Army, Navy and Air Force within the next few weeks may request special permission to grant immediate voluntary retirement to thousands of senior Washington-based workers to save the jobs of younger employees. Most of the 80,000 Department of Defense workers here will be affected by the decision.

Defense is the process of a massive reduction of civilian and military personnel at headquarters here that could hit at least two of every 10 jobs.

Locally, Defense is the largest employer in the Washington area. Army has more than 26,000 civilian workers; Navy, 36,000; Air Force, nearly 7,000; Defense Logistics Agency, 2,500, and other Defense operations, 10,328. As of December, 1976, the total number of Defense civilian workers in this region was 82,303.

Last month Defense Secretary Harold Brown announced that his personal OSD staff would be trimmed by 443 civilian and military jobs, down to 1,617 civilian and military personnel by next February.

In addition to OSD, the 20 to 25 per cent cuts will affect the Joint Chiefs of Staff, Defense Security Assistance Agency, Defense Advanced Research Projects Agency, Defense Audit Service; Armed Forces Information Service, CHAMPUS the health program staff); Manpower Data Center and headquarters personnel of the Overseas Dependent Schools. Most of the staff members of these agencies are based in and around Washington.

When Brown announced the cuts, Defense immediately requested permission from the Civil Service Commission to allow "early out" retirements, between now and next year for senior OSD workers. But not for other headquarters units.

Early out means that workers could retire at any age after 25 years old service, or at age 50 with 20 years of service. In that employees would take a pension reduction for each month they are under age 55.

Defense did not, and has not yet, requested the "early out" authority for Army, Navy, Air Force and other service agencies facing cutbacks and reductions-in-force (RIFs). This has led some civilian employees to believe they are out in the cold, facing RIF's that will mean senior working will bump down into other jobs, pushing younger, shorter-service employees into unemployment.

But insiders believe that Army, Navy and Air Force will request the early-out authority. And they predict it will be wide enough in scope to cover just about all of the military organizations where cuts must be made.

Defense officials concede that formal turnover - attrition - cannot take care of all the cuts to be made between now and February. So, they are fairly confident that they early-out authority will be requested, and given. By law, agencies can offer employees the option of "volunteering" for involuntary retirement only if a major layoff is taking place, and only if the commission approves it.

Authority for early-out retirement can be given for specific geographic areas, for specific jobs or grade, and for specific periods. In other words, an "early out" for Defense would not mean that DOD workers in Kansas City or Berlin could also take advantage of it. It would be limited to headquarters and related units here facing the RIF, and probably be granted only for a maximum 6-month period beginning this fall.