hey guys....i need you opinions or advice once again. when i fly my plane which has a super tiger 60 engine and i throttle up or down there is a couple second hesitation. it only does it when i'm flying. when its just running on the ground i can go away as far as i want and it responds just fine but as soon as i fly there is a hesitation. its only on the throttle where i get that, the rudder, ailerons and elevator are perfect. so i'm just wonderign if its because of the way the air is entering the barrel when i'm flying or what. so let me know what you think and what i could do to correct that. thanx guys.

It has been suggested before that this could very well have to do with the speed of sound being slower than the speed of light. Like a fastball hitting a catcher's mitt, it takes a second or two for the change in engine noise to reach you.

There may be a more complicated, engine-tuning, type answer, but I can't help you there...

There is what mclina stated, added to the somewhat delayed response of the plane itself.

It takes a small amount of time for the increased thrust to have a visible effect.

It pays to try to fly the plane near to you and listen for the sound increase of the engine.

It the engine is not sounding like it's stuttering during runup, then what you are experiencing is perceptual.

On the other hand if you can hear the engine lag or stutter a bit before it settles into the higher speed, keep in mind that the engine goes leaner in the air, than on the ground. You may need to richen the low end a little.


Now that said, Super Tiger's are notorious for transition problems in the mid-range.

On one of mine I have NO leaks, etc. yet the engine continues to run after I have completely closed down the throttle fully.

I actually have to pinch off the fuel to shut the engine off.

That leads me to believe that there is a lot of air getting by the metal carb piece that has the opening in it, when the engine is in operation.

On that particular ST .75, I had to set the low end a little LEANER to get transitions right.

Try richening the LS needle just a little . 1/8 of a turn in . You may be leaning out a little once in the air .

My bossanova does that if im flying far away, something to do with the speed of sound (as mentioned above), think nothing of it, if its tuning related i suggest leaning it just a click or two (remember, the air is thinner at higher altitudes, so the plane will lean out when its airborne

Opps , I meant 1/8 of a turn out, sry . lol

Sometimes it has to clear out.
If you just pud, pud around the oil is going to settle in your muffler a bit.
Then if you gun it. it'll splutter a little bit.


In nitro cars it's more noticiable.

99% Sure it is time sound travels.. have some one hold the plane, walk out as far the plane would be flying and give it some gas and see what happens, the lag you hear. I suspected my plane was lagging a little when in flight but when I flew it closer there was not lag when I throttled up.

Sound travel and any reciprocating engine takes a moment to change speeds. Flywheel effect. Momentum & Inertia.

Inertia also applys to the effect on the plane itself, so in addition to the sound travel delay and the throttle up delay, there is the delay before you see the end effect on the plane.

Put all of these together and the plane seems to lag behind by a percievable amount....

Something that may be quite unsettling unless you are used to it.

the engine sounds great, it don't sputter and nothing so maybe its just he speed of sound. someone also told me that if i'd put on a os carb i wouldn't have that problem, but i don't know about that. so i'll have someone hold my plane and i'll walk away and try see what happens....thanx

Yup if you don't hear hesitiation at run-up, "fuget-about-it".

Fly and have fun, you have a winner.

How will that work?
Think about it. If you walk a long way away and have someone else move the stick you won't be able to see the stick movement (speed of light) so you would have to rely on instantaneous comunication. Your helper can shout when he moves the stick but then you have the speed of sound again compounded by any delay your helper might add in shouting.
Maybe you can use a 2 way radio but I don't know how fast that will be either and some 2 way radios, including cell phone direct connect have a slight delay built right in to prevent feedback if 2 users are close together.

Or he could possibly take the transmitter with him I guess....

hand signals work they are speed of light visuals

In fact, how an engine reacts to the throttle on the ground to how it acts in the air are often two different things for a very simple reason. The needle settings on the ground and it's throttle response are with the propeller operating in quite a different environment than it was actually designed for. The prop isn't unloaded and the engine is working at significantly lower rpm and gas flow than it will experience in the air. It's actually surpising that throttle response on the ground is as good a predictor of response in the air as it is with SOME engines. Sounds like yours isn't one of those.

Adjusting the needle valves (both or them) on the ground is actually not the end of it. We adjust needles and CGs on the ground to get the airplane close enough to those settings so the airplane has a better than average chance to fly while we do the real testing, in the air where it actually matters.

Speed of sound is a cute idea, but BS also travels at the speed of sound. If you need some clever, magic way to hear the engine while it's in the air, fly the airplane close enough to you that you have no problem hearing it.

And what it does then is what you need to adjust for.

Actually, I believe, BS travels just slightly faster than the speed of sound at 875MPH at sea level

LOL ! How true .

daRock , is right on with his post , some engines do take more tweaking than others . Getting it close on the ground , does`nt mean your done tweaking , sometimes your just getting started .

ITS ALL GOOD!
Nice to see everyone having some fun with this post. A couple of considerations to add to the previous good info would be:
Is the engine FULLY broken in and is there any chance of air leakage? Teeny tiny leaks can be a huge PITA! A bit of fuel tubing on the needle can help as does a tiny bit of silicone to seal metal to metal joints on remote needles and on adjustable needle valve angles.
I once spent a couple of hours trying to set a fairly new engine and got ZERO progress until I threw out last year's fuel and started with fresh fuel[:@]