Martin Marietta Corp. DESCRIPTION: Bethesda-based firm engaged in five principal businesses: An aerospace company making aerospace and defense systems primarily for the U.S. government; an aluminum division producing ingot and mill products; a cement company manufacturing portland and masonry cement; a chemicals divison producing concrete and dyestuff and an aggregrate company that quarries crushed stone, sand and gravel (NYSE). FOUNDED: 1909. TOP EXECUTIVES: J. Donald Rauth, chairman and chief executive; Thomas G. Pownall, president and chief operating officer.

1981 was a year of mixed reviews for Martin Marietta with the aerospace industry experiencing steady growth while the company's aluminum holdings suffered in the face of the continuing economic decline. Sales and net earnings were the highest ever for the corporation, with a sales of $3.3 billion in 1981 and net earnings of $200 million. Earnings per share were up dramatically as well, with stockholders enjoying an increase to $5.39 per share.

For the future the company's investment will concentrate on the aerospace portion of its holdings, plant and capital improvements already having been made in chemicals, cement and aluminum.

The view of the corporation is that Martin Marietta's success "speaks well for the diversification that that has been so carefully and deliberately nurtured in the enterprise.

Fairchild Industries DESCRIPTION: This Germantown-based diversified, high-technology company makes military and commercial aircraft, spacecraft and electronics hardware, domestic satellite communications and specialized industrial products (NYSE). FOUNDED: 1936. TOP EXECUTIVE: Edward H. Uhl, chairman and chief executive.

The 1981 annual report of Gaithersburg-based Fairchild Industries Inc. begins by candidly noting that the year was "mixed with success and disappointment." On the bright side, the company made $18.4 million from its sale of stock in Bunker Ramo Corp., at the same time apparently ending its bid for the Illinois computer concern.

In addition, Fairchild continued development of a new aircraft with Saab, and delivered 142 A10 aircraft to the U.S. Air Force. The company also brought VSI, a California fastener company, under its wing, and the subsidiary, purchased in 1980, broke its sales and earnings records.

Fairchild's American Satellite subsidiary expanded its business communications network, announced plans to operate its own satellites and signed a well-publicized contract with Gannett Co. to transmit the newspaper chain's forthcoming national daily publication to 16 printing plants.

But there was considerable bad news, too. Per-share profits fell to $3.48 from $4.02 in 1980. Over the past year, the price of the company's stock tumbled from almost $27 a share to a low of under $11 a share.

The company's president and chief operating officer, John F. Dealy, abruptly resigned in February, ending 14 years with Fairchild, but reminding analysts and other company watchers of the powerful, sometimes tempestuous, iron hand wielded by the company's chairman, Edward G. Uhl.

Dynalectron DESCRIPTION: A diversified electrical engineering, contracting, aviation services and energy research company based in McLean (AMEX). FOUNDED: 1946. TOP EXECUTIVES: Jorge Carnicero, chairman; Charles Gulledge, president.

Using its electrical contracting division--the third largest in the nation--as a base, Dynalectron has built a diversified technology business that last year produced record earnings of $13.8 million on revenues of $475 million, up from the record $5 million profit on $442.6 million sales in 1980.

The electrical construction business produced $263 million of the 1981 revenues; another $140 million came from technical services, $48 million came from heavy environmental construction and controls and $23 million from hydrocarbon research. The research arm was the only division whose revenues slipped last year, but long term it could be Dynalectron's big winner. The company's H-Coal process for turning coal into oil is among the finalists for federal aid from the Synthetic Fuels Corp., if that financing ever is approved. This year, Dynalectron executives figure the company will benefit from the administration's boost in defense spending and from tax incentives that will encourage construction of the kind of facilities the contracting divisions build.

Pargas Inc. DESCRIPTION: A Waldorf, Md., distributor of liquefied petroleum and equipment for its use and storage with coal minning subsidiaries (NYSE, Phila). FOUNDED: 1936 as Parlett Gas Co. TOP EXECUTIVE: N. L. Langley, president and chief executive officer.

Total volume of liquefied petroleum gas marketed during 1981 increased, with conservation in some areas offset by increased sales of liquefied petroleum gas for use as a motor fuel and by the company's trading operation.

The company founded Pargas Trading in Houston in 1980. The company conducts brokerage operations in propane and other related products. It also owns or leases underground storage facilities in Texas, Arizona, New York and Mississippi to permit acquisition of propane during off-season demand periods to hold for later distribution.

In the past three years, Pargas has made capital investments in plant and equipment of $44.5 million. Most of the investments were financed by internally generated funds and short-term debt. Capital expenditures for 1982 will be at a lower level than in 1981 to help reduce the cost of short-term debt.

Pargas had planned to purchase the retail propane business of Sun Gas Liquids Inc. of Dallas in 1980. In 1981 that purchase was terminated prior to completion because of the high cost of financing the takeover of those operations. Pargas officials have said that they are continuing to look for chances to expand propane markets into new areas.

Earlier this year Pargas said that Kentucky Utilities Co., the major customer of its River Processing coal unit, had notified the LPG firm that it was suspending its coal contract temporarily because of a breakdown in unloading equipment. Pargas said that because the Kentucky utility accounts for "substantially all" of the coal unit's sales that earnings for the year would be affected by the temporary halt in the contract.

UNC Resources DESCRIPTION: A diversified resource and manufacturing company, with principal activities in mining and milling, oil and gas support, nuclear components manufacturing, and machine tool production. The Falls Church-based firm is among the nation's largest uranium producers (NYSE). FOUNDED: 1978, as a holding company for United Nuclear Corp., which was founded in 1954. TOP EXECUTIVES: Keith A. Cunningham, president and chief executive officer; James R. Bancroft, chairman.

A company whose fortunes once were timed primarily to nuclear power through its uranium mining and milling activities, UNC Resources was in transition last year. An aggressive diversification program was aimed at expanding growth opportunities and "making the company less dependent on any individual market or customer," the company's top officials told shareholders in the 1981 annual report. ". . .Almost half of our 1982 revenues will come from sources that were not part of our business at the beginning of 1981," they said.

During 1981 and the beginning of 1982, UNC made some major acquisitions and developed new activities in some of its existing divisions. In May, UNC entered the automated machine-tool business with the acquisition of National Automatic Tool Co., a company that specializes in the manufacture of custom and standard automated heavy-machine tools. In August, it entered the oil and gas support business with the acquisition of Normco Contractors Inc. Normco fabricates, installs and services a variety of large components and assemblies for offshore oil production platforms. In January, UNC completed the acquisition of Swift Group Inc., whose subsidiary, Swiftships, is the world's leading producer of large aluminum marine vessels.

UNC's 1981 earnings totaled $6.9 million, but officials said the numbers and comparisons with prior periods are confused by changes in its operations and accounting, including a change in reporting from a fiscal year ending March 31 to calendar year basis.