Final Report: Wing ice cited in Caravan crash

 - January 28, 2008, 8:56 AM

CESSNA 208, DILLINGHAM, ALASKA, OCT. 10, 2001–At about 9:26 a.m. Alaska daylight time, Peninsula Airways (dba Pen- Air) Flight 350, Cessna Caravan N9530F, crashed shortly after takeoff from Dillingham Airport (DLG). The pilot and nine passengers were killed and the airplane was destroyed. One passenger was airlifted to a hospital in Anchorage but died the next day. The impact site was located about 0.7 nm northeast of the departure end of Runway 01 at DLG. There was no post-crash fire. Flight 350 was destined for King Salmon, Alaska (AKN), on a scheduled Part 135 flight. VMC prevailed at the time of the accident.

The Safety Board determined the probable cause of the accident to be an in-flight loss of control resulting from upper-surface ice contamination, which the PIC failed to detect during his preflight inspection of the airplane. Contributing to the accident was the lack of a preflight inspection requirement for Caravan pilots to examine at close range the upper surface of the wing for ice contamination when ground icing conditions exist.

N9530F had been parked outside the night before the accident and was subjected to rain, snow and temperatures that dropped below 32 degrees F. Other pilots whose airplanes were also parked outside overnight stated that between a quarter and a half inch of snow and frost covered a layer of ice on their airplanes that morning. Subsequently, ramp personnel de-iced the accident airplane before the flight with a heated mixture of glycol and water.

The PenAir ramp supervisor who conducted the de-icing stated that he believed the upper surface of the wing was clear of ice but that he did not physically touch the wing to check for the presence of ice.

Investigators were unable to determine whether the accident pilot checked the wing and tail surfaces for contamination after de-icing, but the Caravan’s high-wing configuration would have hindered the pilot’s ability to see residual clear ice.
Company records indicate that the certified commercial pilot completed his initial Caravan flight training two months before the accident and had accumulated a total of 74 hours in the turboprop single.

A witness observed that the airplane’s flight appeared to be normal until it suddenly pitched up, rolled 90 degrees to the left and yawed to the left. The airplane then descended nose down until it disappeared from view. Data from the engine monitoring system revealed that the maximum altitude obtained during the accident flight was about 651 feet msl; Dillingham Airport is 86 feet msl. The airplane crashed in a level attitude.

Investigators found no evidence of pre-impact failures in the structure, flight control systems or instruments. Examination of the engine and propeller revealed no pre-impact failures and confirmed that the engine was running when the airplane hit the ground.