I flew today for the first time in about a month. I'm still newbee. I noticed today that the engine sounds a little deeper when the main tank is empty and only running off the header tank. So I checked the head speed when running off both tanks and only off header. It loses around 60 rpm running on a full header tank. Which seems to be enough to cause my gyro not to hold as well. The fuel lines have been replaced about 2 1/2 months ago. Is this normal.
Thanks
Robert

You should never fly the heli when the main tank is almost empty, header tank's main purpose is to ensure that fuel availability for flyer to land heli & not to lean-up engine.
When flying using reserves fuel in Header Tank will leaned up engine coz pressure issue, in long run, it will damage the engine.

If you require your engine to have more power just lean it up a little. But advise to have engine running a little rich, more power to heli, will also depends on your throttle & pitch curve settings. There is any easy way out, purchase a governor - constant heli rpm.

Hope info helps you.

Thanks. I didnt know you shouldn't fly on your header tank. It seems to run richer on the header tank.Because the sound of the engine gets deeper and the rpm decreases.

Also I usually run the engine completely out of fuel. Is this not a good idea. Usually I land it to run the rest out.

When engine leans up, sound of engine would be more of high roaring-up rev-up. with lesser smoke coming out, and muffler will be very hot. When engine is rich, more smoke will come out of muffler, less stress noice will come from engine.

When fuel runs out, the engine will never be richer, it will be more leaner coz no fuel means no lubricant more friction, engine piston will be stressed. It is advised not to run-out fuel from engine during flight or when it is idle. To protect engine damage, you just need to put in at least 5 drops of After Run-Oil thru fuel line located at carb. Then use a starter to pump-in oil into engine, stop when oil is in engine. But, please bear in mind that, if you're flying weekly, then just skip this process. This process is when you'll be keeping your heli in storage for more than 3 months.

Dear Rlmarch,
It seems that you are running your engine on the Lean side already when fuel in the main tank is present ;
When fuel finishes from main tank , the engine will run lean on header tank fuel and if you are already at lean side ; the engine will get leaner , heats up significantly and losses rpm (no oil)- and potential damage. Adjust fuel needle valve to run Engine a bit richer (good visible smoke when reving up) and land heli the minute you hear Engine rpm revs up suddenly (without increasing throttle)(which happens when) see fuel in main tank finished. Good luck.

It does sound like your running on the lean side.

Here's simple test, fire up the heli, hover or fly around for a few minutes and land and shut down. Put your finger on the back plate of the engine. If you can't hold it there for atleast 3 seconds before it becomes too hot, then your running too lean and need to richen up the main needle a click or 2 at a time until you can.

If you can hold it there longer than 3 seconds or its actually cool to the touch then your running rich. The engine produces less power but will last longer.

as stated, the header tank is not a reserve tank, it is to ensure fuel during all aspects of flight when there is fuel in the tank.

When you are done flying, just shut it off and empty the tank. Don't worry about running the fuel out. The nitro will evaporate in seconds leaving only the oil to keep things lubed. I have been doing that for almost 30 years and never lost an engine or bearing. Friends that run them dry are always replacing bearings. If you are going to store it for any length of time, use a good oil in it before you store it and oil it once or twice a year.

Thanks for all the replies.
That day I hovered it around and checked the rpm at intial hover and after with slow forward flight. It was exactly the same
Engine temp by glow plug highest reading right after shut down was 163 F. average 153 F. Outside temp 86 F.
With moderate foward flight the rpm is the same at beginning and end. And engine temp is about the same as stated before.And Lots of smoke hover and foward flight.
The only time it doesn't smoke and rev's up is when I run the last bit of fuel out.

When the main tank runs out and the engine draws fuel from the header tank only, the mixture will be richer. Why? Because the fuel does not have to travel the long fuel line from the main tank to the header. Only air pressure is in that line now and air has a much lower 'friction' coefficient than liquid. So the engine finds it easier to suck the fuel and the mixture richens. Try it yourself at home. Get a long straw and suck on a coke and then get a short one and suck.

Fritz

Where's Rusirus when you need him?

I'm going to respectfully disagree Fritz, I don't think the coke anaology has anything to do with our header tank systems but I'm going to do a little research before I fully put my foot in my mouth.

I was kind of thinking the same as Fritz.
On long runs of electricity you have to size up accordingly, so there is no voltage drop.So the longer the tubing the more resistance and less fuel comes out making it leaner.
Robert

Yes but you arent considering the muffler pressure and the weight of the fuel in the main tank pushing down and creating a head pressure. As the main tank runs out there's less pressure behind it and now your not force feeding it your drawing it.


Hold the coke above your head and see how much suction you need. Then hold it below and see the difference.

That is correct. That is also why fuel mixture changes as the main tank empties. A Uniflow setup will cure that but lets not get into that.
The fuel mixture change we are talking about occurs at the very end of the main tank run. At this point the mixture will be leaner than at the start of the flight partly because of fishpucks observation. Now as the main goes completely empty, the fuel doesn't have to travel from the main tank clunk through the fuel line to the header anymore. Essentially you are now looking at a small, completely full tank much closer to the engine with a big, long muffler pressure line. So the mixture will go rich.

Fritz

One other question?
Rapter 50 v2 with hyper 50. I'm getting about 10 minutes of flight time with just the main tank. That was why I was using the header tank to. With both tanks I was getting around 14 minutes and I thought I read normal flight with a 50 size heli was 15 min.
Should I be getting 15 minutes on the main tank?
Thanks
Robert

With my Raptor 50 Hyper. I also get about 10mins on main and 14mins with header, but I quit when the main empties. My heli gets richer when I start drawing on the header only until the very end of the header tank where it will lean out just before quiting (not good to do). I think I am running just about the right mixture. I can hold finger on back plate indefinately after flight, but it gets pretty uncomfortable. If anything I may still be a little rich, but I'd rather be there than lean. So I think 10/14 mins for Raptor 50 Hyper is about right.

Thanks.
Ya that sounds like me. Definitely do not want to be lean.

I see alot of recomendations for Raptor Technique, so here is his info on header tanks. just my 2 bits

"Why do some say a header tank cures the problem of the engine getting too hot toward the end of the flight. It has to do with a couple of reasons, incorrect engine/throttle-pitch/mixing or vibration. The effects of either of these two will cause the engine to get hot. If it's due to vibration, then the header tank will help take the air bubbles out and therefore mask the true problem. If it's due to incorrect engine/throttle-pitch/mixing settings, then by having a header tank up high will give a rich run toward the end of the tank which would help cool the engine and therefore again mask the true problem."