Hey guys,
please dont laugh, this is a very UNtechnical way to ask a question..
anyone willing to tell me the stick sequence to perform a lomcevak?

I was told that the way to go about it is
moderate speed flat and level,
pull up and immediately move the sticks down and towards the middle(full right rudder, full left aileron, throttle to idle and full up elevator all at the same time),,,,, like a snap roll but with full up elevator and throttle to idle
and then as the plane goes over flying tail 1st
continue holding both sticks to the middle and push straight up..

Sortof opposing "J" patterns. left stick is a "J" pattern and the right stick is a "J" but backwards.

I've done it and it looks really cool. It seems to give the general effect of the plane flying backwards momentarily, but Im not totally sure if its the proper way to go about it.

Have a look at this site Dadio, it is Schweeet.

http://www.geocities.com/festacom/

HI, Nathan Farrel-Jones of [link=http://www.3drc.info/]3DRC.info[/link] told me this is how you do it.

Lomchevak

45 deg, roll so ur usin left rudder to hold knife edge, then push full down, full leftail n rud, then come back toward centre on the ailerons, with a model youll get max 3 tumbles then fly out

Ive done it by climbing at a 45 deg angle then doing a snap roll in either direction. When the plane is inverted give full down elevator and this will cause the nose to spring back. Im gonna try it the way edible engine described..sounds easier

very cool website flatspin. I can get a lot of use out of that!!![8D]

Definately gonna have to try Ian's method

In the method that I gave Ian (edible engine) by maximum 3 tumbles I was referring to smaller models... with a 40% there tends to be enough weight to get the motion going without so much control inputs doing the work.


Some models need you to come back to the centre on the ailerons more than others.

I do it the way DP's book says. Take a 45 degree up line and roll (left) to a right rudder climbing KE. Snap with full right rudder, full up elevator, full right aileron. After 1 and 1/2 (or so) snaps, move the right stick from the bottom right corner immediately to the upper left corner. Hold that with 3/4 to full power. If you have the coordination to do so, click in 3D rates just a half second after the right stick switches position.

The first snap and a half is to get the plane "wound up", and lose it's airspeed rapidly. After a few tumbles, the plane will fall into a nice inverted flat spin.

A Lomcevak involves gyroscopic precession due to the rotational inertia of the prop. Due to scale factors and low prop mass, most models (99.99%) can not Lomcevak.

OK... assuming a grossly overpowered scale aerobatic type model.. this will usually do it.. or close....
Establish a 45 degree climbing line, reduce power to say 60% or so, full HIGH rate left roll, After 1 and 3/4rolls, or 2 and 3/4 or 3 and 3/4 rolls.. (Get the 3/4 part?) stab in full HIGH rate down elevator. Some planes like the aileron left in, some don't. some like no aileron, but some left rudder. variations of this will get you into a LOM... often if you hold it, it will decay into a knife edge spin.... if done wrong, you will be in a flat spin!!!


back_it_up.zip

You can retrieve this file at http://141.248.186.227/asisite/upload/2952

The userid is: asi2952

The password is: satcom

Right click on the file in your browser and select -Save Link As- to download.

The file will be deleted after 72 hours.

enjoy

The point where theory and reality intersect is at the flying field.... If I were a betting man, I'd say that more than 1 in 10,000 models will Lomcevak.

Here....try this link it will answer all of your questions.

[link]http://members.cox.net/moorman1/Hotdog.htm[/link]

http://www.djaerotech.com/dj_askjd/d.../lomcevak.html
http://www.fightercombat.com/maneuvers/Lomcevak.pdf


Most RC pilots will call any tumble they started on a 45 degree line a Lomcevak. Fine, what ever makes 'em happy. I mean it really doesn't matter as we are all out to have fun. But any ole tumble is not a Lomcevak. A Lomcevak has a very unique look and can only be produced by gyroscopic precession. I believe there are five major Lomcevak variations, and they all have a very precise definition. If the plane does not undergo precession in the tumble due to prop inertia, it was not a Lomcevak. Only very large models (probably 40%+) would have a chance, and they would really need those light carbon fiber props replaced with metal to increase prop mass. My 35% will not Lomcevak. Sure, it will tumble like mad, but I can't get significant gyroscopic precession. Maybe my 99.99% figure is stiff, but I have only seen one model ever that looked like it might have significantly precessed. It had a wood prop, but was a magneto engine with a massive flywheel.

I have to agree with REDRUM. But timing on applying the full down elevater is critical to make it look right. And alot of planes CAN do it. I have an Eagle trainer that will do it(It has no diheadrel)
This was the way I was taught anyway. Been doing it this way for ove 20 years now. I use to love to watch Art Schols do it in airshows and still have some vids of him. He was the MAN on the Lomcevak.....( he even use to take his dog up with him )= a cockpit full of puppy chuck[:'(]

I always seem to hold an unpopular position on Lomcevaks with fellow RC pilots... Shanes300, I seriously doubt your Eagle does a Lomcevak. I would readily believe it tumbles, but not a Lomcevak.

OK, my 35% will sometimes do a very sloppy lomcevak. If I catch it just right and open that DA100 up, the kick from going from idle to full throttle will sometimes precess such that the second tumble is KE, but it is rare. It will always flip, but it will rarely precess. This is the same reason torque effects on takeoff are more readily seen on full scale compared to models, etc.

Here is some vid of a full scale Lomcevak, variation on a main lomcevak
http://www.goldentriangleima.org/AS/mvc-313v.mpg

Here's another full scale that looks like a positive conic lomcevak, but it is hard to tell.
http://www.collmer.com/jcas/images/airshow5.mpg

Look closely at the vid, esp the first one. A lomcevak is not a three rotation tumble. It is not a end over end tumble. It is not a back flip or anything like that. If you do perform a 45 up 3 flip Lomcevak, such as shown in the first vid, the first tumble is sort-of forward, the second tumble is rotated so it looks like a KE spin and the 3rd is rotated again to ~level flight. The orientation change in each tumble is due to gyroscopic precession, NOT flight control surface movement.

I realize this may seem like splitting hairs to some, but it is really no different than calling a barrel roll a snap... if you don't depart, it wasn't a snap; if you don't precess, it isn't a lomcevak.

I don't doubt some model has performed a decent Lomcevak and I'd love to see it. Please post if anyone has model lomcevak vid.

Cheers!

I read a book by Dave Patrick, in which he asked several people how to Lomcevak. Not one said that models couldn't do one. Advice on the maneuver is given by, Dave Patrick, David Von Linsowe (TOC Pilot), Clint McHenry (full scale aerobatic champ, PAC instructor), Tim Nealy (full scale champ), Jim Stanton (PAC intstructor), John Conrad (adviser to US aerobatic team), Joann Osterud (full scale Ultimate pilot), Wayne Handley (needs no introduction here). These pilots were giving DP input on how to get models to do a Lomcevak. Again, none said that models won't do one. Several did say that the plane ends up in a flat spin or outside spin. None said KE spin.

Clint McHenry(full scale aerobatic champ, PAC instructor), even stated that a KE spin counts as a Lomcevak, only is is on a downline.

The phrase gyroscopic maneuver is used twice, and neither time does it relate this to big planes at all, just that a Lomcevak is a gyroscopic maneuver, and that Wayne Handley is a recognized authority on gyroscopic maneuvers.

Reference "Raido Control Aerobatics For Everyone" by Dave Patrick page 42 through 44.

Sadly, I think I have found a controversial subject in RC.
Looks like some folk are measuring the size of their ****'s on this one. It is an interesting discussion on physics though.
I dont know about "gyroscopic PREcession" or whatever, but I do know that it looks really cool when I get my plane to tumble end over end on a horizontal line, call it whatever you want.. I THOUGHT is was called Lomcevak, apparently I was wrong.

I guess its a brand new maneuver and I will give it my own name, cause when I do it people watching go NUTS and want to know what the heck that COOL looking maneuver is called. I'll let you know when I come up with a name, I will also try to come up with a video.

I've seen this same discussion before, and there will always be a difference of opinion, but I do think that what I did with my Ultimate and Edge (60 size planes with Webra 120s) were Lomcevaks. Last time, someone referred to a different maneuver name of "cauldrun". I do not remember what the difference was, but it was a variant of a Lomcevak, that was of a more extreme nature.

I gave the commands that DP said to, and my plane did what he described in the book. If it's not a Lomcevak, them I too am at a loss regarding a name other than just calling it a tumble. Any violent spin or snap probably could be called a tumble, I guess

I guess that all Lomcevaks are tumbles, but not all tumbles are necessarily Lomcevaks.

I'm not trying to give JW any crap, just posting a difference of opinion and giving reference to the information that lead me to it.

Maybe at your field, you could call it a "Nedcevak"?

Nedcevak, Sounds pretty good to me! Although I do take my flying serious and I am working to improve my skills all the time, its never serious enough to get fired up about. Its all for fun anyway [8D]


Mike

I can get a tumble or lomchvok or whatever by simply putting full down elevator, full right aileron, and full right rudder. This worked well on my tipo 750, calypso, and four star 120. Looks cool!

Is there a little test one could do to see how substantial the effect fo propeller momentum is on the a model?

I can think of one.: Run the engine at idle, pick up speed in a dive, now quickly yaw the plane and observe the resulting pitch that occurs as a side effect. (It may not pitch at all.)

Next do the same thing but this time flying straight at level, or on an up line, with the engine running at a higher speed. Yaw the plane the same way at the same speed and observe the result. If it pitchs more than when the engine was running slowly, then there is a noticable gyroscopic force.

Unless... of course, the prop blast has some effect that cause the plane to pitch. I'm not sure if that can be ruled out.

Nedcavak... I like that. Ned, nothing to be sad about, there is just a difference in opinion as to the description of a lomcevak. I'm not trying to ruffle any feathers; instead, I am attempting to provide information based on what I understand to be a lomcevak.

Twister... I never said models can't lomcevak, just that it is much more difficult for a model to lomcevak compared to a full size, so most models can't lomcevak. The smaller the plane, the less likely it can lomcevak. I've never heard any of those pilots say that models can't fly to the moon either... that doesn't mean models can fly to the moon.

Part of the problem is that the IAC doesn't have the lomcevak on the list of possible maneuvers, so many have come up with their own tumble and called it a lomcevak even if it doesn't meet the criteria of the maneuver. There is no governing body to enforce the lomcavak definition, but the important thing to note is that the definition still exists. So, how can we have multiple maneuvers all be the same thing? I have seen a dozen different descriptions of a main lomcevak here, everything from a end over end tumble to who knows what... that makes no sense.

All I am doing is regurtating info I have seen. A lomcevak is a gyroscopic maneuver. Scale is ALWAYS a factor. That's why we have reynolds numbers. With a full scale plane, prop mass compared to aerodynamic forces have a different ratio compared to a model. Models tend to have low mass props and they are flying with very different aerodynamic forces. The net result is that with models the aerodynamic forces greatly outweigh the rotational inertia of the prop, which makes precession in a tumble very unlikely because the aerodynamic forces will always win.

In the end I know I'm at the losing end of this dicussion because many will call any tumble a lomcevak and will continue to do so regardless. Hey, have fun, tumble your plane and if you want to call it a lomcevak, nedcavak or whatever that is fine, but it does creates confusion. 3D to a certain extent has that problem now. I have see three different maneuvers called a Heartattack... all were very different. Confusing.

For those that don't understand precession, please look at the first video I posted a few posts back. First there is the 45 up line. The a ~1-3/4 positive snap to the left, then full down elevator is applied to start the tumble. Note that the tumbles are end-over-end, and the flight path stays straight. Notice the actual orientation of the plane as it flips. It is always flipping end-over-end, but at one point the planes orientation is yawed 90 degrees with respect to the flight path. The nose of the plane is pointed straight up! It then rotates orientation on the next flip such that the plane swings back to normal. The reason why the end-over-end tumbles rotate orientation is due to rotational forces from the prop, i.e. gyroscopic precession. Remember, the plane is flying at basically zero airspeed, the control surfaces are basically useless once in the spin. The orientation chance is due precession. Spin a kids top, you can see the precession as the top handle slowly scribes out an ellipse.

Cheers!

Hey guys,

I am fortunate to be able to go flying in a full scale extra 300. The IAC (International Aerobatic Club) does it like so:

Pitch the airplane up 45 degrees

Rotate to left to 90 degrees (1/4 roll to left)

Full right rudder, down elevator, and left aileron, all at the same time

When the airplane breaks, go neutral on the ailerons.

The reason that we use this procedure is to further increase our tumbling by working with the gyroscopic procession, p-factor, and gyroscopic slipstream to a degree. Just a thought,

See ya,
Dan Payne

Hey Let's Roll. OK, 45 up, you roll to a KE. An then outside snap in same direction of the roll. Once you break, you hold rudder and elevator but move ailerons to neutral. That all makes sense as it is identical to what I have heard from other full scale pilots.

I'm curious. Is the direction of the roll in entry important? By that I mean could you have rolled right 1/4 and then go full left rudder, down elevator and right aileron and produce the same maneuver? I'm curious because I suspect the direction of the prop rotation may prevent the maneuver from looking the same if done the other direction but would like input from a full scale aerobatics pilot.

Also, where do you set power during the maneuver on full scale? Thanks!

Hey John,

We are flying lamcevaks in a 1991 Extra 300 with a Lycoming AEIO-540 L1B5. A 300 horse engine turning a three-blade MT composite laminate prop. There are actually five different types of lamcevoks, in fact there is a book that covers the flight dynamics of each and every one. I will try to find out the name of it and email it to you within the next 48 hours.

BUT FOR NOW...

John, a Lomcevak is a much-misunderstood class of negative-"g", near-zero-airspeed maneuvers invented by the Czechs, where the gyroscopic precession of the engine and propeller is used as an additional flight control along with the three usual ones, aileron, elevator and rudder. Yup, that's right, you can't do a true Lomcevak in a glider unless you bring along some sort of VERY BIG gyroscope. In fact, it's very difficult to do a true Lomcevak with any type of model airplane, because the inertia of a model propeller relative to the inertia of the airframe is very low, in comparison with full-scale aircraft. Although to many folks they look like a totally out-of-control gyration, they are actually precision maneuvers, with a specific definition of how they are supposed to look. However, they are NOT in the Aresti aerobatic dictionary, which is probably just as well; if they were, then they could be specified in compulsory sequences at aerobatic contests. There are a number of English translations of the Czech word "Lomcevak", but the most popular I've heard is "Headache".

There are many variations of the Lomcevak, but they are generally divided into five major categories:

The one most commonly seen, the classic Lomcevak is entered from a 45° up line, at cruise speed or below, with full throttle applied. To begin the maneuver, full right rudder is applied and held simultaneously with full left aileron and full down elevator. Neutralizing the aileron after the break. (If aileron is held in, the result is what we call the "centrifuge" where the airplane just kinda high g slow motion outside snaps.) The response varies considerably from aircraft to aircraft, but the usual result is a graceful end-for-end tumble on all three control axes, finishing with the aircraft in an inverted spin.

The "cap" Lomcevak starts out much like a hammerhead turn, but as the fuselage rotates to horizontal at the top, a combination of precession and down elevator cause the aircraft to pivot about the wing in a perfect pirhouette. The wing remains vertical during the maneuver.

In the last two categories, the "positive conic" and "negative conic", the aircraft sweeps out the shape of a cone while pointed nose-upwards, with the bottom of the wing tangent to the surface of the cone during the entire maneuver. In the positive version, the nose is the apex of the cone, while in the negative version the tail is the apex.

Lomcevaks are terribly disorienting but otherwise fairly gentle for the pilot. We only experience about -5 g's. The same CANNOT be said for the aircraft! All sorts of strange loads appear on the airframe, ones that were probably never conceived of in most aerostructures texts, such as high centrifugal forces on the wings. The worst effects seem to be reserved for the engine mounts, crankshaft and prop. There have been quite a few cases of major damage to these components during Lomcevaks. Something like 70,000 lbs of centrifugal force on the prop tips during the manuever. The Yak 18 for example, experienced four crankshaft and prop failures, and one where the engine was literally yanked off of the firewall by the roots.

I just remembered! Probably the best explanation of the Lomcevak (and where most of the above comes from) is in the book "Aerobatics", by the great British aerobatic champion Neil Williams. This is an excellent book, one of the best available on the entire subject of aerobatics. It has an entire chapter on Lomcevaks. Look for it in your public library, I recommend you pick up a copy! It will give you the ultimate edge in competition and you will be able to do stuff to better help your routine. When it comes down to aerobatics, knowing how and why the gyroscopics of the propeller work is the key to awesome manuevers.

As for the entry to the right, let me go flying and find out! Ha! Never done that before, If I am thinking correctly however, you have to understand that manuevers like the lamcevak, and other gyroscopic maneuvers are maneuvers that take full or partial advantage of the gyroscopic precession generated by the spinning propeller. We usually apply the controls in such a fashion as to maximize this force, and then basically we become a spectator until the energy of the tumble dissipates and it is time to recover the aircraft. aka "The ride is over" Thus is why everyone uses the left roll entry.

So, in closing try the right entry with your model, but I seriously doubt that you will like the end result better than the "left roll" entry which has gyroscopic procession, p-factor, and gyroscopic slipstream working for you. Let me know how the model turns out, and I'll let you know how the Extra does. Oh, by the way. We run the Extra full-throttle, full prop, full mixture all the time everytime. So yes, it is wide open when we enter just about any manuever except for a tail slide. What the heck, it's only 36 gallons per hour...

Sincerely,

Dan Payne