PHOTO OF THE MONTH BY CHRIS ROSE THE JOBY S4. THIS EVTOL AIR TAXI COMBINES TRADITIONAL, CARBON-FIBER WING AND CONTROL SURFACES WITH six electric tiltrotors-two on each wing and two on its V-tail. The motors not only drive the propellers, they also control the engines' tilt and propeller pitch and run the coolant pumps. Power for the motors comes from four liquid-cooled battery packs, two in each wing, each with seven individual battery modules. Knowing that quiet operation will be a critical issue to public acceptance, Joby has fitted the S4 with long, specially shaped propellers that turn slowly (250 to 800 rpm) to create barely perceptible noise levels (an average of 45.2 dBA at 1,640 feet) in an urban environment. During takeoff, one observer likened the Joby's noise level as that of an electric weedwhacker.-Thomas A. Horne FLIGHT TRAINING MAY 2023 21