A passenger plane that crashed on the sea ice off Alaska, with no survivors, was carrying half a ton more than the allowed weight for the weather conditions, as reported by the National Transportation Safety Board (NTSB) in a preliminary report released on Wednesday.
The report indicates that the plane was too heavy for the conditions that cause ice formation at the speed and altitude at which it was flying. A final report is expected later on.
The accident, which occurred on February 6, was one of the deadliest to happen in Alaska in this century and the third major aviation accident in the United States within an 8-day period. A commercial plane and an Army helicopter collided near the country's capital on January 29, resulting in the deaths of 67 people. A medical transport plane crashed in Philadelphia on January 31, causing the deaths of the six people on board and another person on the ground.
The Bering Air single-engine turboprop plane was on a scheduled evening flight between the communities of Unalakleet and Nome, a journey of approximately 240 kilometers (150 miles), when authorities lost contact less than an hour after takeoff, said David Olson, Bering Air's director of operations at the time.
A review of the plane's contents after the accident indicated that its estimated gross weight at takeoff was approximately 4,475 kilograms (9,865 pounds), around 480 kilograms (1,058 pounds) above the maximum gross takeoff weight for a flight expected to encounter icing conditions, according to the report.
As of Wednesday, requests for comments from the NTSB and Bering Air, the flight operator, had not been answered. The Cessna Caravan disappeared about 50 kilometers (30 miles) southeast of Nome. After an extensive search, the wreckage was found the following day on a drifting ice floe. The pilot and the nine passengers had perished.
Radar data provided by the U.S. Civil Air Patrol indicated that the plane rapidly lost altitude and speed, but the reason for this was unknown, stated the U.S. Coast Guard. The agency had no knowledge of any distress signal from the plane.
The plane was flying in an area where moderate ice formation was possible between 610 meters (2,000 feet) and 2,438 meters (8,000 feet) and where the weather could be hazardous for light aircraft, said NTSB Chair Jennifer Homendy at a press conference held in Nome last month. She mentioned that the plane, last seen on radar at 1,036 meters (3,400 feet), was equipped with an anti-icing system on its wings and tail, which would be examined as part of the investigation.
Preliminary NTSB reports typically do not disclose the cause of an accident, as the investigation is still ongoing. A final report, which usually does contain the cause, will be released later on.