CBS Entertainment Friday announced that in mid-March it will introduce a two-hour block of situation comedies on Tuesday nights between 8 and 10 ...

CBS already has a similar block on Monday nights, which will undergo a slight revision with the mid-March changes, which include the introduction of four new sitcoms ...

The establishment of a second night of comedy in the 8 to 10 timeslots marks a major strategic retreat at CBS, once the home of a great (and sometimes not-so-great) comedy tradition that usually ensured the annual primetime ratings leadership among the three major networks ...

But sitcom development lagged at CBS, starting in the late 1970s, when ABC suddenly moved up through the pack with bright new sitcoms (e.g., "Laverne & Shirley," "Happy Days," "Three's Company") for a brief stay at the top. In the early '80s, CBS recouped, even though "M*A*S*H," "Archie Bunker's Place" and "The Jeffersons" were fading ...

But by the mid-1980s, doormat NBC had seized the sitcom strategy to race to the top of the ratings heap. With its strong Thursday and Saturday laugh lineups, NBC has become unbeatable in recent years ...

New CBS Entertainment president Kim LeMasters recently pledged to get his network back in the comedy business on at least two nights as part of an overall strategy to restore broad audience appeal to the CBS lineup, which had skewed to an older viewership with a mix of solid, if sometimes stolid, one-hour dramatic series ...

Joining the revised Monday and Tuesday lineups in March will be four new sitcoms: "Eisenhower & Lutz," "Trial and Error," "The Dictator" and "Coming of Age" ...

To make way for the four new half hours, the network will move CBS News' new "48 Hours" from Tuesday at 8 to Thursday at 8 and "Jake and the Fatman" from Tuesday at 9 to Wednesday at 9 ...

In addition, "Frank's Place" will move from its spanking new 9:30 Monday slot (which starts tonight) to 9:30 on Tuesday in the new comedy lineup; "Tour of Duty" will move from Thursday at 8 to Saturday at 9 to make room for "48 Hours"; and "Magnum, P.I." will move from 9 back to 8 Wednesdays ...

To further accommodate the upcoming changes, "The Law & Harry McGraw" will be Disappeared after this Wednesday's broadcast at 10 (who or what replaces Harry for the nonce remained something of a mystery Friday), while "Houston Knights" will head for Hiatus after its Saturday, March 12, appearance at 9 p.m. The new comedies: ...

"Eisenhower & Lutz" stars Scott Bakula, Henderson Forsythe and DeLane Matthews in the story of a one-man Palm Springs law firm. The "Eisenhower" in the firm's name doesn't exist but it sounds good in one of the late president's former vacation spots ...

"Trial and Error" stars Eddie Velez and Paul Rodriguez as two lifelong Hispanic best friends who reunite as roommates after attorney Velez joins a prestigious L.A. law firm and Rodriguez has become "the hottest T-shirt hustler on Olvera Street" ...

"The Dictator" stars Christopher Lloyd as a deposed South Sea island dictator now running a laundromat in Queens with his family ...

"Coming of Age" stars Paul Dooley as a "reluctantly retired airline pilot" who with his wife (Phyllis Newman) buys a home in an Arizona retirement community ...

The revised CBS schedule with program changes IN CAPS and start dates:

Monday: "Kate & Allie" at 8; "Designing Women," 8:30; "Newhart," 9; "EISENHOWER & LUTZ," (March 14) 9:30; "Wiseguy," 10 ...

Tuesday (all changes March 15): "TRIAL AND ERROR," 8; "THE DICTATOR," 8:30; "COMING OF AGE," 9; "FRANK'S PLACE," 9:30; "Cagney & Lacey," 10 ...

Wednesday (both changes March 16): "MAGNUM, P.I.," 8; "JAKE AND THE FATMAN," 9; "The Equalizer," 10 ...

Thursday: "48 HOURS," (March 17) 8; "Simon & Simon," 9; "Knots Landing," 10 ...

Friday: "Beauty and the Beast," 8; "Dallas," 9; "Falcon Crest," 10 ...

Saturday: "High Mountain Rangers," 8; "TOUR OF DUTY," (March 19) 9; "West 57th," 10 ...

Sunday: "60 Minutes," 7; "Murder She Wrote," 8; CBS Sunday Movie, 9 ...

ABC Entertainment announced its own mid-March schedule changes a week ago. NBC Entertainment is expected to announce spring revisions of its number one primetime lineup later this week ...

Now This Channel 9 has named Henry K. Yaggi III to the new post of vice president and station manager. He had been vice president and general sales manager at the station ...

The move follows the appointment of Hank Price, WUSA's vice president for programming and marketing, as vice president and general manager of WFMY in Greensboro, N.C., another Gannett-owned station ...

In divvying up Price's old job, station president Ron Townsend also increased the responsibilities of Sandra Butler-Jones, vice president of broadcast operations, to include syndicated programming. Promotion manager Mark DeSantis adds the graphics and arts departments as well as daily and long-range promotion to his responsibilities ...

Butler-Jones has been responsible for local program production, CBS network relations, program standards and practices, licensee renewal, production facility scheduling and community affairs ...

In taking on the key syndication assignment, Butler-Jones is expected to appoint a community affairs manager in charge of locally produced programming and community affairs ...

In his new post Yaggi will be responsible for engineering, marketing and research, programming, sales and traffic ...

"In the last two years," Townsend said yesterday from Phoenix, where he is attending a CBS affiliates meeting, "the business has become much more complex. In the restructuring, Hank will report directly to me along with Dave Pearce, vice president for news." Townsend will also continue to oversee finance ...

Townsend himself had served as station manager at Nine when the Evening News Association owned then-WDVM. But the job was eliminated after Gannett assumed control a couple of years ago, when Townsend was named general manager of the station ...

Yaggi, general sales manager at Nine since 1979, has been in broadcast sales for more than 18 years. Butler-Jones first joined Nine in 1980 ...

Now This

David Letterman's sixth anniversary primetime special on NBC Thursday night earned a 19.3 national Nielsen rating and a 31 percent audience share (each rating point represents 886,000 TV homes) ...

NBC estimated he drew more than 40 million viewers, Letterman's largest audience ever. His late night show averages about 4.7 million viewers, according to the network. In Washington, Letterman did a 21.4/34 on Four (a local ratings point stands for 16,116 homes) ...

Earlier that night on CBS, Democratic presidential candidate Lyndon H. LaRouche Jr.'s paid political half hour averaged a low calorie 4.9 national Nielsen rating and a 7 percent audience share. In Washington, LaRouche did somewhat better, attracting a 6.3/9 on Nine ...

In the Arbitron overnights in 14 major markets, LaRouche averaged only a 3.4/5 in the big cities. Washington and Houston had the biggest turnouts, both averaging a 5.0/8...

According to ARB, LaRouche drew the least attention in Los Angeles (2.1/3) and Denver (2.1/4) ...

CBS Entertainment is negotiating with "Wheel of Fortune" host Pat Sajak to host a late night talk show, opposite Johnny Carson on NBC, as the network looks for alternates to its current action drama lineup ...

Meanwhile, ABC, which never has figured out what to do with audiences after "Nightline" signs off at midnight, has two one-hour pilot projects that could be ready for a look-see sometime next month. Network sources said both late night pilots are "compatible" with "Nightline," but beyond that, details are sketchy ...