More than two years after his aircraft crashed following an intelligence-gathering mission in Afghanistan, the Army has released the results of an investigation into the death of Sgt. Drew M. Scobie, the only Hawaii National Guard soldier to be killed in fighting in the country.

Scobie, 25, an aerial sensor operator, was one of three aboard the specialized turboprop RC-12 Guardrail on Jan. 10, 2014, when it likely went into a spin, stall or roll on final approach just under 2 miles from the end of Runway 03 at Bagram Airfield, the Army investigation said. All were killed in the crash.

The spy plane apparently encountered wake turbulence from a much bigger C-17 cargo carrier it was following into Bagram, but the exact cause of the crash likely will never be known.

“Based on the findings and recommendations, I find pilot error resulted in the aircraft crash,” said then-Lt. Gen. Joseph Anderson, deputy commander of U.S. Forces Afghanistan. “With a lack of video, a flight data recorder, or cockpit voice recorder, the evidence does not allow for a definitive conclusion as to the other contributing factors in the accident.”

Anderson, whose findings were entered on March 12, 2014, said the “three most probable, although not exhaustive or conclusive explanations,” appeared to be:

>> The RC-12 experienced wake turbulence as it passed through the descent path of the C-17 jet, causing an unrecoverable spin.

>> After experiencing severe wake turbulence, the aircraft ended up in an unusual attitude from which the pilot was unable to recover.

>> In an attempt to remain a safe distance behind the C-17, the pilot slowed the aircraft to the point of stalling and was unable to recover.

The Honolulu Star-Advertiser sought the investigation report in late 2014 through the federal Freedom of Information Act. The Hawaii National Guard was unable to determine which command had the report, and U.S. Army Central, the eventual release authority, took more than a year before providing it.

“We acknowledge an unusually lengthy response time that can be attributed to many things, none of which prevented us from clearly articulating why the delays were occurring,” said Brig. Gen. Dave Glaser, chief of staff for U.S. Army Central, in an email.

Glaser, who was first contacted Feb. 4 by the newspaper, said he was expediting the information request.

The command previously cited a need to update families and a legal review as part of the explanation for the delay. McKenna Panui-Scobie, Sgt. Scobie’s widow, said she received a thorough briefing from Army brass later than she expected, around April 2015.

Anderson’s memo states the aircraft is an RC-12, but the executive summary and other parts of the investigation refer to it as an MC-12, an Air Force aircraft that also has intelligence and surveillance capabilities. Also left unexplained is why there was no flight data recorder or cockpit voice recorder. The Army redacted portions of the report for what it said were security reasons.

Defense contractor Northrop Grumman said the RC-12 Guardrail was the Army’s most successful airborne signals intelligence targeting, collection and reporting system. The aircraft — derived from the King Air B200 and bristling with antennae — intercepts and determines the location of hostile communications and radio signals and sends it via satellite to a ground station.

“The evidence collected shows that up until the final approach course and subsequent crash, nothing out of the ordinary occurred during the mission,” said the investigating officer, whose name is blacked out.

Although Anderson found pilot error, the investigating officer said crew actions on the flight, known as Pursue 46, met regulatory requirements for air separation during the final approach. Further, the investigating officer found no conditions or circumstances with the flight warranting immediate change in procedure.

Pursue 46, which took off at 8:30 p.m. and returned to base at midnight, crashed steeply nose down with the left wing lower than the right facing approximately 180 degrees opposite the approach course, the investigating officer said.

“It’s totally a human error thing that happened,” Panui-Scobie said. “It’s no fault of anything other than they thought they could clear it (the wake turbulence), and they couldn’t.”

In addition to Scobie, who was from Kailua, killed in the crash were pilot-in-command Kristopher Noble, 31, a civilian, and Chief Warrant Officer 3 Andrew McAdams, 27, a Wyoming Army National Guard soldier listed in the investigation as a “pilot.”

Noble was a contracted pilot with Avenge Inc. out of Sterling, Va. The company’s website says it specializes in military flight operations dedicated to intelligence, surveillance, reconnaissance, targeting and acquisition.

The Pentagon’s release of names associated with the crash listed Scobie and McAdams, but not Noble.

Lauren Noble, the pilot-in-command’s wife, said in a 2014 The Intelligencer/Wheeling News-Register (Ohio) news report that “we’re not sure who was flying — it’s not clear,” adding, “there was another pilot in the plane that day.”

The investigation does not state who was at the controls. The mixing of contractor and military pilots “is an acceptable procedure for meeting operational requirements” and was not breaking any new ground, the report said. The catastrophic nature of the crash precluded recovery of the majority of the aircraft and crew documents, it said.

Anderson said as a result of the crash he was ordering an information and education campaign on wake turbulence for the aviation community in the region.

“It (the crash) helped for all the other training because then they were like, ‘Oh, now we really need to make sure that everybody is staying really far back and being more cautious when they are landing and taking off,’” Panui-Scobie said.

Scobie, who was assigned to the 1st Battalion, 487th Field Artillery, volunteered for the Afghanistan duty. He also was a perioperative technician at Straub Clinic &Hospital.

He left behind a 4-year-old son, Duke, and his wife pregnant with their second child. Daughter Drew now is nearly 20 months old and Duke is 7.

The challenges in dealing with the loss continue, and Duke has been going to an organization called Kids Hurt Too Hawaii for children experiencing trauma, Panui-Scobie, 27, said.

“It’s been helping us — helping both of us,” she said.

One of Drew Scobie’s favorite bodyboarding spots was Makapuu Beach. His ashes were scattered there, and the family goes often to remember and stay connected to the father and soldier who gave his life for his country.

“We drive past and he (Duke) yells, ‘Hi Dad!’” Panui-Scobie said.