BY MARK BRAYKOVICH
The Cincinnati Enquirer

Thomas Watson learned years ago that airplane crash investigations - at least in their early stages - are not about learning what brought a plane down.

Instead, the retired National Transportation Safety Board investigator said, ''They are a process of proving what didn't happen.''

That philosophy underscores the approach NTSB investigators will take as they examine remains of Comair Flight 3272, which crashed Thursday afternoon in a fireball into a snow-covered field in Michigan.

The probe - likely to be slow and unlikely to yield any answers for several months - will begin with the idea that every cause is possible, from human error to mechanical failure to bad weather. Mr. Watson and current NTSB staffers say the secret to a successful investigation is not to rush and not to rule out anything.

''The important thing is don't get in too big a hurry. You might miss something,'' said Mr. Watson, who, in 20 years at NTSB took part in 679 accident investigations. He recently wrote a book about his experiences, titled Unhappy Landings: Why Airplanes Crash.

During the course of an investigation, numerous obstacles can be expected. Already, investigators are facing bitter cold and blowing snow at the Michigan crash site.

But even more difficult will be finding easy answers to easy questions. Was it ice that caused the Comair flight to crash? Mr. Watson said that can be difficult to determine quickly since the ice isn't there when investigators arrive.

Was it the engines? If they have been destroyed or badly damaged in the crash, the evidence can be obscured.

To get to the answer, the 11-member NTSB investigation team - headed by Richard Rodriguez - will methodically pick apart the wreckage, interview witnesses, inspect records, and study the plane's so-called black boxes - the cockpit voice recorder and the flight data recorder.

Among the initial steps:

• Assigning guards to the wreckage. Protecting the integrity of the crash scene is vital, said Mr. Watson.

• Surveying the scene. Investigators need to know what natural elements they are up against, how large the crash site is, what parts of the plane still appear intact. This will help them determine what assistance they will need.

• Organizing the investigation. After surveying the scene, Mr. Rodriguez's team from Washington, D.C., will lead working groups, each with specific duties. This is to ensure that investigators don't focus on any one possible cause until much later in the probe.

NTSB spokeswoman Shelly Hazle said likely groups on the Comair Flight 3272 crash are structures, systems, weather (was icing possible, for instance), maintenance, air traffic control (what communications took place), power plant systems, human factors (how did pilots respond), aircraft performance (what did it do shortly before crashing), and operations (a detailed look at Comair).

Key to the investigation are the black boxes. Mr. Watson said that the data recorder might disclose if de-icing equipment on the plane was working properly. It also could yield other vital clues as to what happened.

The voice recorder may provide the last communications on the plane. Both units, once found, will be immediately sent to NTSB headquarters in Washington for processing.

Other parts of the plane will be gathered and shipped to another location for review. If the engines are intact, they would be sent back to the factory to see if they still work.

CRASH
FAMILIES
CREW
MINISTER
SCENE
TRAVELERS
COPING
INVESTORS
TODAY'S SUMMARY

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FIRST-DAY COVERAGE Jan. 10, 1997

Victims

First Officer
Kenneth Reece

Flight Attendant
Darinda Ogden

PASSENGERS
Adams, Dexter
Cincinnati

Barrow, Gregory
Detroit

Bransford, Roger
Atlanta

Brice, Arthur
Brookhaven, Miss.

Brownlee, Christine
Helena, Mont.

Brownlee, Scott
Helena, Mont.

Davis, Geoffrey
Detroit.

DeMarco, Maureen
Englewood, Colo.

Douchard, Greg
Brookhaven, Miss.

Felteau, Leo
Atlanta

Herman, Mark
Detroit

Jones, Betty Jean
Detroit

Jones, Charles
McComb, Miss.

McClain, Steven
Detroit

Muskovitz, Teri
Detroit

Passariello, Kim
Detroit

Raymond, Roy
Twin Falls, Id.

Raymond, Vernamarie
Twin Falls, Id.

Rosiak, Jennifer
Pensacola, Fla.

Rosiak, Nicholas
Pensacola, Fla.

Sharangpani, Arati
Colts Neck, N.J.

Stearn, Richard
Detroit

Takenami, Keita
Lexington, Ky.

Thomas, Douglas
Detroit.

Wansedel, Charles
Detroit

Zagar, Darlene
Danville, Ky.