Stanwick Corp., an Arlington management systems and consulting firm which suffered a substantial loss of business in Iran after the revolution in that country, yesterday reported a net loss of $3.2 billion in the year ended April 30. Revenues were $11.2 million.

In the previous year, Stanwick had posted profits of $902,421 (87 cents a share) on revenues of $18 million. But when contracts for work in Iran were severed in the fourth quarter of 1979, Stanwick lost operations that had resulted in 72 percent of annual revenues.

Not counting the Iranian impact, Stanwick said yesterday, revenues in the recent year were up 121 percent from non-Iranian related revenues of the prior year.

The local firm's business gains came in such sectors as naval design and publication engineering services as well as technical support services.

As of Jan. 31, Stanwick wrote off funds on deposit in Iranian banks and amounts due from contracts with Iran's previous government. On April 2, Stanwick went into court with a lawsuite against the curent Iranian government, seeking $7 million. Chairman Tad Stanwick said yesterday his firm has "every intention of making an appreciable improvement in our sales volume and earnings fisical 1981."

Two large bank holding companies reported mixed results yesterday for the second quarter of 1980. First Maryland Bancorp, of Baltimore, posted an increase in operating earnings to $5.6 million ($1.19 a share) from $4.6 million (99 cents) from $4.7 million (68 cents).

Among other banking companies reporting 1980 results:

D.C. National Bank said second-quarter net income was $474.601 ($2.33 a share) vs. $268,447 ($1.31), a gain of 67 percent. Assets rose to $113 million from $101 million.

Bank of Columiba, of Washington, which is negotiating a possible sale of the institution to foreign investors, reported six-month earnings from operations of $273,574 (62 cents) vs. $167,509 (38 cents), a gain of 63 percent; second-quarter results were not available. Assets rose to $51 million from $49 million.

First American Bank of Virginia, a McLean unit of Financial General Bankshares and the largest bank in Northern Virginia, reported a 21 percent increase in earnings for the first six months to $4.5 million ($2.68 a share) from $3.8 million ($2.24) last year. Second-quarter earnings rose to $2.3 million from $2.1 million.