How to set up a groundloop

There is simply no substitute for one wheel practice on the ground. I tell students that, while you will use this technique in a crosswind, perhaps the more important lesson to be derived from it is that you CAN control the airplane, even at very slow speeds.

I see students early in their tailwheel lessons allowing the airplane to roll and yaw pretty much at random, with every little whiff of wind.

The one wheel drill forces them to CONTROL the airplane at very slow speeds, and improves landing approaches immensely, not to mention hopefully preventing ground loops as well.
MTV

Nice write up, well said. However, there is nothing wrong with ground loops when done properly.:lol:

i'm a pretty low timer in taildraggers, and there's a lot of great advice here, lately I'm in a super decathalon and doing 3 pointers, I was doing alot in a C185 and an RV6 for a while and although my 3 pointers are good ,accurate landings (not necessarily greaser though) I have never been really confidant with wheelers, just can't seem to get past the habit of holding it off ,I guess it comes down to practice and while the 3 point landings are working for me I rarely try the other way. One question I have is ,I know how to get into a ground loop, but once it all turns to crap am I really a passenger or can I salvage the situation somehow?
cheers Mat

You are a passenger, according to everything I've read and the one time it happened to me with a few hours solo in my Taylorcraft on a perfect summer's evening just before dusk. I became distracted by dropping it in from a couple feet. My aw **** declaration was enough to find the aircraft swinging off the runway to the left. At that moment, I remembered the book Stick and Rudder by Langeswiche (?) who said something to the effect there's nothing you can do about it so you're there only for the ride. The Taylorcraft circled back to the runway so I opened the throttle and did another circuit hoping my instructor didn't see it. When I landed, he said, "I saw that. You learned something. It won't happen again." And it hasn't.

This old thread is just so very, very good that I had to bump it to the top again!

Good thread, but the OP is missing a detail that gives me pause. I've watched a guy total an aircraft by holding the stick back. It was in combination with "a little power" to control the settle to the runway. He ended up pointed at the sky at 15-20 ft, stalled and cartwheeled. I'd rather see it described as maintaining an appropriate nose high attitude; ...which will likely require full aft stick, but if you have too much speed or power, you can over do it.

Cheers!

Bill, what your saying makes sense, almost 99% of my landings are wheel landings, mostly due to me being short, and off airport, I like to see where I'm going. They are tail wheel low, and right as I'm about to touch the mains I ease forward stick. I have watched others do this, and even in a 3 pt when your bouncing if you ease forward into wheel landing attitude it stops the bouncing. Which also leads me to my next question. With worn out tail springs and or big Bushwheel tail wheels, and that wonderful shimmy, I've noticed that forward pressure eliminates the shimmy, and when you slow down and ease the tail wheel down, it usually stops. The problem I see is when the tail wheel starts shimming and you pin the stick back, it adds more weight and makes the tail wheel shimmy more. Couple that with the long Paul in the Tw and it's quicker releasing, the tail wheel will un lock and your going around. Just something to think about.https://vimeo.com/127226710

Here is that forward stick and stoping the bouncing.

No mention of use of proper use of throttle. It's a control too.
1 use: if it's getting away from you (full rudder and braking aren't working and the tail is down) then a burst of throttle can add airflow past the rudder thus increasing its effectiveness. Very counter-intuitive.
Additional use: full throttle and go around.

Okay Bill, you said something about pitch attitude and you would cover it later. It's been 5 years,it's later.

Thanks bill

Saw the title of this thread and jumped right to it. Then I realized that it was a pilot thing, not an avionics thing. Sigh

Web

Web - pretty funny

CuBob, and others. I guess I've been a little distracted lately. But lets try to get this thread back up to speed.

THE FOLLOWING NOTES ARE GENERALIZATIONS - THERE ARE EXCEPTIONS TO EVERYTHING -

Traash - You make an excellent point and one I had not covered so lets talk about that a little.

In life we sometimes get "Negative Transfer". This is when a motor skill that works in one situation is wrong in another situation. A perfect example is kids sleds. The rudder bar on the front of the sled, for your feet (or hands), works exactly the opposite from an aircraft rudder. So kids that do a lot of sledding have to unlearn that hand/eye muscle memory motion when learning to fly. The problem is that in a "panic" situation we often revert to a previously learned skill set. As I recall that falls under the "Law of Primacy" ie you will revert to what was learned first.

A taildragger is pretty much the opposite of the trike in just about EVERY respect on the ground.

Throttle - If you get in trouble with directional control on the ground in a tricycle gear airplane the correct action in almost every case is throttle idle and get on the brakes. In a taildragger - when having directional control issues - throttle up gives more tail authority and is the correct response most of the time, but that is the opposite of what you would do in a car, or with a horse, or with most other things in life. We pull back and slow down. But in a tail dragger we need to push up and lean forward.
Brakes - again...... in a trike - get in trouble - get on the brakes. With the mass in front of the mains this is stabilizing. In a taildragger it will make things worse (unless using just one brake to supplement rudder).
Elevator - in a trike letting the stick/yoke come forward, lowers the nose and thus AOA and is again stabilizing and generally good. In a taildragger if we let the stick come forward (three point or while high speed taxi - landing rollout etc) it lifts the tail so we loose the tailwheel steering component and we loose the drag pulling back on the tail so it is DESTABILIZING. Again the opposite of what works in a tricycle gear airplane.
Rudder - in a tricycle gear airplane the center of mass in front of the mains means it will pretty much auto correct and it WANTS to roll straight. In the tail dragger it WANTS to go backwards. So the tricycle gear pilot learns to minimize rudder on roll out to avoid over correcting or PIO (Pilot Induced Oscillation). The taildragger pilot MUST use rudder. Again - almost an exact opposite control input needed.

Bottom line - a taildragger is pretty much the opposite of a trike on the ground. They are not the same. One of my mantras............is......

Airplanes are different and each must be flown according to its characteristics in order to maximize utilization, performance, and safety

You do not use rudder in an F-16 but it is critical in a sailplane, you use the elevator and throttle differently in a tricycle gear airplane Vs a taildragger (on the ground). A high sink rate in a swept wing aircraft can be deadly, much less so in light wing loading, high lift wing like a Cub. The bottom line is that you don't fly a Cub like a Cirrus, or a Pitts like a Waco. Fly each airplane differently according to what it needs.

Controls while taxiing

Remember the axiom when getting your private pilots license "Climb into - Dive away"? That is the one that says to "position the controls when on the ground taxiing so that you are climbing into a headwind and diving away from a tailwind". With a headwind we have the stick back, ie climb, and the aileron into the wind thus "Climb into" the wind. With a tailwind we put the stick forward and the aileron away from the wind thus "dive away" from a tailwind. That is only about 1/2 correct for a taildragger. You should ALWAYS have the aileron into the headwind but the elevator depends. We have our forward speed and the propwash over the tail so MOST of the time in a taildragger the elevator should be full aft while taxiing. If you are not sure where to put the elevator (you don't know if the air is flowing over the elevator from the front or from the back (tailwind)) just stick your hand out of the window. Is the wind hitting your hand from the front or from behind? You will find that about 95% of the time it is coming from the front thus - stick back. It takes a LOT of wind (probably over 20knots) before you need to taxi with the stick forward. You could argue that the wind is not the same from where you have your hand out to where the tail is and there would be merit to that argument but it takes a LOT of wind from the rear to make a 180 degree change in that 10' difference in distance. Furthermore I am an advocate of stick ALL THE WAY AFT - WELDED TO THE STOP when taxiing. If you let the controls flop around you beat up the elevator and back end of the airplane when it bounces over every bump. Additionally you loose directional control with the tailwheel when it is not on the ground or when it is so light it slides sideways rather than gripping and turning. Now as I said before there are exceptions to everything - if you are on ROUGH ground you may need to lighten the tail to keep from pounding the tailwheel over the rocks. You may need to lift the tail to turn over an obstacle. Etc. But I see guys all the time taxiing with the elevator bouncing stop to stop, pounding the back end of the airplane all to hell, and I just want to run out there and tell them to hold the stick back because they are tearing up their airplane. Be kind to your airplane, treat it with respect, STICK BACK, STICK BACK, STICK BACK.
To adress shimmy. FIX IT!!!! The tailwheel should not shimmy. Period!! Yes Tom - your technique is good and will help -until you can get it fixed. But I would maintain that regular use of stop gap measures is not really all that good and the best solution is to fix the tailwheel.
This area - Control position while taxiing - is probably the area with the most exceptions. Some of these rules must be modified when taxiing downhill, or on a side slope, or based on the particular type of airplane, etc etc. Please don't beat me up too much, just remember...... MOST of the time keep the aileron into the wind and the stick aft.

GROUND CONTROL EXERCISES

Someone mentioned it earlier so lets take a few minutes to talk about ground control exercises. Some have called it flying while on the ground. You MUST have complete control at all times when on the ground or in the air (unless doing aerobatics, then it can be kinda fun to momentally be totally out of control).

Exercise 1
You should be able to do one wheel "touch and goes" anytime, every single time. Okay - exceptions - (man I get tired of trying to think of every possible exception) but here are a few. Doing a one wheel touch and go on asphalt with NO crosswind might work but it will be exciting and scrape a lot of rubber off. With grass there is usually enough sliding ability that the tire can slide a little sideways and you can do a one wheel T&G even without a crosswind. Wet grass in the early morning helps too. Obviously a crosswind makes it better. So......with a little crosswind you should be able to land on the upwind tire and roll along for as much runway as you feel comfortable, and NEVER touch the tail or downwind tire. A one wheel T&G if you please. Get good at it. Everytime!! MAKE THE AIRPLANE DO YOUR WILL.

Exercise 2

If the is no crosswind then land on one wheel, roll a few seconds, switch to the other tire, roll a while, go back to the first tire. Practice, practice practice.

Exercise 3

Not really an exercise but in fact something that can be practiced in a light or strong X/W. A proper wheel X/W landing is a three pointer. 1st point - is the upwind wheel, 2nd point - slowly "fly" the tail down, 3rd point - the downwind wheel touches when you run out of aileron authority. Upwind, tail, downwind - IN THAT ORDER. Practice, Practice, and Practice. A three point landing might be tail, upwind wheel, and downwind wheel. The difference is this will all happen in very quick succession Vs the wheel landing above where there might be several seconds between each wheel.

Exercise 4

If you have a nice wide grass runway, or can get to one, do a wheel landing on one edge of the runway, while rolling down the runway on the mains, move to the other edge of the runway. Go back and forth. This will actually be uncomfortable the first few times.

Exercise 5

Try dragging the tailwheel down the runway without ever touching the mains.

Exercise 6

Landings. There are lots of different types of landings. You should be able to wheel land (in a Cub) at about 70MPH. You should be able to wheel land at 50mph. These two landings are quite different. Then there is the tail low 40 mile an hour wheel landing where you touch town in a very tail low attitude (but not on the tailwheel) and then roll it up on the mains.
Three point landings can be 1) tail first, 2) three point, and 3) tail low but not completely three point until just a moment after touchdown. I think that even if you prefer wheel landings and rarely do three points you should try to maintain proficiency in all types. It will make you a better pilot. It's like tools in a tool box. The more tools you have the more jobs you can do, and the better you can execute those jobs. But that tool needs to be rust free and well oiled when you take it out of the box to use it, even if you do not use it often.

Exercise 7

Turning takeoffs and turning landings. Good stuff to practice if you can find a place to do so. Just remember, turning takeoffs to the left are higher risk, due to torque, "P" factor, Slipstream effect, Gyroscopic effects, and opposite rotation.

Exercise 8

Highly dangerous and not recommended. Do a wheel landing, add power as necessary, brake to a stop with the tail in the air. Take off without having ever touched the tail. In NO WIND/CALM WIND conditions, after coming to a stop as above, do a 360 piroutte, then take off, again never touching the tail. Learn to land with the brakes locked. On final get behind the power curve so you are below stall speed. At the landing point, chop the power, drop flaps and plop down, brake hard. These are dangerous exercises and I do not recommend you do them.


Attitude landings

In higher performance taildraggers you will set a landing attitude and maintain that through the flare/float to touchdown. Normally higher performance airplanes touchdown in a three point attitude well above stall speed so the aircraft is still flying and still has a lot of energy at touchdown. This is commonly seen in aircraft like the Pitts, Thorpe T-18, RV's (a little), and most other high performance types. Here is what I mean. Once you get in the flare in a Cub we hold it off (assuming a three point) until all the airspeed is gone and the airplane effectively stalls into the touchdown. If it stalls a foot or so above the ground its is no big deal, just keep the stick back and it will plop down just fine, though perhaps a little unceremoniously, but it will be safe. If you get a Thorpe T-18 in the flare then hold it off like this it will eventually get pretty nose high, touchdown on the tail first, but when the mains come down you will get into a fore/aft pitching (PIO) motion - porpoise- I like to call a "crowhop" and things will get exciting really fast. You can not just get in the flare and "hold it off" in a high performance taildragger. Before you take off you take a moment to fix the attitude you are in while sitting on the ground firmly in your head. Where does the horizon hit the glareshield/windscreen? What angle is the horizon relative to the wing? What do you see over the nose? How high is your rear off the ground? When you get in the flare you find this attitude and maintain that, using throttle but NOT increasing AOA/attitude, until touchdown. If you float in the flare you must use the throttle to control sink and attitude to keep from dropping in, or dropping it in tail first.


OK folks. Probably lots of opinion here so take it all with a salt lick

Hope this helps

Fire away

Bill

Yikes, I've gone 3400 TW hrs without a ground loop because I thought it was easy. Now that Bill needed a thousand words to explain it I'm afraid to go flying Thanks Bill

Glenn

Good stuff Bill and and pertinent exercises. Makes me want to go practice one wheel landings in the morning again.

I have two takeoffs I remember that were almost ground loops. The first time I landed on the side of an open hill side aimed uphill. It was probably a 15% grade or so. When it was time to leave there was some wind blowing downslope so I had a tailwind. Because of the terrain I took off with a quartering tailwind from the left. Full right rider wasn't enough to keep the tail from swinging to the right and I had to stab in hard right brake to straighten it out. That did it and about that time I had enough airspeed to fly on down the mountain level with the grade.

The second time was last month flying up the Trench in BC. Showers were blocking my way near Mica Dam and rather than fly back to Golden to wait I landed on a piece of road that didn't get flooded by the reservoir.



Road is above jury strut.

I landed with a tailwind and that was no big deal. But later when the path north opened up I had to takeoff with a tail wind.



I was was up tight against the trees to start the roll and there wasn't any wind. But once past the shadow of the trees the wind turned into a quartering tailwind from the left and once again it took quick brake action to keep things lined up on the narrow road.



Looking towards the the reservoir from my takeoff location.

I guess the lesson that was reinforced was takeoffs with a tailwind from the left may exceed rudder control at lower air speeds.

Seems like the baby bushwheels are more prone to shimmy on pavement. I have the new HD Bushwheel spring and it will still shimmy from time to time.

Tom - Not entirely sure why they do, but I agree.

Bill

I wasn't flying during the landing I remember best. I was riding front seat as we were doing search and rescue in a J3, refueling on the top of the White River levee in eastern Arkansas. My brother was pilot. All was well till someone parked his pickup in front of us so that we had to slip in, then immediately lock the brakes and slide to a stop before we reached him. All still well, BUT the right hand brake elbow fitting blew out while we were still doing about 25 mph on the 11 foot wide top of the levee with left wheel locked and suddenly no right brake at all. We did an immediate left turn straight down the side of the levee toward the trees at the bottom. I remember thinking, "We're gonna take this sucker home in a basket". But my brother firewalled the throttle, applied down elevator to blow the tail off the ground, and full right rudder using the prop blast to swing the plane around backwards. He then halted the turn with us descending the levee backwards, sat the tail back down, used the propblast to stop us and to taxi back up to the top of the levee. As an aside, when you pop the top of the levee, you gotta be ready to shut down right then so you don't repeat the whole process on the other side of the levee.

Golly, I need to go to Poplar Grove!

Usually I fly off asphalt because it's more common here and I figure if I can handle asphalt, grass is always easier. Also, I usually three-point unless it's gusty or things don't go as planned.

If I'm going to have a problem it's most likely due to flaring a bit too high or a bit too low. I've worked on the three-point sight picture but have trouble determining wheel height… so if I'm beginning to fall the last foot I massage the throttle into an extended landing. I hate that. 75' or wider runways are the worst… you've really got to concentrate. I don't have flaps and enter the flare about 45+/-. Directional control is not normally a problem, just the wheel height.

I've always had a problem with wheel height on the levee tops. That, and the lack of ground effect, and there always seems to be a gusty crosswind, so you have to contend with the updraft on the windward wing, and the erratic burble on the leeward wing. Directional control is easy though -- it's immediately obvious when a wheel starts getting close to the edge of the levee.

A bit of humor (humour?) to lighten up a serious subject: http://www.supercub.org/forum/showt...-Your-Taildragger&highlight=groundloop+musket

Folks, threads like this make this one incredibly valuable website. Honestly, the type of heavyweights who weigh in with their inputs is incredibly valuable.

This is one of those threads that I will bookmark for many days to come.

Randy

Bill Rusk said:

Tom - Not entirely sure why they do, but I agree.

Bill

Click to expand...

1) longer fork arms increase the effective caster angle.
2) larger tire diameter raises the tail and increases the effective caster angle.

From what I have read, the majority of ground loops occur because of incorrect technique in a cross wind, Bill's lessons to practice also lead me to believe this. While rereading Mr. Imeson's book " taildragger tactics" he states never land when the cross wind component exceeds 20% of the stall speed. When asked the question of what individuals max cross wind is on this forum I get answers that go well above 75% of the stall speed. What is a proper limit you use? With some of the numbers quoted is it even possible to be done safely on a day to day basis?

When current, my maximum direct crosswind limit on grass in a J3 is about 27 kts, gusting 33. You have to accept that the plane will be scrubbing sideways and compensate for it. Throttle and rudder are your friends. It is not safe on a day to day basis, and I will go out of my way to avoid it. I see those limits maybe once or twice a year. I'd rather not see them at all. The maximum direct crosswind that I am comfortable with in a J3 is a little over 20 knots, and taxiing is still an unpleasant chore.

When not current, my limit is more like 12-15 kts. Depends on how long it has been since I've flown in significant crosswinds.

I had fun with one wheel landings and high speed taxi work on one wheel this morning Bill. I went to a nice long grass strip and worked both directions on alternating mains. I probably put a couple of miles on one tire this morning.

It it had been a few years since I practiced these and there was a little rust but it didn't take long to get oiled up. And near the end I had an actual crosswind to work with too.

My favorite tailwheel practice is to place the tailwheel on the ground and attempt to hold the mains off while I run the length of the runway. I don't do it as well as when I was young.

PerryB said:

1) longer fork arms increase the effective caster angle.
2) larger tire diameter raises the tail and increases the effective caster angle.

Click to expand...

More mass in the wheel is the primary culprit.

MTV

mvivion said:

More mass in the wheel is the primary culprit.

MTV

Click to expand...

I'd like to know how mass creates the issue. The heavier wheel will likely occilate at a lower frequency/higher amplitude, but I maintain the problem lies strictly with the geometry. I've worked on numerous trucks with this issue in the front end (commonly referred to as "death wobble ") and reducing the weight/size of the rotating mass is not how you solve it. Taking out caster is.

When the tailspring is heavily loaded, the bottom of the kingpin still needs to be forward of the top. If it is, no shimmy.

Thanks for the write up Bill. I don't post very often, but I am on this site every evening learning a tremendous amount from all of you more experienced SuperCubbers.