US National Transportation Safety Board investigators have revealed that the commercial pilot flying nine skydivers home from a weekend event in Idaho on 7 October did not obtain an official weather briefing from the Federal Aviation Administration before departing under Part 91 visual flight rules. The flight was made in twilight in a Cessna 208B Caravan from Star, Idaho to Shelton, Washington.

Although visual flight conditions prevailed for much of the route, FAA weather specialists say there had been a cautionary note for instrument flight conditions with icing, low-level turbulence and mountain obscuration in the Cascades and Western foothills. A witness who saw the aircraft descending and heard the crash reported that cloud bases were below the mountain tops, with misty rain and low visibility at the time.

Minutes before the crash, radar returns showed the aircraft making a "tight 360e_SDgr turn" at an altitude of 14,400ft (4,350m), descending rapidly to 12,890ft, stabilising there briefly, but then plunging nearly 10,000ft, into the terrain. All on board were killed.

Investigators accounted for all major components of the aircraft at the site and found an oxygen bottle and "stowed oxygen mask" in the wreckage. FAA rules call for pilots to use supplemental oxygen above 14,000ft.

The NTSB is certain to focus on whether icing played a part in the accident, as the agency has made recommendations to the FAA based on numerous ice-related Caravan accidents, sparking FAA action on many. In addition to installing placards on the panel alerting the pilot to maintain 120kt (220km/h) airspeed and disconnect the autopilot on first indication of icing, the FAA in May ordered Caravan operators to fit a low airspeed awareness system by 21 September.

The system is meant to supplement the aircraft's legacy stall warning, which the FAA says does not give sufficient warning of an incipient wing stall when ice accumulates on the wing.

Source: Flight International