'Big carrier' advocates on the House Armed Services Committee yesterday refused to yield to Pentagon pleas to let the Navy shift money to design a smaller and cheaper aircraft carrier.

"It's incredible," said Rep. Les Aspin (D-Wis.) after his committee voted yesterday, "that a bunch of yahoos are blocking" the "overwhelming" desire of the House and Senate to switch to a cheaper carrier.

Aspin was reacting to committee votes yesterday of 12 to 7 and 12 to 9 against reconsidering earlier refusals to allow the Navy to reprogram $6 million in fiscal year 1977 money to finance medium-size, or "midi," carrier designs.

Defense Secretary Harold Brown, who opened the hearing with a plea not to "tie our hands" by refusing the funding request, stood up from the witness table after the committee voted against him and said: "I'm sorry . . . I don't think this will advance the cause of a new carrier for the nation."

Navy Secretary W. Graham Claytor Jr. told the committee before the votes that the Navy needed the $6 million right away. Otherwise, he said, the designs would not be finished in time to include the midi-carrier in the fiscal 1979 budget going to Congress January.

Asked after the hearing what he would do to keep the mid-carrier from slipping behind schedule, Clayton replied: "I don't know." He said several avenues of redress will be explored.

Aspin, who is allied with the Pentagon on the carrier issue, said that perhaps the Senate, in its imminent conference with the House on the fiscal 1978 Pentagon procurement bill, could make some kind of trade to free the $6 million.

The basic argument is whether national defense would be better served by building two mid-carriers costing $1 billion each instead of continuing with the large Nimitz class ehich costs $2 billion a ship. The Navy already has three nuclear powered Nimitz carriers at sea or under construction.

The House approved on March 3 the revisions President Carter made in the fiscal 1977 Defense budget he inherited from former President Ford, including elimination of funds for a fourth Nimitz. The House on the same day rejected, on a 252-to-161 vote, and amendment to restore the Nimitz funds. The Senate on March 15 passed the fiscal 1977 Pentagon budget as revised by Carter.

Building two midi-carriers of 60,000 tons each for the price of one Nimitz of 90,000 tons, Brown said yesterday, would enable Navy carrier planes to patrol two different areas of the world.

Although stating that the midi "is not a budgeteer's ship," he said its lower cost would enable the Navy to afford more ships at a time the numbers of Soviet ships are of prime concern.

Brown refused to commit himself to making the midi nuclear powered. He said there is no nuclear power plant in sight that is small enough for the midi.

Rep. Samuel S. Stratton (D-N.Y.), a leading advocate of the Nimitz, said yesterday it would be "idiotic" to switch from the nuclear powered Nimitz to an oil fueled carrier at the time the world is running out of petroleum.

Brown replied that the planes on carriers would have to burn either natural or synthetic petroleum in the future, regardless of what kind of carrier they are based on. The carrier itself, he said, could burn the same fuel as the planes - perhaps a derivative of coal.