Page:CAB Aircraft Accident Report, Northwest Flight 293.pdf/7

 served about 2-1/2 hours after takeoff. It is also noted that the flight, from Port Hardy north, was conducted in conditions favorable to icing.

The failure of the crew of Flight 293 to acknowledge the Sandspit radio operator's transmission advising that the 18,000—foot level was occupied by PNA 5 may indicate the time that the emergency occurred. Whatever the emergency was it must have either been of such a nature as to require the concentration of all the cockpit crew and/or caused a loss of airborne communications.

The location of the impact area, the last known ground speed and the last reported position combine to indicate that the aircraft was airborne from five to nine minutes after its last radio transmission. Because of the inherent inaccuracies of Automatic Direction Findings (ADF) bearings due to instrument interpretation, atmospheric interference with radio signals, and the radio beam width at Domestic Annette, it is possible that a position error of as much as 10 nautical miles could have occurred when the crew believed they were over Domestic Annette.

Since a number of the adult life vests were recovered still incased in their plastic containers, with the zippers closed, it is believed that either there was insufficient time to alert the passengers to prepare for a water landing, or they were unable to take appropriate action due to unusual aircraft attitudes.

The fragmentation of the aircraft indicates that it struck the water at a high speed and the damage to the seat backs shows forces applied to the top of the seat indicating that the airplane fuselage struck the water nearly inverted. The concentration of the observed wreckage and the failure to find any ﬂoating wreckage outside that general area shows that the aircraft was probably intact at impact.

There was no available evidence to substantiate a fire or explosion in flight; however, fire after impact burned portions of items floating on the water.

Because of a lack of evidence the Board is unable to determine the probable cause of this accident.

BY THE CIVIL AERONAUTICS BOARD: