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Taildragger Landing Technique

Old 02-01-2010, 12:10 PM
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ScienceisCool
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Default Taildragger Landing Technique

So I was out flying the new 4*40 this weekend and have a question related to a hard landing. It was cold (39) and no wind. Was flying around fine and came in to land. Over the end of the runway and about 5 or 6 feet up cut the throttle to idle it in. It floated a minute and then nose-dived. I was able to bring the nose up so most of the impact was on the mains but also hit the prop.

I'm thinking this was due to either not enough speed or when I cut the throttle to idle I lost airflow from the propwash over the elevator or a combinate of both. The plane is a bit nose-heavy anyway.

Thanks!
John
Old 02-01-2010, 12:19 PM
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Default RE: Taildragger Landing Technique

Nose heavy will do it..You need more airspeed with a nose heavy airplane. If you try to hold the nose up it will stall. You can keep the throttle higher or come in at a steeper angle. But most of all - make sure the plane is balanced.-BW
Old 02-01-2010, 12:26 PM
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GaryHarris
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Default RE: Taildragger Landing Technique

Hummm. John I cut my throttle before I make the upwind turn. You must be nose heavy. Sometimes theres some wierd up and down drafts at Scoobe. My buddy crashed my big stick right before the run way not too long ago. It just nosed down.

BTW, I wasnt going in that cold yesterday. Brrr!
Old 02-01-2010, 12:27 PM
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Default RE: Taildragger Landing Technique


ORIGINAL: ScienceisCool

So I was out flying the new 4*40 this weekend and have a question related to a hard landing. It was cold (39) and no wind. Was flying around fine and came in to land. Over the end of the runway and about 5 or 6 feet up cut the throttle to idle it in. It floated a minute and then nose-dived. I was able to bring the nose up so most of the impact was on the mains but also hit the prop.

I'm thinking this was due to either not enough speed or when I cut the throttle to idle I lost airflow from the propwash over the elevator or a combinate of both. The plane is a bit nose-heavy anyway.

Thanks!
John
If the plane is nose heavy then the forward stall is going to occure at a faster flying speed than if you had the CG set more to specifications. If your used to landing with a head wind and now suddenly had calm air then you will need to carry more forward momentum into the landing aproach as well as that head wind is essentailly added to your plane's airspeed.

Practice flying that plane to the ground. Get as slow as you are comfortable but still at flying speed with power slightly above idle and shoot touch and goes. be sure you do full T&G's (you know, roll out 10-15 ft on the mains, don't bother slowing to let the tail drop) and not just bounce and goes When you are comfotable doing this (landing at flying speed) you will find the suprise hard landings don't happen.
Old 02-01-2010, 12:31 PM
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Default RE: Taildragger Landing Technique

A 4-Star stalled???? I could never get mine to stop flying. It does sound like you might have a CG issue. It should balance perfectly when holding it upside down with your fingers on the spar.
Old 02-01-2010, 12:38 PM
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GaryHarris
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Default RE: Taildragger Landing Technique


ORIGINAL: ChuckW

A 4-Star stalled???? I could never get mine to stop flying. It does sound like you might have a CG issue. It should balance perfectly when holding it upside down with your fingers on the spar.

Same here! If theres no head wind, I have to use the elevator to bring mine down. Itll float forever with the Magnum 52 RFS and an 11x7
Old 02-01-2010, 01:45 PM
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Default RE: Taildragger Landing Technique

I don't use a different technique for landing tail dragger vs nose wheeled planes. As others have suggested, it sounds like you have a balance issue and the plane stalled.
Old 02-01-2010, 03:32 PM
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Default RE: Taildragger Landing Technique

I'm going to provide a link for a bit of self help trimming info from Dean Pappas. www.flyama.org/mag/FTGU/titlespageftgu.htm Check out parts 29 thru 31.

Then maybe your overall "landing" plan can be refined. See www.rcuniverse.com/university/showtopic.cfm

HTH
Old 02-01-2010, 03:40 PM
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Default RE: Taildragger Landing Technique

Thanks for the responses. I think the nose-heavy issue is what's going on here and related to this stall, the plane has a very hard time steering on the ground. I'm guessing not enough weight on the tailwheel.

What are some options for adding weight to the back? I can't move the battery or rx.

Thanks!

Gary - yeah, it was pretty cold out there but with no wind it wasn't too bad for a while. I didn't get out there until after 1.
Old 02-01-2010, 03:56 PM
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Default RE: Taildragger Landing Technique

Can we get some details on this plane. What engine, battery and receiver? Where did you locate the flight battery. The easy answer is to put on stick on weights available at most hobby shops but I hate adding weight to a plane. The 4 Star has the excess wing loading it realy wont make a difference though. If you want to do it the hard way you can relocate the rudder and elevator servos to the tail as seen in my picture here of my 4 Star 120. But unless you put a 60 size engine on the 4 Star 40 then you should not have to. I did put a TT .61 Pro on a GP Big Stick 40 and had to relocate servos on it as well also pictured below.
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Old 02-01-2010, 03:59 PM
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Default RE: Taildragger Landing Technique

The coldest I've ever been was 45 degrees in Houston - can't hide from the humidity.

Either lighten the front or weight the rear (using Homer Simpson's best "doh!") - just kiddin' ...

Was this a kit or ARF? What's the engine?

I usually take some kind of incremental weight (bearings, BB's, bullets, cat litter) that can be put in a zip lock and weighed. Then you can sling the bag on the bottom of the fuse when you check the balance CG. Figure out how much you need to move the CG. You are balancing the plane upside down, right?

Then guys have used a number of 1/4 oz lead weights epoxied to the side of the fuse under the stab. Cut a bit of film to expose the balsa & epoxy in place. I've been known to drill 1/16" holes thru the lead to allow the epoxy to squeeze thru and provide a bit better mechanical bite.

Other things include swapping a heavy hub on your engine with an an aluminum one.
Move the fuel tank to the back of the tank "bay".
Lighter wheels (foam) because that's in front of the CG.
Move the servos back (easier with a kit) - some mount an elev or rudd servo to the back just in front of the fin / stab. Requires a long extension.
Tie your neighbors pet mouse to the tail (just messin').

HTH

Just sign me - Angleton visitor in a couple of weeks ...
Old 02-01-2010, 04:06 PM
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ChuckW
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Default RE: Taildragger Landing Technique

If you need tail weight, it is pretty easy to remove the covering from one of the lightening holes toward the rear of the fuselage. This will allow you access to glue in something to strap your receiver battery to. You may have to use an extension on the battery wires depending on how far back you go. Once you have it all secure just put a covering patch over the hole and nobody will ever know.
Old 02-01-2010, 04:22 PM
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Default RE: Taildragger Landing Technique

Being a bit realistic - this being the beginner's forum the priority should be flight characteristics ahead of cosmetics. Truth be known, I am truly anal about how my planes look! Also, my 1st, 2nd, 3rd, 4th and 5th planes do not exist any more. That really pains me to say.

Like others told me - just get her flying well and then fly the heck out of her. As your flying skills improve you may decide that you need 1/2 oz on the left wing to get a good lateral balance - cut-n-epoxy another tab of lead. You tear off a LG - oops - recover. Oops, hanger damage. Somewhere along the line you will have an opportunity to move the battery and or servos back and get rid of the lead.

When ya quit learning, God takes your membership card away ...
Old 02-01-2010, 04:35 PM
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ScienceisCool
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Default RE: Taildragger Landing Technique

It was a kit and has a Magnum 52 4-stroke on the front. I have the servos towards the back of the fuse opening and the rx and battery towards the front. I'm thinking what I'm going to have to do is add a little weight to the back.
Old 02-01-2010, 04:54 PM
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Default RE: Taildragger Landing Technique

Just for comparison - the Mag 52 FS weighs 15.5 oz and an OS 46 LA weighs 12.0 oz. Little things like this might give you a hint that there might be some balancing issues when you build it by the book.

Really hope that this is not your only kit. I'm on my 7th or 9th or something. I keep running into things that affect the balance - like really heavy stock used for the stab & fin. Didn't think much about it until I had to add a bunch of weight to the nose. I've rebuilt it and the added weight is history. If I only knew then what I know now ...

Em, how about adding a pilot? A chubby pilot.
Old 02-01-2010, 05:20 PM
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Default RE: Taildragger Landing Technique


ORIGINAL: ScienceisCool
I think the nose-heavy issue is what's going on here and related to this stall, the plane has a very hard time steering on the ground.
CanI just correct some misapprehension concerning the use of "Stall".
A forward CG does not cause the aircraft to stall at a higher airspeed. A heavier airframe does, in level flight.
When an airfoil (or aerofoil asI prefer) stalls. this is due to an abrupt separation of the airflow from the surface of the wing. The air no longer conforms to the shape of the airfoil and, typically, becomes turbulent. Because the air is not now deflected downwards, lift is lost and the netremaining lift usually moves its point of effect further aft, causing a downwards pitch. Out of compressibility, the stall depends only on the angle of attack to the airflow. If the aircraft is heavier, then all positive G regimes of flight will need a higher angle of attack than a lighter airframe, meaning the airfoil is closer to the stall.
If the aircraft is nose heavy (has a forward CG) then the elevator will be commanding "UP" for most of the flight, aided somwhat by the propwash. If the airframe has an odd response to throttle, ie it pitches down when throttle is applied, what could happen if you close the throttle on approach is that reduction of power causes a pitch up, followed by loss of airspeed and loss of authority of the elevator that is no longer able to keep the nose up at the reduced speed. The nose drops and speed builds again. At altitude. the speed would build until the nose could be raised again.
This type of swooping is called a phugoid and quite often you will see indoor models do this kind of thing. You were unfortunate that the ground appeared in the middle of your swoop.
My suggestion would be to use the throttle to control the rate of descent on the crosswind leg and on final and use the elevator trim to take the strain off your thumb. Just use the throttle lever a click at a time to bring the model in a constant line of descent to the threshold and just before the end of the runway, at knee height or less, smoothly reduce the throttle while trying, with elevator, to level the model into the 3 point attitude. If you get both things smoothly synchronised, you should plop it down under full control.
Old 02-01-2010, 05:46 PM
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Default RE: Taildragger Landing Technique

psuguru-

That up elvator also causes more drag wich slows the plane down faster causing a stall. Without the extra airspeed or throttle it will seem to happen fast. Right when you don't need it to...4 feet off the ground at low throttle.-BW
Old 02-01-2010, 06:47 PM
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Default RE: Taildragger Landing Technique


ORIGINAL: ScienceisCool

It was a kit and has a Magnum 52 4-stroke on the front. I have the servos towards the back of the fuse opening and the rx and battery towards the front. I'm thinking what I'm going to have to do is add a little weight to the back.

Can you place the RX pack behind the servos? I was able to fit mine back there and all I had to do was move the reciever to balance it without adding weight. I think I posted a pic on your build thread.

Also, I didn't have to add any weight to balance it latterly. <sp> I guess the weight of the Magnums muffler was equal to the weight of the throttle cable etc.
Old 02-01-2010, 08:10 PM
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Default RE: Taildragger Landing Technique

I have a 4 star 40 with a magum pro 45 on it... and i have no problem getting it to land... I cut the Throttle before the upwind turn and it still wants to just glide... I have to bring it down with the elevater.... this is my first low wing plane and the lost my high wing trainer on its second time at the field......after the first flight of having this four star in the air I was doing touch and goes in no time ........
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Old 02-01-2010, 08:12 PM
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Default RE: Taildragger Landing Technique

Also remember that when taxiing a tail dragger, hold full "up" elevator. This applies downward force on the tail wheel giving it traction. I just hold full "up" all of the time on the ground until my takeoff roll, then I slowly reduce elevator as needed through the roll out.
With the WW1 aircraft, we have to add "down" elevator with a blip of throttle to get them to turn. I just love the little quirks of the tailwheel. I do not even fly trikes anymore.
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Old 02-02-2010, 01:56 AM
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Default RE: Taildragger Landing Technique

psuguru said it best. The wing always stalls at the same angle of attack. The only thing that will change the airspeed you reach said angle of attack is wingloading. Wingloading is determined by the weight of the aircraft, and flight loads ie: high G manuevers, and the elevator pulling down on the tail to counter a nose heavy A/C. The key word in all of this is airspeed. Many beginers fly mistakenly in reference to ground speed. A decrease or lack of a headwind means you need a higher ground speed to maintain your airspeed. Your ground speed and track can change drasticly with wind and can cause a lot of dangerous (mostly for the plane) miss-conceptions about how the plane is performing. A great tool for learning to fly a model A/C is reading up on the physics of flight. Another great idea is to get it up high, slow it down and fly it on the verge of stall in all directions and see how it feels crosswind, into, and against the wind. Once you are comfortable with this you will find you can better feel if you are slowing down to much.
Old 02-02-2010, 04:54 AM
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Default RE: Taildragger Landing Technique

I got a suggestion and I am by no means an autority. I have never liked dead weight. If you can,make a bug a feature. Think of something you can put in it to add tail-weight and add some use-fullness at the same time. Maybe an on board glow with the batts for it at the back. I even put a sound system in one of mine for weight. Never liked putting any-thing in my planes that was "just there for the ride." Just my 2 cents. And one more thing I have noticed. Cold air has a lot less lift than warm air. Just ask my Twists' nose!
Old 02-02-2010, 07:48 AM
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Default RE: Taildragger Landing Technique

And one more thing I have noticed. Cold air has a lot less lift than warm air. Just ask my Twists' nose!
Not true! Cold air is denser than warm air (PV=nRT), and consequently provides MORE lift. However, it is still dependent on air speed. Denser air will increase the drag on the plane, causing it to lose airspeed sooner in the approach.

Cold air also makes our engines run better, as we get more air into the mix, which is why we have to richen the mixture in cold air.

Now back on topic. Yes working weight is better, but there are times when you have to add some small weights on the tail to balance the aircraft. I like to use the lead strip weights and just tape them on with packing tape until the plane performs the way I want to. Then its just a matter of moving equipment or adding weight to adjust it to that point.

Nominally what you're looking for is for the plane to adopt a very slight nose down angle when the throttle is reduced to idle and no elevator inputs. The nose down angle should be somewhere in the vicinity of the planes nominal glide angle (1 or 2 degrees down). Now on approach, just a little up elevator is all thats required to hold the plane level. With this setup, you can easily get the plane into a nose level attitude while it is sinking to the runway. As you practice, don't ever try to push the nose down to get the plane onto the runway. This just adds airspeed, and complicates the problem. Pull more up elevator to reduce speed, and the plane will sink down. Add throttle to increase altitude (actually bring the plane back onto glide path from below). Use small blips of the throttle and let it off so as not to add too much airspeed. Before long you'll be landing like a pro.

Brad
Old 02-02-2010, 09:33 AM
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Default RE: Taildragger Landing Technique

Thanks for all the responses, guys. I appreciate it. Looks like I've got a little work to do as well as some practice.
Old 02-02-2010, 01:10 PM
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Default RE: Taildragger Landing Technique


ORIGINAL: bkdavy

And one more thing I have noticed. Cold air has a lot less lift than warm air. Just ask my Twists' nose!
Not true! Cold air is denser than warm air (PV=nRT), and consequently provides MORE lift. However, it is still dependent on air speed. Denser air will increase the drag on the plane, causing it to lose airspeed sooner in the approach.

Cold air also makes our engines run better, as we get more air into the mix, which is why we have to richen the mixture in cold air.

Now back on topic. Yes working weight is better, but there are times when you have to add some small weights on the tail to balance the aircraft. I like to use the lead strip weights and just tape them on with packing tape until the plane performs the way I want to. Then its just a matter of moving equipment or adding weight to adjust it to that point.

Nominally what you're looking for is for the plane to adopt a very slight nose down angle when the throttle is reduced to idle and no elevator inputs. The nose down angle should be somewhere in the vicinity of the planes nominal glide angle (1 or 2 degrees down). Now on approach, just a little up elevator is all thats required to hold the plane level. With this setup, you can easily get the plane into a nose level attitude while it is sinking to the runway. As you practice, don't ever try to push the nose down to get the plane onto the runway. This just adds airspeed, and complicates the problem. Pull more up elevator to reduce speed, and the plane will sink down. Add throttle to increase altitude (actually bring the plane back onto glide path from below). Use small blips of the throttle and let it off so as not to add too much airspeed. Before long you'll be landing like a pro.

Brad
Off topic-

Cold "air" is more dense. Cold atmosphere is usually less dense... because cold air is denser it cannot hold very much water vapor. Air with a lot of water vapor creates more lift but allows for less O2 for the engine to run. So in very cold weather an engine will run great but the plane won't seem to fly as well. In hot humid weather the engine will not run as well but the plane will seem to float.-BW

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