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