TURBO 4NT

With a trump suit agreed & cue-bidding engaged, 4N TURBO arrives!

TURBO is 100%  integrated with Cue-bidding. For an overall and detailed look at this 'union' see Cue-Bidding.
In this text we simply explain TURBO itself.
Some people my favour it over Blackwood then read on - but if not intending using Beta  ignore the following exceptions.

The exceptions in which TURBO is NEVER used in Beta are:  

• All sequences following a 2 opening bid - 4N can be bid ONLY by the 2C bidder and asks for number of Kings!
  
• following a 3N distributional inquiry after  disclosure of a 5-5 or better - 4N is only used by responder and asks for an exact LTC! in steps from 5C(7)....5S(4) OR when 5-5 are declared as <=5LTC from from 5C(5).....5S(2). See 5-5+
  
• In any sequence where a suit has not been explicitly agreed a new suit then 4N Blackwood route may be taken.
• An important exception : a further new 'suit' that is bid after partner has rebid his suit (always showing 6+ cards in Beta) at the 3-level is to be taken as a cue-bid and agreement of trumps and Blackwood may not be used as now cue-bidding and TURBO are the order of the day!
  
• 4N is bid directly following explicit suit agreement -  is then our ERKCB
  

To avoid duplication See cue-bidding for details of bidding up to 4S & beyond...
The great advantage of TURBO is that one partner gets to know the partnerships key controls (RKCB+) as 4NT is bid or bypassed and cue bidding may continue! But also his partner can make inferences too! TURBO is therefore much more informative with less bidding space consumed as it is GIVING information rather CONTRARY to Blackwood which is merely asking about key cards. The value of TURBO is clearly easy to see: Blackwood only gives numbers of KC whereis TURBO linked to Cue-bidding has also placed them! So direct jumps to 4N should be condemmed as grossly wasteful.

Whereas with (E)RKCB key cards are only determined when a 5-level response to 4NT is given and may be even more limited especially in relation to minor slam contracts - where Blackwood is practably useless - a blind way to bid it and hope!

So, you're cue-bidding (see the rules!) and you're approaching the 4NT zone!
remember any suit you miss DENIES a valid cue feature in that suit - so one may NOT jump to 4N or above while further cues below 4N if there are still an unannounced cue-bid that can be made.

In the special cases of 5-5+ hands there are 6 key cards in the 5 card suits (yes the Q is counted!) and in the short suits only the A or void count opposite a singleton and AK or Ace singleton count against a doubleton. A 3 card side suit only occurs in a 5530 distribution - the responder must take special in respect of this possibility. In 5-5 hands the maximum LTC allowed is 7 and this is LENIENT. In any 55.. hand there are 6 potential losing tricks in the 2 identified suits and 3 in the side suits!

Just like with (E)RKCB, a TURBO 4NT is just about all Relevant  Key Cards (RKC) -TURBO's count of relevant controls includes ces & kings & in 5-5 hands the 2 queens. In the agreed key suit or 2 suits announced early in the early bidding, one from each partner  - usually announced in the 1st round of bidding.

Statements:

1. Actually bidding 4NT shows an EVEN (2 or 4 or 6!) total number of  Key Cards (KC) held - it also denies any further control cue-bid in any remaining bids under 4N!
2. By passing over 4NT shows an ODD total number of KC (3 or 5 or 7!) which may would include a key card in the bid made above 4N - EXCEPT if bidding the agreed trump suit - which would be CLOSURE when made in the agreed suit and could be  indicating missing the Q of the suit.. which must be shown directly over the 4N level also pinpoints a further control. Bids made beyond 4NT must be either 1st round controls or 2nd round controls where a first round control has previously been expressed.
   
3. One more little rule: responder must not pass 5 of the agreed minor suit or Major suit without holding the  Queen of trumps! Simply continue cue-bidding if one believes in a slam contract. However your closure can be broken by your partner.
   
4. One should not initiate cue bidding without at least 2 KC! or a KC and a useful void.
5. Cue-bids may continue above the 5-level in the agreed suit showing any additional feature NOT bypassing 6 of the agreed suit.
6. 4, 5 or 6 level bids in the agreed suit may be passed or bypassed by partner!
   

So in the 3rd rule above, without the Queen of trumps you need to bid the agreed suit - never cue bid above it unless your judgement is already confident of a SLAM. This bid is neither FORCING nor a command to end the bidding - that's entirely up to your partner. It simply signifies  not possessing the Queen of the agreed trump suit. If partner now continues after you bid game it neither shows or denies the Queen of trumps BUT it does show slam intent and he is aware his partner may or may not possess the Queen of Trumps.

TURBO takes a little effort to master, but i'm sure once it is well understood, it would always be the preferred  route to bid good slams (even thin ones) and equally to avoid bad slams! Except for clearcut cases where ERKCB is all that is required.. It also adds more clarity on whether to go on to a grand as cue bidding continues after 4N! Most importantly of all it efficiently uses bidding space more while simple Blackwood is wasteful.
It also allows for termination at the 5 level where Blackwood responses to 4N may commit to the 6-level!