Piedmont Aviation Inc., the Winston-Salem-based airline that Norfolk & Western Railway is buying into heavily, more than doubled its profits last year although revenues went up just one-third, Piedmont officials reported yesterday.

Piedmont earned $32.6 million ($4.12 a share) in 1981, compared with $16.1 million ($2.72) for 1980. Revenues last year hit a record $560.8 million, up 34.2 percent from $101.8 million in 1980.

For the three months ended Dec. 31, Piedmont reported profits of $9.3 million ($1.16) compared with $5.2 million (80 cents) posted at the end of 1980. All earnings per share are fully diluted.

"Piedmont was able to overcome" adversities such as rising interest rates, falling ridership and the air traffic controllers' strike that hampered much of the industry during 1981, said T. W. Morton, senior vice president.

"We had strong traffic growth, particularly in the fourth quarter, which helped offset an industry tendency toward lower ticket prices. This response to Piedmont's marketing strategies was most gratifying," Morton said.

He attributed the firm's dramatic gains to expense controls that allowed revenues to increase faster than costs.

N&W of Roanoke, which plans to merge later this year with Southern Railway of D.C., has agreed to buy up to 20 percent of Piedmont stock, and N&W and Piedmont recently put directors on each other's boards.

Third-quarter and nine-month sales increases in 1981 helped Schwartz Brothers Inc. recover from losses the year before, representatives of the Lanham retail firm reported.

Schwartz, which operates 25 retail outlets through its Harmony Hut subsidiary, reported earnings of $669 (negligible per-share profits) during the quarter ended Oct. 31, on sales of $11.1 million. Those figures compare with a net loss of $63,463 (8 cents) for the same period of 1980. For the nine months, Schwartz had sales of $31.2 million, producing earnings of $10,907 (one cent), compared with sales of $22.2 million and losses of $433,953 (54 cents) for the first three quarters of 1980.

The Acacia Group of Companies, a D.C.-based insurance group that includes Acacia Mutual Life, reported record levels of sales, operational gains and insurance in force for 1981.

Net gains from operations, after taxes and before dividends, were $29.5 million, a 5.8 percent increase. More than $23.2 million in dividends was paid to policyholders and to beneficiaries, company officials said.

New insurance coverage increased 35 percent last year, to $962 million. Total life insurance in force grew $340.1 million to a record $5.1 billion, 7.2 percent more than in 1980.

Fast-food purveyor Gino's Inc., a Pennsylvania-based company that is being acquired by Marriott Corp., had a net loss for the fourth quarter of $289,000, Gino's officials said yesterday.

A year earlier, Gino's had earned $591,000 (23 cents) on sales of $77.6 million. Sales for the latest quarter were $76.2 million. For all of 1981, Gino's earned $577,000 (22 cents), down from $4.4 million ($1.65) in 1980. Sales increased in 1981 to $323.1 million from $321 million.