Landing a federal civil service job remains the best 5-day per week employment security package available to the average American worker.

But the image of the tenured bureaucrat, who cannot be fired unless he commits mass murder on the Capitol steps is suffering a bit these days. The 1970s have been tougher for the federal work force which has seen a large (for government) number of workers canned or laid off.

Fiscal year 1970 was an unusually unstable time for the government's 2.8 million full and part-time workers. The Vietnam buildup was over, and firings hit a near-record high with 26,308 fired. That number plus the 27,720 who were dismissed the next year represented only a relatively small percentage of the total work force but the numbers are significant for the government, which has the reputation of never firing anyone. And the trend toward more dismissals and more layoffs appears to be going up again, after a brief downturn after 1971.

In fiscal 1974 the government fired 17,008 person for cuse, meaning anything from leave abuse, chronic tardiness to poor performance. Most of those were dismissed before they had completed the first-year probation period.

The next year, fiscal 1975 (the most recent data available) showed the number of outrignt dismissals had jumped to 19.341. During that time period 637805 people left government employment for all causes, ranging from just plain quits, transfers to death or retirement.

The thing that worried most government workers - particularly in an era when talk about cutting back government fat is everywhere - is the fear of layoff. In governmentese it is called RIF (for "reduction in force") and RIFs also are on the increase, mainly because Defense activites, which peaked during the Vietnam war period, are being cut back or eliminated.

In fiscal year 1974 the government riffed 44,039 persons. The next year 50,081 were given 60-to-90 day notices to find other jobs - not because of any work problems of theirs, but because their jobs had been abolished. If the Carter Administration is serious about cutting back military outlays and expenditures the number of RIFs thiw year could be much higher.

The number of employees who are being suspended for short periods os time is also increasing. The suspensions are for relatively minor offenses for which the government feels is should not, or could not justify, dismissal. In fiscal 1974, 28,473 employees were in that category although the suspensions group also includes persons given leave without pay for study or other assignments.

Data for the latest period available, fiscal 1975, shows that 32,380 persons fell into the suspended category although some of them were undoubtedly given LWOP on their own request.

During the 1974 and 1975 years that number of persons leaving government for all reasons - but mainly due to retirement or to seek other jobs - dropped from 143,000 in 1974 to 110,000 in 1975.

Federal officials say the reason for the drop in retirement and quits from government can be explained by the tighter job market in private industry and increased government pay.

Although the government doesn't have more current data on firings or RIFs or suspensions, some officials expect the upward trend to continue. They don't know exactly why, but some suspect that the increasing desirability of a government job is making it easier for supervisors and angencies to crack down on marginal employees knowing that they can easily be replaced by federal job hunters who in some places - Washington included - are practically beating down the doors of federal personnel offices looking for work.

The odds of a governmnet worker being fired diminish with time. The firist 365 days literally are the most dangerous because employees can be fired up until that time for almost any reason, and without any appeal rights. After that time they acquire "status" which makes it tougher and more cumbersome to fire someone at least by privated industry standards.

Many employees are fired for abusing leave although that often isn't the "real" reason they are dismissed. In private industry, in many cases, employees can be fired because of personality conflicts with bosses or co-workers. The same problems come up in government offices but their are more difficult procedures involved, so often supervisors use leave abuse - which frequently accompanies personality problems and/or poor performance as the legal reason to dismiss an employee.

Many government workers argue correctly, that the firing statistics are misleading. There are ways to dive people out and when that happens the departing workers is put into the "quit" statistics.

Statistics, of course never tell the full story and often don't tell the true story. But the numbers are there: and are being fired and - for whatever reasons - more of them are going out the door either with dismissalletters or RIF notices.