Piper Arrow ulykken - Oppdatering - Curt Lewis

NTSB investigates wing detachment in deadly ERAU plane crash

DAYTONA BEACH - Federal investigators are working to determine what caused a small plane's wing to fall off mid-air, resulting in a crash that killed an Embry-Riddle Aeronautical University student and his instructor, a Federal Aviation Administration pilot examiner.

Witnesses, which included air traffic controllers, said that following takeoff the plane's wing "departed the aircraft," causing it to spin out of control and then slam into a cow field about a half mile from Daytona Beach International Airport on Wednesday morning, said Aaron McCarter, an air safety investigator with the National Transportation Safety Board.

"With the wing departure, we are focusing our efforts initially on that part right now," he said during a news conference Thursday.

"We are looking at the engineering, and any kind of maintenance records."

Maintenance records for the plane - a Piper PA-28R-201 aircraft, better known as an Arrow - have already been provided by the school, he said. The student and instructor, he said, were working on "touch-and-go maneuvers," which basically means the student was practicing how to take off and land the aircraft. The wing fell off the plane during the "cruise climb" following takeoff, he added.

Determining what caused the plane's wing to fall off will take an investigation lasting between 18 months to two years, which is the typical length of time it takes for the NTSB to reach a conclusion about what caused a plane to crash.

The investigation into the crash will include metallurgists examining the plane's wreckage, McCarter said. He said that a wing detaching from a plane in mid-air is "very uncommon" and that "there is no reason to think there are any holistic problems" with the plane. A search of NTSB records examining crashes involving Piper planes found no mentions of a wing detaching.

A 2015 FAA bulletin, however, warned that the plane's model has the "potential for corrosion on the wing rear spar at the fuselage attach fitting." There were also two separate bulletins in 2011 that said there is the the potential for corrosion "on the wing front spar at the fuselage attach fitting" and "on the "aileron hinge fitting."

All three bulletins say variables increasing the potential for corrosion include age, incompatible materials, and certain environmental conditions, such as "high moisture or salt water."

The FAA makes clear on its website that Special Airworthiness Information Bulletins are "an information tool that alerts, educates and makes recommendations to the aviation community" and that they do not require mandatory actions. The 2015 bulletin recommends that all Piper PA-28 models and others receive inspections and take certain steps if damage is found.

Jacqueline Carlon, senior director of marketing and communications at Piper Aircraft, said that the company is working with the NTSB in its investigation but can not comment on the accident. Flight operations at Embry-Riddle resumed Thursday for all of the school's planes except the Piper Arrow, the model involved in Wednesday's crash, said Ginger Pinholster, assistant vice president for news and research communications. Those planes will remain tied down until full inspections can be conducted, which will probably take at least a week.

Two YouTube videos published last month show Roy Williams of Airframe Components in Indiana going over how to inspect a Piper plane's main wing spar and aft wing attach fittings for corrosion. Both inspections require a hole be cut in the plane's wing to allow for the insertion of a camera scope to see the wing's interior.

In the video for the aft fittings, he shows corrosion on the rear spar at the attach plate.

"This is an extreme case, with so much corrosion that we actually have deformation of the rear spar and also metal missing," he says in the video.

He goes on to explain how the "most dangerous situation" is when corrosion is hidden between the outside steel plate and the aluminum spar.

"Where the problem lies is the mating surface," he says. Williams could not be reached Thursday.

Brian Willis, director of aviation safety with the University of North Dakota John D. Odegard School of Aerospace Sciences, said that Piper planes are commonly used in flight training. He said that the aviation program there has more than 30 of them and that the single-engine planes with retractable landing gear are used in training pilots of varied experience, from those seeking their private pilot license to those looking for commercial training.

He said maintenance standards are strictly regulated by the government and that routine annual inspections would have examined for corrosion.

"We look at our planes all the time," he said. "We pride ourselves on maintenance, and I know Embry Riddle would do the same on what they are putting out."

News of the deadly crash had already filtered through much of the tight-knit community involved in aviation training, Willis said.

"We have been in contact with Piper and been in touch with Riddle," he said. "We understand what they are going through, and any way we can be of assistance we are willing to do it."