Flannery is defined as an opening bid of 2♦ to show a mininum opening(11-16 HCP) with 4 spades and 5 hearts. We play it is 4+ spades and 5+ hearts.
Some of my favorite benefits are:
-1♥ 1♠ shows 5 plus spades. This makes it much easier to handle hands when opener has 3 spades and can raise to the appropriate level with out risking getting passed out in 2 of a minor.
-1♥ 1NT does not deny 4 spades. This makes it much harder to defend as the defenders are put in a position that they are guessing more about declarer's hand than in standard bidding.
-You can get to some difficult to reach 3nt's with an 8 card major suit fit when your shortness is facing strength.
-2♦ opening and the response preempts the opponents out of partscores, and suprisingly often out of 5 of a minor.
-With minimal structure you can have very constructive auctions on Flannery hands.
-Soloway liked it, and I pretty much like everything Soloway liked.
Here’s the basic structure that Bobby Levin and I use:
2♦ -2M = To play, now 3m is 4-card m
-2N = Inquiry
-3♣ = To play
-3♦ = Invitational
-3M = Mixed raise – semi-preemptive
-4m = Corresponding slam try in major with shortness in other major
2♦ -2N, 3m = Sing. (or void with min.). Could be 4-6
3♥ = 4-5-2-2 minimum
3♠ = 4-5-2-2 maximum
3N = 4-5-2-2 with cards in both m’s
4m = 4-card om, ok for slam, now 4N is Straight Blackwood
4♥ = 5-6 minimum