A 1956-built Douglas DC-6BF (DC-6 Freighter) was to operate a domestic positioning flight, between Togiak Village Airport and Cold Bay Airport, both in the state of Alaska, USA. On board for the ~280 miles (~447 kilometer) flight, a crew of 4.
The aircraft resting on its belly in August 2013 (© Joseph Barbera)
Once flight preparations were completed (which would be operated under Visual Flight Rules) the four Pratt & Whitney R-2800 were started. A short while later de four 2400 horsepower engines powered the aircraft into the air. The crew settled in for the flight and the climb, cruise and descent towards Cold Bay were uneventful. The weather at Cold Bay at the time of the accident was recorded as;
Wind - 280º / 20 knots gusting 29 knots
Temperature - 6ºC
Dewpoint - 5ºC
Clouds - Broken / 900 feet AGL
Altimeter - 29.76 in Hg (~1007 hpa)
Visibility - 10 miles
Precipitation - Light drizzle
As the aircraft approached runway 26 at Cold Bay the flight crew discussed a boat dock which they observed from the flightdeck. As the aircraft descended towards the runway neither crew member heard the landing gear warning horn, indicating the landing gear is not down and locked, while the rest of the aircraft is configured for landing.
The wreckage in August 2013 (© Joseph Barbera)
When the crew landed the aircraft the landing gear was still retracted and the aircraft settled down on its belly and slid down the runway coming to a stop. The damage to the aircraft was substantial and was written off as damaged beyond repair.
The accident was investigated by the National Transportation Safety Board (NTSB). The captain of the flight provided a written statement to the investigators. In his statement, he reported that there were no technical issues with the aircraft prior to the gear-up landing, but also state that non of the crew had heard the landing gear retracted warning horn.
In their final report, available by clicking here, the NTSB determined that the probable cause for the accident was;
"The flight crew's failure to extend the landing gear, resulted in an inadvertent wheels-up landing. Contributing to the accident was the flight crew's diverted attention"
In 1981 the FAA had introduced a formal requirement to be applied to all commercial flights which was designed to stop flight crews from engaging in non-essential conversations and activities, during the critical phases of flight. This rule is FAR 121.542, also known as the "Sterile Cockpit Rule" FAR 121.542 is available for your reference by clicking here.
EASA covers the requirement for a sterile cockpit in Opinion No 05/2013, available for reference by clicking here.
The aircraft in better days (Source www.oldprops.ukhome.net © Unknown)