If radio and television hadn't already invented Detective Joe Friday and his "just the facts" demeanor for "Dragnet," Richard A. King could be used as the prototype.

King, the former patrol officer, homicide detective and police chief who becomes Fairfax County executive when J. Hamilton Lambert retires Jan. 1, has the same dour expression as Friday. He has the same cool, calm manner. He doesn't smile a lot. He doesn't raise his voice.

King, who has been deputy county executive for public safety for 10 years, is about to start a new job that he didn't ask for and, if truth be told, he doesn't particularly want. But duty calls, and here are the facts: Dick King is a good soldier, and he's ready to serve.

"It wasn't on my agenda, but this county has been good to me," said King, 59. "I haven't spent almost 36 years of my life with the county to abandon it now."

The Board of Supervisors unanimously appointed King acting county executive until a permanent replacement is found for Lambert, the longtime chief executive officer whose sudden retirement was accepted by the board last month after a dispute over his salary.

King's tenure as the county's top administrator is likely to last at least 18 months, during which few major initiatives are expected. The current Board of Supervisors has said it will be the prerogative of the next board, which will be elected in November 1991, to select an executive. That means the search, which could take months, will not begin in earnest until January 1992.

It is not the first time the county has turned to King in a time of need. When he was appointed chief of police in 1975, his primary assignment was to rebuild public confidence in the force. At the time, the department was under investigation by the state and was rife with allegations of misconduct and racism.

King is credited with restoring the reputation of the department and helping modernize it. During his career, he created a minority hiring program despite resistance from the Board of Supervisors and was instrumental in introducing computerized record-keeping and dispatching.

Board members said King is seen as a source of continuity at a time when the county -- the area's largest jurisdiction with 800,000 residents and an annual budget of $2.3 billion -- is facing an uncertain economic and political future.

As such, political and government observers expect King, who was born in Highland Park, Mich., and moved to Fairfax in 1947, to serve primarily as a caretaker until the next county executive takes the helm. His salary will be raised from $110,000 a year to $118,000 when he assumes the post.

County staff members and supervisors said they expect King to be fair and firm in making sure supervisors do not use county staff members to gain an advantage over other supervisors or their opponents in the coming elections. The board also will redistrict the county next year -- carving new political boundaries based on updated census data -- which will intensify partisan politics.

"I think Dick is eminently suited to the job. He's going to be highly resistant to pressure," said board Chairman Audrey Moore (D). "We wanted experience, stability and judgment in that job, and we all trust him as having good judgment and institutional knowledge."

"He's a good election-year choice," said Supervisor Thomas M. Davis III (R-Mason), a likely challenger to Moore. "This is a guy who is serving on his own terms, who can leave any day he wants and get a big pension from the county . . . . He is the ideal guy to say 'Shove it' if things get out of hand."

The perception of King as a caretaker is born of a sense that, as someone who has spent the majority of his career in the police department, he might not possess the imagination necessary to pursue innovative measures.

King said many of the county's best ideas percolate up from the staff's ranks, adding, "I expect this county to be as creative in the future as it has been in the past, and I expect staff will make sound decisions."

One of the toughest challenges King faces is living up to Lambert's legacy. The two are holding a series of meetings and retreats with upper-level staff to ensure that the transition is smooth.

Although Lambert is as colorful as King is buttoned-down, the two are close friends. It is the sort of friendship, Lambert said, that comes from flying in helicopters together during hurricanes and working side by side when riots erupted at the D.C. prison complex in Lorton. They own a condominium together in Ocean City, Md., and two rental properties in Leesburg.

Like Lambert, King does not have a college degree, though he has taken courses in law, psychology and sociology from the University of Louisville, American University and the FBI National Academy.

Political and government observers say they expect several changes with the departure of Lambert, who in 31 years worked his way up from assistant county map draftsman to become one of the area's most admired administrators. Many observers believe that he had too much power and virtually ran the county.

Where Lambert frequently would make unpopular decisions on behalf of the board and take the political heat, observers say they expect King to forward controversial issues to the board and let it decide what action to take.

King said his priority will be sound fiscal management. As the county's chief operating officer, he must recommend to the board a balanced budget at a time when the slumping economy has hurt tax collection. A money crunch also is looming for capital projects such as roads and schools.

"It will be a significant challenge to maintain the county's financial integrity, which translates into the provision of services, in light of the current fiscal stress we're under," he said.

Another tough issue, he said, will be finishing the county's Comprehensive Land Use Plan that will guide growth. That plan, which the board is scheduled to consider in March, has been beset by trouble.

King said he has no interest in being the permanent executive and will continue as head of public safety. He said he would like to return to that post when his stint as acting executive is finished, or he might consider retiring.

King was eligible to receive his maximum pension from the police retirement fund in 1981, the year he was appointed deputy county executive. He deferred collecting the pension while working for the county, and is not enrolled in the pension plan for civilians, he said, because it would be improper to receive two pensions from the county.

Officials with the police retirement fund said King would draw an annual pension of about $46,000 for his years in the police department -- far less than Lambert's pension of $102,000.

King lives in Baileys Crossroads with his wife, Bobbi, whom he married in 1957. Their son, Edward, 18, graduated last year from JEB Stuart High School, and is a freshman at Randolph-Macon College.

Lambert said the county will be in good hands with King as the executive. "This is a man who has developed and run outstanding police and fire departments," Lambert said. "The deputies, the county attorney and the department heads are all familiar with his style of operation. He is wiser than a tree full of owls."