COLUMBUS, IN — The 2,800-pound arm of a radioactive cobalt therapy machine fell yesterday and crushed the skull of a cancer patient, killing her instantly, officials said.

The machine's 2,800-lb arm fell and crushed the patient's skull, killing her instantly.

Officials at Bartholomew County Hospital did not know the cause of the accident that killed Alice Fleetwood, 59, of Seymour. A hospital official, Wally Glover, said a technician using a hand control had lowered the arm to about 18 inches above Fleetwood's head when it abruptly fell.The machine's 2,800-lb arm fell and crushed the patient's skull, killing her instantly.

Glover said the 2-year-old machine, routinely used for 14 procedures a day, is tested daily for mechanical and radiation safety.

AFTERWORD:

A report from the U.S. Food and Drug Administration in July 1987 said a vital link supporting the 4-foot-long arm of the machine disengaged before the accident. The FDA suspected that a steel coupling supporting the moving vertical column of the machine, may have become disengaged, allowing the shaft to run free.

The manu- facturer was quick to note the accident "definitely had nothing to do with radiation."

Although the units have been used worldwide for 30 years in the treatment of over 13 million people, Fleetwood's death represented the first cobalt machine-related fatality.

Fleetwood's husband filed suit against the manufacturer and the hospital, alleging, respectively, negligence in the device's design and failure to ensure its safety.

In its own behalf (and probably already sniffing the negative publicy), the unit's manufacturer, Atomic Energy of Canada Ltd., was quick to note that the accident "definitely has nothing to do with radiation."