A surge in Christmas sales at Woodward & Lothrop Inc. stores anchored a stronger performance in the second half of the company's fiscal year, pushing profits for the fiscal year up 6 percent, the big retailer said yesterday.

The company said strong sales in December and January contributed to a 25 percent increase in earnings for its fourth quarter ended Jan. 29, while revenues rose 12 percent. Meanwhile, VSE Corp. of Alexandria reported an 84 percent increase in earnings on continuing operations for 1982, while Penril Corp. said its earnings had fallen in the second quarter and first half of its fiscal year.

Woodies said it earned $10.8 million ($4.39 a share) in the fiscal year, up from $10.2 million ($4.18) the previous year. Sales rose 7 percent to $357.5 million from $334.8 million.

For the fourth quarter, the company said it earned $7.6 million ($3.11) compared with $6.1 million ($2.51) a year earlier. Sales rose 9.7 percent to $116.8 million from $106.5 million in the period.

VSE Corp., an Alexandria-based engineering firm, said it earned $1.6 million ($1.11 a share) from continuing operations in 1982, up from $881,000 (60 cents) a year earlier. Revenues rose 4 percent to $50.6 million from $48.5 million. The company noted that in 1981 it had nonrecurring gains from discontinued operations of $1.4 million, making 1981's net income $2.3 million ($1.54).

For the fourth quarter, VSE said it earned $554,000 (38 cents), up 292 percent from $141,000 (10 cents) a year earlier. Revenues rose 2 percent to $12.2 million from $11.9 million the previous year.

Penril Corp., a Rockville-based high-technology company, said earnings in its second-quarter ended Jan. 31 fell 40 percent to $343,000 (17 cents a share) from $577,000 (29 cents) a year earlier. Sales also fell, to $9.7 million from $10.4 million. Six-month earnings dropped 26 percent to $640,000 (32 cents) from $808,000 (41 cents) the previous year. Revenues slipped to $18.8 million from $19 million.