sentences:  After the success of Tridair's Gemini ST twin-engine conversions of the 206L in the early 1990s, Bell produced the equivalent Bell 206LT TwinRanger based on the 206L-4.Only 13 206LTs were built between 1994 and 1997.The 206LT was replaced in Bell's lineup by the Bell 427, a mostly-new development of the Bell 407, itself a four-bladed single-engine derivative of the 206L.