Where the Plot Thins : IN THE BLUE LIGHT OF AFRICAN DREAMS <i> By Paul Watkins (Houghton Mifflin: $18.95; 310 pp.) </i>

Paul Watkins may be working a formula threadbare.

In his first novel, “Night Over Day Over Night,” published in 1987, Watkins, then 23, pulled a setting from his winter wanderings of Europe and World War II battlefields. He wrote of a 17-year-old German who joins the Waffen SS and ends up at the Battle of the Bulge--and Sebastian Westland escapes boredom and adolescence to lose innocence in a more graphic life.

In his second book, “Calm at Sunset, Calm at Dawn,” Watkins, an Eton-Yale scholar, replayed his summers aboard a scallop trawler. He wrote of a 20-year-old who goes to sea aboard a scallop trawler--and James Pfeiffer escapes Rhode Island’s ruling class to launch a personal odyssey in search of more solid human experience.

In his third and latest volume, “In the Blue Light of African Dreams,” Watkins, now 26, leans on two months he spent in Morocco and the lonely Sahara. He writes of a young American flier in North Africa with the French Foreign Legion--and Charlie Halifax is escaping the drudgery of life in the Pennsylvania coal fields for the higher purpose of military position and heroics.

Using one’s own life as research is, of course, a preferred literary form. But the triple reprise of a basic theme--one man, one search to discover that the grass is just as brown on the other side of life’s experiences--reduces good fiction to the level of Rocky and Indiana Jones.

Youth may be Watkins’ temporary enemy.

He obviously is an intelligent, interpretive, fluent writer. He has learned much from travels contrived not simply to see but to live the present of an environment and to meet its ghosts.

What Watkins has not learned is that simply changing the stage of his work--going from the land to the medium of the sea and now the air--does not really alter the plot. Also, that all the world’s searching and wondering is not performed by young men too callow to realize that personal happiness is neither a matter of geography nor occupation.

With a few more years attached to his understanding, Watkins may escape the restrictive denominator of characters who cannot see the endless subtleties of existence between the extremes of living and dying, lies and truth, boredom and adventure, frustration and fulfillment.

Yet in “Blue Light,” Watkins has succeeded admirably where most non-flying authors fail. He has completely captured the peculiar rhythms of men who fly.

Tom Wolfe, for example, confused professionalism with courage and saw flying as some racy, undisciplined divinity. He earned the ultimate bad review when Chuck Yeager said, years later, that he had not bothered to read “The Right Stuff.”

Because there is no right stuff. Just the very ordinary stuff of men like Charlie Halifax, the African dreamer of Watkins’ novel.

In the air he finds fidelity and emotional cleanliness. There is deep satisfaction from exercising personal skills until his mechanical inclinations evolve into human instincts. Yet glamour isn’t a part of his flying. Mystique is something that nonpilots create around airplanes. And courage is quite incidental.

Or as Watkins says of Halifax: “When he first began flying, he was always worried, but after months of working on his Spad, he trusted himself enough to know that if something went wrong, he would do everything that could be done.

“Beyond that, he figured, there was only luck. If his engine gave out . . . either there would be a place to land or there wouldn’t. He’d die or he wouldn’t.”

Watkins, according to a publisher’s press release, flew in biplanes so he would better know the element. That’s how he knew that a plane’s shadow follows the machine like a gray beetle. And that the monotony of an engine’s drone eventually produces silence in a pilot’s ears.

His Charlie Halifax leaves the pits of Brackenridge, Pa., after the death of his brother, Tom, in a cave-in. He has no money, no girl, no parents. Just the continuing nightmare of entering a bottomless mine in an endless search for a dead brother.

In World War I, flying first for Lafayette Escadrille, a squadron of American pilots, and then the French Air Service, Halifax finds a place, combat victories and a Croix de Guerre . He is on his way to the dream: Come home an officer, come home a hero, and quitting Brackenridge will be justified.

Then Halifax is shot down. In the hospital, he recognizes his mortality and knows that at that moment, if he returns to an airplane, he will die. Charlie Halifax deserts and his dream disappears.

He is recaptured and the sentence is his choice. Execution or a transfer to the Foreign Legion and flying in North Africa. Halifax, no dummy, chooses the Legion.

From that point, the story becomes Beau Geste meets Waldo Pepper to a concert of murder, betrayal, extortion, cheap cognac and psychotic despair in the solitary confinement of the Sahara.

Halifax escapes once more. He resumes his dream of returning home as a somebody, this time, as a competitor for the Orteig Prize--the trophy that in actuality was won by Charles Lindbergh for his New York-Paris flight in 1927.

Watkins paints good images. He sets the paths of nonsense we find in half-sleep. He knows that people do not die whole but are dismembered by airplane crashes. He makes us understand the weariness at having to find more energy to forget the death of a friend.

He excels at chronicling action--such as the visceral upset of aerial combat or the cold passage of flying a Levasseur across the Atlantic--but falters noticeably when it comes to varying dialogue to fit individual characters, or setting their appropriate emotional responses.

Halifax, in truth, is flat and formless, and it is hard to build any affection, sympathy or dislike for him. He appears short on humor and long on demons without any great reason for either condition. Is he a big man, an instinctively violent man, a patriot or an apologist or apolitical about his role in war?

Halifax certainly must also be the only fighter pilot in history to pass through training, combat across France, many years in the Legion and several months in Paris while remaining celibate in thought and deed all that time.

Despite a sprinkle of technical inaccuracies (the combat maneuver is an Immelmann Turn, not an Immelmann Roll), Watkins writes beautifully.

Now he must learn the change-up to better sculpt fresh yarns around more vivid characters and stronger plots than boy meets life.