off. Yours is likely fuel or air. I've had a few flameouts with my P-80 and I know the cause in every case. So, on the air front, just because you have a UAT doesn't mean you have no air going in the lines. I have just recently witnessed a case where the fuel tube at the festo fitting at the engine case wasn't quite all the way in, had a bend near the fitting and was leaking air into the fuel system right at the engine. No visible sign of air anywhere but 4 unexplained flameouts until new tubing with a straight shot and fully seated was installed.

Fuel starvation. I use Tygon everywhere but from the pump to the engine. That's not a problem. I think BV has 6mm clear tubing everywhere (did you use any of that) but I don't like it because it's not tight enough on my fittings for me. Try draining your full fuel system with your fuel jug pump and see if there's significant restriction getting the fuel out. Could be not enough flow through your lines which causes significant vacumn in your system starving the engine. Are you running 3/16 or 5/32 tubing into your tanks or Tee's that are small?. If it runs OK statically and bad in the air, it could be a vent issue that is causing suction on your tanks combined with marginal fuel flow to where the pump can't overcome it. Check the max pump voltage after a flight and compare with a ground run. Of course you can pressurize your fuel system by pointing the vent tube into the wind.

Probably heard all this before but my $.02

PS - in every case where I have seen an airborne flameout due to an air bubble I saw a 50 foot white vapor tail out the back from unburned fuel. Did you see this in your case - could be a clue as to an air problem or fuel starvation problem.

Scott,

My question is what does the GSU say the reason for the shut down was. That will give us a starting point. What was the max pump voltage at shutdown? I am wondering if you have a fuel line leaking at hte festo on the front of the motor. Need to know this stuff before we proceed. From there we will get you in the air untill the tanks are dry.

John Redman
Team BVM, Jet Cat USA

Hi Scott,

You are getting some pretty good advice already, but I will try to help.

As John asked, what was the last off condition? If you have not run the motor on the ground since the last off condition, then it has stored the values from the last in flight shut down.

Also as Thud_Driver mentioned, the presence of a smoke trail is telling...if there is no smoke, then the shutdown was almost certainly commanded by the ECU. If there is smoke, it is most likely fuel system related, usually an air leak.

A last off RPM of 90K is pretty strange? Oh and the sunlight thing is no longer an issue. If sunlight affects the sensors, it reverts to a backup mode, same thing is the EGT sensor fails or falls out. The motor will still run.


Anyway try to get the last off condition and a call on the smoke trail and we will go from there.

There was evidence of smoke at shut off on the first two flights for sure. I did all the lines over, making sure all were on fully. There may have been smoke today, but I'm not sure. I was staying pretty high in preperation of a flameout. I see no bubbles in the system. I just checked last off conditions:
Last off pump 1.25
last off temp 443
last off cond RC-off
max temp 683
min 443
max rpm 118500
max pump 2.5
Thanks for the help
Scott

The off condition "RC-Off" indicates that the ECU was commanded to shut down. This can be from a normal shutdown command on the Aux channel (if in 2 channel mode) or by bringing the throttle (in combination with throttle trim) to below the normal low throttle setting.

I would check all of the mixes, the programming, etc to make sure that you are no inadvertently shutting the motor off, or getting a failsafe that is not programmed properly.

Normally a failsafe condition will show up as "failsafe" as the last off condition, but if the failsafe was not programmed correctly in the ECU, then it might show up a "RC off"

If all the shutdowns were like this one, it is definitely not your fuel system. I am going to dinner now but will be back in a couple of hours to help some more

Matt
I currently have it set up in the single stick config. I do have left over channels to do the 2 channel mode which I havn't tried yet. The throttle and trim were not brought to idle and I'm pretty sure I've cleared all my mixing channels. Again why would this happen in the air and not on the ground.
Thanks
scott

Well you have hit it, that is the thing to look for....ground versus the air

For example, we used to have problems with Futaba battery failsafe. If the RX battery went below a set point (for even a brief moment) , the throttle went to some predetermined position....if the position was outside of the programmed range, instant shutdown.

So in the air, the gear are up, the servos are moving more, with greater loads, etc.

Keep chasing that side down, you will find it.

As Matt stated about the batteries I would do a couple of full cycles on them to see where they exactly sit.

I would go over every mix option in your radio and make sure not one of them is tied to the throttle.

If you have programmed in the failsafe function into the ECU I would deprogram it and try again. Have the throttle in the transmitter programmed to idle in the event of a failsafe just for a couple of flights.

Also do you have the throttle trim level all the way up for the run mode, or in the middle? (a-la like the old Rams). It should be all the way up.

Are you using any type of flight modes? If you are and it is a JR 10X (not familure with the Futaba stuff) you might have the throttle going somewhere at the flip of a switch.

Places to start looking. But as Matt said, an RC-off condition says it is coming from the radio side of the system.

John Redman
Team BVM, Jet Cat USA

If you are using flight modes, there may be a mode which you use only in the air. A friend of mine had a problem whereby the engine in his pattern plane kept dieing only at a particular part of his sequence. Took him a while to figure out that that was the only place where he used low throttle in a specific flight mode, and that particular flight mode had a different (lower) setting for the throttle end-point than any of the other modes had.

Might be worth a check.

Gordon

Well one thing we have left our it is a range check. All radios tested went 1/2 mile with airplane on a card table and antennae out. We started turbines at this location. Move to a new frequency.
Darryl Usher

Thanks for the help guys. I am using a 10x. I am not using flight modes and throttle trim tab is all the way up for start. I will reprogram the ECU. Of course I won't if this did anything till I fly next weekend. How frustrating.
Scott

One more thing. My receiver pack is on its second year. It is a sub 'c' 1800ma JR pack 4.8. It doesn't show any signs of weakness. You think replacing this would be worth a shot. I've been wanting to go to a 6 volt pack like Violett recommends.
Scott

The plane has been range check with and without the turbine running. Another thing I thought of is, after the first flight we checked everything over with plane on. So, I bumped up the receiver battery with my field charger. This may be why I got nearly an extra minute and a half on the next flight? I also charge the turbine battery every flight. Hopefully were on to something here.
Scott

HI Scott:

Just to add to all the good advise up there. We had a P120 shut down in a Eurofighter due to low Rx battery voltage/current getting to the ECU. So, change that 4.8v to a NEW regulated 5 cell for starters.

Program your FS to engine idle and test on ground from full throttle and turn off Tx and see what happens.

Run engine at 3/4 in the ground and flipe plane upside down and shake it as much as you can while someone else moves all sticks to all corners (keep engine at 3/4).

Reprogram you ecu to your Rx with trim all the way up.

Range check at all throttle settings and at four angles of the plane.

Can you DEFUEL ALL the fuel from full to empty using your ground fuel pump?

I am assuming your ran at full throttle on the ground when the UAT was new!!

make sure your thermocouple in the nozzle is in the center of its space, not touching anything.

DO NOT shut your TX off IF you have another dead stcik. Bring it back and record ALL conditions on paper before turning Tx off.


If all does not help, send it back to jetcat for inspection and call BVM and tell him his plane is so slow it is causing turbine shut downs!!!!

Ehab
I'll change the battery to a regulated 5 cell. Question though is anyone using anything other than the Minni Hobby regulator. I can get MPI regulators at my local hobby store. I was at full throttle on the ground for 7 1/2 minutes shaking everything I could. Also the GSU says a Failsafe did not occur. Does that Matter?
Scott

I reprogrammed the failsafe and did the "learn RC" again. One thing I somehow had wrong is I did not return to the travel menu and set the min. and max. throttle travel to 75% before teaching it to the ECU. Could this have been the problem? It was set at 100%

That was the problem. You have been getting a failsafe in the RC system, which has been shutting off the engine. The ECU will now just record that as a normal shut-off. You must reduce at least the idle Travel to 75% before teaching the ECU. Only in that way will the ECU record a failsafe.

I'll bet if you fly now, without making any other changes, the engine will keep running but you will see failsafe's recorded in the post flight data. You're going to need to make some improvements in your RF link.

A word of caution about the MPI regulator...they seem to generate more noise than two other brands I have tried. Be sure and range check to make sure you don't further degrade your RF link. What sort of ground range do you get with the antenna off?

As for the battery, I'd change it. At a minimum, you should use a cycler to determine what the present capacity is. Anything less than its advertised capacity means its time to change it.

Chris H.
BVM, JetCat rep

Tony
Thanks. Any ideas on improving the RF. It's a Bobcat, the receiver sits almost right where the antenna exits the fuse(center section) a good six inches from the ECU. All other equiptment is where Bob says to put it. It is the receiver that comes with the 10x radio. I'm getting around 300 ft(antenna down) with engine running.
Scott