Communications Satellite Corporation yesterday reported net income of $20.109 million ($2.51 per share) for consolidated operations in the first quarter of 1981, but that figure includes a nonrecurring item in the amount of $11.769 million ($1.47).

The nonrecurring figures result from a change in accounting policy, specifically a shift as of Jan. 1, to a flow-through method of accounting for investment tax credits on property which is not considered public utility property. The effect of the change is to speed up the reporting of earnings from those investment tax credits.

Comsat said it adopted the change in recognition of the growth of its diversified businesses, net income for the first quarter represents an increase of $10.22 million ($1.27) from the same quarter a year ago.

Net income for the quarter, ignoring the change in accounting, amounted to $8.34 million ($1.04), a decline of $1.549 million (20 cents) from the same quarter a year ago and a decline of $1.377 million (18 cents) from the last quarter of 1980.

Comsat said the decrease from the first quarter of 1980 primarily reflected planned increases in costs related to Satellite Business Systems, a partnership of Aetna Life & Casualty, IBM and Comsat General Corp. (a wholly owned subsidiary of Comsat). SBS was formed to provide advanced communications satellite services for business customers.

The decrease from last quarter in 1980 reflected a reduction in charges by Comsat for its services through the Intelsat System.

Comsat's board of directors declared a quarterly dividend of 57 1/2 cents a share, payable June 8 to shareholders as of May 8.

Operating revenues for the first quarter of 1981 were $77.934 million, up by $7.904 million from the first quarter of 1980. Operating expenses for the first 1981 quarter increased $7.807 million from the same quarter a year ago to $67.340 million.

The Black and Decker Manufacturing Co. reported a 4 percent decline in sales and a 64 percent drop in earnings per share for the second quarter of fiscal 1981.

The company said that sales for the quarter ended March 29 were $375.5 million compared with $389.6 million in the second quarter of fiscal 1980. Net earnings were $9.5 million (23 cents a share) compared with $27.2 million (64 cents) in the second quarter of fiscal 1980.

Six-month sales were $787.1 million, up 1 percent from $780.8 million a year earlier. Net earnings for the six-month period were $43.7 million ($1.04) compared with $53.5 million ($1.27) a year earlier.

"Depressed economic conditions in most European markets and the U.S. have been the major factor behind our sluggish sales and profit performance," said Francis P. Lucier, chairman and chief executive officer of Black & Decker.

The Ryland Group, Inc., one of the nation's largest builders of suburban homes, yesterday announced first-quarter earnings of $453,000 (15 cents a share), a decline of more than 60 percent from earnings of $1.272 million (41 cents).

"Discount points that we are paying now on customer mortgages are the main reason our profits are down," said James P. Ryan, chairman of the Ryland Group.

Settlements in the first quarter of 1981 were $52.747 million compared with $52.904 million in the same quarter a year ago.