The government's half million blue collar workers are in for a rude financial jolt if Congress buys a Carter Admministration plan to gear down the complicated system Uncle Sam now uses to set their pay.

Many officials claim that the current wage board pay system, which is linked to the prevailing rate paid by private industry on a local basis, actually forces the government to pay its people from 8 per cent to 12 per cent more than private mechanics, carpenters and maintenance workers.

Unlike white collar civil servants (and military personnel) who get a national average catch-up-with-industry pay raise each October, wages of the 511,000 blue collar government workers are set locally. The largest federal employer of blue collar workers (usually Defense) in each area surveys the going rate for private industry blue collar jobs, applies them to the "average" pay step of federal blue collar workers and the raises go into effect automatically.

In the Washington area Navy is the largest employer of both white collar and blue collar workers. It makes a midsummer survey and the raises here for 32,000 blue collar employees go into effect sometime in October. In other parts of the country the surveys are made in the same way, with different effective dates.

The problem, government officials say, is that federal blue collar workers now enjoy a five-step longevity pay system that guarantees them maximum earnings for their grade after only 6 years. By comparison, most white collar workers must wait 18 years to move to the top of their pay grade.

Under the current federal system - which President Carter wants to change - beginning federal blue collar employees start out in step one which is 96 per cent of the rate (as determined by the government) for a similar job in private industry.

In six months, however, the blue collar workers moves into the second pay step, which is (again according to government data) euqal to 100 per cent of the going rate for that job in industry. The third pay step is 4 per cent more than the rate for industry, the fourth step is 8 per cent above the private pay line and the fifth step, which employees reach in six years of service, is equal to 112 per cent of the local private industry rate for a similar job. Most federal blue collar workers are in the third, fourth or fifth longevity steps, meaning - according to critics - they earn from 4 per cent to 12 per cent more than private industry workers.

Blue collar employees, and their unions, naturally disagree. They claim government wage experts rarely propose fair or equitable blue collar pay raises, and say that the quick movement (6 years) to the top of the pay scale is typical of industry practices.

The authority President Carter has asked from Congress would give the administration power to change the number of longevity pay steps. "We think it would be more than one, but less than five," an official said. "It will depend on what we find is the private industry practice" but he said he doubted any study would support the idea of a five-step, or even a four-stop grade system for federal blue collar workers.

Part of the Carter plan would also eliminate automatic night shift differentials for government workers in areas where private industry doesn't pay a shift differential, and also drop the so-called Monroney Amendment that requires the government to go outside a local wage area if private industry doesn't have employees doing the same specialized work as government aides. Any way the plan is sliced, it would mean smaller future raises for government blue collar employees and a slowing of the multimillion blue collar pay system costs.

AFL-CIO chiefs, who saw Carter's election as the greatest advance for civilization since dues checkoff, are furious over the blue collar plan. They have demanded an immediate audience with him to discuss it.

The big American Federation of Government Employees union said it is shocked and stunned at the proposed blue collar changes. Vice President Joseph Gleason says White House failure to consult with unions on the blue collar pay changes is "another glimpse of the new Administration's misunderstandings of its obligations" to employees and their unions.

"During Mr. Carter's impressive campaign," Gleason said, "we were often told that he would never lie to us. We sincerely hope that he doesn't mean he won't lie because he doesn't intend to speak with us at all."