A Navy officer has ruled that Cmdr. Donal M. Billig, a heart surgeon charged with five deaths at Bethesda Naval Hospital, will face a general court-martial in mid-January, ending a year-long Navy investigation into his surgical competence.

Navy spokesmen said yesterday that five counts of involuntary manslaughter and 24 counts of dereliction of duty were reviewed and approved for trial this week by Rear Adm. Robert C. Austin, chief of Navy technical training. The charges had been approved for trial in October, but they were sent back to officials for a new investigation after Billig's defense lawyers argued that the hearing officer in the early investigations was not impartial.

Pretrial motions in the case are scheduled for Jan. 6 and jury selection and trial are expected to follow the next week, Navy spokesmen said.

Billig's court-martial will begin at the same time as the trial of Capt. Reginald E. Newman, one of the recruiters questioned in the hiring of Billig. Newman has been charged with dereliction of duty, making false statements and perjury before the internal Navy board that investigated Billig, spokesman Lt. Stephen Pietropaoli said yesterday.

A general court-martial is the most severe of the three types of military courts-martial. The proceedings are part of an extensive look into the practices of the former chief of head and chest surgery at Bethesda and, at times, into the hospital itself.

If found guilty, Billig, 54, could be dismissed from the Navy, lose his pay and allowances and receive a maximum sentence of 27 years at hard labor, Navy spokesmen said yesterday.

As a result of the investigation that began in November 1984, 10 officers -- including the former commanding officer and executive officer at the Navy's premier hospital -- have received or may face disciplinary sanctions for their roles in hiring and retaining Billig.

Billig, a protege during the 1960s of well-known heart surgeon Dr. Michael DeBakey, was commissioned in the Navy in December 1982 and assigned to Bethesda the next January. He became chief of the head and chest surgery unit in June 1983, according to Navy records, and held that position until his clinical privileges were suspended by the hospital in November 1984 when questions were raised about his performance and the hospital began investigating.

In April 1985, his surgery privileges and appointment as head of the department were revoked by Bethesda and an investigation was begun by an internal Navy board.

Public documents in New Jersey courts and Navy documents obtained by The Washington Post under the Freedom of Information Act revealed that Billig had been asked to leave a civilian hospital in 1980 when doctors at Monmouth Hospital raised questions about his competence. Former doctors at Bethesda said in interviews that Billig had not practiced heart surgery for six years before arriving at Bethesda, and naval doctors who worked with him during a retraining period recommended that he not be allowed to practice major heart surgery without supervision.

In June, the naval investigators recommended Billig be charged with four deaths and dereliction of duty in 24 operations that the Navy said he undertook without the proper supervision. Navy spokesmen said the investigation also revealed that Billig suffers from a severe loss of vision in his right eye and has problems with depth perception that impede eye and hand coordination.

Separate pretrial investigations requested by the defense began later in the summer. A fifth involuntary manslaughter charge was added in September during one of those hearings.