By Mary Pieper, Mason City Globe Gazette

MASON CITY — Icing was the probable cause of a Mercy Air Med helicopter crash near Ventura that killed three people on Jan. 2, 2013, according to the National Transportation Safety Board.

A report released by the NTSB Thursday stated, “It is likely that the pilot inadvertently encountered localized icing conditions, which resulted in his subsequent in-flight loss of helicopter control.”

The helicopter was carrying pilot Gene Grell, nurse Shelly Lair-Langenbau and paramedic Russ Piehl. They were on their way to pick up a patient in Emmetsburg when the helicopter crashed into a farm field.

According to the final NTSB report, observations from the nearest Automated Surface Observing System, located about 7 miles east of the accident site, indicated visibility appeared to be adequate for nighttime helicopter operations and did not detect any freezing precipitation.

Although an advisory for icing conditions was current for the route of flight, and several pilot reports of icing conditions had been filed, “none of the reports were in the immediate vicinity of the intended route of flight,” the report stated.

Witnesses and first responders reported mist, drizzle and icy road conditions at the time of the accident, according to the report.

The helicopter had heated ports but the rotor blades were not equipped with ice protection, according to a preliminary NTSB report released in August 2014.

“The helicopter was not certified for intentional flight into known icing conditions,” that report stated.

Lair-Langenbau’s husband, Jay Langenbau, two minor children and her parents, Gerald and Karen Lair, filed a lawsuit in Cerro Gordo County District Court in July 2013. It was moved to federal court the next month.

The defendant in the case is Med-Trans Corp., Lewisville, Texas, which operates the helicopter service under contract to Mercy Medical Center-North Iowa.

The family is alleging negligence on the parts of Med-Trans Corp. and pilot Grell for taking off in icy conditions.

A jury trial has been set for Nov. 9 in the U.S. Courthouse in Sioux City.

The suit claims Med-Trans knew that Bell 407 helicopters were not safe to operate in certain weather conditions, including icing.