Boeing Co.'s 1982 earnings dropped 38 percent from 1981 results, affected not only by the continued slump in the airline industry but also by continued high expenses for its new 737-300, 757 and 767 jetliners, the largest U.S. producer of commercial aircraft said yesterday.

In other major reports:

* United Technologies Corp. said its net income for the fourth quarter rose 16 percent over a year earlier, but full-year earnings fell.

* Uniroyal Inc. said it lost $6 million in the final 1982 quarter, and its full-year profit was down 50 percent from a year earlier.

Boeing's 1982 earnings fell to $292 million ($3.02 a share) from $473 million ($4.90) in 1981; sales, to $9.03 billion from $9.79 billion.

The profits slide was arrested by increased military orders here and abroad, with sales to the U.S. government rising $1.04 billion to $3.2 billion.

Boeing ended 1982 with an order backlog of $19 billion, 78 percent of it commercial orders from domestic airlines or foreign governments; the rest, from the U.S. government.

United Technologies Corp.'s fourth-quarter net income was about $112.8 million ($1.68 a share) compared with $97.5 million ($1.45) for the same quarter in 1981.

Net income for the year was $533.7 million, which UT said included the cumulative effect of an earlier-announced accounting change for investment tax credits in the first quarter and a tax-free, extraordinary gain in the second quarter.

Excluding their cumulative effect, 1982 net income fell to $426.8 million from $457.6 million.

Earnings per share were $8.01 compared with $7.05 for 1981, UTC officials said.

Sales were $3.54 billion for the quarter compared with $3.51 billion last year and $13.6 billion for all of 1982 versus $13.7 billion.

Uniroyal Inc. said its fourth-quarter loss of $6 million on sales of $470 million compared with net income of $300,000 on sales of $558 million a year earlier.

Uniroyal attributed its loss to the depressed economy, the devaluation of the Mexican peso and the expiration of a favorable contract to buy natural gas for chemical production.

Uniroyal earned $26 million (78 cents a share) last year compared with $52 million ($1.76) in 1981. Sales fell to $2.0 billion from $2.3 billion.