Switch_639

when attempting... must all controls be in HIGH rates? the method is simple, full power straight up into the air, full left rudder, full left aeleron and full down elevator... flying a X100 Funtana... also I am a bit concerned about HIGH rates on the Funtana, the manual suggests 50 degrees... this sounds extreme as low rate is only 11 degrees... any idea on this?

AA5BY

Of fifteen planes in my hanger, only one will do the maneuver... that a 1.20 size PT-19 that I currently own. Among those that won't do it are several very aerobatic planes so it is no given that every plane is capable.

What works for me on that plane is to climb at full power, pull a full power snap roll to the left, wait about a three count until the snap roll has time to get about 2/3 through its process and then move the elevator full down while holding full power, full left aileron and rudder. If the timing is right when making the move... it does the reverse tumbles. Success rate is about 66%. A really pretty wings level to the horizon four tumbler happens about one of thirty tries.

A lumcevak is said to be a four axis maneuver, pitch, roll, yaw and the 4th being gyroscopic effect of the engine so it must be at full power. In fact, my PT-19 had a mishap that broke the firewall loose and after repairing, I found the lumcevak very difficult to do and success rate went from positive numbers to very poor negative numbers of perhaps 1 in 10 tries. After about a year of difficulty in doing the maneuver I happened to buy a new transmitter and after programming for the various planes in my hanger, I noted that the lumcevak was again quite easy to do.

Curious to why, I tried again with the old transmitter and again had difficulty. The thing that was easy to recognize was that there was a slight bit of power difference between the two transmitters. The throws were identical and evidently I'd used the same numbers from the old transmitter... both JR, except for the throttle throw, which evidently I set with the new transmitter to the point of barrel stop.

On the old transmitter, evidently after the firewall repair, I'd not checked to see that the barrel was opening fully and it had been a year since repairing so had lost my memory comparison of the power ability of the engine. The throws on control surfaces were the same.

Best of luck with the lumcevak maneuver, it is a thing of beauty.

gboulton

My Feedback: (15)

Agreed. It seems to be the sort of thing that only certain planes will do...at least in terms of "looking right". ANY airplane can be put into the "correct" attitude, of course, but that sudden "flip/tumble" characteristic of the maneuver seems to be the domain of only certain aircraft. Indeed, in the RC world, even 2 examples of the 'same" airplane seem to perform the maneuver with varying degrees of 'success"

Of the 9 airplanes in my hangar, the only one that does it with jaw-dropping success is my 110" EF Yak. NO Edge i've ever had would do it well, never had luck with any bipes (sport or aerobatic), Extras seem to be hit and miss for me.

For the Yak, I've found it can enter the maneuver in two ways, and produce "oh wow" results.

I can enter at high power on a 45 degree upline, initiate a slight roll left, then full left runner and full down elevator.

Optionally, I can fly straight and level inverted, and go full left elevator, wait just a heartbeat, and then full down elevator. notice, NO aileron input there.

Both of those, with the right timing, produce stunning results with that airplane...particularly if the smoke's on.

Speaking to the OP's original question, I've noticed that the amount of elevator travel seems to be "irrelevant", past a certain point. If there's enough down elevator to stall the airplane at high speeds (in other words, can you do, for lack of a better word, an inverted "wall"?) then there's enough to tumble it through the lomcevak, ime. Additional elevator doesn't really seem to impact thge maneuver, for me anyway.

Thunderbolt47

My Feedback: (8)

Super Chipmunks do them well.



http://www.youtube.com/watch?v=A-kHTmYjBQk

yellerchamp

My Feedback: (42)

A great man and a great pilot..............

GreaTOne_65

The shorter coupled, bi-planes are the planes that I believe made the lomcevak special. The Pitts, Eagles, and the Weeks, that I've had all would do tumbling manuvers on demand. Yes it takes lots of control throws, too.

Quazimoose

Throttle management is probably required with todays setups, I think many current power setups may be too strong and power themselves out of the tumble.

AA5BY

I suspect you're right. I will play with some various throttle settings on a couple of planes that I've had no luck getting them to tumble.

Bax

My Feedback: (11)

A "traditional" Lomcevak used to be initiated from an inverted 45-degree climb. Then, perform an outside snap and hold the controls in the pro-snap position. The plane would start to snap and then go into the tumble. An inverted spin would result, and you'd recover by using a normal spin recovery technique.

In order to do the maneuver cleanly, the airplane must be able to deliver a good outside snap roll. Usually, too, the CG would have to be a bit farther back than usual. It all depends upon the airpalne. I remember seeing a video in the late '70's of the DuBro arf seaplane doing tumber after tumble. It was a wonderful sight, watching it enter and recover. .....and then I had a so-called aerobatic airplane that wouldn't tumble worth a darn, even though it would snap beautifully.

rmh

My Caps -all did this easily from upright inverted - whatever - they have perfect force setup for tumbles .

daveopam

My Feedback: (9)

I also have only only one plane that will do one. It's a Goldberg Ultimate. Most of my newer 3D and aerobatic planes don't have the inertia. If they were heavier they would Lomcevak but stink at everything else.

David

zacharyR

My Feedback: (5)

I'm not the great'st but I think your doing the " polsih" move wrong lomevak is started from a declerating 45 degree up line . and much like a( blinder ) you gain momemnt in the airplane by doing left axiel rolls when the canapee is faceing down vary fastly go to nutrel sticks while your momentium is still there you at the same time push eveything down and over to the left add power . and i bleave you lead in with down elvator before you start to blind the rudder



anyhow thats my understanding


the book says tstarted for a declatred 45 dergree upline and as the modles slows roll to a knidge edge posiston at the apporiate time initate and agressive outside right snap roll and add full thorrlge for hte snap add full down elvator and full right rudder the moddle with pitch down yaw right and roll rapidl to the left as the modle transistions to a 1 /14 roll leve uprage 45 dgree flight nutralize the rudder and airl and conturn full down elvaator this should occur persicly at the same time the modle stops foward motorion

" scott stoops "

just some ideas to give a try another way
another thing airplanes taht are extream 3d are not going to do it as nicely as heavy wing loading more mass planes becouse they are going to want to start flying again sooner then the scale radio type planes

thats why full scale does it much more voilent becouse they don't want to start flying as soon as we do " we as in model planes "

MetallicaJunkie

my old heavy aerobatic planes of the 90s would do them and tumbles verry well, not so good flatspins, now its quite the opposite imo

Silvanskii

My Feedback: (17)

http://www.youtube.com/watch?v=HQ14vTTc7pA

AA5BY

That was some good flying... but I didn't see what I thought was a lumcevak. I might be all wet, but I thought the maneuver included three consecutive tumbles (reverse I think) of the aircraft with the best being those with the wings level and no roll during the tumbles.

AA5BY

An attempt to describe what happens in the maneuver that I do. In a 45 decelerating climb, while there is still airspeed to do a violent snap roll, a left handed one is induced under full power, full left rudder, and full left aileron. Then patience is required for the snap roll to develop. The snap roll throws the plane into full stall and the momentum forces an outside half somersault.

As the tail plane approaches the 180 degree point of the somersault, the elevator is moved from hard up to hard down while holding all other controls. What this does is present the elevator to an onrush of reverse airflow which creates a reverse force, which slams the brakes on the tail plane and helps force the plane to reverse somersault to the inside along with the forward momentum of the fore section of the plane, which is now still trying to go uphill under the tail plane. The inside somersault force is accelerated when the stab slams broadside against the up line momentum.

The plane is in full stall with the engine and prop acting like a gyro stopping roll. Now with the plane reverse somersaulting in a free fall, the elevator again sees reverse flow in fresh air as the tail plane falls and continues the reverse tumble until fall speed accelerates enough to force forward regular flow over the stab and stop the tumbling.

A good lumcevak will have three reverse tumbles with the wings near level and no roll. I've managed on a Hanger 9 1.20 PT-19 to do four with the wings level and no roll. It was a sight I'll never forget.

Btw... after some damage and repair to the plane, it became very hard to do the maneuver and nearly a year later I found out why. I didn't get the throttle adjusted for full rpms of the Enya 1.20 four stroke. When programing the plane to a new transmitter the throttle was correctly setup and the lumcevak returned to the airframe with regular predictability.

For me, the most difficult parts are first judging the right point of deceleration to initiate the snap roll as there is a zone of speed that works. Then the timing of the pause as the snap roll develops before going down elevator is critical... too early or late and no cigar.

I also believe if there is too much elevator travel, that it then does not present the right edge to catch the reverse flow that slams the brakes on the forward snap roll tumble and reverses it.

As far as I know, holding the rudder and ailerons over simply insures they stay stalled. I don't think they otherwise play a function. High engine rpms is crucial to killing the roll components of the snap roll that threw the plane into the stall.

This is my interpretation of what happens... I could be all wet.

RTK

My Feedback: (1)

Have to try that