The family of a retired Bethesda business executive who has been missing since his plane left a Richmond airport Friday has called in a psychic to help in the search and offered a $5,000 reward for the individual who locates his downed airplane.

Friends of the Chester William Martin Jr. family were reluctant yesterday to discuss the psychic's role in the search. "When you're down to your last straw, what do you do?" asked Mike Colgan of Manassas.

Martin, 69, "could be 10 miles from here. We just can't see him from the air," said Colgan's father, Virginia state Sen. Charles J. Colgan, who is a business associate of the missing man.

Martin's family offered the reward to induce people to "look in their own back yards," said Charles Colgan, president of Colgan Airways Corp., a commuter airline. Martin is a major stockholder in the airline, and Colgan was taking an active part in the air search.

Civil Air Patrol search officials said Martin's plane probably went down on a farm or in a pond, most likely in a heavily wooded area where it cannot be seen from the air. "I haven't seen foliage this thick since Vietnam," said Charles Colgan Jr., another son of the senator and a searcher.

Martin, a former chairman and president of the Pepsi-Cola Bottling Co. of Washington, has not been heard from since he flew out of the Chesterfield County Airport near Richmond on Friday. He was headed for Fredericksburg, where he was to spend the night before flying to Manassas Saturday.

The search for Martin, a former president of the Washington Board of Trade, reportedly was centered yesterday on a wooded area northwest of Richmond.