First gasser throttle setup
 

I maidened my first gasser yesterday- a DLE20 on a Phoenix Extra 60-90 (64"). The engine has a lot of grunt for the airplane- infact I ended up flying at 20% throttle just to keep it from climbing. I didnt do too many aerobatics by my trainer was able to do a rudder loop without too much effort at what I think was 50% throttle.

I noticed that I seemed to be having a lot of power gain as I went from 10% to 40% on the stick but there didnt seem to be as much gain subsequently going from 50% to 100%. I havent actually setup the throttle geometry as per Jody's guide, just by setting 50% on both horns and then adjusting from there with a linear curve. Is it correct that gas throttles are non linear. If so, how do you adjust the throttle curve to set 50% throttle at 50% stick?

Ameyam

RE: First gasser throttle setup
 

All gas engine do this, You have to adjust it with your throttle curve.

Milton

RE: First gasser throttle setup
 

Geez....
You know the answer to your question, do it. If that doesn't fix it 100%, use the radio to tweak it.

RE: First gasser throttle setup
 

First, fix THAT and then fine tune in your tx afterwards IF needed, and be done with it!

Linkage should be somewhat close to shaft on servo, and farther out at carb arm.

RE: First gasser throttle setup
 

Its actually almost 1-1 on the linkage. I must have done something right because no one (I showed the setup to a couple of experienced fliers) asked me to change anything except open the thread a bit because the engine doesnt cut when throttle-kill is activated. I will see it next week at field when I get more time with the airplane

I also had another question. I did the testflight with borrowed fuel- most guys use klotz gas lube (I think its KL305). After the flight I noticed a lot of black residue inside of the silencer. There were a couple of leaks from the silencer (screws) and that had gone black as well. It was similar to the burnt-on castor stains on the glow engines. Now, I dont want to open the "which oil" controversy again but is this natural and is it harmful to the engine? If so, how can I avoid it?

Ameyam

RE: First gasser throttle setup
 

Mufflers will get carbon in them to varying degrees with just about any oil. Was there any on the belly of the fuselage? The smaller engines require more oil so you will get more out the muffler. Look at the tailpipe of most cars. The only oil in the fuel is what leaks past the rings. They still get black.

RE: First gasser throttle setup
 

Lots of black oil/crud at first is a good sign. It's telling you the oil is rinsing the breakin crud from the engine. That'll get lighter in color as the engine breaks in, and there may be less of it as you get your carb adjustments closer as you use it a little more.

Your borrowed fuel. Was it mixed 32:1 or something very close to that? Many are running 40 and 50 to 1. You need to pretty careful of that, especially this early in the break in process. The manf. suggests 32:1 all the time, so it's really important early on....

Gassers are pretty much wide open at 1/3 throttle opening. They're no where near close to being linear.... and as you've now seen/realized that fact is very apparent from the time you land one the first time.

Having a second set of eyes, especially more experienced ones, go over your new plane prior to flying is a good plan. Depending on others to spot your setup issues isn't a very good plan. If you know of something better at least try it. If it works out well for you, then you'll have something to share with others at the field.

RE: First gasser throttle setup
 

Here is a typical throttle response curve for those interested. Notice the very small gain past 50% throttle.

RE: First gasser throttle setup
 

They both knew that I was flying gas for the first time. I learnt flying from one of them. They knew what they were doing

There was no black stuff on the belly of the airplane. It was quite clean. Even the fine carbon which formed on the outside of the muffler due to leakage just rubbed off as apowder later. I will keep an eye on the exhaust stain colour though

I borrowed fuel because I am still getting the setup right. I have ordered a gas can and an electric pump. Unfortunately all the hand pumps here are for glow only. I also needed to get the oil for my fuel mix, someone leant me that on the field after I did the test flight. The fuel was 32:1 for sure. Everyone was using some from the same can including the owner

I am thinking of starting with a -15% throttle curve. I havent used this before, I will need to see the manual of my 9CAP. I didnt land the airplane yesterday, I figured that if these guys can fly A330s, they surely and test-land my airplane and tell me how it handles. That was a good idea, I did see the thing squat-stall as he was landing it. I need more practice with scale landings though and this airplane is over weight (3.85kg instead of 3.2-3.6kg stock)

Ameyam