Dr. Murdock Head, the Airline Foundation director charged with scheming to bribe two congressmen, was acquitted yesterday by a federal jury in Alexandria of two counts of tax evasion.

The jurors -- seven men and five women -- failed to reach a verdict, however, on a bribery conspiracy charge -- the main count on which Head was indicted. Also under consideration by the jury is a third tax-evasion charge.

Judge Oren R. Lewis sent the jurors home for the night and instructed them to return this morning to continue their deliberations on the two remaining charges.

Head, 55, the founder and executive director of the sprawling 19-year-old Airlie Foundation near Warrenton, Va., is charged with conspiring to bribe Rep. Daniel J. Flood (D-Pa.), former Flood aide Stephen B. Elko, former representative Otto E. Passman (D-La.) and a now-retired Internal Revenue Service agent.

Federal prosecutors allege that the payoffs -- including $49,000 in cash and an $11,000 loan -- were given in exchange for help in obtaining federal funds for the Airlie Foundation and favorable tax treatment for Head's enterprises.

In his instructions to the jury yesterday, however, Judge Lewis made it clear that Head could be convicted of the conspiracy count, even if the jurors did not believe he had ever sought to bribe government officials.

The conspiracy count also charges Head with scheming to evade or falsify income tax returns. Lewis told the jurors they could find Head guilty of conspiracy solely on the basis of the tax charges.

Head declined to comment on his acquittal on the two tax-falsification charges, announced in the courtroom at 5:25 p.m., although he smiled broadly.

"Two down, two to go," said Brain P. Gettings, one of Head's lawyers. Then Gettings added, "Or should I say, "Ten down, two to go?"

In addition to the two tax-evasion counts on which Head was found innocent, eight other charges against Head have been dismissed by Judge Lewis. These include five bribery and three tax-falsification counts.

Prosecutors declined to comment on the verdicts returned yesterday.

The tax charges lodged against Head allege that he attempted to evade income taxes owed by Raven's Hollow Ltd., a film-making company linked with Airlie. The two counts on which Head was acquitted dealt with tax returns for the company's 1974 and 1975 fiscal years.

The jury has not reached a verdict on similar charges centering on Raven's Hollow's tax returns for 1973 -- a year in which prosecutors allege considerably more taxes were due.

The prosecutors charged that Head manipulated the company's financial records to escape more than $43,000 in taxes in 1973. The prosecution had contended that the company owed more than $9,000 in taxes for 1974 and more than $6,000 in taxes for 1975. Raven's Hollow allegedly paid no U.S. income taxes in any of the three years.

At issue in the tax charges was whether Head sought to reduce the company's tax liability by claiming improper deductions for fraudulent business expenses.

Head's lawyers argued that the tax deductions were properly taken for legitimate business expenses. Gettings told the jury, during his closing statement yesterday, that no fraud or concealment was involved in the deductions and that any dispute over the company's taxes should have been settled in civil, rather than criminal, proceedings.

"We'll fight that cut in Tax Court any time," Gettings declared.

The prosecution argued that Head contrived to avoid taxes by arranging a series of phony deductions for Raven's Hollow -- including a "slush fund" created by double-billing for travel expenses, which allegedly was used to pay bribes.

The jury's verdicts on the two tax counts were disclosed after about 4 1/2 hours of deliberation, when Lewis summoned the jurors to the courtroom to tell them he would allow them to go home for the evening. There was no indication of what factors led to their decisions.