Channel 4 announced yesterday it is abandoning its multi-million-dollar experiment in a two-hour early evening news program and will move to a one-hour 5:30 to 6:30 p.m. local news show in January. The "NBC Nightly News" will be re-scheduled at 6:30.

Jim Vance and Jim Hartz will co-anchor the 5:30 segment each night while Sue Simmons will become co-anchor with Hartz at 11. WRC will also drop at least eight free-lancers as a result of the time reduction.

Robert S. Walsh, vice president and general manager of WRC, said the "move is being made in the wake of audience studies which show area viewers prefer a single hour of news in the evening."

But industry sources indicated yesterday that the cutback at the NBC-owned station also is directly connected to the recent economy wave instituted by Edgar H. Griffiths, president and chief executive officer of RCA Corp., NBC's parent, which has sent shock waves through the giant communications firm.

NBC reportedly invested more than $2 million in preparations for the expanded news show, which began in July 1976, filling the 5-to-7 p.m. time slot five nights a week.

Similar two-hour shows on NBC-owned stations in New York and Los Angeles both reportedly have done better financially than the Washington operation.

In the late 1960s, WRC lost its No. 1 rating in the local news market and the station has failed to muster a successful counter-attack on No. 1 WTOP in the early evening news competition.

It also has trailed WJLA at 6 o'clock recently - although both Channels 4 and 7 have gained on Channel 9 over the past year during the time pend according to the October 1977 hearings.

All three stations are competitive so far this year in the 11 o'clock news. Again, WRC and WJLA have gained viewers on WTOP over the past year.

Walsh, who was responsible for adding Jim Hartz to the WRC news team in May at a reported salary of $200,000 a year, yesterday noted the audience gain over the past 12 months.

"We've been moving up," he said. "Maybe not fast enough that it is definitely up. And Hartz has proven he's added strength for us. Now we have a tighter show and I think we have the best possible teams working now."

Network news officials in New York also have been unhappy over the competition at 7 p.m. between their John Chancellor, CBS' Evening News with Walter Cronkite - the runaway No. 1 network news show in Washington - and the ABC Evening News.

Chancellor's showing had suffered from the comparatively work "lead in" provided by Newscenter 4 from 6:30 to 7.

Thus, the shift of the NBC Nightly News to 6:30 probably also reflects another decision made in New York to make the network presence more visible in news-conscious Washington.

News directors at both WJLA and WTOP yesterday pointed out, though, that in their view the move only underscores the fact, as WJLA's Sam Zelman put it, that "Cronkite is unbeatable in this town."

Walsh made it clear that he does not consider Sue Simmons' move a demotion, pointing out that "we have major plans for her in the future."

The teaming of Vance with Hartz was viewed as a good move by rivals here, who noted that Vance consistently show up in audience surveys as one of the most popular anchors in the market.

As WRC pares down, the station has dropped all free-lancers from its news budget.

These include Ron Hendron, drama critic: Judy Bachrach, movie critic; and "rotating commentators" Tom Braden, Nick Thimmesch, Jeffrey St. John, Mark Shields, Mark Russell and Julian Barber.

In addition, consumer reporter Marian Burros will now do only two shows a week, including for the first time, occasional live segments at 11 p.m.

Jim Snyder, news director at WTOP, said the time change "will have no effect whatsoever on our news schedule from 5:30 to 7, I feel the people who do the news and the content of the news are much more important than the time period."

Snyder said he wasn't surprised by the cutback at WRC. "More expensive experiements have failed, so now they can try a less expensive method. I'm not being mean about this - I'm being your friendly accountant."

Zelman, whose Channel 7 news operation may add another half hour to its current 6 to 7 p.m. time slot, said the WRC action probably won't affect those plans.

He added, however, that "it sure influences some other plans for the future." Zelman said he feels the move will help both second-place WJLA and WTOP at 6 p.m. because WRC, staring at 5:30 p.m., will have only a "recap" at 6.

Walsh scoffed at Zelman' theory. We'll have a very hard news lead again at 6, don't worry about that." he said. "We've designed the show to have a fresh show at 6 and viewers won't miss anything."

Zelman said that he 'hates to see the availability of any local news diminish in this market. WRC had a good broadcast with a big budget and it's difficult to say why it didn't click."

Walsh said he plans to move "The Mary Tyler Moore Show" from its current 4:30 slot to 5 p.m. as a lead-in for the revamped news show. He said no decision has been made on what entertainment programs will replace Moore at 4:30 and "NBC Nightly News" at 7.

Walsh said that a survey of 400 viewers conducted during the first two weeks of November showed 230 preferred a one-hour news show. He said the survey was a major factor in his decision.