After years of red ink, Perpetual American Bank started its fiscal 1985 year by moving decisively to the profitable side of the ledger.

Perpetual yesterday reported earnings of $5.2 million (77 cents a share) for the first quarter, ending Jan. 31. For the same period in 1984, before Perpetual offered its stock to the public, the savings institution had a net loss of $4.2 million, representing a 61-cent-a-share loss.

Less than half of Perpetual's $5.2 million in earnings -- $2.4 million (35 cents) -- came from bank operations. Stock distributed to savings and loan institutions by the Federal Home Loan Mortgage Corporation (Freddie Mac) contributed $1.5 million (23 cents), and a tax benefit added another $1.3 million (19 cents).

Perpetual officials acknowledged that by earning $2.4 million from operations in the first quarter, they had moved ahead of their predictions for fiscal 1985. For all of fiscal 1985, President Thomas J. Owen had predicted the bank would earn $7 million ($1.03 a share) from operations. Based on the first-quarter earnings rate, bank earnings for the year would be $9.6 million ($1.41).

When asked about the $7 million projection, Owen said, "The math would tell you that we will do better than that, but we are a very interest rate-sensitive company. . . . "

Future earnings, he said, would depend in part on the direction of interest rates.

The bank, meanwhile, expects to add another $7 million to 1985 earnings ($1.03) in the third quarter from a land sale. In June, the bank will sell a parcel of land, now used as a parking lot, between 11th and 12th streets NW. It is adjacent to Perpetual's former headquarters at 500 11th St. NW. Perpetual is now based in Alexandria. The $7 million sale figure represents the difference between the sale price and the amount at which the property is carried on the books of the bank.

Perpetual's earlier projection of a $14 million profit ($2.06) has helped the bank's stock more than double in six months. Perpetual, which went public at $7.50 in August, closed yesterday at $15.63 a share.

Perpetual shares have moved up steadily since November, when officials began to indicate that they would be able to move into the black after losing money in five out of six years. Perpetual lost $2 million in fiscal 1984. The stock's climb has been aided by interest from institutional investors.

Chief Operating Officer Ross C. Towne said of the stock, "The direction was expected. The rate of ascension was more than we expected."

Vice Chairman Richard S. Lawton said that the bank had 6,000 stockholders "that we know of." Many shares, he noted, are held in "street name" by brokerage houses that hold stock bought by investors.

Key elements in the bank's first-quarter performance, officials said, included $2.7 million in gains from the sale of investments and mortgage-backed securities and $7.5 million in net interest revenue. The latter was made possible, it was said, by the decline in interest rates coupled with "significant" asset growth. The net interest revenue increased 34.2 percent over the same period in 1984.

Perpetual assets reached $3.8 billion, an $800 million increase in one year, and return on assets was .57 percent.

Deposits increased to $2.5 billion, a 21.9 percent rise. Total loans and mortgage-backed securities increased from $2.2 billion to $2.9 billion, or 32.5 percent.