Columbia First Federal Savings and Loan Association of Washington reported a $1.9 million profit for its fiscal 1986 second quarter, after suffering a loss of $32,000 in the same period a year ago. The association cited falling interest rates as one of the major reasons for the improved results.

Earnings per share were 77 cents for the 1986 second quarter. Columbia First converted from a mutual to a stock association last fall.

For the first half of the fiscal year, ended March 31, Columbia First reported profits of $3.6 million ($1.48 a share), after a $1.3 million loss for the first half of fiscal 1985. As of March 31, Columbia First reported deposits of $972 million and total assets of $1.46 billion.

*Avemco Corp., whose subsidiaries provide insurance, financial and other services, reported that earnings grew 46 percent in the 1986 first quarter.

The company said net earnings for the three months ended March 31 totaled $2.3 million (76 cents) after $1.6 million (52 cents) in the 1985 first quarter. Revenues grew 47 percent, from $12.6 million to $18.5 million, Avemco said.

The company attributed the improved earnings in part to profitable growth in its three aviation distribution systems.

*Dominion Resources Inc., the holding company for Virginia Electric and Power Co., reported a slight dip in profits for the first quarter of 1986. Net income totaled $89.0 million (97 cents), compared with $89.5 million ($1.02) in the first quarter of 1985, the company said.

*Equitable Bancorporation of Baltimore reported that net earnings grew 17 percent during the first three months of 1986. The bank holding company said profits totaled $8.7 million (56 cents a share), from $7.4 million (52 cents) in the 1985 first quarter.

The company said earnings per common share have been adjusted for stock dividends. Equitable said a dividend of 17 cents will be paid on July 1 to holders of common stock.

Total assets were $3.9 billion as of March 31, up 17 percent from $3.3 billion the previous year, the company said.

*Media General, the Richmond communications company, said that earnings were virtually flat for the first quarter of 1986, with net income reported at $6.93 million (97 cents). That compared with $6.90 million (97 cents) in the 1985 first quarter.

Revenue rose 8.2 percent during the quarter from $139.9 million to $151.4 million, the company said.

Media General also said that long-term debt has risen sharply -- from $120.2 million to $193.7 million -- in the last 12 months, reflecting expenditures for construction of a cable television system in Fairfax County and its 40 percent investment in Garden State Newspapers Inc., a company formed in 1985 to acquire medium-sized daily newspapers. To date, Garden State has completed the acquisition of four newspapers, and two others have been announced.

"The lower plateau in Media General earnings continues to reflect our consolidation of the communication acquisitions and investments of the past four years," said James S. Evans, president and chief executive officer. "An earnings recovery is anticipated from the opportunities provided by these acquisitions and investments."

*USAir Group Inc., citing the continued proliferation of low fares, moved into the red in the first three months of 1986. The airline holding company said it lost $9.1 million (34 cents a share) for the three months ended March 31, after earning $10 million (41 cents) in the 1985 first quarter.

The company said revenues grew 3.2 percent during the quarter, from $394.5 million to $407.0 million.

Results for the first quarter include a pre-tax, non-operating gain of $4.7 million on disposition of flight equipment, compared with a similar gain of $1.9 million for the first quarter of 1985, the company said.

*Crown Book Corp. reported an 11 percent drop in profits for its fourth quarter, which ended Jan. 31. Earnings from the 190-store discount-book chain dropped to $3.6 million (44 cents) from $4 million (50 cents) for the same period a year ago.

Sales for the quarter, though, increased by 24 percent to $51.5 milion from $41.6 million. Crown officials were not available to explain the drop in profits.

For the year, Crown's profits increased 3 percent to $6.7 million (83 cents) from $6.5 million (81 cents) the previous year.

Revenues for the year increased 20 percent to $137.3 million from $114.4 million the previous year.

*MBI Business Centers Inc. reported a 33 percent drop in profits for its fourth quarter that ended Jan. 31, to $487,000 (10 cents) from $724,000 (24 cents) a year earlier. Sales for the quarter rose 34 percent to $23.7 million from $17.6 million.

For the year, MBI posted a 19.5 percent increase in earnings for its fiscal year that ended Jan. 31, with profits climbing to $2.4 million (60 cents) from $2 million (75 cents) last year.

Sales for the year rose 89 percent, from $50.5 million to $95.7 million.