An Andrews Air Force Base mechanic was arraigned yesterday on federal charges of attempting to destroy a commercial aircraft, after FBI agents said he placed a bomb in his wife's suitcase before she left National Airport Tuesday morning.

The homemade bomb, containing one pound of plastic explosives, two pounds of gunpowder and a large number of two-inch nails, passed undetected through security at National and Dallas-Fort Worth International airports and was discovered only when the woman began unpacking at her room at Sheppard Air Force Base in Wichita Falls, Tex., where she was to attend a training session.

According to an FBI affidavit, Airman 1st Class Martin Thomas Bradley, 27, of 6920 Pickett Dr., Morningside, placed a homemade plastic explosive device in the suitcase of his wife, Staff Sgt. Mary Jo Bradley, sometime before she boarded a 7:45 a.m. Braniff Airlines flight bound for Dallas-Fort Worth Airport.

She then took a commuter flight on Metro Airlines to Wichita Falls before using ground transportation to Sheppard Air Force Base, where she is enrolled in a three-month course in pharmacology.

At the base, "she opened her suitcase and saw a device that looked like a bomb," according to an affidavit by FBI agent Thomas E. Drewry. She called military police on the base, who contacted both the FBI and the Air Force Office of Special Investigations. Her husband was arrested while on duty at an Andrews Air Force base hangar at 4 a.m. Tuesday by FBI agents and is being held at the Prince George's County Detention Center in Upper Malboro on $400,000 bond.

The Federal Aviation Administration, which is responsible for airport security nationwide, is investigating how the bomb was permitted aboard Braniff Flight 111.

"The bomb, as I understand it, was in checked luggage," said FAA spokesman Fred Farrar. "That kind of luggage is normally not X-rayed, though we do have other procedures for screening luggage," he said. Farrar would not detail what those procedures are. He said the commuter airline would not normally subject luggage checked at a major airport, such as National, to any security checks.

"Apparently, something went wrong," he added. "Anytime you have a system that depends on people you're going to have an occasional lapse.

Bomb disposal units at Sheppard Air Force Base safely removed the device from the suitcase. Officials would not comment on why the bomb failed to detonate.

"Thank God that it didn't go off," said Air Force spokesman Lt. Col Robert Thatcher after Bradley's arraignment. "I'm no explosive expert, but that thing would have taken a lot of people with it," Thatcher said.

According to the FBI affidavit, on Feb. 17 Bradley discussed marital problems with a friend over beers. According to the FBI, the friend suggested: "Why don't you get rid of her?"

Bradley, according to the affidavit, responded, "I am--just wait and watch."

Since last November the Bradleys have shared a rented bungalow with Ellen Van Deusen, a Marine sergeant also stationed at Andrews. FBI agents searched the house late Tuesday night and found a cardboard box containing black powder, electrical wiring similar to that found on the bomb, and two sections of the Feb. 8 Washington Post. The classified section of that edition was found with the bomb in Texas, the affidavit said.

Van Deusen told agents that she had seen a new wind-up clock on the china closet Feb. 26. A similar clock also was found with the bomb, the FBI said.

Van Deusen said she met Mary Jo Bradley last October when they played on the base softball team. She met Martin Bradley later, she said.

"I've never seen a mean streak in him," Van Deusen said of Bradley.

Bradley, who was arraigned before U.S. District Court Judge George Burgess, had a clean record in the Air Force, according to spokesman Thatcher. A preliminary hearing on the charges is set for March 11 in Hyattsville.