This is my third year flying, and my first year at 3D. I have a UCanDo 46 with a Magnum 70 four stroke, and a 14x4 APC prop, with Omega 15% fuel. I have about two gallons of fuel throug the motor, so I would consider it broken in. I have the high speed needle adjusted with a Tach exactly as per the instructions - about 200 rpm below (richer) than peak rpm. *Note: I do not have my engine inverted as the airframe design calls for, I mounted mine upright (see photo).

The engine has been running fine, except for the last three times out I have dead sticked. The motor seems fine and then about 5 or 6 minutes into the flying it just quits. I checked everything, fuel filters, different fuel, glow plug, high speed needle, fuel clunk seems freely moving, not out of fuel etc. Everything seemed ok. And then I started to realize that I had been doing a lot of hovering the last few flights, and I remember that the last dead stick was right after hovering... I decided to do a flight without hovering, and I made it through the whole flight (about 10 minutes) without a dead stick.

My question: Does hovering contribute to dead sticks? Is that a known problem with 3D?

if u r lean yes yes

When the engines tune is a little lean pointing the nose in the air will exacerbate the problem and cause the engine to surge or die completely. Next time you run the engine on the ground run it up to full throttle, pick the palne up and point the nose in the air and wait. Listen to the engine If it starts to surge or tries to die it is to lean. Also I would reccomend a smaller prop for the Magnum. That is alot of prop for a .70 and it may be overloading the engine in combination to a lean mixture. Try the APC 13x4W.

I have a saito 100 on my mojo and i can hover for a whole flight and it not dead stick. so its definitely not a 3d issue

If it's shutting off during hovering check to see how long the tube to the clunk is. If it's too long it can hang up against the back of the tank. It will look good sitting in the corners of the tank but as you position it toward the back of the tank it can stick there and not draw fuel correctly.

I have conducted the test where I point the nose in the air (while on the ground) at full throttle. I haven't noticed any change in pitch.

I should also point out that I can hover several times, for up to a minute each, with no problems from the engine... no surging, hesitating, etc. I was wondering if the engine may be overheating. It is ventilated good for air flow over the fins, but I thought that the increased load on the engine (from hovering), and the fact that the only airflow it is getting is from the prop, might cause overheating???

I know that a 14x4w is at the high end of the prop envelope. But, I was thinking that since a 13x6 is in the recommended range from Magnum, that to reduce pitch by 2, would allow me to get away with a 1" increase in prop diameter. Anyone disagree?

Extended periods of hovering can make the engine run a little hotter. If you are on the verge of lean it can push it over the edge. When a plane is in hover the engine only has prop wash for cooling. In level flight it has prop wash plus the speed of the plane. (to oversimplify)

david

no

I don't think a 14x4 is too much prop for a 70 4 stroke a Saito .72 loves that prop. If you suspect the motor is working too hard and overheating, check the glo plug. If it is at all frosty or turning white then it could be getting lean and hot. It should look nice and silvery. Also, when you disconnect the battery after starting, if you notice a drop in RPM that is also probably a plug problem. (it should never do that with a new plug assuming the motor is tuned right and is running within limits). Glo plugs on my 4 strokes have lasted several seasons flying multiple times each week. An OS F plug is what I use.

Your motor is fully exposed so I don't think it's an airflow cooling problem.

I suspect a foaming tank situation. I have seen several 4 stroke installations turn a tank into a foamy milkshake (very bad for consistent runs). This problem gets worse as the tank empties. Since you have an internal tank, when the problem happens again, land the plane and DO NOT FILL the tank. Let the engine cool and then start it up again and go hover some more. If it quits immediately (before the motor has a chance to get too warm) it is probably the tank. If you had a profile plane this would of course be easier to diagnose as the fuel tank is exposed. For kicks, if you have a spare tank, I suggest mounting it to the outside of the plane with some rubber bands and this will help you see what's going on. If you can soft mount the tank internally with some foam, that would probably help too.

One other tip: I normally run only 30% heli fuel (ie, Cool Power) which has much better anti-foaming agents than standard fuels. The 4 strokes really love the higher nitro too. IT's more expensive, but it turns all my four strokes into very reliable and happy motors so it's worth it to me. When I dont' run this fuel, I need to use a LOT of very soft foam around a tank to get the vibration isolated to the point where the tank is reliable.

What fuel are you running? Are you at full bore during a hover? I would throttle up about 3/4 and then hold in up and listen for your engine to surge. You may still have a lean problem.

One other thing to check is the line inside the tank going to the clunk. It may have a pinhole leak in it somewhere that will cause this problem only after the tank level has gotten down. I never use the cheap line that comes with a tank when you get it. that pinhole in the fuel line will cause it to run lean only after you have been flying for awhile.

I 2nd the idea of strapping a different tank to the outside of the plane to see if you can see any foaming issues.

I'm running Omega 15% fuel. When I hover I am probably between 75%-100% throttle. I don't notice any surges when entering verticle.

TruBlu02 makes a really good point. I've had that happen a couple of times. Runs good on the ground but behaves different in the air... vibration induced?

You say there is no change in pitch?
Shouldn't the rpms pick up a bit after a couple of seconds therefore changing the pitch? If it stays the same or the rpms drop then it is to lean isn't it? I'm not 100% sure so I'm asking first

Your overheating. Increase cooling or step down to a 13x4. You'll see a difference.