RE: Mix Elevator with Throttle for Scale Flight?
 

The problem is that you continue to describe flight characteristics of a nose heavy airplane. No airplane has to be flown at 70 to 80 mph to support it's own weight. Please go turn the airplane on with everything kept to the trim you have and I bet you that you are have some up trim or an even better question, on the maiden did you have to apply up trim?

RE: Mix Elevator with Throttle for Scale Flight?
 

flandrumjr
If you want to program that in you probably can but not a good idea it better practice to adjust your trim at any given airspeed to maintain straight and level flight. To maintain straight and level flight at reduced speed you must trim the airplane at that speed. Keep in mind at lower airspeed the plane has to fly at a higher AOA to maintain the same lift, it not just the throttle setting alone that determines what is going on.

RE: Mix Elevator with Throttle for Scale Flight?
 

A plane does not have to be out of balance to display the characteristic the OP described. For example... if a plane had slightly too much positive wing incidence, the elevator would need trimmed down to counter the resulting climb at full speed and then when slowing, the down trim would likely cause an abnormal loss of altitude with the pilot leaning back on the stick.

Another example would be an asymmetrical wing on a plane with too much power. At full power the plane climbs because of the increasing lift of the asymmetry and needs down trim to counter, again with the down trim causing altitude loss when reducing speed.

A third example is a plane with the drag couple such as seen on parasol winged planes where the lever arm pitches the nose up under power and down trim is needed and when coming off the power, the lever arm is reduced and the plane again doesn't hold altitude because of the down trim.

All three examples above could very well be in balance.

RE: Mix Elevator with Throttle for Scale Flight?
 

What you describe is exactly what the OP asked about doing... with one minor exception... he asked about doing a mix to make the trim adjustment rather than having to fumble with finding the elevator trim and re-trimming. And... it is likely that he will forget to retrim it back before taking off the next time.

What is the problem if the OP does a mix to do what you say to do manually? I say it would be better than manually given the likeliness of forgetting to move the trim back before the next flight.

RE: Mix Elevator with Throttle for Scale Flight?
 

You would be correct on example 1. This is why I reccomended the OP to correctly trim the airplane. This includes measuring and adjusting incedences.

Example 2 can still be adjusted with CG. 99% of plyon anirplanes and 100% of high performance sailplanes have have semisymmetrical wings. My pylon airplanes track the same weather they are at 1/2 trottle or full tilt. I set my sailplanes up so that at high speed there is actually a slight dive. This is done through CG.

Example 3. OP is obviously not talling about a parisol airplane and it is a poor example to attempt to prove your point.


CG is often the most mis-understood adjustments on an airplane. The Myths are that a forward GC is more stable or it's set as per the plans and just from guys who don't have a full understanding on what it does for the airplane trim. I can guarantee that if your airplane changes trim with airspeed changes then a CGadjustment will help if not correct. That is if the airplane is strait to begin with. Please give it a try before dismissing it.

RE: Mix Elevator with Throttle for Scale Flight?
 

I think a lot of it has to do with what type of flight training you have received.
If he wants auto trim go for it, no problem there.:D
Last night at our club meeting there was a discussion about a auto recovery systems that cost something like 400-500 dollars that will return your plane to the spot it took of from. Kinda neat but not for me. too much like a 747 or airbus flying with dials...

RE: Mix Elevator with Throttle for Scale Flight?
 

Iron. you would be surprised how little AOA it takes to support the weight of your airplane. On a 40% 38# airplane it is about .5 degree depending where the CG is placed.

RE: Mix Elevator with Throttle for Scale Flight?
 

Yep, I have a plane that will hold level flight at +0.015 degrees at a given airspeed or so the computer software says.
And your right COG has a lot to do with how the plane will fly and respond to controls or throttle setting no argument here.:D

RE: Mix Elevator with Throttle for Scale Flight?
 

There is no poor example in my post. The examples were not any attempt at describing the OP's situation any more than your sailplane illustration and the OP certainly didn't claim to have a sailplane.

RE: Mix Elevator with Throttle for Scale Flight?
 

Correct the sailplane is an off example but my pylon airplanes are warbirds with semisymmetrical airfoils. Very close in configuration to what the OPdoes have. It blows me away that some guys resist sound advise to this degree. If you don't agree with it then don't try it but please don't continue to argue with someone with 30 years of competitive flying whom is just showing guys how to set up their airplanes to be easier to fly.

RE: Mix Elevator with Throttle for Scale Flight?
 

I'm with speedracerntrixie. Unless the OP is running a fairly strange design, speed and power sensitivity can be fixed with mechanical flight trimming instead of electronic bandaids. You see the same conversation going on with pattern and IMAC guys. The more impetuous pilots run straight to programming mixes into their whiz bang radios to fix planes that aren't set up right to begin with. The guys who take the time to get everything as perfect as they can with airframe trimming before resorting to radio helps have a smaller pilot workload and generally better overall flying airplanes. I've already laid it out pretty clearly what the negatives of the OP's idea are since I've done it before. If he still wants to use an electronic band-aid instead of fixing the aerodynamic problem with his plane, that's his business. But I'd wager my Kaos that with some fine tuning of his CG, incidence, and thrust line he can have a plane that flies right on its own with none of the negatives of using a mix.

RE: Mix Elevator with Throttle for Scale Flight?
 

What happens when the engine fails after you have set all these mixes based on a running engine? Are you going to put the mixes on a switch? Are you going to have them turn on/off based on throttle setting? Will you remember to throttle back or flip the switch on a dead stick?

RE: Mix Elevator with Throttle for Scale Flight?
 

Hi!
You are both absolutely correct!
Many who have'nt flown competitivly in Pylon racing or F3A (Pattern) tend to miss that a "correct" Cof G is something that must be obtained by constantly flying the plane in question aiming for the least amount of up elevator throw as possible and at the same time moving the Cof G rearwards...untill the plane flies perfect!
This is a trail and error thing to do and is something you have to have in mind if you want a good flying airplane.
The Cof G position written in the manual is at best something to start from.

RE: Mix Elevator with Throttle for Scale Flight?
 

You guys are so right!
COG and lateral balance are probably the two easiest fixes for problems that are most commonly overlooked, I had hoped that the OP had actually tried to adjust the COG to see if it changed the results.
Today far to many people try to use technology to solve simple problems, and rather than fix the issue a electronic band aid is applied.
I think it would be a good idea to have beginners build a couple of free flight planes so they get an idea of how to set up a plane properly before they even touch a radio.

To this day I have no clue of how to set endpoints and centering on my radio because it is something I do mechanically.
Heck I just recently learned how to set up expo as I had never used it before, because of a design error on a plane I built resulting in one very sensitive elevator function using elevons.

I am so glad to see there are a few others, other than myself, who think this mix thing isn't that good of an idea and he should investigate other solutions.

RE: Mix Elevator with Throttle for Scale Flight?
 

Troll in the house.

RE: Mix Elevator with Throttle for Scale Flight?
 

I have done this with my stick for years and love it, but I put the mix on the landing/flap/airbrake switch instead of mixing it to the throttle. I can turn the mix on or off when I want. You are absolutely correct about the need for a new trim setting for a slower speed. Most guys zip around at full throttle and then wonder why their plane comes in so hot on landing - yet they never change the trim. Those guys need to go fly a full scale plane and and see how much we change the elevator trim during flight.

Kurt

RE: Mix Elevator with Throttle for Scale Flight?
 

I was wondering when someone was going to throw full scale in here LOL So now that it has been brought up, have you ever expereinced a situation where you had been carrying passengers and/or baggage that loaded behind the CG and needed less trim at approach speeds?


It may not be too PC to bring this up however there was a full scale P-51 pilot who thought the answer to his trim issue was to keep dialing on the trim tab. Right up to the point where it broke off in flight. Sadly we all know what that result was.

RE: Mix Elevator with Throttle for Scale Flight?
 

Is that what they figured out happened at the Reno races? How did trimming the tab cause it to break?

RE: Mix Elevator with Throttle for Scale Flight?
 

Oops...was I not suppose to do that??

Kurt

RE: Mix Elevator with Throttle for Scale Flight?
 

Here is what the NTSB came up with:

"Deteriorated Parts Allowed Flutter Which Led to Fatal Crash at 2011 Reno Air Races
August 27, 2012

WASHINGTON - The National Transportation Safety Board determined today that deteriorated locknut inserts found in the highly modified North American P-51D airplane that crashed during the 2011 National Championship Air Races in Reno, Nevada, allowed the trim tab attachment screws to become loose, and even initiated fatigue cracking in one screw. This condition, which resulted in reduced stiffness in the elevator trim system, ultimately led to aerodynamic flutter at racing speed that broke the trim tab linkages, resulting in a loss of controllability and the eventual crash.

On September 16, 2011, as the experimental single-seat P-51D airplane "The Galloping Ghost," traveling about 445 knots, or 512 mph, in the third lap of the six-lap race, passed pylon 8, it experienced a left-roll upset and high-G pitch up. During the upset sequence, the airplane's vertical acceleration peaked at 17.3 G, causing incapacitation of the pilot. Seconds later, a section of the left elevator trim tab separated in flight. The airplane descended and impacted the ramp in the spectator box seating area, killing the pilot and 10 spectators and injuring more than 60 others."

RE: Mix Elevator with Throttle for Scale Flight?
 

Well it looks like I may have opened up a can of worms. I brought up the Galloping Ghost simply to illistrate that the airplane was dependant on the trim tab. The loss of the trim trab for whatever reason caused the airplane to pitch up.

RE: Mix Elevator with Throttle for Scale Flight?
 

Kurt, please don't think I had an issue. IMOin these threads anything you or anyone else can contribute is fair game. This is how we learn others methods. My point was simply that some of what is considered standard operations for full scale need not apply to our models.

RE: Mix Elevator with Throttle for Scale Flight?
 

Speed your right trim is critical to a airplanes operation, and that was a perfect example as to how critical. The sad part is 11 people died and scores injured because of a few corroded lock-nuts on the trim tab hinges...
Some of the more interesting parts of the investigation were that the plane had had undocumented and untested changes to made to the horizontal stab incidence as well. Along with some pictures of it in flight showing the fuselage skin wrinkling up in turns from the g forces (not determined to be a factor in the crash) that illustrated the extreme stresses the airframe was under (as well as the nearly 70 year old pilot flying it). Keep in mind were talking about a 70 year old airframe it shows you just how hard these guys are pushing these planes in those races.

And your also right about what applies to full scale may not apply to the typical operation of a model plane. But as was said in an old move they just redid "The principals are the same".:D
The one thing that struck me was this sentence the OP had included as his problem: "Now without the throttle/elevator mix and as I pull back on the throttle to say 1/2 throttle the plane will begin to slow, as it slows the plane begins to gradually loose altitude due to the lose of speed."
Well that is exactly what is supposed to happen.
This is when you adjust your trim to return to level flight at the lower speed, at least that's what I was taught when I learned to fly full scale.

RE: Mix Elevator with Throttle for Scale Flight?
 

Iron, agreed thAt the airplane will lose altitude as speed drops. The way he described it made me visualize that the nose was dropping as well. IMO if the CG is not too far forward and the nose remains relitivly level then adding a mix that gives up trim at low power settings is a pretty quick way to induce a stall. I actually do a simular mix on some IMAC airplanes that gives a touch of down elevator at idle so that downlines do not pull to the canopy.

RE: Mix Elevator with Throttle for Scale Flight?
 

speedracerntrixie - I was playing - We usually are on the same page.

Kurt