The TLD stairs I wish to use with larger aircraft ie 757 and A330. The CDS stairs I only want to use with the 737/A320.
You mean "exclusively", so you *always* want the TLD stairs on larger airplanes, and you *always* want the CDS stairs on the smaller ones ? If yes, considering the A320 door is about 3.8 from ground and the 737 is lower, you might set-up a "cutoff" point at 3.90, like this:
FSDT_Staircase_CDS_2438
condition = ( %(exitAlt)f >= 1.80 ) and ( %(exitAlt)f <= 3.90 ) and ( %(isCargo)f == False ) and ( %(isCargoStand)f == False )
FSDT_Staircase_TLD_ABS-580
condition = ( %(exitAlt)f >= 3.90 ) and ( %(exitAlt)f <= 5.38 ) and ( %(isCargo)f == False ) and ( %(isCargoStand)f == False )
FSDT_Staircase_TLD_ABS-1740
condition = ( %(exitAlt)f >= 3.90 ) and ( %(exitAlt)f < 6.40 ) and ( %(isCargo)f == False ) and ( %(isCargoStand)f == False )