CBS Still Ahead in Ratings Derby : Television: The network takes the second week of the new season; NBC shows signs of weakening; beleaguered Roseanne Arnold is No. 1.

CBS easily swept to its second weekly ratings victory of the new prime-time season, led by “Murphy Brown,” while NBC’s longtime comedy base anchored by “The Cosby Show” and “The Golden Girls” showed signs of weakening.

With “Cosby” slipping to 17th place and “The Golden Girls” nose-diving to 55th in its new 8 p.m. time slot, NBC finished in the basement last week among the Big Three networks, according to figures released Tuesday by the A. C. Nielsen Co.

NBC, which has won the ratings race for six consecutive seasons, built its success around “Cosby” on Thursdays and “The Golden Girls” on Saturdays.

Thus far in the new season, CBS’ Monday lineup has replaced NBC’s longtime powerhouse Thursday schedule as TV’s strongest night. However, NBC’s “L.A. Law,” a potent Thursday entry, has yet to make its season debut, and the slipping network is counting on it heavily. The Emmy-winning series returns Oct. 10.

Only one NBC series, “Cheers,” made it into the Top 10. But, like the previous week, all four of CBS’ Monday sitcoms--”Murphy Brown,” “Designing Women,” “Major Dad” and “Evening Shade”--placed in the Top 10. CBS’ other series on that night, “Northern Exposure,” tied for 11th with another of the network’s hits, “Murder, She Wrote.”

ABC’s “Roseanne” was the No. 1 show of the week, but the network now must cross its fingers that the series won’t be affected by the lastest controversy involving the star, Roseanne Barr Arnold, whose disclosure that she suffered child abuse has been denied by her parents.

In 1990, the actress was involved in a national uproar after screeching her rendition of “The Star-Spangled Banner” at a San Diego Padres baseball double-header. The furor also involved several of her other gestures, including spitting, and she was criticized by President Bush.

The star recently told of childhood abuse at a gathering in Denver, and she deals with the subject again as the cover story of the latest People magazine. However, her parents, Helen and Jerome Barr, denied the allegations on “CBS This Morning.”

“Roseanne” not only survived last year’s uproar over the national anthem, but seemed to be building again to a blockbuster level that is ABC’s key to finishing atop the ratings.

It was a bad weekend for NBC. On Friday, it was a distant last among the Big Three as its lineup of “Real Life With Jane Pauley,” “Expose,” “Dear John,” “Flesh ‘n’ Blood” and “Reasonable Doubts” managed only a 6.8 ratings average. (One rating point equals 921,000 homes.)

Bush’s Friday speech at 8 p.m. EDT pushed back all network shows by half an hour. But NBC at least could look for some hope from “Reasonable Doubts,” a new cops-and-the-law show with Marlee Matlin and Mark Harmon, which built on the earlier flops and registered a 16% audience share, the network’s best showing of the night.

On Saturday, NBC’s “The Golden Girls” attracted only 21% of the audience--far below its usual level. Although NBC won the night handily, it was hardly overwhelming as “The Torkelsons” earned 19% of viewers, “Empty Nest” 27%, “Nurses” 24% and “Sisters” 21%.

On Sunday, NBC suffered the embarrassment of finishing fourth--behind CBS, ABC and even the smaller Fox network--as four of its new series, “The Adventures of Mark and Brian,” “Eerie, Indiana,” “Man of the People” and “Pacific Station,” went nowhere in the ratings.

The Sunday night movie battle was won by CBS’ “Mission of the Shark,” a World War II navy story, which outscored ABC’s “Keeping Secrets,” in which Suzanne Somers played herself in a tale of her difficult childhood.

CBS now is a substantial 1.6 ratings points ahead after only two weeks of the season. For last week, it earned a 13.4 rating and 23% audience share. ABC, which benefited from the season premiere of “Doogie Howser, M.D.,” in which the title character lost his virginity, was second for the week with a 12.5 rating and a 21 share. NBC had a 12.3 rating and a 21 share.

Fox TV, meanwhile, continued to look impressive with an 8.2 rating and 14% of the audience. Once again, it fared strongly on Thursdays, finishing second only to NBC with “The Simpsons,” “Drexell’s Class” and “Beverly Hills, 90210.” “The Simpsons” has effectively brought “The Cosby Show” back to Earth in their publicized head-on competition.

On Sundays, meanwhile, Fox continued to find strength from “Married . . . With Children” (27th among 97 shows for the week) and “In Living Color,” a soaring success as an offbeat, satirical entry; it came in 30th and held its own even against the formidable “Murder, She Wrote.”

With ABC offering many of its season premieres last week, the Big Three attracted 65% of the total audience, up 2% over the same week in 1990.

The total was also a tad up from the 64% that ABC, CBS and NBC registered in premiere week this fall, when they hit another low compared to past seasons. Adding Fox in the new configuration of network TV, however, brings the total to about the 70% level or higher.

Despite a bad week overall, NBC at least could point with some pride to its devotion to the 10 p.m. dramatic form as “Law & Order,” “Quantum Leap,” “Sisters” and “Reasonable Doubts” all pulled respectable shares of the audience despite tough time slots.

“Reasonable Doubts” was on twice, pulling 23% of the audience in a special preview in the regular “L.A. Law” slot.

Much of NBC’s season may depend on another drama, the new entry “I’ll Fly Away,” which premieres with a two-hour pilot Monday and deals with a 1950s Southern family during the start of the civil rights movement.

The new ABC drama “Homefront,” about GIs returning from World War II, also did respectably in its premiere last week as 20% of the audience tuned in.