"Blue Thunder" chops through the sound barrier in this louder-than-life, high-velocity "Smokey and the Bandit" meets "Apocalypse Now." With Roy Scheider as a helicopter cop at the controls, it leaves you shell-shocked: The only thing more thunderous than the score is the crowd's satisfied roar.

Director John Badham (his own best competition this summer with the upcoming "War Games") shamelessly plays to the fans. This includes high-altitude T&A: "It peeks down dresses at a thousand feet," exclaims Murphy (Scheider) to his pal Lymangood (Daniel Stern), the greatest "golly-gee" sidekick since Robin took up with Bat Man.

Of course, the star is Blue Thunder -- a hooked-nosed, overarmed, attack-capable killer bee of a whirlygig. It hears all with its electronic ears (moaning in the bedroom) and sees all with its infra-red eyes. It's computerized and has whisper mode. Shhhh. It can sneak up on you, spy on you and look you up in the phone book.

The film is an unabashed opportunity to wallow in the legacy of Watergate. Stoke the paranoia. Get burning mad at the power- mad feds who're stirring up a race riot just to test the crowd-control capabilities of Blue Thunder.

And for the forces of good: Murphy, a Vietnam veteran subject to flashbacks -- like Clint Eastwood in "Firefox" and Sylvester Stallone in "First Blood" -- snatches the big bird and leads a merry chase through Los Angeles. He's followed by heat-seeking missiles fired by one of two F-16s scrambled to put the kibosh on his caper. There are always three explosions when one would do. And the action, which rarely touches down, even maintains a ripping groundspeed during a car chase with Murphy's madcap girlfriend (Candy Clark) at the wheel.

It's not all metallic mayhem. The late Warren Oates' performance is the best in the film, which is dedicated to him. He plays the wisecracking, head-cracking, tail- chewing chief of the helicopter squad. His rogue's delivery makes the most of some super lines written by Dan O'Bannon and Don Jakoby. Example: "You're supposed to be stupid, son, don't abuse the privilege."

But mostly, the sky's the limit: Choppers career just above the concrete bed of the dried-up Los Angeles River, smashing into pylons. There's a hide-and-seek inside, outside, all around the skyscrapers.

"Blue Thunder" hovers just this side of trash and the other side of credibility, but it propels a willing audience into adrenaline heaven. BLUE THUNDER At area theaters.