Pilot Terry Smith's temporary incapacitation for reasons unknown likely caused the August plane crash that killed five people, including himself and former Sen. Ted Stevens, in Southwest Alaska, the five-member National Transportation Safety Board said Tuesday.
The board did, however, call the FAA's decision to re-certify Smith two years after the pilot suffered a stroke "inappropriate" – not because the pilot shouldn't have been certified, but because the FAA's medical evaluation wasn't thorough enough to make an informed decision.
Exactly what happened in the three minutes between the plane's last known, on-course position and its steep crash into a hillside remains a mystery, something that caused the NTSB in its findings to urge that small planes carry more data-collection devices that could help fill in the gaps when things go wrong. While the board ruled out a problem with the plane, and didn't believe weather conditions were to blame, analyzing Smith's health and mind, and whether he suffered a medical problem while at the controls, proved elusive.
PLANE CRASH: More coverage of the accident and Ted Stevens
"The human will always, always be more complicated than a machine," said NTSB chairwoman Debbie Hersman.
Investigators looked at whether lingering neurological effects from a past stroke, fatigue, depression or other factors could have affected Smith's performance. Because the plane drove into the hillside in a left-hand, climbing turn, investigators believe Smith was making aggressive maneuvers at the time of the crash.
They have theorized that something caused him to become temporarily unaware of what was going on, then return to responsiveness after a warning system went off alerting him to his position in relationship to the terrain. Doctors aiding the investigation said the accident is consistent with someone dozing off, or perhaps suffering a seizure, but there's no way to know for sure.
After a lengthy hearing Tuesday morning, the NTSB's probable cause finding was simply this: "The pilot's temporary unresponsiveness for reasons that could not be established from the available information."
"We cannot conclude with certainty that this individual had any kind of medical event," said Dr. Mitchell Garber, a member of the NTSB's investigative team.
The Aug. 9 crash claimed the lives of Stevens, pilot Terry Smith, lobbyist Bill Phillips, General Communication Inc. executive Dana Tindall, and Tindall's 16-year-old daughter, Corey. Four people survived, including former NASA administrator Sean O'Keefe and his 19-year-old son, Kevin; Washington, D.C., lobbyist Jim Morhard, and Phillips's 13-year-old son, Willy.
The crash occurred 20 miles north of the coastal fishing community of Dillingham in Southwest Alaska. The GCI-owned plane -- a 1957 DeHavilland DHC-3 Otter -- was ferrying guests from a lodge, also owned by the Anchorage-based telecommunications company, to the Nushagak River for silver salmon fishing.
Smith, 62, was a career pilot, a former chief pilot for Alaska Airlines in Anchorage with thousands of hours of flight time under his belt. GCI had hired Smith to replace the company's regular pilot at its lodge, where GCI has for years invited employees, clients, friends and sometimes politicians and regulators. Smith had worked for GCI on and off for years, and he and other well-respected pilots had been brought in to fill the summer vacancy in shifts.
NTSB medical investigators considered a wide range of possibilities about what might have caused Smith to lapse in ability or judgment while in-flight.
It had been an emotional summer for Smith. A daughter got married, then weeks later another daughter lost her own pilot husband when a military plane crashed in Anchorage. Investigators considered whether Smith, who slept long hours, might have had a sleep disorder.
They questioned whether the stroke he suffered in 2006 left ongoing neurological problems or put him at risk for another stroke or seizure. They looked at how all of these possible factors might intersect. Was the grief-struck pilot in the grips of a depression that clouded his thoughts? Was he fatigued? Did he suffer an incapacitating health problem while at the controls? Did he doze off? After three autopsies and combing through medical records and other data, investigators had only one sure conclusion: There was no way to know.
But unknowns have also led the NTSB board to pointedly single out as "inappropriate" the Federal Aviation Administration's choice to re-issue Smith's flight certification following his stroke.
"The Alaska Regional Flight Surgeon's decision to issue the pilot an unrestricted first-class airman medical certificate, based largely on a local neurologist's in-office evaluation and without conferring with any other Federal Aviation Administration physicians or consultants or attempting to address the etiology of the hemorrhage, the likelihood of recurrence, or the extent of any remaining cognitive deficit, was inappropriate," the board wrote, admonishing both the FAA doctor who approved Smith to fly and the agency's internal policies for making such decisions.
The board added in its report:
It is not clear that a sufficiently thorough aeromedical evaluation of the pilot would have denied the pilot eligibility for a first-class airman medical certificate; however, a more rigorous decision-making process for evaluating this pilot with a history of intracerebral hemorrhage would have decreased the potential for adverse consequences. The Federal Aviation Administration's internal guidance for medical certification of pilots following stroke is inadequate because it is conflicting and unclear, does not specifically address the risk of recurrence associated with such an event, and does not specifically recommend a neuropsychological evaluation (formal cognitive testing) to evaluate potential subtle cognitive impairment.
'Turned over every stone'
The NTSB also underscored how having crash-proof data recorders on the plane could have helped investigators better understand what happened: "Contributing to the investigation's inability to determine exactly what occurred in the final minutes of the flight was the lack of a cockpit recorder system with the ability to capture audio, images, and parametric data."
The ambiguity of the plane's last minutes of flight and how much the pilot and his passengers may have been aware of in those final moments was a disappointing end for the board to an exhaustive inquiry aimed at answering why the crash happened and how it could have been prevented.
"Our staff turned over every stone," said Hersman, the NTSB chairwoman, said at a press conference following Tuesday's hearing, but "at the end of the day we did not have significant evidence to support any single theory."
While what caused the plane to veer off course appears to point to a problem with the pilot, the NTSB also suggested that had Smith not turned off a piece of safety equipment, he could have had significantly more time to attempt to get the plane out of trouble. A different warning system did give a visual and aural alert about five seconds before impact, which "likely prompted the pilot to take aggressive action on the flight controls, resulting in the airplane nose-up pitch and left-bank angles evident at the accident site," according to the NTSB's findings. But a second piece of equipment, if activated, could have given the pilot up to 30 seconds to respond to a warning.
Pilots have the option of using a "terrain awareness and warning system" – or TAWS – to help keep them oriented amid variable terrain. But because Alaska's pilots often fly over frequently changing elevations – mountains, valleys and streambeds – the alert system can become a nuisance, causing many pilots to turn it off, the NTSB said.
Recognizing that flying in Alaska is unique, the board stopped short of listing Smith's disabling of the TAWS system as a contributing factor in the crash. "If (pilots) are inhibiting it, it is not working for them," Hersman said.
Contact Jill Burke at jill(at)alaskadispatch.com.