Can anyone explain the Bell numbering system?
Sure, the Model 30 and 47 may have just been the sequence of drawings on pieces of paper, but how did the rest of them evolve?
204 - B model Iroquois. 2 blades, turbine model number 4
205 - d, h models and the civvy version, progressing by one
206 - well, at least the number follows, but the machine is much smaller
212 - maybe 2 blades, 2 engines?
412 - ah hah! Logic! 4 blades, 2 engines
214 - ooops... lost it again. Maybe 2 blades, 1 engine, 4 dozen of them sold to the Shah of Iran.
407 - 4 blades, and 1 model later than a 206?
427 - 4 blades, 2 engines, 7 pob ?
690 - oh, boy - 6 blades - YES! 9 passengers? - maybe.. 0 hope? definitely.