Dear All,

I am currently flying a phoenix Topstar 60 (same as Flip3d). This is a 3D plane capable of hovering. I am getting there with regards to the hover but not quite pro yet.

One problem I am having with the plane is that in every flight when hovering, after having hovered for a few minutes, the engine cuts off and I have to land dead-stick. Needless to say that I hover at a good height to allow myself time to recover. This happens in every flight and may be at approx same point with respect to fuel levels. Point is, on landing there is usually half a tank of fuel still left.

I am attaching pictures to this post that show my fuel tank installation. Note that the engine is installed inverted and the tank centreline sits at crank level i.e. above carb line (inverted engine means carb is below crank). So much so that when fueled and awaiting my turn, the engine usually floods. So I dont connect the line to my engine untill its my my turn to fly. To do this I have seperate lines connected to tank and carb and I join them outside the cowl by joining piece. Hence also fuel line is a bit but not very long.

What I want to know is am I missing out on something here? This is a OS75AX without pump. Prop is 13x8 Master Air screw. Is this config OK for hovering? I have already checked the system for leaks.

Please tell me what I could do to resolve the issue, since, if this goes on, I will very soon become an expert dead-stick lander

Ameya

first thing I would look at is replacing the fuel lines inside the tank.....

It is possible that maybe you have it too lean and just richening the mixture a little would solve it. If that gets you nowhere then replace the fuel lines and shorten them as much as possible. You can get a small pinch clip like is used to clip office papers together to put on your fuel line to prevent the flooding while the plane is sitting. Your prop doesn't seem to be what is normally used in 3D and hovering. The 3D flyers at my field prefer the longer less pitched props. Yours is typically a high speed prop. I would try something like a 14x4 or 15x4 if you can to see how they help out, but whatever you like best is what I would suggest you stick with.

Too slow, what Brett65 said


It might be overheating and leaning out. What size openings do you have in the cowl? Does it still do it without the cowl attached? Also, try riching the main needle jet by a couple clicks.

Sounds like a clunk line has fallen off or is split.

Definately the wrong prop for hovering. Get a 14-4

Lets take it one by one.

A 14size prop will hit the ground on our rather bumpy field. Also, the landing gear is a bit short

Everytime I open the cowl (once every two weekends) to scrub the engine, I have to remove the needle and hence I have to adjust it on field everytime. So if it was possible to correct this that way, it would have already happened.

Not Likely the engine is overheating I scrub it clean with soap externally every second weekend. The clunk has not fallen off.

Am attaching the photo of the cowl to indicate openings

I have ordered a dubro tank and it will be here before the weekend. I will try to get it in this weekend and check

Basically what I am asking is, should the tank be mounted any other way and is this engine suitable for 3D?

Ameya

I don't think the tank is the problem. The tank being to high or low means nothing when the nose is straight up. If you are stuck using the short prop, so be it. I think part of your problem is over heating. Mostly because during a hover you are not getting a lot of air flow. I have a profile running a Saito 1.25 that will get hot during extended hovering. I stood next to Jim Flanigan last year hovering a DA-150 powered Yak. After 60 seconds of hovering you could smell the engine getting hot. It's the nature of hovering. Second thing to try would be a Cline regulator. This would keep a little better pressure on the tank. Part of the problem with a 8" pitch prop is the engine speed to hover will be lower than using say a 4" pitch prop. This is cutting back on how much pressure you are getting in the tank. Again adding to the lean/overheat problem.

David

Make some new wire landing gear and throw a longer / less pitch prop on it. It does sound like it's overheating or running lean. Hovering for an extended amount of time will do that.

Where is your exit ventilation hole? You have to have an exit hole larger than intake. This will make a negative pressure at the rear to suck the hot air out. Only having an intake will just create a pressure bubble inside and recirculate hot air.

Other than that if you are in fact running a bit lean, then after you get to half a tank or so the pressure may drop with it fighting gravity. If it's already lean it's going to lean even more.

I would cut an exit vent and try running just a bit more rich and see what it does.

Check the inside of the tank too, make sure your clunks are still attached. I don't think you should have a problem with this setup so check the clunk, cut a vent, and run a bit rich.

i had a problem like this and what i found was the clunk tubing was just the right length to suction the clunk to the back of the tank leaning it out, i shortend it by a few mm and it stoped leaning out.

Good point nitrofevr. That is why I take a cut off wheel in a Dremmel and make a groove in the back of every clunk. Some come with a groove but a lot of them dont.

David

I think the tank being as high as it is causes your problem. You adjust engine when plane is level therefore are then adjusting for a flooding engine. this then causes it to lean out when in hover since now it has to draw from a very different tank level. lower tank it appears this should be possible.

Im going to have to steal that idea from you.

well, i have a lot of experience in 3d flying and eng tunning for 3d, and this is the smartest explanation.

i am 100% sure ur engine is leaning out and overheating at vertical, most probable cause is not enought back pressure, there is hundreds of cheap solution for this.

to make sure ur plane is overhitting at vertical, tune it to less than full rpm at horizontal, if u put it vertical and u can hear it rpm up, it will get a lot hotter.

Actually that's how we tune it..pointing nose-up. Then we point it up and then quickly down. However, I did hear my instructor remark that the engine is leaning out mid flight (though my ears are not tuned it enough to hear it myself). Isisn't this not supposed to happen?

Ameya

well, if ur eng is leaning at midrange and not full, ull need a temperature gate to tune it right, but then try to richen the low end as much as posible as long as u have good idle and decent throttle response for pulling out of the hover.

make sure ur glow plug is good and the fuel too before u richen it out, other wise it will not hold idle for longer than 15 +0- secs.

i dindnt want to mention this, but oviously you didnt take apart the muffler right?, it needs the buffle and make sure its not leaking by putting the piston heat at top dead center, blow on the exaust and u should feel its air tight.

forgot to mention to climb the presure line.

ps: i meant before, piston head at top dead center.

I run most of my glow engines without a baffle...never a problem... guess I'm lucky

Ameya, tunning with the nose up is the best way. However when you are tuning your throttle is wide open. Your problem is not long verticle lines, it is hovering when your throttle is only part way open. One last thing to try. If you are holding a constant throtle setting when hovering, try pumping it a little bit. You know work the throttle back and forth. This may increase your tank pressure enough to help with the problem. If not I suggest again the Cline Reg.

David

yes, u r very lucky, u will not have problems unless ur eng overheats. also the lack of back pressure make the eng very uneven when flying vertical compare to horizontal, i mean if u enter a loop at full throttle and u hear ur eng leaning out when vertical, it means it could use more back pressure.

i also take the buffle out of some of my eng for planes that are not 3d, but if u can hover indefinite time the way ur eng is, then just leave it the way it is, but ameya is having problems and his eng quits when vertical, the 1st thing i recomend him to do is to put the buffle back on if he had removed it.

ps: i dont know why in my 15 years of rc plane expirience, since ive become a very good 3d pilot, most people come to me to ask me for help to tune their engs they dont believe the buffle helps with back pressure until they have problems and they put it back on.

Hi,

flew without the cowl today. It helped...but not with the dead sticks. The plane became tail heavier and hence easier to hover but more difficult in a straight line. However, it still cut... and in every flight. We used all the tricks. Ran it rich to the point it smoked very well while level..even dead sticked while at idle for too long. But it continued to cut-off in hover.

Devopam, I am not expert enough to hover indefinately. So I keep correcting with throttle, rudder and aileron all the time... the plane is never still. Thus the throttle keeps going back and forth as suggested by you out of reflex action. I dont have to think about it... happens automatically.

Another thing i noticed...without the cowl I could see the tank...It usually came back deadstick after 50% of the tank is used. The tank is centerline capped and every time after deadstick, the fuel level was just below this. I am going to configure a second 12OZ tank which has the cap more towards the top and try tomorrow.

FKY1000 has a point...I took off my baffle even before running in as it was fokelore at my field that the baffle reduced power ever so slightly. I notice now that the muffler back-pressure port is upstream of the baffle i.e. fitting back the baffle may increase the back-pressure to the tank. I am putting back the baffle right now and will only put in the new tank if the problem continues even tomorrow, thus changing one variable at a time.

For the record, I am still using the 13x6 prop as I couldnt get the 14x4 locally

Ameyam

I think you will find the baffle helps a lot with your problem. The engine getting leaner as it the fuel level goes down is normal. If the baffle does not fix the problem. You might try a header tank. maybe you could fit a 2oz tank between the engine and the firewall.

David

Well I made a number of changes:

1) Put the baffle back
2) Installed larger ID hose (which I had got with my dubro fuel pump) between tank and engine with straps (of wire ties) on both sides to hold the tubing to the tank metal piping and engine port
3) Shortened tubing between engine and tank while still allowing connection outside the cowl to prevent flooding while sitting.
4) Made holes in the bottom of the cowl so it resembles a perforated sheet. This allows it to retain more strength than one hole

If this doesnt help, I am going to give up and be ready for the deadstick everytime I hover.

I am also looking at an OS FS91 Surpass II 4 stroke engine without pump which will be available this week locally. However I wont be using it this season. In first week June, the season will come to an end as the monsoon will flood our field for 3 months. I did want to ask however, Is this engine worth the international price?

Ameyam