Protecting the federal pension system, multimillion dollar pay changes and probes of corruption and mismanagement should take up most of the session for the House committee in charge of the people-side of the bureaucracy.

The Post Office-Civil Service Committee will be the launching pad (and maybe graveyard) for a new White House plan to "reform", and slow the growth of, federal and military pay. It will sponsor investigations, ranging from corruption in the General Services Administration to an examination of why there is a new Department of Energy and what it is and is not doing to put the brakes on energy prices.

A major job for the committee -- often the lone congressional protector of rank-and-file government workers -- will be to block any merger of the Civil Service Retirement system with the financially-troubled, less generous Social Security system. That threat has united most federal, postal and retirees groups. It worries and frightens long-time civil servants who see the possibility of a lifetime of bought and paid for pension benefits being diluted.

James M. Hanley, a Syracuse, N.Y., Democrat, is expected to take over the Post Office-Civil Service Committee. Once a congressional powerhouse, and major generator of news (because of its control over federal-military pay, and the Post Office, the committee in recent years has almost legislated itself out of business. Presidents, special interest groups and unions have taken to going around the committee to new-found power sources on Capitol Hill.

Under the prodding of LBJ, the committee okayed the present semiautomatic federal and military pay raise system. It took Congress out of the business of setting wages, and cost the committee clout within the Congress, and some of its special ties with federal unions.

In cutting loose the Post Office Department to become a government-owned corporation, the committee gave up control over the second largest federal operation, and the one most directly effecting the daily life of Americans. Postal officials who once came hat-in-hand to the committee before changing a small-town post-mark now ignore it when making major policy, service and rate changes. The price of stamps is no longer set by Congress. Postal patronage -- the bulwark of bureaucratic payoffs for nearly 200 years -- slipped out of the committee's hands.

With the power erosion, other committees moved into the turf. Once the keeper of the federal supergrade (GS Grade 16 through 18 slots) pie, the committee now sits by fuming as other congressional units legislate the birth of new $47,500 jobs for pet projects in pet agencies. It now faces the combined weight of other committees, and probably the administration, in an attempt to blend the generous federal pension system (and its dollars) into Social Security.

To stage a comeback, insiders expect Hanley will start a muscle-building campaign including generous doses of newsworthy investigations. He is worried about corruption in contracting. He also questions whether the Energy Department is doing anything other than growing bigger as it feeds on crisis after crisis. Energy is a hot topic for any politician, especially one from Syracuse, where it gets mighty cold.

Of special interest to federal, postal and retired government employes is the fate of their pension system. Hanley's committee may provide the only publicly sympathetic ear for them when it comes to protecting the integrity and independence of the civil service fund.

Although still under study, the proposed merger of Social Security and Civil Service almost happened last year. Experts expect various study groups will conclude it is a good idea. HEW is believed anxious to get its hands on the liquid cash assets of the CS fund, and politicians are looking for a way to roll back Social Security taxes that jolted most Americans with their first 1979 paycheck.

The pension merger plan could be one of the hottest political items of the year. It involves the future retirement of just about everybody, billions of dollars' tax rates and other pocket-book items. It also will provide any politician who wants it a chance to kick a faceless bureaucrat whose primary crime was to join a "company" (Uncle Sam) with a good pension plan.