 "Bunker Hill's" armor protecting the machinery spaces below had proven effective.A significant improvement of "Essex"-class ships like the "Bunker Hill" over the other US carriers at the time was that they were equipped with a more heavily armored deck, plus a second armored deck on the hangar level designed to detonate bombs before they reached the vital machinery and electronic spaces below.Ogawa's bomb blew a large hole into the flightdeck close to the bridge.