Four-thirty p.m., 500 feet above Washington and jiggling. The rotor whacks overhead in that odd fwop-fwop. Condor -- the same type of ancient chopper you see on "M*A*S*H" -- leans in a tight circle over the bank robbery that isn't happening, and one's stomach -- perhaps the rest of the body, but consciously the stomach -- pulls toward a long . . . long fall through a giddy space in which there would be nothing whatever to grab.

The robbery isn't happening because they usually don't, false alarms being the rule, but three squad cars are parked in front, green numbers visible on their roofs. A lot of people don't know that police cars and buses have numbers on top. Officer-pilot Jim Trainor tries to explain what's happening over the intercom. That isn't easy because helicopter intercoms are almost insuperable barriers to communication, and anyway you wear earplugs under the headphones if you're smart: "Choppers are noisy in the high frequencies," Trainor says. "You don't notice it until you're suddenly tone deaf . . . Rawk . . . scree . . . prozzbaly . . . rarf . . . some guy set the alarm . . . you know, you got 30 seconds to get out after that and eeee . . . four-oh-four Rabbof? Roger . . . forgot his hat, so he goes back to get it, and the alarm goes off. Happens all the time?

Trainor is 33, good-looking in a boy-next-door way, too practical to be sophisticated in the Washington scene. He can understand that squawking racket. He got his training in Hueys during combat runs in places like Nha Trang, more harrowing than clear air over Dupont Circle, so there is not a great deal about helicopters that strikes him as fundamentally mysterious. As long minutes drift by, he conveys in so many words that it can be boring to jiggle around up there on the Great Plag Pole in the Sky, peering down from a plexiglass fishbowl in search of evil. When things get busy on the ground, sometimes they just hang there for two hours.

It's even more boring in the ready room at National Airport, in the big hangar beyond the north terminal. Here the four choppers of Helicopter Branch of SOD -- Special Operations Division of the Washington, D.C., Metropolitan Police -- sit in a glorified concrete-floored quonset hut the police share with the aerospace technology department of the University of the District of Columbia. Most of the helos are used, bought from various sources -- two from the Army, one from Los Angeles Environmental Protection Agency. One was bought new from Bell Helicopter. The plexiglass bubbles and long tail booms make them look like erector-set dragonflies stored for some curious future use.

In the police room at the south end, the flying cops drink a lot of coffee. They talk a lot of police talk, which sounds like: "We get this family fight, so we head for the address, and I call for a back-up. We go in. The old lady says she wants her husband in jail, says he's beating her up. He's drunk and raising hell. You sure, Lady? I ask. Oh yeah, she's sure. Okay. We put him in cuffs. Then she runs for the bureau. I've seen that before, so I rush her. A gun. She's gonna kill us for taking him away. Domestic cases, they're the worst . . ."

Pilots fly two hours at a time, and get $2,270 a year flight pay above their regular salary. They inspect their birds very carefully before take-off. The mechanics are good, but the pilots care. There are ways of landing a chopper, sort of, if the motor quits, provided that the rotor doesn't hit telephone wires, and that the pilot doesn't land on Connecticut Avenue and get hit by a Metrobus.

The pilots look at the motor, the oil, the fuel and the nut that holds the rotor on -- the Jesus nut in military parlance, because if it comes off, there is nothing to say but, "Oh, Jesus."

Two men make up a helicopter crew, the pilot and the observer. The observers usually want to go to Ag-Rotors school in Gettysburg, Pa., and learn to be pilots. In daytime, the observer's job is look for whatever is going one while the pilot keeps the thing in the air.

All night the observer aims the Nightsun, a spectacular 3.2-million-candlepower searchlight on a motor-driven mount. Automobile headlights, quite powerful actually, run to about 20,000 candlepower. To a fugitive on the ground, a Nightsun is a blinding, eerie illumination that makes hiding impossible. Hippies of other times and places, when discovered in various illicit occupations by airborne searchlights, have said it was terrifying to the point of inducing psychological disorientation -- a painful beam from an invisible helicopter, the threatening motor noise that stays relentlessly overhead and an unbearable feeling of being watched. They called the flying patrols "space pigs."

Night, maybe 8 p.m., jiggling in circles over Washington on the Great Flagpole. It's darker than a tax collector's heart and the city is laid out below, a platter of glowing jewels. Darkness improves Washington. Highway cloverleafs turn into dropping graceful necklaces of taillights, bridges into moving strands of luminescence, parking lots and disasters of federal architecture into patches and cubes of cold blue mercury lights.

Higher up, night is unsettling in a chopper because the world beyond the fish bowl stops. Sensory deprivation sets in. You can't see anything above the ground level, can't feel much but the vibration, can't hear anything over the engine racket. The mind can get a little strange. One could start wondering what's out there in that Stygian undersea nothingness -- birds, unlighted airplanes, maybe Rodan the Reptile Bat from Childhood movies.

A call comes. Some poor crazed son of a gun just leaped off Key Bridge. The pilot, John Kolanko, puts Condor into fast forward and heads for Georgetown at 90 knots. The chopper doesn't seem to move, instead the platter of jewels tips slightly, picks up speed and flows under, a river of light. Condor 2, the companion chopper, dangles in the darkness behind.

Key Bridge rushes below, crawling with headlights. The water, beneath the bridge is clear, but the rest of the river is covered with rotten ice. Icy air whips through the bird. What with the wind and weather, it's an awful night for suicide. There is no jumper aboard the bridge. Maybe he is already dead, or maybe he changed his mind and went home. A less pleasant possibilitiy is that he changed his mind after hitting the water, but couldn't swim in the cold. Both helos bank into tight circles, one at 500 feet, the other at 300. A tight circle means everyone would fall out without seat belts. Like balls on a string, the helos swirl around and . . . around and . . . around.

"Rawk -- probably under ice. Let's find that body."

From the air one begins to take a detached view of human scurryings below. A helicopter is psychologically as far from the ground as Calcutta is from Washington -- no one wants beggars to die of grotesque diseases in sewerless slums, but no one can get emotional about it either. Some guy is probably down there twitching his last under six inches of filthy ice, for some reason that seemed better than it probably was -- but from the air he is just another jumper, an interesting puzzle for 15 minutes, and where the hell is he?

A police dinghy appears from somewhere and rushes around, its occupants peering at the ice. The other chopper puts the Nightsun on the water as the two birds go round and round, a long blue beam of light. A ghostly white shape erupts from down river and shoots toward the bridge: a Park Police helo, zipping over the ice. It is so low that for a wild second it registers as a boat breaking its way through the ice at 75 m.p.h. It flies under the bridges. Probably won't put that in the report.

The jumper isn't under the ice. The Nightsun finds him swimming unnoticed in open water beneath another span. The dinghy goes to pick him up, whereupon he tries to slug the officers and stay in the water. Some jobs are thankless, but some are utterly thankless.

A matter of considerable concern around the hangar is that some elements in the department want to get rid of helicopter operations. One reason is money. It costs about $30 an hour to keep the helos in the air. Helicopters are expensive, even secondhand ones, and some think the money could be better spent on other things.

Lt. Jim Hampton, commander of Helicopter Branch, had doubts himself. "Before I came to the outfit, if you had asked me how to save money for the department, I probably would have said get rid of the helicopters. I've changed my mind now that I know something about it. Running the helicopters for a year costs as much as paying five officers. They do more than five men could ever do."

According to some people in the department, another reason may be resentment of men who are imagined to be glamorous flyboys, having nice, safe fun in the air. In fact, it isn't that much fun, and the two fliers who died in the crash last year might not think it's too safe. Still, there's low-key friction with the rest of the force. Some officers think the squad cars don't call for a chopper if they can help it.

Over 14th and U. Below are trashy lots, piles of rubbish, bulidings with collapsed roofs, people standing idle on corners. It is a bleak, violent world.

A few weeks before, people here laughed and clapped as a punk drug dealer gunned down a policeman. Jim Trainor seems neither surprised nor bitter. He says philosophically, "Those are different people living down there, with different ways of seeing things. You gotta remember that."

He lets it go at that: a different way of seeing things. The airborn cops have all spent years walking the streets, often in the city's slums. An officer has to be in the force three years before getting into helicopters. They know 14th and U in its seamy detail and individuality, know the pimps by name and hookers by family history. Sociologists deal in stereotypes, but cops deal in people. They know the motivations of the slums, and to a degree, are not unsympathetic.

"Our most active nights are Friday -- payday -- and Saturday," says Trainor. "You get a lot of burglaries and cuttings while the liquor lasts. By Sunday they're getting sober again. Crime's picking up now because the economy's getting worse. If a man's family is hungry, he's gonna rob a 7-Eleven. He's not gonna let his kids starve. No man can do that." Hang around the ready room and you hear the same thing -- the economy, jobs are scarce, people are hungry. Maybe they get a little liquored up and, bang, the liquor store gets robbed.

Hovering over an apartment complex in Southeast. Two squad cars are parked in front, answering a complaint that a stranger is wandering in the corridors. It turns out that he isn't there any longer. "GOA," says Trainor. "Gone on arrival. That's mostly what police do -- check on things that aren't really happening and do social work. Police work is mostly social work. You know, family fights, looking after drunks. Same thing up here, really."

Sometimes things do happen, especially but not exclusively on warm-weather weekends. A call comes, a stabbing in Southeast. The radio squalls and hisses, the pilot, Officer Stan Robers, acknowledges, and the rotor slopes forward. In daylight a chopper doesn't seem to go very fast. It just drifts with determination. In the clear slanting light of afternoon, the city glows brick red and sharply defined. Washington is a different city from 500 feet, sometimes prettier and sometimes uglier, a crust of buildings stuck to the earth. Over the radio someone says, "Two suspects, male in blue jacket and male in brown jacket."

Below, the streets lie in a crossword puzzle in black and brick, with a crowd at the corner, an amublance, a squad car, and fire enginge. The relevance of a firetruck to a stabbing isn't clear. People in the crowd look like bees on a hive, most in a clump but with detached individuals going and coming.

Condor circles, looking for blue and brown jackets. By an unalterable law of helicopter work, everybody in the street seems to be wearing blue and brown jackets. Three of them look at the chopper and spring down the street. Roberts veers the helo after. These are the suspects?

"Can't tell. Kids do that, run for the fun of it. They know you're looking for somebody and they like to fool you. The guys you want, they may be wandering around with their hands in their pockets, if they're smart."

If the helo is after the right people, they will have a hard time escaping. Almost the only way to get out of sight is to go into a building, and then you're caught. The helo flies high enough that it can watch the streets on all four sides. The Nightsun lights enough area that it can do the same thing at night.

The chopper also makes a fearful racket, which results in angry calls to the police. "Sure, we get complaints," says Lt. Hampton, "but in 99 percent of the cases, when we explain that there was a robbery or rape in the neighborhood, they understand and tell us to keep at it."

A squad car radios up the name of the victim. Roberts says. "Yeah, I know him. I've arrested him several times." It used to be his beat. Meanwhile, the suspects have come to a halt and are waiting for a bus. Sure enough, they are the wrong guys. Elsewhere the attackers are being arrested by patrolmen. Condor drifts over to prov ide extra security.

Condor flies up the Potomac from National, sailing over gray water and narrow mud beaches. In winter the river has a dreary, peaceful solemnity that can be nice, a relief after the human ferment of Washington. An occasional lone man walks with his dog. "When the water's low it looks a little like Nam," says Trainor, who is explaining that the choppers are good for finding bodies, a regular part of a pilot's job. "Every year a couple of people drown -- suicide, accident, whatever. You lose 'em beneath the ice. When spring comes they bloat and come up. Sometimes we find 'em. It's part of the job."

Hour after hour of circling, boredom, false alarms, robberies, jumpers and a few bodies. It could be worse. It could be better.