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Old 11-27-2017, 07:36 PM
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Down Elev. mixing with Low Throttle in Pattern?

I just watched a Futaba "How to" video by Chip Hyde. He mentioned that many/most Pattern fliers mix some down elevator with low throttle.
What is the purpose of this?
Is it to "steepen" down lines?
Do pattern planes typically climb on low throttle?
I had not heard of this before, but it's hard to question HIM about what's best...
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Old 11-27-2017, 07:48 PM
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When you do a down line the plane tends to pull toward the canopy. This keeps it tracking vertically

You ouly have the mix enabled when your throttle is all the way down. Say last 3%. This way it never kicks in unless your pointed at the ground.
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Last edited by Keith Cannon; 11-27-2017 at 08:07 PM.
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Old 11-27-2017, 08:55 PM
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It is a very common mix used in most IMAC and Pattern models. I also tend to recommend this to most people for the simple fact it helps keep the nose pointed down when on approach.

Andrew
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Old 11-28-2017, 09:27 PM
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I thought I recall reading an article that explained the mix by suggesting most airplanes have a little down thrust which at higher throttle has the tendency to pull the nose down. When the airplane is trimmed for higher throttle level flight there is actually a bit of up elevator or horizontal stab incidence to keep the airplane tracking level. So the airplane at low throttle can have a tendency to climb because it lessens the pull of the motor.

Iím sure someone here will correct me if Iím off base but thought Iíd toss it out there for consideration.

Iíve personally used it for my downlines and landings. Iím not a precise enough pattern flier to really detect the change in tracking on straight and level.
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Old 11-28-2017, 09:53 PM
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an airplane in level flight has to have a positive angle of attack on the wing to create lift. when diving, that same AoA causes a pull into the canopy. It does not indicate any fault with the set or design. A downline mix is used to keep the nose vertical. What you describe is a condition where too much down thrust results in a trim change - "ballooning" when power is retarded. Pretty uncommon in aerobatic airplanes, but does signal improper set up or design where it does occur.

A friend of mine bought a used 35% Edge years ago that did exactly what you described. Since I had flown many others with no issue I suspected a thrust problem by the builder, which turned out to be the case. Made new motor stand offs, and it flew fine.
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Old 11-29-2017, 02:07 PM
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I only use it in my IMAC planes.
You must set a switch that turn it on while you fly pattern or IMAC when you land you must turn it off.
I use conditions so I have one for IMAC with all the mixes I need and one for landing that disables all.
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Old 11-29-2017, 03:15 PM
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Dk, thanks for asking and thank all of you for responding. I had assumed it was due to thrust angle- but the concept of the wing having at lest some positive incidence makes sense (how else would it produce lift in level flight?).

I feel like I learned a lot from the futaba/Chip Hyde videos. Now we need a Jesky videos thrown in!
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Old 11-29-2017, 04:29 PM
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The Chip Hyde videos are definitely added value!
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Old 11-29-2017, 04:36 PM
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Fwiw I've never had the mix on a switch.. Doesn't affect landings.
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Old 11-29-2017, 07:36 PM
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I don’t notice it either. On a landing your going a lot slower than in a down line so it’s not as effective. Also note that it is a very small mix in the first place. Mine is less than 3% if memory serves correct
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Old 11-30-2017, 03:15 AM
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I put mine on a switch so that I can turn it off during landings. It is not as noticeable with our IMAC planes, but in Pattern where the most critical phase of flight is actually scored, I prefer to have it off. I was noticing a slight issue when I would hit low throttle and the rate of decent would change slightly.
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Old 11-30-2017, 07:39 AM
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It’s noticeable especially when you close the throttle second before you stall and land.
try to land without it and see the difference.
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Old 11-30-2017, 08:00 AM
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I have mine on my timer switch because I always turn it off when it starts beeping, that way I dont forget it
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Old 11-30-2017, 10:18 AM
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Trim is changing because the model is accelerating. This is true for a model in a vertical climb as well. Models sometimes have power to accelerate in a climb.

Thrust angles and power distribution have little to no effect.

A lighter model and or one with less pitch prop drag needs less depending on the length of the down line. IE it doesnít slow as much near as fast.

If you would fly the whole program at the same speed and and trim setting, no mix would be needed less sideslip.

The final factor is mass of equipment and location in the fuse. IE big heavy cans at the bottom of the airplane affects vertical deceleration more than most give it credit for.
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Old 11-30-2017, 02:25 PM
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Since I use an idle up switch for flying and down for landing, the slight down elevator is only engaged when the idle up switch is engaged and disabled for landing. Kudos Tyler McCormack for showing me this one!
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