does fuel choice effect flight time?
 

Hiya forum guys!

I am a new pilot and i have a question about my flight time. I am in training at a local club. I Bought a nexstar select trainer to train on, as that is what most of the instructors at the club use to teach on, and what most of the trainees have to learn on. I must admit that i find this ironic because after buying this trainer they had me take all the training aids off the plane except the speed flaps! But alas i digress. Anyway, this plane has the OS .46 engine. I am not sure about the fuel tank size, but i believe that it is either 8 or 10 ounces. I fly at about 50% to 60% throttle for most of the time. We both use the 11x5 stock nexstar prop. I use 5% nitro fuel in the plane. I am getting about 11 to 12 minutes of flight time before the tank is empty. I was fine with this until my trainer brought his nexstar selectout that has the same engine and tank as mine. We fly his for over 20 minutes at a time. When i asked him about the difference, he said," Oh, your engine just needs time to break in." I accepted his statement and moved on.

At this point i have run about 8 to 10 tanks of fuel(the better part of a gallon) through the engine and I am still getting the same run times. The only difference is that the instructor uses 15% nitro fuel, and i use 5%. Our engines are tuned with the needle valve to the same pitch, so i am also assuming that the engine is tuned correctly. My enginedoes run a little richer. Should i consider stepping up to 10 or 15% nitro fuel to get these same run times? Or how many tanks of fuel will i run through this before my engine gets 20 min run times?

All in all i am having a blast with the hobby and my local club has been awesome.

Thanks for reading my massive run on sentences.

RE: does fuel choice effect flight time?
 

I generally see excessive fuel consumption as running the engine too rich. Having trained a lot of people with the stock Nexstar I would say that a properly tuned engine should give about 13-15 minutes flight time with a 2-3 minute reserve of fuel. You could have a leak somewhere but I think I would lean the engine out a little and see how it goes. In looking at my notes I see the fuel tank is 270cc, about 9.1oz. . At about 1/2 oz per minute you should get more time. Are you sure the instructor still has the stock fuel tank? He may have forgotten he installed a larger one to give more run time for trainees. Good Luck in learning to fly.

RE: does fuel choice effect flight time?
 

More nitro will result in shorter flight time. With more nitro, the engine needs a richer mixture to run "right". It will sound the same, but fuel consumption will be a little higher (and it will make a little more power). My two Irvine 53s used quite a lot of fuel when new, but during the first gallon of fuel I could gradually lean the needle valve. My Four-Star 40/Irvine 53 could stay in the air for more than 20 minutes on an 8 oz tank. I agree with oldvet70; your engine might be running too rich. Most of my engines have required that both the high speed needle and the low speed needle be leaned by quite a bit during the first one or two gallons of fuel. When they get properly run-in, they run on a much leaner carb setting than when new.

Good luck, and let us know how it works out. ;)

RE: does fuel choice effect flight time?
 

I did bring up the topic of leaning out the mix with him.  If i remember correctly, my instructor said that running too lean will shorten the life of the engine and it was good to run with a "slightly rich" mix.  He did a basic test where the throttle response was good after idling a while, then he lifted the plane and pointed it up and down and all around and it did not stall.  Apparently if the engine was too rich throttle response would have been slow.  If it was too lean the plane would have stalled when he pointed it all over. He does have the stock tank, it was the first thing i asked him. 

As far as i can tell there is no leak, but the tank in the nexstar was factory installed, and getting it out looks like it involves unmounting the engine, something i must admit i am a little fearful to do.  So hopefully nothing is wrong with the clunk inside the tank or something like that.</p>

RE: does fuel choice effect flight time?
 

You can adjust the high speed needle by ear quite easily. With the engine running full throttle turn it in a few clicks at a time, wait for the engine to settle into the new adjustment. Eventually you will hit a point where it will begin to slow down, this is to lean. From this point rich-en the mixture a quarter turn or so. What you are seeking is a high speed adjustment that is several hundred RPMs below the maximum RPMsetting. At this point you may have to readjust the low speed needle also.

Additionally do a search for Pinch Test here in the forums for a procedure to use to verify you are not to lean or too rich. What the instructor did can be done if the engine is still too rich. You do indeed want a slightly rich setting as a lean setting will indeed damage your engine. It is possible to ruin an engine with a single excessively lean run.

If you engine is properly adjusted then you need to check your fuel system for leaks.</p>

RE: does fuel choice effect flight time?
 

I wa getting 8 minutes of flight time out of my lt40 before running out of fuel and i thought that was the normbecause I had a small tank for the size of the engine, ran like this for months. Turns out the low end was set far to rich.Nowafter retune flying 14 minutes and landing with fuelin tank.

RE: does fuel choice effect flight time?
 

8 to 10 tanks of fuel isn't really a break-in. Try it when you have had 2 or 3 gallons of fuel run through that engine. Have a little patience and I think you'll see an improvement but probably not as much as you are expecting.

RE: does fuel choice effect flight time?
 

Guessi am just trying to optimize my field time. My last 2 training session have been cancelled. One due to high wind, the other due to rain. Just a new guy anxious to get maximum stick time when mother nature decides to cooperate i guess. not that i am impatient, just trying to get ready and maximize the good weather days.

RE: does fuel choice effect flight time?
 

It should not take 2 or 3 gallons of fuel to properly break in an OS  .46. It should take less than a gallon and should be giving you good mileage after just a few tank fulls.  Our club was given 2 Nexstars a few years ago and I was the head instructor. I broke in the engines as called for and neither took more than 10 flights, maybe 60-75 oz of fuel. I still think you have a leak or are too rich.

RE: does fuel choice effect flight time?
 

Ihave an Aviastar53 that has been installed and flow on 3 different planes and it is just now starting to break in really good. Isuspect Iwill own this particular engine a very very long time.

RE: does fuel choice effect flight time?
 

Thats great but the OP has an OS 46 which does not require any extended breakin. I'm sure he will have it for years also.

RE: does fuel choice effect flight time?
 

You are probably right about the richness, I have checked the ship over completely after running a tankful on the ground earlier today. I could not find any signs of leakage anywhere in or under the plane.
Thank you Oldvet for taking the time to reply to my thread.
Fly safe!

RE: does fuel choice effect flight time?
 

True, true, true!!! We used to break in the .46 FX by gassing them up and running it in until it would keep running then fly the plane doing a lot of vertical up and down lines just to heat them up and cool them down. Three tanks and that was about it. Today I follow the instructions no mater of brand, well, the SKs are another story. By the third tank the engine should be in fine tune and running well then just require use. They do get better with use and you will notice a difference but it isn't earth shaking. Being a gas hog is usually just the engine being run too rich. I even figure one ounce per minute with a trainer when I'm installing a tank and there is always plenty of fuel left after a flight.

RE: does fuel choice effect flight time?
 

im running some of my engine 20+ min on 8oz of fuel and still landing w/ a third of a tank. most of the time at half throttle or above.
your way too rich, lean your engine till it peaks out (till you cant hear the rpm's increase anymore then back it out 1/3 ish of a turn, that should be plenty rich)
your idle is harder to adjust, sit around at the field and watch people fly their planes. ask someone for help that never seems to have problems with his engines, get his advice on how to set the idle and highspeed correctly


ive flown for 47min and 15 sec on 8oz of fuel before (wildcat 10%). with a gms.47 for the engine and the gp rapture as the plane. your nextar should be able to get 30+ min w/ a properly tuned engine and throttle control.

RE: does fuel choice effect flight time?
 

Don't turn the needle in until the engine begins to sag. Just do the pinch test, and continue to lean the needle valve for as long as the engine picks up rpm each time you pinch. When it no longer gains rpm with the quick pinch, back off the needle to the last place it did and fly with that setting.

Fuel is cheap, engines are not. If you normally run them flat out, they lose the piston and liner fit much much faster.

RE: does fuel choice effect flight time?
 

Are you able to visually see that the tank is empty? I don't think that the mixture being a little rich would cause a drastic change in flight times. My guess would be the clunk fell off and it isn't drawing all the fuel (unless you can see that the tank is dry). I've got a .46 that I always run rich and can easily get 18 minutes out of a 10 oz tank. If it was that rich it wouldn't be running remotely right.

RE: does fuel choice effect flight time?
 

And are you sure that the tank is really dry after your 11 or 12 minutes of flight? Can you see the tank and verify that it is indeed run dry? Or are you just assuming it is empty because no more fuel comes out the carburetor line? One common situation is that the clunk gets stuck somewhere inside the tank and you think you have run out of fuel, but really there is still some left.

RE: does fuel choice effect flight time?
 

this may be the case, but hobbico in all their wisdom put a white, non-see through fuel tank up front.... i tried running it and using a high powered light.to see into the tank, but no luck there. if the needle valve is set correctly i might have my instructor come over and help me disassemble the engine mount to access the tank.

I just checked and shook the plane all over, i dont hear the cluck rattleing in there...(sigh)

RE: does fuel choice effect flight time?
 

A fairly easy test is to measure how much you get into the tank when filling it up and then to drain it through the fuel line to se much useful volume that you actually have in the current setup. There might be errors both in the vent position and in the fuel draw/clunk.

If the engine runs well, don't change the setting.

RE: does fuel choice effect flight time?
 

The difference in flight time can also be in the way two individuals fly. If one is running flat out most of the time and another is generally cruising and only throttling up for climbs and manuevers, the one who is using less throttle for the majority of the flight is going to use less fuel per minute and thereby experience longer overall flights with the same amount of fuel.

In my experience I've noticed that my warbirds run out of fuel relatively quickly from maiden through the first 8-10 times out. After that the flight times increase substantially and max out after about the 15-20th flight. I know it's a factor of throttle use since the engines are always proven and well broken in and the fuel type stays the same. It's a matter of my keeping the speed way up while I'm getting comfortable with the plane and determining it's personality, once we get well aquainted fuel consumption eases up since I'm not keeping it wide open, or close to, for most of the flight. In some cases my flight time can more than double as half throttle is discovered to be plenty for level flight once the powercurve and energy needs for a particular airframe are learned and aerobatic throttle management get smoother as the "tinglies" wear off with the new plane.

Those newer to the hobby tend to show the same type habits, keeping a lot of juice on. As your skill set develops and you become more comfortable with flying, your throttle management will get better and yield longer flight times. Two areas where a lot of fuel is consumed unneccesarily is being "late" backing off the gas coming out of the backside of a loop, and "jack-rabbit" accelerations as opposed to smooth power increases. Both of these can really gobble up the fuel.

If all of your settings and set-ups check out then I would suspect that this is your case. Even if you find a set-up issue in this case, I think that over time you'll notice that there seems to be more fuel in the tank than you expected at the end of your flights and you'll begin to stay aloft a bit longer and longer.

Welcome to the hobby, happy flying:D

RE: does fuel choice effect flight time?
 

I didn't read each post in this thread, however, one point is that fuel does three things.. of course, the obvious is that it burns to run the engine.. :eek:;) , it lubricates the engine, and it cools the engine.

Running to lean will cause the engine to run hot and it will not provide enough lubrication.. both of which is how a lean mixture will ruin an engine.

So, the compromise here is to have the mixture just right so you get the proper burn, good power/RPM, and that the engine is sufficiently lubricated and cooled.

CGr.

RE: does fuel choice effect flight time?
 

My trainers would run 20 minutes or more on a tank of fuel but I'm not able to concentrate on flying for that long. After 10-12 minutes, my neck hurts from looking up, and I start feeling pretty uncomfortable overall.

Most of the people in my club set a timer for 10 minutes and land pretty soon after it beeps.

Even though your engine is running well, if your run time is that much shorter than your instructor's, it is running richer than his.

RE: does fuel choice effect flight time?
 

IMO I think your engine is just running a bit rich. Or simply you have a engine that uses a bit more fuel. As a instructor myself, I agree with CARRELLH, about 10 minutes is all you want in a flight at one time when learning. Many fliers who are not a regular instructor trying to help other people to learning to fly tend to fly the trainers way too fast. Once a trainer reaches safe altitude you can usually throttle back to 1/2. When I plan to fly my glider (30 minutes+) or any aircraft over 15 minutes, I bring out a chair so I can sit in.

RE: does fuel choice effect flight time?
 

OP: I have the same plane, same setup. I have maybe a gallon through the engine and I get 20mins + out of a tank all day long.

RE: does fuel choice effect flight time?
 

I have a Nexstar, when you are finished flying, before you defuel it, take the wing off and hold the plane vertical, and see how much fuel is left.