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first flight good, second flight BAD.

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first flight good, second flight BAD.

Old 05-22-2011, 03:52 PM
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Rendegade
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Default first flight good, second flight BAD.

Hey guys. A friend of mine at the field has been having trouble with all his motors, and all exhibit the same symptoms, and I've racked my brain trying to help him, now I put it out to the gurus to help.


Here's the issue:

The first flight of the day is fine, he can drain the tank and everything is hunky dory. The second flight of the day usually ends up dying after about 60-90 seconds of airtime, with no changes to needle setting.

The third try usually results in his getting his panties in a bunch, and not even taking off.


Now let me talk you through the finer details and things we've tried.

Fuel, it's premixed, roughly 17% oil (with about 2-3% castor, the rest klotz), incidentally I'm using the same fuel (same methanol, same oil at least) and I'm much more lacksadasical about what I do with mine (stored in the garage, on the floor, his is elevated and stored indoors with a cover over it). I've not had the same issues.

Filters, all the filters have been cleaned and checked for debris, nothing's appeared, we've flushed needles, run with and without filters, and replumbed two of the aircraft. I've warned him that occasionaly in the filtering process some filter fibres stay suspended in the methanol and can clog needle seats over a period of time. After flushing everything no sign of fibres appeared. I don't beleive this is the issue.

Engines. As I say this is happening to ALL of his motors, which at this point are as follows.

saito 72
ASP 61
Enya 40
Royal 46.

I'm stumped. Any ideas on what could cause such funny runs?
Old 05-22-2011, 04:32 PM
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summerwind
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Default RE: first flight good, second flight BAD.

let me get this straight, all of his engines run one flight fine, then all the engines have the same exact issue on the 2nd flight of the day?
so if you go out on say this coming Sat. and fly, you will get 1 flight in with no issues, and then the next flight is a dud?
and then you can go out the following Sat. and the same scenario repeats?
nothing in the book of laws that i know of can explain this.

but if you are using the same exact fuel and not having issues, then try your fuel in his planes next time.
if that and the glow plugs are fine then he is just unlucky.......NO?
Old 05-22-2011, 04:42 PM
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TedMo
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Default RE: first flight good, second flight BAD.

He is not getting fuel is how I see it.Give more info. Tank location as well as tank.needle valve relationship. What engine, inverted?Adjust low speed needle. That seems to be most problems these days.
Old 05-22-2011, 04:58 PM
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Rendegade
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Default RE: first flight good, second flight BAD.

Each aircraft is different.

Lets go through this.

Saito 72, inverted, tank postion a little high compared to needle.
Rossi 40, upright, top of tank in line with needle.
Enya 40, canted @ 80°, top of tank in line with needle or just above it.
ASP 61, inverted, top of tank well above needle.

tweaking the idle needle will produce what? Generally it seems that he has a flameout on full throttle, even when tuned slightly rich on the ground.
Old 05-22-2011, 05:02 PM
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Rendegade
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Default RE: first flight good, second flight BAD.

As regards fuel, haven't tried my fuel as I've not brought a glow aircraft to the field for some months (well I have, but my .020 runs different fuel to the rest of my planes).

Will try and report back.

One other thought I just had, is perhaps, it's atmospheric. I know he likes to tweak his motors til they're on song, so maybe a tune for the cold morning won't work for a hot midday.

Wait, that should work in reverse shouldn't it? It should richen up as the day progresses? Density of air and all that?
Old 05-22-2011, 05:25 PM
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summerwind
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Default RE: first flight good, second flight BAD.


ORIGINAL: TedMo

He is not getting fuel is how I see it.Give more info. Tank location as well as tank.needle valve relationship. What engine, inverted?Adjust low speed needle. That seems to be most problems these days.
but he gets in one full flight at the beginning of the day.........none of it makes sense if all the other usual items check out like glow plug fuel line, etc.
Old 05-22-2011, 05:28 PM
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summerwind
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Default RE: first flight good, second flight BAD.


ORIGINAL: Rendegade

As regards fuel, haven't tried my fuel as I've not brought a glow aircraft to the field for some months (well I have, but my .020 runs different fuel to the rest of my planes).

Will try and report back.

One other thought I just had, is perhaps, it's atmospheric. I know he likes to tweak his motors til they're on song, so maybe a tune for the cold morning won't work for a hot midday.

Wait, that should work in reverse shouldn't it? It should richen up as the day progresses? Density of air and all that?
well your fuel may be the problem, but who knows, you don't use yours.
all the other things you reported on in regards to fuel tank posistion sound fine, but what throws this into a questionable topic is that you say he gets one full flight in at the beginning of the flying day, then has problems............does this happen each outing?
sounds fishy
Old 05-22-2011, 05:36 PM
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Rendegade
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Default RE: first flight good, second flight BAD.

Yeah, almost every time he flies, he leaves in a huff, or scratching his head.

I'll mix a batch for him next weekend and we'll see what comes of it.

Other than that, more musing on temperature. What sort of effect does CHT have on a glow engine? Surely a hot plug and no nitro fuel would be not nearly as touchy in this regard?

Let say there's a change in air temp of 15-25°C that would have THAT much of an effect would it?
Old 05-22-2011, 05:46 PM
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summerwind
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Default RE: first flight good, second flight BAD.

ORIGINAL: Rendegade

Yeah, almost every time he flies, he leaves in a huff, or scratching his head.

I'll mix a batch for him next weekend and we'll see what comes of it.

Other than that, more musing on temperature. What sort of effect does CHT have on a glow engine? Surely a hot plug and no nitro fuel would be not nearly as touchy in this regard?

Let say there's a change in air temp of 15-25°C that would have THAT much of an effect would it?
depends, head clearance with FAI (no nitro) fuel can be a challenge in climates like yours.

in Free Flight comps our FAI engines needed head clearance adjustments from morning to afternoon to maintain performance...........shouldn't be that critical with your friends engines, but i'd try different fuel first as the temp change may be the problem.
maybe try some fuel with 5% nitro added.

what's strange is that one of the engines is a 4 stroke...........and all are running on a no nitro fuel right?

what it sounds like is that all the engine/tank setups are running fine, then not as if the pickup like has clogged up........but all 4 setups?
Old 05-22-2011, 05:59 PM
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Rendegade
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Default RE: first flight good, second flight BAD.

Mysterious, no?!

I beleive he may have been using 10% with the saito, but started having problems with that initially, so it's in line to get torn down and inspected.

After this, every other motor started having similar issues. IRRC the content of nitro has dropped to zero, and then the same issues appeared with the two strokes.

The timeline may be a bit skewed though.
Old 05-22-2011, 06:08 PM
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Default RE: first flight good, second flight BAD.

I would suspect that the engines are adjusted too lean. When you lean them out too far, they may work for the first flight OK, as the temperature is cooler then. Later it warms up more, and because the engine is too lean it flakes out on the next flight. Some people like to adjust the engines to run at peak or near peak RPMs on the ground too. Some people are what I call incessant needle valve tweakers, as they are constantly tweaking the needle valve.

Anyway, if the temperatures is cooler and then warms up, you'll need to set the needle valve differently. it depends on your locale as to how much though.


Old 05-22-2011, 06:12 PM
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summerwind
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Default RE: first flight good, second flight BAD.


ORIGINAL: Rendegade

Mysterious, no?!

I beleive he may have been using 10% with the saito, but started having problems with that initially, so it's in line to get torn down and inspected.

After this, every other motor started having similar issues. IRRC the content of nitro has dropped to zero, and then the same issues appeared with the two strokes.

The timeline may be a bit skewed though.
OK so all else is good, and then after the first flight in cooler weather is done, then the next flight proceeds during a warmer temp. you mentioned already that you guys have richened the HS needle to compensate, so it's got to be his fuel.
Old 05-22-2011, 06:23 PM
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rambler53
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Default RE: first flight good, second flight BAD.

You're below the equator, so your vortex turns the opposite of our region. I bet it's fine if you fly up here.

He's got a lot of planes, just fly each one once and he'll be fine.
Old 05-22-2011, 07:20 PM
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Rendegade
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Default RE: first flight good, second flight BAD.


ORIGINAL: rambler53

You're below the equator, so your vortex turns the opposite of our region. I bet it's fine if you fly up here.

He's got a lot of planes, just fly each one once and he'll be fine.

hahaha, I'm sure he'll like that!

Old 05-22-2011, 09:22 PM
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rambler53
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Default RE: first flight good, second flight BAD.

Had to have fun with that one.
With a variety of engines in the list, especially the Saito, being one of the most reliable engines I've ever used, if you're having problems with all of them, there is a common denominator that all are subjected to. Fuel would be the first thing I"d check, but it just doesn't make much sense that it's inconsistent, giving you ANY good flights at all to start out with. Bad fuel is bad fuel, first tank to the last.
I've had more than one plane (engine) give me trouble on a particular day when flying, and I immediately go over to a flying buddy and ask if I can fuel from his jug just a 1/2 tank to see if the problem disappears, of course sucking out all the fuel I had from my tank first.
More than once I had contaminated fuel. But I didn't get one whole flight that day from it and then have problems later. Just seems something in the details is missing on this one. Nitro content wouldn't effect the 2 strokes very much, just a little less peak power.

Mixing a batch??????
How much oil, nitro, and how old has the source been around? Does he mix his fuel too?
Old 05-22-2011, 09:54 PM
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Rendegade
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Default RE: first flight good, second flight BAD.

Precisely my thinking.

Unless something untoward has contaminated his methanol whilst in storage, I'm really at a loss as to what else would do it.

He initially purchased the methanol (we have a local industry manufacturing 99% methanol) and I gave him my drum to refill at the same time.

I've sourced the oils, so we have all the same components in our fuel, and mix in virtually the same way (I tought him).
Old 05-23-2011, 03:11 AM
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Default RE: first flight good, second flight BAD.

A change in the weather will affect the tuning. Going from early cold and damp morning to hot mid day I often see a little change in the tuning, I rarely fly a full day without tweaking on everything.

My guess is that he sets the engines too lean and they are over-sensitive to changes. The first run might also be a little different if he uses a lot of after-run oil between trips too the field.
Old 05-23-2011, 03:18 AM
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Default RE: first flight good, second flight BAD.

The only element shared by all planes is fuel and owner... try first changing fuel; if it doesn't works change planes' owner!!!!
cheers
Old 05-23-2011, 04:58 AM
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Default RE: first flight good, second flight BAD.

One thing is certain - there isn't any magic involved in this hobby of ours. There is a reason for things happening the way they do. Tell your friend to stop blowing his stack and concentrate on finding the problem.

When people appear to be guessing a lot, especially experienced people, it is usually because of a vague or inaccurate description of the problem that they have been asked to solve. This is not always the original poster's fault, as the experience necessary for a proper description are the same skills that would have prevented the problem from occurring in the first place.

Tank position is very important. Engines featuring sophisticated fuel delivery systems (YS) are not particularly sensitive to tank position, but suction fed and non pressure regulated are extremely sensitive to tank position/size/etc.


Ed Cregger
Old 05-23-2011, 05:43 AM
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Default RE: first flight good, second flight BAD.

If it flies fine in the cool morning then dies in the afternoon after the weather gets warmer. In many cases his high speed needle is on the LEAN side. Because after flying in the morning air then flying in the afternoon when it is 10-15 degrees warmer it leans out, gets hot and quits.

Rossi engines don't care about nitro content. I have many of them most of mine I run on "JUNK" fuel. That is real old fuel those partial gallons that sit all winter or won't run in anything else.

The only other possibility is the glow plug itself. (That is if everything else is correct.) But If he is tuning his engine to a "song" in the morning. In the afternoon he will have to richen it just a touch (1-3 clicks)to let it get more fuel to help cool it. Then odds are he will be fine. Because your saying every engine is doing it sounds to me more like a lean situation done by the pilot more than anything else.
Old 05-23-2011, 06:56 AM
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Default RE: first flight good, second flight BAD.




  As a suggestion,  here are a couple things to take a look at.

Are the engines run with the fuel system pressurized?

 If so,  Are the muffler pressure fittings on the low or bottom side of the muffler?

If this is the case then the excess oil in the muffler that is not pushed out the exhaust is being forced right back into the fuel tank thru the pressure fitting  adding more oil to the fuel in the tank.

First tank of fuel will usually run thru OK but the second fill-up will add more oil to what was forced back into the tank from the first run resulting in doubling the oil content of the second tank and tripling it on the third tank.

End result is the glow plug is drowned out by to much oil content causing the engine to quit running (That is if you can get it to run).

    I experienced this exact same problem some time ago.   It wasn't caused by bad fuel because I used the same fuel from the same jug in other planes and put 3, 4, or more consecutive flights on without a problem


                Hope this helps,

                                                        Dick

Old 05-23-2011, 09:44 AM
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Default RE: first flight good, second flight BAD.

Instead of waiting hours between flights, land, refuel and fly again right away and see if the second flight goes ok. Before the weather changes.
Old 05-23-2011, 10:12 AM
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mike early
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Default RE: first flight good, second flight BAD.

keep us updated
Old 05-23-2011, 10:30 AM
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Default RE: first flight good, second flight BAD.

Well i remember this problem well from my days of pylon racing many years ago. Everyone racing would always try to get a few extra RPMs on the top end by tweaking the needle valve. If you went a hair too lean, the engine would lean out too much part way through the race on you. So you had to develop a feel and touch for how lean you could go without going too far. Later in the day when the temperatures changed the needle valve settings would change. Everything could affect your engine when racing as well, not just the temperature, but humidity and barometric pressure too. Some guys would change out to different glow plugs depending on the conditons changing during the day. Even the nitro percentage in their fuel could change during the day too (if you didn't have to use the club fuel for racing). the propeller used could change too.
Everyone kept a notebook or log of everything they did too.

Anyway I would still suggest that the OP have his friend run the engines on the rich side. Find the peak RPM setting and back it off about 500 to 1000 RPMs off of peak. Some engines have better fuel draw than others to. Then after it starts to work OK, then lean it out a little more, but careful. Point the nose of the plane to the sky and adjust the needle at WOT and back it off a little from peak, say 500 RPMs. Then the plane should work fine.

On really hot and humid days the engines can really lose a lot of power and you have to run them even more rich to prevent them from overheating or detonating even. You just have to live with the lack of power in these cases. I remember a few days where I would show up early and when it was cooler get in a few flights no problem. But then others would show up, and I'd help some guys out and later when it heated up more, I would find my engines were too lean now and needed to be richened up a little, before I could fly the planes again.



Old 05-23-2011, 11:27 AM
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Default RE: first flight good, second flight BAD.

My first guess is bad fuel.

I always run the center of the tank in line with the needle. Given that:

 Saito 72, inverted, tank postion a little high compared to needle.
Rossi 40, upright, top of tank in line with needle.
Enya 40, canted @ 80°, top of tank in line with needle or just above it.
ASP 61, inverted, top of tank well above needle.
The Saito would be a bit rich (OK for a 4-stroke), the Rossi and Enya would be a touch lean, and the Asp would be fairly rich.

I agree your friend should first check all fuel lines, especially the tanks, for integrity, and get a second or third flight in before conditions change. A little more oil or Klotz wouldn't hurt, and castor.

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