McGinty

— Plaintiffs file this petition for extraordinary relief from an order precluding them from using their expert witness and from presenting certain evidence. We find merit in the petition and will issue a peremptory writ to vacate the challenged order.

Facts

In this wrongful death action, petitioners assert a product liability cause of action against real party in interest, Avco Corporation (hereafter, Avco). Avco had designed and manufactured the engine of the private aircraft which crashed, killing all the occupants therein. Petitioners are the heirs of the deceased occupants.

Petitioners’ expert witness, Craig Hood, is of the opinion that the engine failed because an internal bolt had malfunctioned due to stress fatigue. The bolt was unduly stressed because the connecting mechanism of which it was a part did not have a locking nut which would have prevented loosening of the bolt and consequent unacceptable tension load on it. The history of the engine design shows that at one time the design provided for a fatigue-rated bolt and a crimp nut which prevented the bolt from loosening, but the design was subsequently changed to provide for a fatigue-rated but nonlocking…