Reynolds Metals Co., the nation's second-largest aluminum producer, yesterday reported a loss for the fourth quarter and 1981 profits less than half of those for 1980, and said it expects another loss during the first quarter of this year.

Separately, Fairchild Industries Inc., a major aerospace and communications firm based in Montgomery County, said it expects a sharp drop in fourth-quarter profits.

The Richmond-based metals company reported net income for the year of $86.7 million ($4.40 a share) compared with $180.3 million ($9.32) for 1980. Sales were $3.5 billion compared with $3.7 billion.

For the fourth quarter, the company had a loss of $21.1 million compared with a profit of $33.5 million ($1.72). Revenues were $778.7 million compared with $906.2 million for 1980.

The net loss for the fourth quarter included foreign currency translation and exchange losses of $300,000 compared with gains of $6.4 million (33 cents) in the fourth quarter of 1980.

"The combination of the recession and a cost price squeeze adversely impacted our markets and performance in 1981," said Chairman David P. Reynolds. "With these conditions continuing in the early part of 1982, we anticipate an operating loss in the first quarter."

But Reynolds added that "with the recovery in the economy, we anticipate improved performance for the balance of the year."

Aluminum shipments for the year were 1.13 million tons compared with 1.32 million tons in 1980.

Meanwhile in Germantown, Fairchild Industries said that, based on preliminary unaudited results, it expects 1981 earnings to be $64.3 million ($3.48 a share) compared with $54.5 million ($4.02) for 1980. Revenues are expected to be $1.3 billion compared with $906.2 million.

For the fourth quarter, earnings are expected to be $4.6 million (25 cents) compared with $15.6 million (97 cents). Revenues are expected at $359 million, up from $285 million.

Earnings per share were affected by an increase in the number of shares outstanding from 13.5 million in 1980 to 18.5 million in 1981. The increase was because of the acquisition last year of VSI Corp., a California-based commercial and industrial products company, a company spokesman said.

Fourth-quarter earnings were hurt by development and start-up costs on commercial aircraft programs, company officials said, citing difficulty in bringing its Boeing 757 aircraft sections into production. The company said it expects positive operating margins on the remaining work connected with the 757s.

The company said it also experienced problems with its other commercial aircraft projects such as the Fairchild Swearingen Merlin and the Metro Turboprop series.

Solon Automated Services, which supplies laundry equipment services to apartment buildings and owns a Vermont ski resort, reported earnings for its fourth quarter ended Sept. 30 of $1.315 million (46 cents a share) compared with $1.239 million (43 cents). For the year ended that date, earnings of the D.C. firm were a record $6.379 million ($2.23) compared with $5.374 million ($1.88) a year before.

Revenues rose from $17.9 million to $21 million in the quarter and from $73.9 million to $85.8 million in the full fiscal year.

The company said that revenues and earnings from laundry equipment manufacturing and services had grown steadily and that revenues and earnings from the company's Sugarbush Valley ski resort in Vermont were up significantly.

Bank of Virginia Co. reported 1981 income before securities transactions of $16.4 million ($2.93 a share) compared with $13.2 million ($2.40) for all of 1980. Fourth-quarter income before securities transactions was $5.3 million (95 cents) compared with $2.7 million (47 cents).

Software AG Systems Group Inc. of Reston reported earnings for the second quarter ended Nov. 30. of $739,000 (12 cents a share) compared with $683,000 (15 cents). Revenues were $6.6 million compared with $4.6 million for the same period last year.

For the six months ended Nov. 30, earnings were $1 million (17 cents) compared with $1.5 million (32 cents). Revenues were $11.1 million compared with $9.2 million the year before.

Earnings per share for the second quarter and six months were affected by an increase in shares.