Rotor blade separation caused crash of medical helicopter

Thursday, April 1, 2004 | 11:45 a.m.

A 16-monthlong investigation of the crash of a Mercy Air Services helicopter that killed three found that the main rotor blades separated in flight.

But why that happened, the National Transportation Safety Board says will never be known.

The federal agency's final report of the Sept. 7, 2002, accident near Nipton, Calif., was released Thursday. Investigators determined the official cause of the crash of the Bell 222U helicopter was "main rotor blade separation while maneuvering for unknown reasons. A factor was the dark night condition."

The crash of the helicopter that was en route to an auto accident, killed 30-year-old native Nevada nurse Ana Coburn and her co-workers, Kalaya Jarbsunthie, 31, a paramedic from Las Vegas, and pilot Marshall Butler, 46, of Pahrump. No patients were on board.

"Examination of the accident site revealed evidence of a main rotor blade separation with a debris field consisting of main rotor blade skin, honeycomb, and paint chips located 938 feet upstream of the main impact crater," the NTSB report said.

"Post-accident examination of the helicopter's component parts, including the main rotor blades, failed to reveal the cause for the main rotor blade separation. Examination of the aircraft's engines revealed no pre-impact anomalies."

The helicopter took off at 4:01 a.m. from the Pahrump Hospital en route to the traffic accident on Interstate 15 near Bailey Road, the NTSB report said, noting that at 4:27 a.m., the dispatch office lost contact.

"After passing over an interstate highway, the helicopter impacted terrain in a near 45 degree nose low attitude," the report said, noting that witnesses saw the craft flying low and slow and shining its searchlight before crashing.

"Another witness ... said the helicopter appeared to be trying to land."

The report further found that the helicopter, manufactured in 1984, had its rotor blades overhauled on Dec. 27, 2001, and on Oct. 23, 2000.

"The teardown and examination of both of the helicopter's engines disclosed that the type and degree of damage was indicative of engine rotation at the time of impact with the ground. No pre-existing condition was found on either engine that would have interfered with normal operation," the report said.

"Post-accident examination revealed no evidence that power lines, which bordered the impact site 51 feet to the west, had been impacted by the helicopter," the report said.

The report said it was relatively dark at the time of the crash and that the instrument-rated commercial pilot had filed a visual flight rules flight plan. Toxicological testing of the pilot's body found he was "negative for drugs," the report said.

The helicopter was registered to Wells Fargo Bank Northwest of Salt Lake City, Utah, and operated by Mercy Air Service Inc., of Rialto, Calif., the report said.

In a Sept. 10, 2002, Sun story Tony Renner, Coburn's boyfriend and a one-time pilot for Valley Hospital's Flight For Life helicopter, said he believed a mechanical problem caused the accident.

"It looks like something broke," Renner said at the time.

"The last call Marshall made (to dispatchers) was when they were three miles out, which is procedure. Then the helicopter turned back toward Primm, made a right turn of about 90 degrees and crashed 300 yards off the highway. Marshall may have seen something was wrong and tried to make it to Primm."