Riggs National Bank and Suburban Bancorp., two of the area's largest banking companies, yesterday reported higher profits for the third quarter of 1977.

Federal National Mortgage Association, which supports a secondary market for home mortgages, also reported a gain in earnings.

Riggs chairman Vincent C. Burke Jr. said increased loan and investment volume, including a higher level of tax exempt securities, contributed to his company's higher profits.

For the third quarter, Riggs earned $4.04 million ($1.33 a share, assuming conversion of preferred stock) compared with $3.70 million ($1.22) in the 1976 period, an increase of 9 per cent. There were no gains or losses from selling securities in either quarter.

The quarterly profits brought the nine-month total to $10.75 million ($3.55 a share), up 15 per cent from $9.33 million ($3.08) in the comparable 1976 months. All results include earnings of Central Charge Service, a Riggs subsidiary.

Burke said Riggs is shifting away from short-term money market instruments in favor of the higher loan and investment activity. Loan volume on Sept. 30 was $882 million, up 17.4 per cent from a year earlier.

In another development, Frederick L. Church Jr. announced plans for an early retirement on Dec. 3331 as executive vice president for trusts at Riggs. His career there began in mid-1936 and Burke said the resignation was "acceeded to . . . will great regret." Francis J. Lyons, 55, was named to succeed Church in charge of the trust department. Lyons joined the bank in 1950.

Suburban Bancorp. of Hyattsville, parent firm of Suburban Trust Co., reported a 5.7 per cent increase in third quarter profits to $2.87 million (66 cents a share) compared with $2.72 million (62 cents) a year ago.

Nine month earnings at Suburban totaled $8 million ($1.83 a share) compared with $7.5 million ($1.70), a gain of 7.6 per cent.

President Robert F. Tardio said the modest increase in earnings for both periods reflected higher interest income from increased consumer and real estate lending. Outstanding loans on Sept. 30 totaled $550.5 million, up nearly 13 per cent in the past year.

Suburban Trust is the largest bank based in the Maryland suburgs, with 60 branches. The firm also owns Thurmont Bank in central Maryland. Deposits of the banks totaled $978 million on Sept. 30, up from $871 million last year.

National Savings & Trust Co., the District's fifth-largest bank, reported nine month profits of $2.2 million ($4.83 a share) compared with $1.58 million ($3.45) a year earlier. Directors approved an increased dividend of 60 cents a share, payable Nov. 1 to stockholders of record Oct. 21. NS&T previously paid 54 cents quarterly.

Federal National Mortgage Association earned $37 million (62 cents a share) in the third quarter compared with $33.8 million (58 cents) for the same period last year. That brought profits for the first nine months to $121 million ($2.04) compared with $96.5 million ($1.66).

The Washington corporation said it earned a return of $62.4 million on its mortgage portfolio in the recent quarter.

Ryland Group, a home builder based in Columbia, reported third quartter profits of $1.3 million (49 cents a share), off from $1.4 million (54 cents) in the 1976 period. The total volume of settlements rose to $26 million from $24 million..

For the first nine months, Ryland profits were up 15 per cent to $3.9 million ($1.48) compared with $3.4 million ($1.29). Sales volume rose to $81 million from $62 million.

Officers said Ryland settled on fewer houses in the recent quarter because of an unusually large volumes in June. They also cited some labor shortagaes and delays in drywall and insulation deliveries but forecast no significant impact on fourth quarter business. Directors approved a dividend of 5 cents a share, payable Oct. 30 to stockholders of record Oct. 15.