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bad landing plane HELP

Old 05-15-2005, 09:54 PM
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jship
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Default bad landing plane HELP

I have a Sig 4*40, that is balanced. It takes off good but when you try and land it wants to hop around on the ground. It is not solid on the ground when landing. Regardless of how you flair when tires touch the ground it wants to hop like a rabbit untill all the speed is used up. Been flying for five years, flow all sorts of planes. This one does not land rignt. Have been working with it for over two years off and on. PLEASE HELP.
Old 05-15-2005, 11:12 PM
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gnirwin
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Default RE: bad landing plane HELP

I currently fly a 4 Star 60 and I have owned a 4 star 40 . They can land a little bit floaty wanting to hop if you come in at too high of an angle where you aren't burning off enough air speed. These planes are real floaters and have a long glide. I try to land mine in a pattern where I fly a box reducing airspeed and elevation where the last leg I'm low and coming in at maybe a 10 to 15 degree angle and jest drop her down. I notice too if I have the idle set to high they want to float, make sure your idle is set low. You may also want to check your gear, they may be too springy as well.
Old 05-15-2005, 11:24 PM
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gene2586
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Default RE: bad landing plane HELP

Why don'tyou try to use a larger and softer set of tires! the slight extra weight foreward
cant hurt and the lowest idle you can get. Also a couple of mph slower landing speed
by using a 1 inch lower pitch prop. too.
Old 05-16-2005, 04:24 AM
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GRANT ED
 
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Default RE: bad landing plane HELP

Hard question to answer without seeing the plane. Make sure your landing gear is not to springy.
I had a plane that did a similar thing. In desperation I lengthned the tail wheel to raise the tail. That was it will lower the angle of attack on the wings and hence lift when sitting on the ground. Don't go to far as it will increase your takeoff run. Might be worth a try.
Old 05-16-2005, 07:49 AM
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DadsToysBG
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Default RE: bad landing plane HELP

Do a wheel landing. don't flair at the end. This will solve your problem. Dennis
Old 05-16-2005, 10:26 AM
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Deadeye
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Default RE: bad landing plane HELP

I have found the best way to land the 4* series is to stall it. Fly with the wheels just a inch or two off the ground, feed in up elevator as you bleed off speed, until you are nearly out of elevator. She should gently touch the ground, and roll to a stop.
Old 05-16-2005, 12:50 PM
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jship
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Default RE: bad landing plane HELP

Cant wait to try all your help. The tires on the front are 1" larger than came with it and I have put a tail wheel on. It came with out a tail wheel. 4*40 in sad shape!
Old 05-16-2005, 02:11 PM
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Charlie P.
 
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Default RE: bad landing plane HELP

I had a G.P. Big Stik with an OS-70 which I had converted to tail dragger using the existing main gear and it was very springy. I ended up adding "flying wires" by drilling a hole on each leg about 1-1/2" below the fuselage and another above the axle stud on each side and sticking a wire fishing leader between cotter-pins placed in the holes, so that they crossed below the fuselage. Worked like a charm, and on low & slow fly-bys it gave the plane a unique whistle.

Distance of hole from fuselage is determined by trial fitting the leader wire, and farther down will produce a stiffer gear response. Use 20lb test or lighter, and you can rerig on hard landings . . . if you have such things.

Bleeding off speed and landing flat also works well.
Old 05-16-2005, 07:54 PM
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WMB
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Default RE: bad landing plane HELP

I agree with Deadeye on this. If it is not at fling speed it won't come back up. I flew my 4*40 a little noseheavy for years. When I played with the CG and got it back, it became much easier to land.
Have fun, Mike
Old 05-16-2005, 08:26 PM
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JohnBuckner
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Default RE: bad landing plane HELP

Any conventional geared aircraft (taildragger) that exhibits excessive porpoise after first runway contact (skipping) can be improved to a marked degree by moving the main gear aft towards the CG a bit. This of course is limited by the need to avoid noseover, i.e. an airplane with the gear too far back will tend to nose over excessively and an airplane with the gear too far forward will bounce and porpoise excessively. Moving the gear aft will also improve directional stabilty anytime the main gear is touching the ground.

There is an old axiom and recommendation with modelers that the gear should be even with the leading edge of the wing. This is just that, a recommendation. There are many varibles including the wings aspect ratio that has it effect on that recommendation and can make this a not very appropriate position for the gear for some aircraft.

John

Old 05-17-2005, 10:52 AM
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jship
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Default RE: bad landing plane HELP

When I first got this plane it would nose over real bad. Put on larger tires and this seem to help.
thanks john
Old 05-18-2005, 01:59 AM
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Default RE: bad landing plane HELP

I have a 4 * 40 and the plane does really want to float on the landings. Here are the things I've done. First, I went to a larger tailwheel. This helped ground handling a lot. When landing, I do as Deadeye describes, bleed off the air just inches above the runway, adding more up elevator. When it finally settles onto the runway, I let the elevator control go to neutral. This prevents it from wanting to jump back into the air. Once the plane slows down on the roll out, I add more up elevator again. This will put more positive pressure on the tailwheel for better ground control.
I've not been able to successfully do a 'wheel landing' with this plane. It'll bounce back into the air every time.
The last thing I did was to remove one bay from each wing. Even with the wingspan 4+ inches shorter, it still floats on the landings and stalls straight and gentle.

Scott
Old 05-18-2005, 11:38 AM
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Rodney
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Default RE: bad landing plane HELP

Take John's advice, check the fore/aft position of the main gear. It should have the axle directly under the leading edge of the wing when in landing attitude. To far forward and it will hop like a bunny, to far aft and taxi problems with noseovers are the result. If you have to hedge, use the more aft position and hold lots of up elevator while taxiing slowly releasing it as you gain speed on take off.
Old 05-18-2005, 12:26 PM
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Default RE: bad landing plane HELP

4-Stars come with the thinnest, springest landing gear. Try a stiffer one.

Cut off 1 rib on each side. The plane will roll better and land better.

Use 2 aileron servos and set in spoilers mixed to throttle.

Stock, it's like a low wing trainer. To get a good landing, you need to try to touch the tail wheel first.
Old 05-18-2005, 08:38 PM
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laker500
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Default RE: bad landing plane HELP

When I was taking lessons to fly full scale aircraft landing was taught to me just as described above. You need to fly just a very little bit above your runway until you bleed off enough airspeed that the planes starts to stall and gently settles down. I ran out of money and wasn't able to continue flying but I soloed at only 11 hours and landings were my specialty. I always heard the stall horn just as the wheels touched down. If you are "pushing" the plane down at to high of an airspeed it will balloon back up into the air when you release down elevator. I have tried this with all of my RC planes and it makes for near perfect landings every time. The 4* I flew last year used up lots of runway if you came in to hot. It flys so well at a really low airspeed. Once you practice it and get used to how each plane flys they are pretty easy to do.
Old 07-05-2005, 10:00 AM
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Default RE: bad landing plane HELP

This plane will slow to a crawl. Do that and it won't have enough energy left to bounce.
Old 07-06-2005, 02:08 PM
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Dave Wilson
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Default RE: bad landing plane HELP

I have had similar experience to DadsToysBG, ie. do a wheel landing, don't flair. Mine stays down good when I do that.

I have also modified the gear to make it more flexible (after ripping it off on a hard landing). I made the holes in the gear slightly larger and put a small piece of flexible tubing in each. Then put the mounting bolts through the tubing, and add a couple of rubber washers between the gear and the fuselage. This gives the gear enough front-to-back and side-to-side flex to allow for less than ideal landings without damage.

Dave
Old 07-07-2005, 06:23 AM
  #18  
Roby
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Default RE: bad landing plane HELP

I've had the 4*40, 60, and I am now currently flying the 120.
All pretty much land the same ,and the reasons for that is that
the gear is springy and too far forward, light wing loading combined
with ground effect from the low wing. If the wheels were only a 1/2
inch in front of the cg , most of the landing problems would go away.

The only advice I can offer is to do a wheels landing and get OFF the elevator
as soon as the mains touch. It will take some practice but it works. The "stall"
method works well too but you can get into some bad habits over time.


Regards
Roby
Old 07-09-2005, 07:07 PM
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Default RE: bad landing plane HELP

A few weeks ago I helped out another guy at the field who was having the same problem. To balance the plane he had a lot, maybe 5 oz's weight in the nose, and that forced him to land faster than necessary, and that caused a lot of bounce. He should have moved the servos forward and saved the weight for slower landings. He also had the elevator set up way too sensitive, when he used dual rate to reduce elevator sensitivity, he was able to grease every landing. He did not realize he was chasing the nose up and down (pilot induced oscillation) with overly sensitive elevator. Just because the CG is set where the plans say does not mean it is right for your specific plane. Slightly off engine thrust, wing or horizontal stabilizer incidence can make the plane need elevator trim to fly level. If this is the case, as you land you are once again chasing the plane up and down with the elevator because the elevator trim needed at speed may be different for landing. Check your slow speed trim and make adjustments as necessary. Once you get the plane trimmed out, land it and look to see where the elevator is. For example, if elevator is pointing up, something is making the plane want to fly nose down, maybe too much engine down thrust or too much horizontal stabilizer positive incidence, or CG too far back. Including all the suggestions in previous messages, you have got a lot of things to check.
Old 07-11-2005, 11:22 AM
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decombs21
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Default RE: bad landing plane HELP

I don't mean to ripoff this jship's post here but for the benefit of us rookies, DadsToysBG and Dave Wilson have recommended a "wheels landing." What is it and how do you do it?

Dave
Old 07-11-2005, 07:19 PM
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Default RE: bad landing plane HELP

A wheels landing refers to touching down on the main wheels (under the wing's leading edge) first. As the plane slows down it must then rotate to either the front nose wheel or rear tail wheel, depending on which one it has. If the nose rotates down, toward the nose wheel, the angle of attack - the angle the wing's leading edge is pointed upward relative to the wind - is reduced and therefore the lift is reduced and the plane stays on the ground. Which is what you want while landing.

However, if the plane has a tail wheel, as the tail drops, the main wing angle of attack increases, increasing lift and the plane raises back into the air if it is going too fast. Which is dangerous because suddenly you are too high and too slow and a hard bounce or crash is pending if you don't get back on the throttle to fly out and try again. Many planes have been totaled when the wing stalls and the plane spins in from just a few feet above the ground. I see this happen just about every week. If you give it down elevator you must quickly reverse to up elevator to prevent another hard impact - pilot induced oscillation occurs as you chase the plane up and down.

If the plane bounces up while you are learning to land, giving it throttle and going around is the safest thing to do. Do not try to chase it up and down with elevator! For tail draggers the best way to avoid this is to land on the main gear and hold the tail up so the main wing stays level as it slows down, eventually the tail will drop by itself. Generally, if the tail can't hold up the rear end of the plane, the main wing can't hold the plane up in the air either, and the plane stays on the ground. This is why I mentioned landing trim is important because if you have the elevator out of trim or CG too far back, it becomes very difficult to make a smooth landing.

If you watch an experienced flier take off a tail wheel plane, you will notice the tail comes up and the plane rolls on the main wheels for a short period of time. A wheels landing is reversed. This is why trainers have nose wheels and the kit manufactures sell so many tail wheel planes.
Old 07-12-2005, 08:09 AM
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Paternguy
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Default RE: bad landing plane HELP

Try moving the CG back an 1/8 to a 1/4 inch.

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