FORT RUCKER, Ala. (AP) _ An Army flight instructor was charged with attempted murder after military authorities said he tampered with 11 Army helicopters, some of which were flown before the damage was discovered.

Chief Warrant Officer Louis H. Plunkett Jr., a helicopter flight instructor at the Fort Rucker training school, was charged Friday with tampering with government property and attempted murder under military law, said Bill Hayes, a spokesman for the south Alabama base.

Hayes said Plunkett was apprehended Nov. 10 and was reassigned to ground duty while military police and the FBI investigated.

The attempted murder charges did not arise from any crash, Hayes said, but from several instances in which OH-58 helicopters that had been tampered with carried pilots and students into the air.

''In the course of these many tamperings, some of the aircraft had people aboard,'' Hayes said.

The first reported tampering was in May and involved damage to helicopter oil pressure lines. Some of the tamperings also involved sand in oil tanks and sugar in gas tanks.

A flight instructor and a student pilot were killed Dec. 9 when an OH-58 helicopter crashed in a clearing about 1 mile northwest of the base, but Army investigators said they found no evidence of any intentional damage to the craft.

Hayes said no fatal crash had been traced to a tampering incident, but the investigation will continue.

Plunkett was not placed in the Army stockade but was under strict supervision of his commanding officer, pending further proceedings in the case, Hayes said.

Hayes could not say how much prison time Plunkett might face if convicted on all charges.