While flight hours are down an estimated 20 to 30 percent from last year, business aviation accidents declined by nearly 50 percent during the first three quarters versus last year, according to statistics released yesterday by industry safety analyst Robert E. Breiling Associates of Boca Raton, Fla. In the first nine months, U.S. business jets and turboprops experienced 27 accidents, including four fatal, as opposed to 52 accidents–17 of them fatal–in the same period last year. In the business jet category, the numbers shrank from 19 accidents, including five fatal for the first three quarters of last year, to just four nonfatal crashes so far this year. The turboprop category saw the number of fatal accidents fall from 12 over the first three quarters of last year to four during the same period this year, while the overall number of turboprop accidents declined from 33 to 23.