The National Transportation Safety Board approved a final report Tuesday that cited pilot Terry Smith’s “temporary unresponsiveness” as the probable cause of an Aug. 9 plane crash near Dillingham that killed former Sen. Ted Stevens, as well as Smith and three other people.

The report, adopted at a board meeting in Washington, D.C., neither assigns blame for the crash nor determines a definitive cause. NTSB chair Deborah Hersman says it's rare for so many people to work so long on an investigation without an agreed-upon conclusion.

Findings in the report do describe a Federal Aviation Administration flight surgeon’s decision to grant Smith an unrestricted first-class airman’s medical certificate after he suffered a 2006 stroke, without consulting other physicians, as “inappropriate.” They also say FAA guidelines on certifying pilots after strokes are “inadequate.”

While Smith, a former chief pilot for Alaska Airlines, had more than 30,000 career hours of flight time, several witnesses reported lapses in his attention last summer. Investigators considered the role Smith’s stroke, stress from the July death of his son-in-law in a military C-17 plane crash or fatigue may have played in the crash, but found inconclusive evidence for any of the three.

Additional findings in the report described the weather on Aug. 9 as unexceptional given conditions in which Smith had already been flying in the week of the crash, and found no evidence of any mechanical failures before impact in the DeHavilland DHC-3 Otter that crashed.

PLANE TURNED INTO TERRAIN BEFORE IMPACT

Smith was at the controls when the Otter, owned by communications firm GCI, flew into a mountain en route from a GCI-owned fishing lodge to a nearby fishing camp. The report said the aircraft was in a climbing left turn toward the mountain’s incline when it hit the ground, with control inputs provided in the seconds before impact.

The plane’s radar altimeter system provided warnings four to six seconds before impact, which the report said likely led Smith to pull up -- but audio and text alerts from the terrain avoidance and warning system, which would have given up to 30 seconds’ warning before impact, had been disabled.

In addition to Smith and Stevens, the crash killed GCI executive Dana Tindall and her daughter Corey as well as former Stevens aide Bill Phillips Sr. The four survivors, all of whom were injured in the crash, were Phillips’ son William Phillips Jr., lobbyist Jim Morhard, and former NASA administrator Sean O’Keefe and his son Kevin.

The report mentioned both an earlier NTSB finding, that the plane’s emergency locator transmitter was disconnected from its antenna in the crash, and passengers’ unfamiliarity with emergency equipment like the plane’s satellite phone as factors in the delay of several hours before rescuers reached the crash site.

While the report credits rescuers with preventing hypothermia among the crash’s survivors, it concludes that the severity of fatal injuries sustained in the crash meant none of the dead could have been saved by prompt rescue.

RANGE OF RECOMMENDATIONS AFTER FATAL CRASH

The five new recommendations issued in Tuesday’s final report on the Stevens crash, mostly to the FAA, include:

  • Clarifying post-stroke pilot certification guidelines to include assessment of a stroke’s recurrence
  • Correcting weather-sensor and ceilometer deficiencies in Automated Weather Safety System stations to make them provide more accurate weather data
  • Initiating an Alaska-based test program involving the FAA, the National Weather Service and the Alaska academic community to retrieve real-time weather data from aircraft
  • Providing aircraft owners with incentives, if the real-time weather data study is successful, to fit their aircraft with the necessary equipment for real-time weather monitoring
  • Urging the Aircraft Owners and Pilots Association to educate passengers about emergency equipment on board their aircraft, including satellite phones

In addition, the report repeated several previous NTSB recommendations:

  • Requiring annual inspection of emergency locator transmitter brackets, as well as a study on whether those brackets are capable of surviving crashes
  • Requiring crash-resistant cockpit-video and flight-recorder systems aboard most turbine-powered aircraft.
The NTSB’s full report on the crash is slated for release in the next two weeks.