LOS ANGELES (AP) _ A special effects man hostile to the prosecution in the ''Twilight Zone'' manslaughter trial insisted he would have felt safe firing a bomb while inside a thatched hut on the ill-fated movie set.

''I don't feel there'd be any big problem,'' Harry Stewart testified about a special effects mortar which the prosecution claims demolished the hut and blew debris into a helicopter, causing it to crash.

The aircraft used in the filming of ''Twilight Zone: The Movie,'' crash- landed July 23, 1982 on top of actor Vic Morrow, 53, and two children - Myca Le, 7, and Renee Chen, 6 - killing all three.

Film director John Landis, special effects coordinator Paul Stewart, production manager Dan Allingham, associate producer George Folsey and pilot Dorcey Wingo are charged with ivoluntary manslaughter in the deaths.

''Mr. Stewart, didn't you testify (at grand jury hearings) that the reason you don't put mortars under huts is because debris can fly up?'' Deputy District Attorney Lea Purwin D'Agostino asked Monday.

''I don't remember,'' replied Stewart, who said he is a close friend though not related to defendant Paul Stewart.

Defense attorneys dispute the theory that debris caused the crash.

Harry Stewart insisted Paul Stewart was careful and safety conscious in his job as special effects coordinator.

Mrs. D'Agostino, frustrated in her attempts to get answers from him about the danger of explosives on the set, finally asked whether live ammunition was used by filmmakers two days before the helicopter accident. Stewart admitted it had been and described Paul Stewart firing a 12-gauge shotgun on the set.

On cross-examination, Stewart's attorney, Arnold Klein, tried to show that plastic pellets inside the shells used were not lethal. He had the witness open the shells and passed them around to jurors.

But on redirect examination, Mrs. D'Agostino asked: ''Can these shells kill people?''

''Yes. Yes, certainly,'' said the witness.

He said he could not remember where special effects bombs were placed on the fatal night or whether he was involved in placing them. Nor could he remember if there were any meetings to discuss the location of bombs.

When Klein showed Stewart a dollhouse-sized replica of the hut and asked if he would have felt safe standing inside it and firing the mortar, Stewart said he would.

Outside court, Mrs. D'Agostino branded the witness ''less than truthful,'' and said, ''He is trying to minimize the danger that existed on the set.''

Asked why she called him as a witness, she said, ''I think it's necessary to call all the special effects people.''

Stewart's appearance disrupted the trial, as he suffers from acrophobia, a fear of heights, and refused to appear at the trial's 15th floor courtroom at the Criminal Courts Building.

As a result, Superior Court Judge Roger Boren moved the trial, including jurors, court staff and principals, to a second floor courtroom in the county courthouse two blocks away.

Ealier Monday, fire safety officer George Hull was silenced by the judge after he blurted out to jurors that the National Transportation Safety Board had concluded that flying debris thrown up by the special effects explosions caused the helicopter crash.

The defense, which says the NTSB conclusions are inadmissible, objected.

The judge refused to strike the testimony but ordered Hull not to mention it again.

The trial was recessed until Wednesday because of the Veterans Day holiday.