I have a .61 sized Cub that needs little help getting on the ground. I guess I spoiled myself with my Twist where I could come in to land at about a 45 degree angle, not gain any speed, and flare out at the end and set it down. The Cub, with it's big flat bottomed wing, seems to float on forever and I usually have to abort a few landings before I can get it landed. The field I fly from has never seemed small until now.
My Twist has a very fine pitched prop (12x4 on a .46) which seems to help it slow down. The fat, symetrical wing helps too. I need to figure out what to do with my Cub.
I have a 12x6 prop on it now and I just bought a 13x5 to try.
I can also program in flaperons or air brakes, and I'm getting some conflicting advice on which to use.
I was told to use flaperons and that would allow the plane to slow down enough to land a bit better but keep it from falling out of the sky. I'm not sure that MORE lift it what I need, but I've never tried flaperons before so I can't comment from experience. I did have a veteran Cub flyer to tell me to stay away from using flaps, especially at low speeds, since the Cub it prone to tip stalls and the flaperons (and using them while already going slow) will make it work.
I can program in air brakes, where the ailerons go up, and that seems like it would be more effective. My Tx allows me to mix in a little up elevator at the same time the air brakes are deployed (the manual cautions to use just a little bit of up elevator, along the lines of 10%). Not sure exactly how far up to move the ailerons though, I imagine it's not much though.
I am going to try the 13x5 prop, and see just how low I can get the idle, but I forsee needing to do some more programming as well.
I have a .61 sized Cub that needs little help getting on the ground. I guess I spoiled myself with my Twist where I could come in to land at about a 45 degree angle, not gain any speed, and flare out at the end and set it down. The Cub, with it's big flat bottomed wing, seems to float on forever and I usually have to abort a few landings before I can get it landed. The field I fly from has never seemed small until now.
My Twist has a very fine pitched prop (12x4 on a .46) which seems to help it slow down. The fat, symetrical wing helps too. I need to figure out what to do with my Cub.
I have a 12x6 prop on it now and I just bought a 13x5 to try.
I can also program in flaperons or air brakes, and I'm getting some conflicting advice on which to use.
I was told to use flaperons and that would allow the plane to slow down enough to land a bit better but keep it from falling out of the sky. I'm not sure that MORE lift it what I need, but I've never tried flaperons before so I can't comment from experience. I did have a veteran Cub flyer to tell me to stay away from using flaps, especially at low speeds, since the Cub it prone to tip stalls and the flaperons (and using them while already going slow) will make it work.
I can program in air brakes, where the ailerons go up, and that seems like it would be more effective. My Tx allows me to mix in a little up elevator at the same time the air brakes are deployed (the manual cautions to use just a little bit of up elevator, along the lines of 10%). Not sure exactly how far up to move the ailerons though, I imagine it's not much though.
I am going to try the 13x5 prop, and see just how low I can get the idle, but I forsee needing to do some more programming as well.
Why it posted twice, and before I even finished, I don't know...
Anyway, right now when I fly I take off, make about 2 laps around the pattern, then start working on my landings. I'd like to get the landings working a bit better so I can spend more time just flying it and less worrying about landing.
When flying my GP Fun One (symmetrical airfoil), if I flew it fast enough to retain control at low speeds, it was going too fast to land.
I got around this by programming the ailerons to both go upward, once I was close to the ground. You have to watch out during the trimming stages of setting up your model with sufficient "down" elevator, not "up" elevator.
When the model is flying with the ailerons deflected in the upward direction, the airbrake function, the center of lift changes on the wing and suddenly the nose will pitch upward. Without fast reflexes to input some down elevator, the model will slow and stall fairly quickly.
I know that logic tells you that you would need "up" elevator, but that doesn't take into account that the center of lift of the conjugate, newly created airfoil, is actually quite a distance away from the point it occupies without the airbrake function engaged. I hope that makes sense.
I don't think that the flat bottomed airfoil will reverse the action that occurs with the fully symmetrical airfoil, but I can't be sure. So beware.
The thing to do is to try the airbrakes with sufficient altitude to make a couple of mistakes. Memorizing the location of that airbrake switch is mandatory BEFORE you rely on instinct to disengage it. My model nearly did a complete outside loop at high speed the first time I engaged airbrakes. At speed, and the model was moving along briskly, the effect of the airbrakes was completely opposite of what it was when the model was slowed down near landing speed. Talk about pucker factor. I was happy that I happened to be high enough to recover without incident.
After getting things set up nicely, I could fly the model down to the ground at a fair clip, not really fast, level the plane and pop the airbrakes and it would settle right down, glued to the ground.
The best thing to do would be to split the ailerons in two about half way out, double their chord and use two servos in each wing. Then program in "crow". Crow is very unbiased about positive or negative AOI. No "tucking" under the way that airbrakes can do if you deploy the airbrakes too soon. Have fun.
Popping the ailerons up will kill the glide AND introduce washout, which is a far safer way to land slowly.
However the secret with a low wing loading plane is to learn to fly it slowly at low altitude.Practice circuits under low power at progressively lower altitude till you can fly it 3 foot off the deck all day..
Another way to slow the plane and increase the descent speed is to put it in a sideslip. Essentially, ailerons one direction and rudder the opposite.This will put the plane pointing one direction while actually flying in a direction slightly off the thrust line(crabbing sideways). Neutralize the controls and straighten it out just before landing. Practice at altitude first, learning this on final could get painful. This is also a useful technique used by full scale pilots(and RC pilots better than me) for landing in a crosswind. I'd like to say I've mastered it, but I'd be lying.
Start slowing the plane down sooner and start your approach from a lower altitude. Loss of altitude generally means increased speed unless you are slipping the plane, which is difficult to do. The majority of fliers land their planes a lot faster than they need to be flown. Experiment (up high) with how slow you can fly it with no problems. You will probably be surprised at how slow they will fly and remain stable.
John VB
the end and set it down. The Cub, with it's big flat bottomed
As that Philosopher fellow said, get to know your stall speed - at a couple of mistakes altitude, practice winding back the throttle until you start to stall, and get to know what that speed is. Then you can adjust (flatten) the slope of your approach so you don't gain too much speed as you descend.
The other thing to keep in mind is that if you're landing on grass, as soon as the wheels touch and the power is off, the aircraft will slow down very quickly, that means, again, assuming you're on grass, you can try an approach where the airspeed/groundspeed is not the critical factor, rather, the rate of descent is. You go for a flatter approach and aim to "grease" the plane onto the start of the strip, get the power off and get ready on the rudder - and the throttle if you need a bit of a puff to turn the plane on the ground.
On Fri, 06 Jul 2007 05:18:53 -0700, JJVB wrote in :
At the other end of the spectrum is the "wheel landing."
Instead of aiming for a flare, stall, three-point, stick-to-the ground landing, you come in hot and plant the mains on the ground with a little down elevator at just the right time.
It's really beautiful to see when it's done right.
Don't ask me for a demo. Sometimes I do it right, sometimes I don't. :o(
On Fri, 6 Jul 2007 22:44:39 +1000, "Poxy" wrote in :
Throttle management is also good for getting the flat rate of descent.
_Stick_and_Rudder_ says that elevator controls attitude (how the nose is pitched) while throttle controls altitude (no power, the plane is coming down; full power, the plane can go up, depending on where the nose is pointed).
So, on final, get the right landing attitude with a little up elevator held in. The slow the rate of descent with a click or two of power at the right time.
Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:
The suggestions made above are all good.
1st, Flaperons can cause a tip stall, especially if they are full length because the wing is stalling along it's full length.
2nd, I suggest following the lead of the full size Piper Cubs - Split your ailerons in half and set the inner half up as regular flaps. Do some practice at a safe altitude so you will see when to add in down elevator (or couple it in with the flaps ). The use of regular flaps allows the plane to fly substantially slower than usual because the flaps provide the lift and the wing tips don't stall.
A couple of other things you can do: If you are using an APC prop switch to a Master Airscrew prop (the black, square tip one ). They are less efficient and will slow the plane down more. Also drop down to a
12x5 in the MAS. The 2 together will slow you down. My Rascal 40 with an 11x6 APC floated down the runway at 18" from the ground (we have a
600' grass runway ). The only way I could get it to land was to kill the engine. I changed over to a MAS 11x5 and I now have no problems landing. Yes, did loose a little top end speed, but the Rascal 40 is not a hot rod, the same with your Piper Cub. I don't think you will even notice the top end speed loss.
Yes, seems a bit counterintuitive, but I'll get up high and give it a shot.
The ailerons are only out at the ends of the wing, they don't come very far inboard. And I have demonstrated my complete inability to build anything that flys even remotely straigth so mods of that degree are out of the question for me.
Ahh, but the trees....
This is what I'm doing now, whether I'm good at it yet or not, but I'd prefer to have another option.
Try "with it's high aspect ratio ..." -- a 12% symmetrical wing would probably give you the same behavior.
High lift at low speeds generates induced drag, so increasing the lift coefficient of the wing helps you fly at a lower lift/drag ratio, which helps you slow down. Thus, flaps help. Many (if not all) aircraft with flaps have a 'landing' position where the deflection is extreme enough that the wing stalls at the flap. This generates even _more_ drag. I know of at least two light aircraft from the '30s (the Cessna C-38 and the Aeronca low wing) that dispense with flaps altogether, and just give you a drag brake between the main gear.
At any rate, real cubs don't have flaps, or drag brakes. The recommended full-scale technique for this is to crab -- give it some rudder (or lots of rudder) and correct for the roll you induce with cross-coupled aileron. You'll present the side of the fuselage to the airflow, which will give you drag. Hence, you can descend at a steeper angle while you keep your airspeed down. When you're close to the runway, you straighten out and land normally.
My home field has a long runway, so I haven't done this much. In fact, I can only do it right on a flight simulator, set to chase aircraft. But I'm sure you'll do fine :-).
While I'm on the subject of full-scale landing techniques -- are you coming in for a 3-point? The full scale cub was designed so that in the
3-point attitude the wing is just short of a stall, which is the highest drag configuration you could do without falling out of the sky. The landing procedure was to glide down to the runway, then keep the wheels a (full scale) foot or two off the ground while pulling back on the elevator. You'd either stall or mush into the ground, gently because you only have a foot to fall.
This is a good technique for a high-wing tail dragger, particularly one with poor ground handling, because you hit the ground at the minimum flying speed, and immediately have weight on the wheels.
On Fri, 06 Jul 2007 11:29:01 -0700, Steve wrote in :
OK.
You've got a "scale" Cub. Ailerons out at the ends are the way the original Cubs were built.
So try learning how to slip the Cub in. This involves crossed controls and some courage.
Bank the plane one way, then use opposite rudder to hold the flight path down the center of the runway. The extra drag from the side of the fuselage acts as an air brake. You are using "crossed controls" in this situation, and I like to stay away from any up-elevator input for fear of entering a snap.
If you have separate servos on separate channels, and if you have a computer radio, you can experiment with flaperons (dragging both ailerons down to act like flaps) or spoilerons (raising both to reduce lift).
In either case, you'll almost certainly have to mix some elevator by hand or in the computer. You'll learn what your plane does with flaps or spoilers by going up high, slowing down, throwing the switch, and then observing the results. Throw the switch back, recover, land, and mix in up or down elevator as needed. Repeat until you've got the plane set up so that it stays neutral when you throw the flap switch.
Nothing like a yellow Cub in the late sunshine slipping down over the trees at the end of the runway!
On Fri, 06 Jul 2007 11:41:07 -0700, Tim Wescott wrote in :
With Cubs, it often then leads to a ground loop because the rudder loses authority as airspeed drops and because the landing gear is so narrow.
Not a big deal with our models if they aren't too heavy and if the gear is adequate. My buddy and I never really conquered his GP Cub. It was designed for a .60 and has a 7 or 8 foot wingspan. Built to specs, it would probably not be a problem. He heavied it up with Ultracote and an OS Gemini (1.70 displacement?).
We took turns bending and unbending his gear for two summers. Then his wife commanded that he stop flying it because she sensed that we were going to break it completely before we learned to tame it.
Steve wrote in news:1183706729.755582.84050 @q75g2000hsh.googlegroups.com:
I had very similar problems on my Ol' Reliable. It was a big, light old- timer and I often had to simply go deadstick to get it to come down. At a basic level, even when it was just idling, the engine had enough thrust to keep the plane in the air.
I, too, went to a flatter prop, and it helped. Another thing, if you haven't already done this - can you push the idle any lower?
Now that everyone else has expressed their learned opinions, it is my turn.
There are two separate issues you are dealing with and your last comment above points to the most important. Learning how to land a model is something that is very difficult for most to learn because there are so very many variables in operation all at the same time. The following is the approach I teach with and most of my students have gone on to be in the hobby for a good long time. A couple even flew their trainers for a decade or longer, albeit significantly modified.
The very first thing you need to do is to get the aircraft set up right. That means the 'right' control throws for your capability and the airframe. Cubs really don't roll much like P-51's so that might be an issue. The following excerpt from an older post about how to set up your airplane and test it. Afterwards I will opine on landings for you.
These are the guidelines I start with. Some aircraft require different final setups, but in general this works.
First flight is strictly a trim and test flight. Before first flight, make sure your engine will idle for 5 minutes and not fail when the throttle is hammered to full suddenly. That must be fixed before you try some of these tests as it is critical that you have power available when needed. You also need to make sure the plane is correctly balanced with the fuel tank empty. I suggest very slightly nose down for trainers because beginners need stable airframes and level (while upside down) for most low wing birds. Do not first fly a plane that is tail heavy as you may not fly it twice.
The first thing to be done in the first flight is to get the plane trimmed out hands free. The second thing to do is to get 3 mistakes height at full throttle and hammer the elevator. If the plane will not do a smooth loop with no 'stepping' or snapping out of the loop, you have too much elevator throw and need to land at higher speeds than you are used to. Do so immediately and reduce the throw and then repeat the fist flight.
If the loop is smooth the next step is to test the wing and stall recovery so you know what it looks like and how the airframe responds. Get three mistakes high and begin reducing the throttle. For newer pilots the goal is to get the elevator stick hard on the bottom of the quadrant and the airplane stepping through stall. The thing you need to watch for is the reputed 'tip stall' which occurs when the root stalls after the tip of the wing. This is common with heavy wing loaded birds and those with sharp leading edges. There are some substeps here for specialty aircraft and I will mention them at the end of this.
The next step is to try some turns at that low speed while still three mistakes high. What you are looking for is how gentle you have to turn to keep the plane from snapping out on you. Some are incapable of any turn at full elevator and others will allow significant banks. The first turns (left and right) will be done with aileron only in both directions. Once you have completed these first turns, climb back to the initial altitude and continue with the test. The second turns will be done with rudder only, again in both directions. What you will probably find that many low winged birds will gently turn on rudder only when at slow speed. That is an important piece of information you need to have in the event of a servo problem (BTDT!). The last set of turns while at altitude is to restore your confidence in the rules of aerodynamics. Get slow again, and do coordinated (aileron AND rudder) turns in both directions.
Now you know what the plane is capable of and what it looks like when it is executing what you want it to do. Changing it to be more reactive for aerobatics is easy when you have a known start point. Once the elevator is set for a new pilot and you are comfortable with the airframe at lower speed, you can increase the throw and add exponential. This gives you the wild throws many 3D folks want, but leaves the center of the control stick movement what many use to make landing approaches. All you have to do is to remember (learn?) not to hammer the elevator.
Landings are difficult unless you are prepared for them. That preparation is mental and physical. If you don't stand still when flying, these pointers may not work for you.
Get your plane three mistakes high again and reduce the throttle to one quarter stick. Keep the plane straight and level with the elevator and rudder. Fly a normal rectangular pattern, upwind over the runway, cross wind on the downwind end of the circuit, down wind about 400 feet out ( I will teach you a trick about how to do that pretty accurately ) and base leg on the upwind end of your flying field with the turn to final/upwind leg in position to land. Practice that a few times at quarter throttle and three mistakes high. We will return to this part of the discussion in a moment, but first lets work on that 400 foot out downwind. It is easier than you think and my "tricks" should provide you a way to improve your skills.
Before flying, get clearance from all at the field and step out to the very middle of the runway. Stand on the centerline with your shoulders parallel to it. Lift your arm up with your hand held in a blade fashion. Hold your arm level to the ground, looking over your fingers observe what you are pointing at on the horizon. Do the same for both sides. Then withdraw to the pilot station and stand exactly parallel to that centerline again. Do the same trick with your arms and hands and put your nose pointing at your fingers, but THEN move the arms and nose so you can see the same sight you saw earlier. The important thing here is to note the change in angle of your head to your torso. You just defined where you should be during takeoff and approach. That is about one half of location control.
Back at the flight station, turn your head so that it is about forty five degrees off your shoulder and note what you see on the horizon, on both sides. Those landmarks define the lines about which you should turn to and from downwind leg. Practice the head movement so you are not looking for some tree or object when you should be watching your airplane.
Until you feel more on take off you should maintain a flat climb until you see daylight between the bottom of your fuselage and the horizon. The flat climb should look like the back of your hand when held level at arms length and tilted up just enough that you can see all of your knuckles. When you see the daylight, it is time to turn and you should turn around ninety degrees into the crosswind portion of the flight. Maintain a gentle climb until you like the height of the airplane or until your nose is forty five degrees off your shoulder. When you reach that point, it is time to turn downwind. In general as long as you follow the take off instructions and the first turn pointers, you will now be about 400 feet from the runway flying parallel to it on the downwind leg of the pattern. When your nose gets to about forty five degrees off the other shoulder, it is time to turn on to the base leg of the pattern. Once established on that leg, as your nose approaches the same angle it was at when you relocated your horizon marker, begin your turn to final/upwind leg.
That describes the pattern you want to do all of your practicing in all of the time until you are comfortable with the aircraft and its capabilities in your hands.
Now back to our slow flight work. Part of the problem many have is knowing what they and the aircraft are capable of and part of the problem is recognizing different flight characteristics as they are encountered. This is a method you can and should use to get that knowledge. We left off at three mistakes high and a one quarter throttle. The next time you turn upwind, reduce the throttle two clicks but maintain aircraft altitude. Fly the pattern. The next time you turn upwind, reduce the throttle one click and fly the pattern without loosing altitude. As the aircraft gets slower you will see that turns are really difficult to do without loosing altitude. Flatten them out and they get a little easier. Keep flying the pattern reducing the throttle one click each time you turn upwind until the plane cannot maintain altitude in straight and level flight. At that time put five clicks of throttle back in and climb back up to three mistakes high. When you get there, reduce the throttle three clicks and begin the next practice session.
In this practice session we will be flying a plane extremely slowly and turning in both directions while maintaining altitude. I have my students fly a horizontal figure eight at this speed with the crossover point when the aircraft is coming at them. This also helps learn left and right with the plane going towards and away from the pilot. Once you are comfortable with that, it is time to try some landings.
Set yourself up on downwind with near idle power, or what you just determined is two or three clicks above stall. Keep the throttle there until you are on base leg. When on base leg, pull the power and nurse your altitude carefully. Remember we just practiced turns at low power? Well, now you get to see how much altitude you loose in the turn up close and personal. Always remember that if it scares you throttle up and pretend it is a takeoff and go around to try again.
Assuming everything is as we want it, you should roll out of the turn to final in a descent and the engine at idle. Allow the plane to come down until it is waist high without trying to manage it with the elevator. We want the plane to come down at its normally trimmed flying speed and will slow it down with elevator when we need to. When it reaches waist high begin pulling back slightly on the elevator. The trick here is that we want the fuselage level and decelerating at knee height. As it slows down the plane will begin to sink and you should put in a little more elevator to arrest the sink. Continue this until the plane touches down. When that happens, just hold the elevator until the plane comes to a stop. If you have too much speed the tail will never come down and if you hammer the elevator you will balloon terribly.
This should work just as well for the Cub as it does for the P-51 because it is not targeted to any specific airframe but to the pilots knowledge and skills in any airframe and at any airfield. The turn points I mentioned can be moved to accommodate over fly restrictions (I used to teach with some significant ones) and the power off point can be changed to meet wind conditions, or power issues, or airframe issues.
I wonder, with some taildraggers, if a rudder gyro wouldn't be a bad thing just to get you through landings. The full scale pilots certainly talk about having to exercise their rudder skills when landing a tail-dragger; it can be hard to react quickly enough when your inner ear isn't helping with the steering task.
On Sat, 07 Jul 2007 02:28:35 -0500, Tim Wescott wrote in :
I'm sure a rudder gyro would help tremendously.
Haven't heard of one on a Cub, but probably someone somewhere has experimented with it.
I loved playing with the overweight Cub, even though it defeated us. If I didn't actually become a better pilot, at least I saw some of the stuff that I hadn't yet mastered. Marty
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