TEL AVIV, Israel — The U.S. Army has joined the Israeli Air Force in a sweeping investigation of AH-64 Apache helicopters following Israel's discovery earlier this month of a crack in the rear rotor blade of one of its aircraft, defense and industry sources here say.

In interviews here Monday, a defense source noted that prime contractor Boeing is working with the Israeli Air Force and the U.S. Army to determine the cause of the crack. So far, he said, only one Israeli Air Force platform appears to be impacted by the potential problem surrounding the safety of flights.

"It's a very thorough investigation. We're checking all the rotors, and that could take another few weeks," the defense source said. "At this point, we can't point with certainty as to what caused the crack. It could be a matter of imprecise production or flaws in the layers of [the blade's] complex material."

Since the investigation began here June 13, Israel's Apache attack force has been grounded and will remain so pending conclusions of ongoing inspections, according to the Israeli military. 

"The investigation in regard to the crack that was found in the blade of the tail rotor is still underway. The Apache Squadrons will continue being grounded until the investigation is completed and all the aircraft are approved for flight. The findings of the investigation are openly being analyzed with senior commanders in the Air Force," an Israeli military spokeswoman told Defense News on Monday in response to queries.

Boeing and the U.S. Army did not respond to requests for comment by press time.

The Israeli Air Force's Depot 122 at Tel Nof Air Base is leading the ongoing inspection.

Opall-Rome is Israel bureau chief for Defense News. She has been covering U.S.-Israel strategic cooperation, Mideast security and missile defense since May 1988. She lives north of Tel Aviv. Visit her website at

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