The House Armed Services Committee voted yesterday to investigate charges that Defense Department officials violated a 1919 law in lobbying Congress for a proposed multibillion-dollar purchase of 50 Lockheed C5B cargo aircraft and possibly for numerous other weapon systems.

Those systems included Boeing B1 manned bombers and Airborne Warning and Control System radar surveillance planes for Saudi Arabia.

The Pentagon pledged full cooperation with the investigation to be made by a subcommittee led by Rep. Richard C. White (D-Tex.). White will also draw on a General Accounting Office inquiry launched three weeks ago by Rep. Jack Brooks (D-Tex.), chairman of the House Government Operations Committee.

White said he expects to hold hearings within a few weeks and said he foresees possible recommendations to "clarify" the 63-year-old law, which forbids officials to spend tax dollars to solicit private organizations or citizens to pressure legislators. The law has never produced an indictment.

Triggering the investigation was the unprecedented disclosure June 22 of Lockheed Corp. computer printouts dealing with a coordinated campaign by the Pentagon, the Air Force and the company for House approval of C5Bs for strategic airlift.

In the early phase of a countercampaign, the rival Boeing Co. won Senate rejection of the C5Bs in favor of military versions of commercial airliners, mainly Boeing 747s. The House is to take up the issue next week.

The printouts recorded in extraordinary detail the assignments, actions and "Congressional Contact Tally" of a team of Pentagon, Air Force and Lockheed officials led by Maj. Gen. Guy L. Hecker, director of legislative liaison for the Air Force.

The printouts cover 19 days in May and June when the group met almost daily in Hecker's office and list more than 260 members of Congress to be contacted by at least 40 Lockheed subcontractors, nearly all of which sponsor political action committees.

Rep. Norman D. Dicks (D-Wash.), speaking for three other congressmen backing 747s or McDonnell Douglas Corp. planes, said the printouts reveal or suggest more than a dozen C5B group activities that were "obvious improprieties" and possibly "significant violations" of the 1919 law, the 1982 Defense Appropriations Act and Pentagon and Air Force regulations.

Dicks urged the committee to endorse a House resolution to compel the Pentagon to supply documents on its involvement in the C5B lobbying effort, saying that public perception of Congress' integrity was at risk and that the committee should seize "the opportunity to destroy the rising specter of the military-industrial complex."

Refusing, the committee substituted its own investigation. "I'm pleased with what they did," Dicks said later.

In heated exchanges, some committee members indicated that nothing unusual occurred in the C5B case, but Dicks and Rep. Dan Glickman (D-Kan.) said it was unique because of the documentation from Lockheed's computers of "collusive behavior."