Share prices of the aviation start-up have fallen 45%, but read this before you decide whether to buy.Archer Aviation (ACHR +4.58%) is one of a handful of recent aviation start-ups trying to develop an electric vertical takeoff and landing (eVTOL) aircraft. The company has made quite a bit of progress toward this lofty goal, but has also taken investors on a wild, turbulent ride so far this year.NYSE : ACHRArcher AviationToday's Change( 4.58 %) $0.32Current Price$ 7.18Key Data PointsMarket Cap$5BDay's Rang ...