Remember "Operation Breakthrough"?

It was a lot of HUD hoopla about mass-producing houses like automobiles, touted 10 years ago by then secretary of housing and urban development George Romney.

Romney's idea was the same dream on which the modern movement in architecture was originally built -- the dream of a marriage of art and technology that would give birth to a better world. Technology, alas, never got in bed with art. Modern architects only made their creations look high tech.

The only kind of housing that became sufficiently industrialized to be mass produced for the downtrodden masses is what used to be called house trailers, more lately upgraded to "mobile homes" and most lately advanced to "manufactured homes." They are considered neither architecture nor modern.

Yet about 10 million Americans live in about 3 million mobile homes.

Last year 276,941 of them were produced by some 175 manufacturers. This year, sales have declined by 20 percent, but the sale of conventional, or "site built" homes, has declined 45 percent.

Selling for an average of $16 a square foot, as compared to $38 a square foot for conventional homes, mobile homes are the only recourse for people of moderate means who want to own a place to live but cannot get government subsidy. Many elderly poor people live in them.

The average mobile-home manufacturer employs 114 non-union, semi-skilled or unskilled workers, working on an assembly line. The large factories make up to 10,000 homes a year.

Now even this modest and inadvertent breakthrough is breaking down -- or so the Federal Trade Commission tells us in a voluminous staff report. The report charges that mobile home "sale and service is unfair and deceptive" and urges more consumer protection.

Walter L. Benning, the president of the Manufactured Housing Institute, the trade association of the mobile-home makers, says these charges "are utterly out of touch with reality."

In reality, Benning asserts, mobile-home owners are as well protected as new owners of conventionally built homes. What is more, he says, the break-through in housing production is at last in the offing. "By the end of the 1980s, half of all new housing units will be mass produced in what are now called 'mobile home factories,' carpets, draperies, and all, and wheeled to the site."

This prediction does not necessarily need to fill us with horror. It does not necessarily mean that America will turn into a continental trailer park. We might tame the trailers and teach them to live in cities. Mobile homes have already come a long way since the Conestoga wagons, which expanded the American frontier.

Horses were replaced by automobiles. Covered wagons were replaced by "house trailers," which became popular after World War II. They were usually 8 feet wide and 25 feet long. Today's mobile homes are 14 feet wide, which is the maximum allowed by state highway departments, and usually 70 feet long. More than a third of them are "double wide." that is, two units are joined.

Nor are mobile homes mobile any more. Not to be confused with "recreational vehicles," built to roam or roam in, mobile homes usually make only two trips: From the manufacturer to the dealer's sales lot, and from the lot to their permanent site. The site is usually a trailer park, where owners pay rent for their space and find not only water, sewer and electric lines to plug in, but also such community facilities as laundromats.

Nor do recent model mobile homes pretend to look mobile, streamlined or somehow from outer space. They increasingly pretend to look like homes -- with shutters, little white fences, roses by the door and all.

Since 1976, mobile homes have been subject to federal construction and safety standards imposed and enforced by HUD.The standards are equivalent to most building codes designed to assure the safety of buildings constructed on the site. HUD inspectors, however, inspect mobile homes only when they leave the factory, and what worries the FTC is that a lot can and often does happen on the road and as the home is "set up," as the industry calls it.

What happens, says FTC, is that travel can rattle and bounce a mobile home out of shape so that leaks develop, windows and doors get out of joint, plumbing malfunctions, walls buckle and furnishings get damaged. A mobile home has some 3,000 parts.

And as the home is installed, the dealer can make mistakes. It is a complex operation. FTC says some homes have simply been dumped on the ground, so that doors and windows did not properly open, creating a fire hazard as well as annoyance.

HUD standards are no protection against mishaps hundreds of miles from the production line. The only protection the purchaser has is the manufacturers' warranty under the Magnuson-Moss Warranty Act. But there seems to be some confusion here, according to the FTC report. Warranties are sometimes vague as to who is responsible for repairs -- the manufacturer, dealer or consumer.

Some mobile-home manufacturer warranties do not cover transportation, none include "set-up," and dealers, says the report, often refuse to assume responsibility. Even if they do, it can take months until the dealers make needed repairs. Repairmen are hard to find. Mobile-home owners often lack the education to insist on their rights. Besides, says the FTC, the mobile-home industry does little advertising, telling consumers what to expect of its products, and individual manufacturers are virtually unknown -- the homes usually have only model names -- and thus the manufacturer does not have a reputation at stake. Dealers, who do not need much capital to get started, are often fly-by-night outfits.

Industry spokesmen complain that the FTC report is based on outdated information, on complaints made before the HUD standards went into effect four years ago. The standards, one manufacturer said, drove some fifty small-time operators out of business. "FTC is just empire building." he said. "It wants something more to regulate."

The most sensible solution, it seems to me, is for Congress to enable HUD inspectors to check mobile homes before the keys are handed to the new owner and hold manufacturers responsible for repairs, as it has done for conventional housing. That will also prompt manufacturers to license responsible dealers.

But if industry predictions are correct, mobile home dealers along the freeways will soon disappear. The trend is for traditional suburban developers to put up a whole subdivision full of manufactured homes and sell developers to put up a whole subdivision full of manufactured homes and sell them in traditional ways. They will have pitched roofs and cathedral ceilings, and not even their salesmen will know for sure that they were assembled in a factory hundreds of miles away and came on a chassis with wheels.

The rising cost of conventional housing construction makes this prediction alarmingly plausible. What is alarming is that this trend, if uncontrolled, would further sprawl housing -- this time low-income housing -- into the countryside, where the land may be cheaper, but roads, sewer and waterlines are be increasingly more expensive. We would gain low-cost housing at a frightful cost of energy.

What is needed, therefore, is not only more consumer protection for mobile-home buyers, but consumer protection for all of us, a.k.a. planning.

Far-sighted planning would do away with the prevailing prejudice against "trailers" and permit safe and attractive manufactured housing within existing communities where zoning now bans it. It would encourage the use of manufactured units, moved on wheels, to be assembled in multi-unit, multi-story apartment structures.

One such "multiple mobile home" building, a 320-unit condominium is currently under construction in Houston. The apartments sell for $36,000 to $52,000, according the Manufactured Home Institute.

More moderately priced housing? Now that would be a breakthrough.