lt schilling

I have a 46 ax on a lt-40 kadet and I notice I am only getting about5-6 min of flight time out of it before it runs out of fuel. is this normal or how can I fix it. thanks

a70eliminator

I had a 46ax on my lt-40 using a 14oz tank and never even came close to running it out before I was tired of flying it., now the same plane has a 61 with the same 14oz tank and flies till I get bored and land it, never have run out of gas. Unless your using an 8oz tank and flying rich at full throttle the whole time? If your in tank line has a slit or hole than as soon as the gas level gets to it your out, is the tank empty when you run out of gas?

Ken Erickson

That is the most common reason for what you describe. Or the fuel line, which has the clunk on it, has come off the tube, which runs through the stopper.

Ken

lt schilling

I am using the stock tank that came with the plane and yes the tank is completely empty my instructors deadstick landed it 3 times we did major tuning on it and its still doing it. Thursday when I get a chance I will check th fuel lines

a70eliminator

If the tank is completely empty than it must just be a that your engine is tuned way rich for break-in and running full throttle to have enough power, once it breaks in trim up the fat and then you'll only 1/4 throttle to pull the lt-40. your fuel consumption will improve dramatically.
Like I said my ax46 seems to go like 1/2hr. on 14oz, 5 mins would barely put a dent in the fuel, are your helpers playing with carb settings 15mins before putting it up or what?

lt schilling

we fly it at half throttle now

a70eliminator

About 1oz per minute at full throttle for a 46ax.

lt schilling

is there a larger tank I can install??

a70eliminator

They have tanks available in all sorts of shapes and sizes, whatever you can stuff in there, 12oz is all you should need.
Check that your fuse isn't all fuel soaked fron a leak. You first need to find out what you have now.

j.duncker

My Feedback: (2)

Is there any chance you have a vent pipe going to the bottom of the tank? If yes it is possible for it to siphon in flight.

GRandolph

What % nitro are you using? Higher nitro means less methanol, so you will burn a larger volume of fuel.

jester_s1

Nitro isn't going to matter. Something is wrong if he's burning that much fuel. Even an 8 ounce tank should be able to give him 10 minutes in a trainer unless he's staying at full throttle all the time.

You said the tank is empty, but have you verified that? Can you actually see that there is no fuel in the tank after the plane deadsticks or when you land because you think it's almost empty? And have you checked the fuel compartment for leaks?

rlipsett

have yo verified visually that it is truly full. if the vent which is normally turned up in the tank so that it is at the top of the tank is instead turned down then fuel would come out of the vent considerably earlier then the tank filling up. if this is not the case visually inspect the lines for a micro nick. I had a small nick in one of my fuel lines with a ys pressurized system. could not find the leak easily but raw fuel on the aircraft pointed to a problem. only found it when it was running and tank pressurized. came out as a very fine mist which did not effect engine running since it was so small and hard to barely see but it adds up over a few minutes

jaka

Hi!
First of all a 14oz tank is way way to large for a .46 Engine!!
Why!
Because our glow engines cannot cope with the vast difference in fuel pressure that a large tank develops. This is noticed in that the engine runs leaner and leaner the more fuel that is consumed and finnaly the engine stops! A remedy to this is to use a tank that has enough volume and still makes the plane fly at least 10-12minutes.
So in your case a 8-10oz tank is the way to go!

So...if you only can fly for 4-5 minuts ,you either have a leak in your tank/ fuel line or running your engine exstreamly rich.
What prop and rpm are you running?

a70eliminator

While I do totally agree that a 14oz tank is overkill, it does fit into the compartment, have never run out of gas and fly till I'm tired, both my .46 and .61 run great on 14oz tank.

jaka

Hi!
Besides the tank being to big, giving engine setting problems, you also will see trim problems from full to empty tank due to the Cof G changing too much! Use a 8-10oz tank and you will see that the plane flies better!

a70eliminator

Yea it's give and take, I do notice the CG changing late in the flight but it's a trainer and I'm learning lol, but honestly, have not had 1 single problem tuning the engine, it runs great starts on 1st flip and can burn the whole tank, idle, midrange, high speed, doesn't matter it's just plain dependable at any speed.

LarsL

I think rlipsett is on the right track/asking the right questions. I in no way can imagine that even with an 8oz tank, It schilling could be only getting 5 - 6 minute flights that are running the tank completely empty. It would have to be running at a sloppy rich 4-cycle that I would question if it could get off the ground without a real fight. The plane would be a gooey mess to boot. If fuel is leaking out of the tank, either it is leaking outside the plane out of a vent or it would be in the plane somewhere and you wouldn't miss that. Are you positive that you are actually filling the tank completely.

I've got a H9 Toledo Special with a stock 11oz tank running a .46AX and I can fly it for 20 minutes using normal varied power levels. I almost never fly it that long just because I'm about tired out after 12 - 13 minutes.

Lars

drac1

My Feedback: (4)

The size of the tank will not make any difference to fuel pressure.

A .46 should run forever on 14 oz's. Even fully rich, I would think that it it would last for more than 5-6 mins. It sounds like either a fuel leak or the tank plumbing isn't correct which doesn't allow the tank to fill completely or empty completely.

jaka

Hi!
Ofcourse the fuel pressure will change from full tank to empty! That's why we modelers set our engines a little rich at the beginning of the flight so that the engine doesn't stop when the fuel level is near empty.
Our engines are airpumps! They suck air through the carb and blows out air combined with fuel vapor trough the exhaust.
If they don't have enough piston to cylinder fit or...if the fuel level changes too much they cannot pump air as good as they should and the result is that they (The engine) stop!

This is the reason why we set our engines a little rich at the beginning of the flight, to help the engine from fuel starvation when the fuel level (pressure inside the tank) gets lower as the tank empties.
And that's why a suitable tank size for a .40-.46 two stroke sport engine is 8-10oz. Not a 14oz tank!

a70eliminator

The original poster has not indicated that he even knows what size the tank is, he did say the tank was indeed empty of fuel at the end of 5 mins. flying time, alot of guessing going on here without enough info, is the tank actually filling completely who knows.

drac1

My Feedback: (4)

My guess would be that the tank is not emptying completely, or not filling completely.

The instructions say that the included tank is 8oz.

drac1

My Feedback: (4)

It seems you may be a little confused on a few things.

Tank size WILL NOT alter tank pressure. Muffler pressure or crankcase pressure is used to pressurise the fuel tank in order to force the fuel to the carby as atmospheric pressure is not enough to provide enough fuel to the engine. Engine speed will alter pressure so when the engine is at low throttle the tank pressure will be less and at full throttle the tank pressure will be higher.

We set the engines a little rich for 2 reasons. 1. The engine unloads once in the air, which leans the mixture. 2. When the tank is full, there is head pressure which assists the carby to draw fuel in, which will give a richer mixture. When the fuel level is getting low, it's harder for the carby to draw fuel in and will result in a leaner mixture.

Our engines are not air pumps. They are internal combustion engines which convert energy created by the combustion process, to torque which tuns the prop. The air/fuel mixture is drawn into the combustion chamber and then the unburnt oil/fuel is expelled through the exhaust.

Piston/cylinder fit will affect the engine performance. As fuel level changes the mixture will change slightly and if it's too lean the engine will stop.

This is a basic over view. Hope it helps your understanding.

a70eliminator

Just got back from flying my lt-40, set timer for 20mins and landed right on Q, the majority of my flying was 1/4 throttle to wide open bursts, was really working that left stick and elevator to manage low altitude flying in windy conditions, did a few full throttle straight up climbs, and a couple speed passes too. Pulled the wing, took a look at the tank and it was still half full, K&B.61 with a header and pipe probably used less than 8oz of fuel. Nothing says I have to fill the tank but the extra nose weight actually did me good today in this wind. Your .46 when in good tune should give satisfying flight times even with that little 8oz. tank.
I put the bigger tank in mine with the K&B .61 swap thinking I needed it, but i guess not afterall.

lt schilling

well the good news is i found out why it was using to much fuel ...... i had a 10-6 prop on it causeing it to spin to fast.... after we change the prop and tuned it it started flying great. the bad news is i was trying to land in high winds and from a right hand turn and it went nose first into the ground. only thing i saved was the electros. so its time for a new plane.