The Rhodesian government confirmed yesterday that a heat-seeking missile was responsible for the crash Sunday of an Air Rhodesia passenger plane in which 38 of the 56 persons aboard were killed. Ten of the survivors were later slain by guerrillas.

Speaking in parliament, Co-Minister of Transport William Irvine said the preliminary investigation into the cause of the crash clearly showed that the inner starboard engine of the Viscount Turboprop was hit by a missile.

It is believed to be the first time in the history of civil aviation in Africa, and possibly the world, that a regularly scheduled passenger plane has been shot down by a surface-to-air missile.

The event is certain to raise major problems now for the safety of civilian planes in Rhodesia, although the government has already announced it is taking special precautions to prevent a recurrence of such an incident. The precautions have not been disclosed.

Joshua Nkomo, co-leader of the Rhodesian Patriotic Front guerrillas, has claimed responsibility for shooting down the plane, but has denied that his men were responsible for slaying the survivors. He also said the plane was believed to be carrying troops or war material.

The incident - and particularly the slaying of 10 of the survivors - have incensed the white population, and led Prime Minister Ian Smith to announce that the government is planning a new course of action.

Government sources said yesterday that Smith would probably disclose his new policy this weekend in an address to the nation.

Speculation as to what he plans to do now centers on some kind of fullscale national mobilization in a bid to wipe out enough of the estimated 7,500 guerrillas operating inside the country to stabilize the deteriorating security situation.

The government has already mounted a massive military operation to track down the guerrillas responsible for the crash, and there is considerable speculation it may take its new offensive to their bases in neighboring Zambia and Mozambique.

There was an unconfirmed report last spring that a small private aircraft had been fired upon, possibly by a missile, near Victoria Falls in northwestern Rhodesia. Several Rhodesian military aircraft, including one Canberra bomber, are thought to have been brought down by such weapons.

But this was the first time Rhodesian guerrillas have reportedly attempted to shoot down a regularly scheduled passenger plane.

Both of the Viscount's starboard engines caught fire and the flaming plane plunged to earth in northwestern Rhodesia. It broke into pieces after hitting a ditch in a cotton field.

Eighteen persons survived the impact of the crash and fire, but 10 of them were gunned down by guerrillas who appeared on the scene shortly after the plane hit the ground.

The exact circumstances in which the plane was shot down are still not altogether clear. Irvine said it was flying at an altitude of 10,000 to 12,000 feet.

However, the plane would have been only 7,000 to 9,000 feet above the Zambezi escarpment - which rises steeply from the lakeside resort town of Kariba from which the aircraft had just taken off - when it was hit.

The range of the Soviet-made should carried SA-7 missile, which Nkomo's guerrillas are believed to have now, is just over two miles.

Several of the survivors said they heard a big bang and that the plane shook all over when the starboard engines exploded in flames, but none could say for certain it had been hit by a missile.

Minister Irvine said that the pilot, John Hood, had only about three minutes in which to land the Viscount before the flames would have destroyed the wing. The site of the crash was 20 miles southeast of Kariba in an African reserve.

Irvine paid high tribune to Hood, who managed to bring the flaming plane down on two engines and land it fairly smoothly in a cotton field. It is thought now that many more persons would probably have survived the crash had the plane not hit a hidden ditch, or donga, in the middle of the field. This caused it to cartwheel and break into pieces.

Most of the 18 survivors were sitting in a five-year section of the body connected to the tail that stayed intact until consumed by flames after they escaped.

The eight who survived the second ordeal at the hands of the guerrillas managed to take over and hide in the bush when the guerrillas opened fire. They were rescued the followed day after spending a cold night in the open.

Smith has warned that some of the measures the government is now planning would not please those countries now involved in helping to arrange a negotiated solution between the multiracial Salisbury government and the Patriotic Front. He was apparently referring to Britain, the United States and South Africa.

Typical of the rage and sentiment for revenge sweeping the 230,000 whites of Rhodesia was Irvine's comment:

"The people of this country will not let those innocent (people) go unavenged . . . I can promise the leaders of the Patriotic Front. That those who seek to ride the wind will reap the whirlwind.