WASHINGTON -- Likening sexual assault in the Air Force's ranks to a cancer, the service's top officer resolved Wednesday to tackle the problem by screening personnel more carefully and ending bad behaviors like binge drinking that can lead to misconduct.But Gen. Mark Welsh, the Air Force chief of staff, underscored the challenge by telling a House oversight committee that the service recorded a disturbing number of reports of sexual assault last year even as it worked to curb misconduct as a sex scandal continues to unfold at its training headquarters in Texas. Dozens of young female recruits and airmen at Lackland Air Force Base near San Antonio were victimized by instructors who sexually harassed, improperly touched or raped them.Most difficult, Welsh said, is transforming a culture in which victims are often reluctant to report what happened because of guilt, shame or fear they won't be believed."Why, on what was undoubtedly the worst day of a victim's life, did they not turn to us for help?" Welsh said during testimony before the House Armed Services Committee. "We are missing something fundamental in the human-to-human interaction that will allow them to feel safe enough to come to us and report."An Air Force veteran who was sexually assaulted while serving -- but not at Lackland -- described how intimidating it is for young enlisted personnel to speak up."You're stuck," Jennifer Norris told the committee. "If you want a career, you don't want to say anything because you get retaliated against." Norris, who said she medically retired in 2010 with post-traumatic stress disorder, said the Air Force and the other military branches have a sexual assault epidemic and a broken system of justice.The scandal at Lackland, now known as Joint Base San Antonio-Lackland, continues unfolding nearly two years after the first victim came forward. All U.S. airmen report to Lackland for basic training. The base has about 500 military training instructors for about 35,000 airmen who graduate every year. About 1 in 5 recruits is a woman; most instructors are men.The initial results of Air Force investigation released in November described abuses of power by instructors who took advantage of a weak oversight system to prey on young recruits.The inquiry has found that 32 military training instructors allegedly engaged in inappropriate or coercive sexual relationships with 59 recruits and airmen at Lackland, according to the Air Force.