Please, it's not "luftberry." Let's remember the WWI Franco-American 17-kill ace Raoul Lufbery by his correct name: http://en.wikipedia.org/wiki/Raoul_Lufbery
And by definition, a Lufbery Circle (or "defensive circle") is something that one plane cannot fly all alone.
The Lufbery defensive tactic is the origin of the term but Lufbery basically now has two meanings. The original, which was used by Mig 17/21 in Vietnam and is still used by some airplanes such as the A-10, is a generalized ACM term which simply describes two adversaries flying the same flat circle.
When you get down to it, all ACM fights boil down to NRG management by trading altitude for airspeed and visa versa. Given that none of the WWII aircraft have close to a 1:1 thrust to weight ratio means all fights will eventually degenerate to turns on the deck if they go on long enough and that's where you'll see the Lufbery and where it'll really get you in trouble. You're both flat on the deck with insufficient E for any vertical moves and now it's nothing but time and turn rate. If nothing is done the airplane with the better rate (whether through inherent aircraft performance or superior pilot skill) will eventually win and there are very few options if you're the one becoming more and more defensive. Even if you've got the best turn rate a Lufbery still sucks because it can take so long to resolve making you perfectly predictable and easy pickings. In the end, a Lufbery is a dead-end trap for both of you in a multi-bogey environment.
Also, as some have mentioned, you need to know what flap configuration for your ride gives the best RATE performance. With some airplanes it's no flaps, others full, and lots are somewhere in between. It's easy to figure this out without charts. Just find yourself an empty airfield, line up on the runway and start a hardest turn. When your airplane stabilizing at it's max sustained airspeed for that turn then time 10 level turns. Divide the results by 10 and you'll know how long each turn takes. Repeat this for all your flap positions and you'll know what works best for your airplane. Also, if you get stuck in a lufbery use WEP until it's gone. There's no reason at all not to use it and the additional thrust will help.
If you find yourself locked in a Lufbery, and regardless of how you got there and who has the advantage, usually the best option is for your wingman to intervene simply to cut the fight short (obviously, not applicable in a duel). Also, obviously, that's not always going to happen. Reversing is a lousy option because you've basically just given him the angles he needs and solved his problem for him and he won't be carrying anywhere near enough speed to cause him to overshoot. You can also attempt to use terrain and obstructions by really getting down in the weeds hoping he'll make a mistake. A better option would be to drift the fight close to something like a ravine and then get over the edge and accelerate for some separation and either escape or use the gained AGL altitude to redefine the fight. If none of these options are available then get your flaps up and flatten your turn a bit to gain some speed. Your adversary may simply think he's gaining the angles he wants (and you will be giving him angles) and he'll keep his turn tight to get his shot while not realizing you're actually accelerating away. Obviously the success of this tactic is completely reliant on which plane accelerates fastest and how long it takes for him to recognize what you're doing. If you're unable to gain meaningful separation you still cannot reverse, even with a yo-yo, without giving him an easy shot.
The two keys to this are related. First, don't get in one. Second, recognize you are and make an early decision to change the fight and/or disengage while you still have some altitude/airspeed to work with. If you see a Lufbery developing on the deck use high/low yo-yo combinations while you still have the E to do it. The high yo-yo gives you relatively sharp turns and the low yo-yo helps you gain/maintain E. Let your adversary keep turning flat and the yo-yo combos should result in your victory. If you still aren't getting any shot opportunities, use the high yo-yo to take your adversary as close to 180 out, accelerate in the low yo-yo and extend or exit.
