The engines went from 2,600 r.p.m. to 2,900 r.p.m.—then suddenly, crazily, dropped to 2,000. With a surge and a howl, engines No. 1, 2, and 3 returned to 2,900. The unnerving sound reminded Reese of a race car revving up in a series of prestart bursts. Soon, No. 4 joined the howling and wandering.