Someone (the name escapes me, but was located in Broussard, LA) had an STC for a conversion of the D model to an Allison C28 or C30 engine. I can't remember if there was a model change or not. It never became very popular.
When I transitioned into the AS350D I thought it was heaven at first - a heater, 3.5 hours fuel, fast, comfortable, roomy, and very responsive. The B206 paled in comparison. And it was a nice ride as long as everything worked the way it was supposed to. When things started to go wrong, it could be a handful. I still recall doing a postflight and wondering where the water on the engine deck had come from. Turned out to be kerosene, and the fuel manifold that was mounted behind the combustion chamber, in a circle around it, had sprung a leak, spraying fuel directly onto the combustion chamber. The good news was that the leak was large enough that the amount of kerosene being sprayed provided cooling, and was too heavy to ignite.
