SPRINGFIELD, Ohio (AP) — Faulty welding caused engine failure that led to the 2011 crash of a Wright Brothers biplane replica that killed two volunteer pilots, federal investigators said in a report released this week.

The two experienced pilots died when the Wright "B'' Flyer replica, dubbed "Silver Bird," crashed during an emergency landing in a field about 3 miles from an airport in Springfield, where they had taken off on July 30, 2011. Springfield is about 45 miles west of Columbus.

The broken propeller-shaft weld led to the loss of the newly built Wright "B'' Flyer's left engine during the test flight, according to probable cause report from the National Transportation Safety Board released Tuesday. However, despite losing one of the two engines, the report said, the pilots "should have been able to maintain control of the airplane during the forced landing attempt."

The report noted "incomplete weld penetration" that led to the failure of the joint and the loss of power to the propeller shaft.

The July 30, 2011, crash killed experienced pilots Don Gum, 73, of Beavercreek and Mitchell Cary, 64, of Yellow Springs. The men were members of Wright "B'' Flyer Inc., an all-volunteer, nonprofit organization that uses the planes to promote public awareness of Dayton as the birthplace of aviation.

The Dayton Daily News reported that both pilots were certified as commercial pilots and had more than 300 hours of combined flight time in the same make and model as the crashed airplane and more than 4,030 of total flight time.

Witnesses told federal investigators that the plane's engine speed began to vary as it flew at a low altitude. "The airplane was then observed in a spiraling descent to the ground," the NTSB report said.

The group's website said its first Wright "B'' Flyer "has been a flying ambassador of Dayton's aviation heritage for more than 25 years." Another non-flying model is on display near Dayton.

Wright "B'' Flyer Inc. President Phil Beaudoin told The Dayton Daily News that the company's management and board of directors were reviewing the probable cause report. The organization didn't immediately respond to phone and email messages Friday.

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Information from: Dayton Daily News, http://www.daytondailynews.com