In the first big flinch on defense spending since the November election, the Senate Armed Services Committee yesterday refused to go along with the Navy's request to take the aircraft carrier Oriskany out of mothballs.

Chairman John G. Tower (R-Tex.) said the vote was unanimous and hailed it as proof that his committee "is not going to serve as a rubber stamp" for the Pentagon's escalating budget requests.

In approving a $2.8 billion supplemental fiscal 1981 defense authorization bill, Tower added, the committee lopped $96 million off the Navy's request for F18 fighter planes to serve notice that the cost overrun problems with his new warplane must be addressed. The F18 was supposed to be a cheaper alternative to the existing F14 fighter plane, but is threatening to cost significantly more.

"We're going to get into these cost overruns," Tower pledged. He added that he was not against the F18 as a weapon, but felt the program should be slowed down in hopes the cost problems can be solved before going into full production.

Sen. Carl Levin (D-Mich.) of the committee said the Oriskany vote was a "harbinger" of a change in political mood toward the record-high defense budgets proposed by the Reagan administration.

Politicians are starting to feel some pressure to justify rising defense expenditures at a time when domestic programs are being cut. Levin predicted that the Reagan defense outlays would be approved but that Congress will make efforts to reduce waste Pentagon procurement.

Tower said he did not see such broad policy implications in the Oriskany vote. He said it was a matter of the Navy not being able to produce firm cost estimates for taking the old carrier out of mothballs and sending it to sea.

Originally, the committee chairman said, the Navy estimated it could refurbish the Oriskany for $305 million. The latest estimate is $518 million, Tower continued, "and these are Class F estimates, meeting they could be off by 40 percent."

Besides the spongy cost estimates, Tower said his committee felt that the Oriskany would have only limited combat potential because only the small A4M Skyhawk fighter-bombers could be used on the carrier. Besides that, he said the carrier would not be much of a match for modern enemy aircraft or submarines. And finally, Tower continued, the Navy is short of the skilled people needed to run such ships.

The Navy also is pressing Congress for funds to take the World War II battleships Iowa and New Jersey out of mothballs. The idea is to turn them into laughing platforms for cruise missiles and perhaps aircraft that can take off almost vertically.

Tower cautioned against assuming that his committee would disapprove reactivating the battleships. The chairman said that he personally favored the idea because of all the firepower that could be mounted on the World War II ships.