USAir Inc. yesterday reported sharply lower earnings for August and blamed the decline on the impact of the air traffic controllers strike.

Net income was $1.036 million (6 cents a share) compared with $7.265 million (58 cents) in August 1980. Revenue fell to $82.036 million from $86.320 million a year ago.

Eight-month earnings were $37.435 million ($2.38) compared with $39.005 million ($3.05) for the same period a year before. Revenue rose to $727.906 million from $625.675 million.

The company said results in the most recent periods reflect a credit of $2.605 million claimed in August in anticipation of a reduction in federal income tax requirements for 1981.

Virginia Electric and Power Co. yesterday reported earnings of $20.749 million (16 cents a share) for August compared with $25.943 million (23 cents) for August 1980. Revenues were $196.730 million compared with $203.605 million.

For the 12 months ended Aug. 31, net income was $230.219 million ($1.73) compared with $212.908 million ($1.69) a year earlier. Revenues were $2.117 billion compared with $2.055 billion.

The company said cooler weather in August reduced sales 6.1 percent from their level a year before. Residential sales for August this year were down 13 percent from August 1980.

Stanwick Corp., an Arlington firm that specializes in work-quality systems, reported a consolidated loss of $167,304 for the quarter ended July 31, almost identical to the net loss of $167,312 for the same period a year ago. Revenues were $3.768 million compared with $4.493 million a year ago.

Company officials said the reduction in revenues reflected a decline in the company's publications engineering services business due to the end of a contract with the Naval Sea Data Support Activity.