Sperry Corp.'s net income rose 10 percent in the last quarter of 1985, but would have declined except for a big charge against earnings in the year-earlier period, the computer maker and defense contractor said yesterday.

At the same time, higher earnings were reported by AMR Corp., American Airlines' parent firm; Bristol-Myers Co.; Ameritech and International Paper Co. Rockwell International Corp., RCA Corp., PPG Industries Inc. and Tandem Computers Inc. reported lower earnings.

Sperry had net income of $67.9 million ($1.20 a share) on revenue of $1.4 billion in its third quarter ended Dec. 31, up 10 percent from $61.7 million ($1.10) in the same quarter a year earlier. However, the 1984 quarter was hurt by an after-tax charge of $12.7 million in connection with the resolution of an arbitration proceeding initiated in 1981 with the government of Israel.

Sperry, based in New York, said its aerospace and defense operations were hurt by a strike at its operation in Great Neck, N.Y.

*Dallas-based AMR Corp., the nation's second-largest airline company, had net earnings of $345.8 million ($5.94) in 1985, compared with $233.9 million ($4.37) in 1984.

Fourth-quarter net earnings for 1985 were $24.4 million (39 cents), compared with $23.6 million (37 cents), AMR said.

*Bristol-Myers Co., one of the nation's largest household and health-care products manufacturers, said it had net earnings of $130.9 million (95 cents) in the quarter ended Dec. 31. That compared with $117.7 million (86 cents) for the same period of 1984.

For the year, Bristol-Myers had net earnings of $531.3 million ($3.86), compared with $472.4 million ($3.45) a year earlier.

*Rockwell International Corp. reported net income for its first fiscal 1986 quarter, ended Dec. 31, was $125.8 million (84 cents), compared with last year's first quarter net income of $140.5 million (94 cents).

Sales in the first quarter were $2.8 billion, compared with sales of $2.4 billion in the comparable period a year ago.

*Ameritech, parent of the Bell companies serving Illinois, Indiana, Michigan, Ohio and Wisconsin, reported a 22.3 percent increase in fourth-quarter earnings, with profit at $248.1 million ($2.55) on revenue of $2.28 billion. During the comparable period of 1984, earnings were $202.9 million ($2.07) on revenue of $2.13 billion.

*RCA Corp., parent company of NBC and soon to be child of General Electric, reported its fourth-quarter earnings were higher.

Earnings for the quarter ended Dec. 31 totaled $94.4 million ($1), compared with $102.8 million ($1.03). For the year, earnings rose 8 percent to $369 million ($4.04), compared with $341 million ($3.30) the previous year.

*International Paper Co. said it earned $44 million (77 cents) in the fourth quarter of 1985, compared with a $74 million loss a year earlier, attributing the gain to a spin-off of 6 million acres of timberland.

For the year, IP earned $133 million ($2.16), on sales of $4.5 billion, contrasted with $120 million earned ($1.88) a year earlier on sales of $4.7 billion.

*PPG Industries Inc. reported lower fourth-quarter earnings and flat income for 1985. Fourth-quarter net income was $59 million ($1), down 10.6 percent from $66 million (94 cents) in the last quarter of 1984. Per-share income rose because PPG repurchased almost 10.8 million shares in September.

PPG said its net income for 1985 was unchanged from 1984's $303 million. Per share earnings rose to $4.54 from $4.33.

*Tandem Computer Inc., based in Cupertino, Calif., said its net income was $11.6 million (28 cents) in its first fiscal quarter ended Dec. 31, down from $14 million (34 cents) a year earlier. Net income slipped 17 percent in the quarter despite a 6.5 percent gain in revenue.