The Upline
 

Hello Everyone,

I have some general questions about uplines. I am struggling to get straight ones and need some help.

The engine produces torque. This torque (from what I have heard) cause the plane to yaw. I have also heard that this torque is non-existent. And I have heard that this torque varies, pulling the plane to one side depending on orientation.

Basically, I have no idea what to think as far as uplines and correction are concerned. If anyone could give me some insight into what exactly happens on a upline and some correction tips for straight, crisp uplines. Thanks.

Oh and also. I was just thinking. If the engine is generating all this torque, wouldn't it cause the plane to yaw in ALL attitudes, not just on vertical uplines????

Thanks for the help,
-Matt

RE: The Upline
 

see if this article helps with your plane as it covers all aspects of trim. I use it these principles for all of my birds.

http://www.mini-iac.com/Portals/57ad...20trimming.pdf

RE: The Upline
 

To specifically answer your questions, it is really a combination of torque and propwash. As the prop turns the slipstream from it is spiraling back along the airframe and once it hits the rudder it tends to push it to the right. The torque of the engine, really the prop, is another reason and the most correctable.

As the plane slows going up, the rudder looses effectiveness and the torque starts to pull the nose to the left. What you do is add right thrust to counter act this problem which is typically done by adding washers between the firewall and engine mount on the pilots side of the plane, this moving the prop to the right. The thing is you do not want to do this until you have decided on the prop you want to use all the time because changing the prop, even when you stay with the same diameter and pitch, will most likely change the right thrust requirements.

Some people will not change the thrust but add a proportional rudder mix to the throttle that once you are close to a certain point with the throttle, right rudder is gradually mixed in. The problem with that is in any other attitude beyond vertical, the more power you feed in the more rudder is fed in and now you are yawing to the right flying straight and level unless you add the mix to a switch. I find that in competing, the last thing I want to have to do is flip a lot of switches. I have enough to do when flying the sequences to worry about flipping a switch for possibly every maneuver.

So basically, the reason you do not see it in most other attitudes is you have good airflow over the rudder, thus helping to keep the plane tracking straight in yaw.

Go with krayzc-RCU's suggestion and do the trim chart and do it in the order it shows. It's a bit of work and could possibly take 20+ flight to finish BUT you'll be amazed at how well the plane will start to fly

RE: The Upline
 

Thank you both for the help,

krayzc-RCU:

Thank you for the link to the trimming guidelines. I will definitely reference this for setting up my next model.

bubbagates:

Thank you as well for your detailed response. Almost everything you said makes sense. I am just still having a hard time getting around how the airplane yaws more or less depending on attitude. I would seem like it would do one thing in all positions. This seems to not be the case. Could you touch on this some more?

Thanks,
-Matt

RE: The Upline
 

Matt,

You will understand it once you see it and learn to trim (correct) for it. Think of it this way, if you are flying slow, say right near the stall, you need more elevator to maintain level flight and more aileron to bank the plane, but as the plane gains speed you need less input.

Now, think of the rudder like it is used in a boat. It steers the nose of the boat left or right, exact same thing for a plane. As the plane slows, the rudder is less effective but if you are holding full power, as you normally would in a vertical climb, the torque or the spinning prop starts to pull the nose to the left. remember back in high school you learned about Newton's third law of motion, for every action there is an equal and opposite reaction, It certainly applies here as well. The prop is spinning clockwise when viewed from the pilots seat (sitting in the plane facing front). That big spinning thing, according to Newton's law, will now try to pull the nose in the opposite direction because you are slowing in the climb and the rudder can no longer overcome the big spinning thing out front unless you add more rudder. Well, we as pilots like to do as little work as possible so what we will do is move the engine in such a way that helps cancel out the torque and to do this you add a bit of right thrust. This does two things, it helps eliminate some torque and also moves the propwash further back so less of it is striking the rudder

I always suggest to my students that want learn more about how a plane flies is to buy a book that was written several years ago (early to mid 50's) called Stick and Rudder. I was given a copy of it when I learned to fly full scale aircraft in the mid 70's. It explains aerodynamics in a very easy to read format. You just have to get past some of the terminology like the elevators are called flippers in the book.

Here's a link to amazon for the book

[link=http://www.amazon.com/Stick-Rudder-Explanation-Art-Flying/dp/0070362408/ref=pd_bbs_sr_1/104-5991507-4843909?ie=UTF8&s=books&qid=1193061582&sr=8-1]Stick and Rudder[/link]

RE: The Upline
 

Alright. Everything about the rudder being less effective at slower speeds makes complete sense and I would agree. I see how the torque varies from fast, full-throttle uplines compared to slow, near-stall level flight. I guess where I was confused was, how could the attitude of the airplane affect the torque, assuming constant throttle. I don't see how it could. How could the torque change from full-throttle, level flight to full-throttle vertical???

I heard someone say that depending on the position of the plane, the torque will vary. I don't see how this can be true. For instance, if you were in a slow roll with constant throttle, they say the torque changes direction from inverted to straight and level. Could you shed some light on this.

Thanks,
-Matt

RE: The Upline
 

Matt,

When you are straight and level, the speed of the plane increases to it's maximum and would not normally drop off unless you lower the throttle, but when climbing, the plane starts to slow down though you may remain at full throttle. The torque really is not changing much in this example but it is changing as the load on the engine is slowing down the rpm, so if anything the torque and it's effect is getting stronger since most times we prop for top rpm but usually top rpm is beyond the torque curve of the engine, but the speed of the plane is slowing and as such, the torque "effect" becomes more pronounced since the plane is slowing and the engine is getting into it's torque curve. Most engines make their most amount of torque well below the max rpm it can achieve and as such the torque curve actually may drop off a bit once you get past it's peak.

I'd think of it in terms of effect based on speed/throttle position and prop rpm, sooner or later the speed has slowed enough that torque starts to pull the nose to the left and the prop wash starts to push the tail to the right, hence moving the nose to the left so the slower you get going up the more you have acting against you.

A good way to see this is to not do anything on the trim chart. Go fly and pull a vertical line and correct the flight path with whatever amount of right rudder you need. Once you have some rudder in, just chop throttle but do not let go of the rudder. Guess what's gonna happen, the nose will straighten out and depending on how much speed you have when you do this, it might even go to the right a fair amount because of the rudder.

When I do thrust changes, I will fly vertical lines and use my rudder trim to get it tracking straight up for about 500 feet. I will leave the trim in and land. I will then use a protractor to see how many degrees the rudder is from center, divide by two and use that number for the amount of engine thrust I need. It usually gets me very close if not right on the money. Mind you, you can never get the plane to track perfectly straight all the way up until the engine can no longer pull the weight, which on a seriously overpowered plane, can easily take you past the point where you cannot even tell what it's doing so it's best to do it to the normal height that you would normally do a hammer head/stall turn and for me it's about 500 feet

The book actually does a much better job at explaining it than I have

RE: The Upline
 

Bill,

So what you are saying is that as the speed decreases on an upline (assuming the throttle is constant), then the "torque effect" on the plane increase, causing the plane to yaw left?

If that's the case, then I'm confused about torque rolls. Let me see if I can get this right. One way to think about entering a torque roll would be pulling to an upline and reducing throttle until the plane stops climbing. So in this case, the throttle is constant and the speed of the plane is now zero. So why wouldn't the plane just yaw to the left and fall out? Why does it rotate about its length?

(I know I'm going a little off-topic, but as we continue to discuss this I have more questions :) )

Thanks again,
-Matt

RE: The Upline
 

it takes rudder & elevator corrections to t-roll

RE: The Upline
 

Yeah. It does take rudder and elevator input to maintain vertical. I guess what I'm saying is how does the plane rotate along the axis of the fuselage if the torque of the engine only causes the plane to yaw not roll?

Thanks,
-Matt

RE: The Upline
 

i have prop my 52.5cc motor with certain props & on up lines it caused the plane to roll very slowly out of position.

RE: The Upline
 

Matt,

A plane that has thrust issues will actually try to fall out to it's left or right in a torque roll if it's side thrust issues (depending out what side thrust is wrong, left or right) or fall front or back if it's up/down thrust issues or a combination of both and of course the less the angles are off the less it will try to fall off.

Most people flying 3D that do not correct thrust angles naturally correct for it with the sticks and in most cases never realize it. I have a friend that's a really good 3D pilot and until he started in IMAC he just built planes, never really checked anything trimming wise and flew the snot out of them. He had a certain plane and was really 3D'ing it last year and finally decided to try his hand at IMAC. We worked to get the plane properly trimmed (thrust angles and the like). Once we got everything done he went to 3D it and was pretty amazed at how much easier it was. He needed less corrections in TR's, hovers no longer pulled one way or the other on pullout, if he got into something that was getting ugly in a hurry he used to have to worry about what the plane was gonna do, but after all the trimming he found out that the plane became very predictable and he pretty much knew what it was gonna do at any one moment.

Now there are 2 common ways to get a TR going. One is to give it left stick and the other is just blip the throttle. The torque change will get the plane moving. You then control how fast it rotates using the ailerons. My Ultimate will sit up right into a hover with little effort but it will not TR on it's own. I just blip the throttle and it starts rotating and if I do not add opposite aileron she will really get going. I like a good straight up TR. A fast one looks good to but to me a nice gentle slow one is where it's at.

RE: The Upline
 

Hey Matt,

I think one of your questions has to do with horizontal versus vertical flight and why we don't see as much effect on torque in horizontal flight? Well, the torque is there all the time, but it's most noticeable when you're slow with lots of throttle. With models, that's hard to do unless you're vertical. If you are flying a full-scale 152 or something like that, you can see the impact of torque big time when you do power-on stalls. The goal here is to bleed off airspeed and get the nose high. You feed in power so you can maintain altitude. It's been a while, but I think you can get the airspeed down to 25 knots or so, depending on temperature and loading. When you are in that position, you have a lot of right rudder to keep things straight. In the model world, you're most likely to experience something similar on takeoff, especially a modestly powered nose-wheel aircraft taking off from a grass runway. If you pull back too soon or too hard, the plane will snap off to the left.

So, the torque is always there, you just feel it most in slow, high-throttle situations. For straight and level flight, we usually trim it out. Problem is that when you slow down or speed up relative to where you trimmed the airplane, you do get some yaw (and other stuff, like roll). Full scale pilots spend a lot of time flying the plane with trim. You set trim to one place for take-off. Trim for climb-out. Trim for cruise, etc.

RE: The Upline
 

Well Matt,

Alot of this yaw is due to the " P " factor. Your prop makes a cyclone around your tail section's and no, it does not only affect your roll axis but as well as your yaw.

I don't program a upline mix in my 9C because i'm learned to huck on a 4 channel:D due to past money issues (im 14). You can make your own mix depending on what kind of tx you have. Also what size aircraft are we talking? Honstley, the best way to learn to fly like a pro is don't use mixes. Most pilots are dependant on these mixes as well as all the pro's. And trust me, it's not hard to learn to get your plane to track a true upline, just pratice is all I can say.

Good Luck,
Matt - Aka Sp33d

RE: The Upline
 

mixes will be a part of my flying for sure along with doing my best to correct issues like up, right thrust....[8D]

RE: The Upline
 

All,

Thank you for all of your responses. That has really cleared things up for me.

Matt

RE: The Upline
 

This is actually untrue.

Every "pro" I have ever talked to or have flown with have mixes setup. Take a look at any of Quiques flight/assembly manuals and he gives you the mixes he uses in them, usually the flight manual and if you ask him he may even send you the backup file from his 10X. Bill Hempel uses mixes on his 14MZ, seen them myself. Chris Maier helped has helped many people setup mixes and trims, seen this in person a lot as I compete with him though not in the same class. Kyle (The Alien) certainly uses mixes though he's that instinctive that I've seen him take a plane on it's maiden and fly it like it already had mixes and trims setup and never touch the trims on the radio.

Most pro's will gladly tell you how they do it, just ask them. Just cause they are really good at what they do, that does not mean they are untouchable