WHAT do you do if your city is known as the car-theft capital of the United States? Get help.
In a helicopter hanging over Boston, just beneath a cotton-ball cumulus, police officer John F. Nolen Jr. is ''deputizing'' about 127,000 radio listeners:
''A few moments ago, a car was stolen at the corner of Arlington and Beacon, '' a typical bulletin starts. ''The suspect is driving a red 1978 Chevrolet Camaro, Massachusetts license number 270HIL. If anyone sees this vehicle, please call the Crime Patrol Hot Line, 254-1030.''
Officer Nolen's twice-daily broadcasts are unique. No other police unit in the country has such a partnership with a leading local radio station.
WBZ radio gives the Boston Police Department 24-hour access to its two-seater whirlybird. In return, WBZ gets an exclusive broadcast that's making things tough for BMW bandits and other car thieves.
Since its start in November, the Auto Theft Patrol has recovered more than 460 stolen vehicles. ''And in January and February, car thefts were down 30 percent from last year,'' Nolen says.
The program has worked so well that it was recently expanded to include reports on all major crimes.
Part of the success can be attributed to the high priority the program receives from the radio station and the police department.
In addition to rush-hour broadcasts, ''I have bulletin status with WBZ. I can cut in anytime,'' Nolen says.
''And (Police) Commissioner (Joseph M.) Jordan agreed to make it Priority One. . . . If a call comes in, say a car-stripping in progress, (we) can fly to the scene. If the suspect flees, we follow him and direct ground units to his location.''
Without public participation, Nolen could buzz over the city all day to no avail. But he says Bostonians are ''fed up'' with carrying the auto-theft crown (and the insurance costs).
''People are aggravated by stolen cars - by crimes that affect the quality of life here,'' agrees silver-haired police commissioner Jordan. ''(With programs like this) the public is saying, 'The apathy is over. We're going to do something about it.' ''
As the emphasis has shifted beyond auto theft to other major crimes, Nolen is making fewer broadcasts from overhead. Often his reports are aired as he guides his police cruiser along the city's brownstone-flanked streets. On a recent morning, before heading out on patrol, he explained what the program has done for him.
''Before I started on this, I spent two years in drug control, dealing with the lowest caliber of people. I came away a cynic.''
When the theft patrol caught on, ''I was flabbergasted that the public would want to get involved. This has been good for my morale and, I think, the department's, too. I had almost given up on society,'' he confesses.
Even as Nolen's program was getting off the ground, auto-theft rates were falling here and across the nation.
Last month, Boston reported that car thefts fell 16 percent in 1983. While national crime figures from the Federal Bureau of Investigation won't be released until later this month, State Farm Insurance says it recorded a 14.1 percent dip nationwide. State Farm is the largest auto insurer in the United States.
Credit for the decline is given to the beefed-up efforts of various state and city auto-theft task forces. Some experts, however, say the decline is due to demographic changes as much as to enforcement measures.
Nonetheless, Boston officials are saying that because of the 16 percent drop, they expect another city will inherit the infamous mantle for absentee autos.
According to the National Auto Theft Bureau (NATB), Boston's closest rival for top auto theft billing in 1982 was Detroit. Police there say vehicle thefts were up in 1983. Even so, Boston's auto pilferage per capita rate was still 13 percent higher than Detroit's in 1983.
One national auto-theft expert applauds Boston's progress but warns it must be put into perspective: ''Most places you catch fish by trolling. In Boston, you just stick out your hand and grab them.''
Maybe so. But the job isn't getting any easier. The recovery rate of stolen vehicles in the US has dropped from 90 percent 20 years ago to 54 percent in 1982. ''Auto theft and fraud has reached the highest degree of sophistication ever encountered,'' says Tim Kett of the NATB.
Auto-theft rings are no longer state or nationwide; they're international organizations. One of the surest ways to get rid of a hot car is to export it, Mr. Kett says.
''A spot-check of a New Jersey dock turned up 100 stolen vehicles,'' Kett says. In Miami, we found 56 on one day, on one dock.'' How many cars go out this way? ''Anywhere from 25,000 to 200,000,'' he guesses.
Currently, a car can be exported without any identification until 72 days after it leaves the country. A bill requiring identification before export has been awaiting a Senate vote for several months now, says Chuck Taylor of the National Association of Independent Insurers.
The rise in exporting stolen cars may be matched by the climb in auto insurance fraud.
Nationally, insurance fraud accounts for about 15 percent of the cars reported stolen, says Kett at the NATB. In Massachusetts, the figure is closer to 25 percent. Some experts say fraud is on the rise; others say insurance companies are just getting better at detecting it.
Finally, recovery is made difficult because many stolen autos today are quickly dismantled for parts in a ''chop shop.'' A car in pieces is worth about three times its assembled price.
Once a car is dismantled, the unmarked parts are sold on the open market. Legislation to put vehicle indentificaton numbers (VINs) on more components and to increase criminal penalties is now before the commerce committees of the US House and Senate. But progress is expected to be slow. The auto industry opposes the section requiring VINs on more auto parts.
Back in Beantown, Commissioner Jordan has his own ideas about how to combat vehicle heists. ''Passing laws is not always the most effective method. Once the public becomes aware and participates, that's when you get positive results.''
Now that Nolen has expanded his beat, the program has a new rubric - ''The Crime Patrol.'' He explains:
About a month ago, ''I was driving through Roxbury, stopped at a light, and another car pulled up with a guy and a girl in it. He rolled down his window and yelled, 'Someone just tried to rape this girl.'
''I drove to the location he gave me and spotted the suspect. The chase was on. We were coming up on my scheduled broadcast, so I gave out a description. We got calls from all over. Then I realized the potential here for all major crimes.''
With information provided by the public, the rape suspect was caught and later convicted, Nolen adds.
The Crime Patrol concept may be getting air time elsewhere. Nolen has received inquiries from Philadelphia and several cities in Florida.