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Down thrust ?

Old 10-26-2004, 03:07 PM
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Default Down thrust ?

Hi Don. How can I determine if I need down thrust ? I need a little bit of down elevator on my down lines and I was wondering if down thrust is the answer. The airplane has one click of up elevator for upright flight and it needs very little down elevator for inverted flight. The airplane is a 40% carden extra. Thanks in advance for your help!

Albert Santiago
Old 10-26-2004, 11:46 PM
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Default RE: Down thrust ?

Down thrust, or up thrust...

Trim model for level flight, cruise speed (where you fly your sequences at). The plane should not climb or dive, but fly generally straight and level.

Next flying right to left, carefully pull vertical and then once perfectly vertical, let go of the sticks (full throttle). Just let completely go of the sticks and see which way the plane goes. Toward the canopy, or to the belly.

Finally, fly left to rigth and carefully pull vertical and then again let go of the sticks to see if the plane tends to go one way or the other at the top of a vertical line.

If the plane pull to the canopy in both of the above instances, add in some down thrust.

Don't worry about looks. I've seen folks be very concerned that the spinner does not match the cowl molding. I disregard that and put in whatever thrust it takes to make sure the plane tracks vertically up.

Some aircraft require up thrust as well, if the plane pulls toward the belly (landing gear). I have a touch of up-thurst in some of my models.

Down lines are another situation all together. Program with the transmitter. For the 10X its one of the 51 through 55 mixes, throttle is master, elevator is slave. Use the throttle offset for this control (move the throttle stick up 3 clicks above idle and store the offset). Finally, disable the trim, so the throttle trim lever will not impact your mix rate.

For the 9303, use the p-mix with throttle as the master and elevator as the slave. Offset appropriately at the low throttle point, while zero-ing the mix rate at throttle above half (you can visually see this on the curve. Finally, be sure to use the #throttle rather than throttle. The #throttle will make sure that the mix is de-coupled from the throttle trim. Same reason as described above- you don't want to change your throttle mix if you change the throttle trim lever position.

8103 is similar, but pick one of the p-mixes that allow ORIG and the throttle trim to be disabled. I can't remember which ones these are, but I know its not all of the p-mixes available, just a couple of them that have this feature.

I have this mix in just about all of my planes. Thrust does not impact down-lines. The mix allows for hands off down lines. Also consider any roll in a downline to be mixed out using the same technique. I leave the mix in at all times.

Don
Old 10-27-2004, 05:29 PM
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Default RE: Down thrust ?

I will give that a try this weekend. Thank you for your help.

Albert Santiago

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