Avemco Corp. Chairman Arnold Johnson revealed yesterday that the Aircraft Owners and Pilots Association, which has a major insurance agreement for its members with the Bethesda firm, is seeking "improved" insurance terms.

As a result, AOPA counsel John Yodice has resigned from the board of directors of Avemco, Johnson told the annual meeting here. Avemco is the nation's largest insurer of private aircraft.

Negotiations on possible modifications to the AOPA-Avemco agreement, in existence for 15 years, will begin shortly. According to Johnson, the AOPA lawyer "would feel more comfortable" stepping down from the board while "the matter is under consideration."

Johnson told stockholders that if AOPA and Avemco fail to reach an understanding, the company could suffer an "adverse impact" for a year from reduced premiums. But Johnson said he expects the talks to be concluded with a continuing relationship, after which Yodice would return to the board.

Under the current AOPA agreement, concluded in 1974, Avemco Insurance is recognized and designated as the "approved" aircraft insurer for AOPA, and an aircraft financing subsdiary is the official financing firm.

Avemco pays AOPA a fee based on membership of the group and insurance premiums and finance charges. Avemco Vice President Robert Roe said negotiations with AOPA normally are conducted every two years or so on revising an agreement signed initially in 1962.

Roe said about half of Avemco's premium volume of more than $17 million reflects the AOPA endorsement. But business from AOPA members is not necessarily related to the group's endorsement, he added.