Fairchild Industries Inc. reported a fourth-quarter loss of $21.97 million ($1.86 a share), compared with a profit of $11.4 million (60 cents) it earned in the same quarter of 1983.

The Chantilly, Va.-based company, which manufactures military and civilian aircraft, among other products, reported fourth-quarter revenue of $262,479, up slightly from $260,826 in the 1983 period.

Fairchild attributed its fourth-quarter shortfall to a pretax reserve of $50 million that it set up because of higher-than-expected costs involved in the development and production of the Saab-Fairchild 340 commuter turboprop airplane.

For the year, Fairchild reported profits of $1.38 million (82 cents), down 95 percent from $28.4 million in 1983. Sales for the year were $898.8 million, up slightly from $891.5 million during 1983.

Although the company had net earnings for the year, it reported a loss per common share because of a change in accounting practices. Because of the standard, the company reported lower restated earnings per common share for the first three quarters of 1984, and for all of 1983 and 1982.

James River Corp., said its earnings for the third quarter ended Jan. 27 dropped to $14.9 million (41 cents), down 28 percent from the $20.7 million (60 cents) reported during the same quarter last year.

The Richmond paper company said third-quarter sales increased 5 percent to $582.6 million, up from $556.6 million during the year-earlier period.

James River blamed its drop in earnings on reduced demand for specialty industrial and packaging papers caused primarily by customer inventory corrections as well as a weakening in the industrial segment of the economy. Declines in prices for market pulp and for uncoated printing paper caused major reductions in earnings in these areas of James River's business, the company said.

For the nine months, net income was $67.3 million ($1.92) on sales of $1.847 billion, up from $65.9 million ($2.02) on sales of $1.6 billion. The company said performance for the nine months was adversely affected by high operating costs associated with the introduction of Northern towel and tissue products into the Northeast.

Washington Real Estate Investment Trust said fourth-quarter net income rose 8 percent to $2.147 million (40 cents), compared with $1.988 million (37 cents) during the same period of 1983.

For the year, the Bethesda firm said its net income dropped 40 percent to $8.4 million ($1.56), compared with $14.13 million ($2.77) for 1983. The company said its higher net income for 1983 included a gain of $7.58 million ($1.49) realized from the sale of the Washington Circle Inn.

Penril Corp., the Rockville manufacturer of high-technology computer data communications equipment, reported a first-quarter profit of $770,000, up 63 percent from $473,000 during the same period in 1984.

First-quarter revenue rose to $21 million from $10.49 million.

American Fuel Technologies Inc., a supplier and marketer of ethanol, reported a loss of $728,209 (6 cents) for the second quarter ended Nov. 30, compared with a loss of $1.95 million (18 cents) during the year-earleir period.

The Federalsburg company said second-quarter sales fell to $1.4 million, compared with $2.29 million.

For the six months, American Fuel reported a loss of $1.3 million (11 cents) on sales of $2.4 million, compared with a loss of $1.9 million (8 cents) on sales of $3.998 million during the same period of 1983.