BOEING 737-890 near Seattle, WA — 2008-12-24

Probable cause

The failure of the deicing crew to follow company procedures by not receiving confirmation from the flight crew before beginning to deice the airplane.

NTSB narrative

Airline personnel reported that the airplane pushed back from the gate with the auxiliary power unit running. As the push back sequence was completed, two deicing vehicles began deicing operations prior to the flight crew configuring the airplane for deicing. Shortly after, the cabin and flight crew noticed fumes within the cabin and cockpit area. The flight crew instructed the deice crew to discontinue deicing operations and the flight crew performed the smoke removal checklist as the deicing operation stopped. The flight crew started both engines and taxied back to gate N14 where the passengers and flight crew exited the airplane via the jet way. The captain reported that he did not clear the ground deicing crew to start their deicing operations. The driver of the primary deicing vehicle reported that he informed the flight crew of the fluid types, freeze points, and concentrations. He added that there was a lot of "radio chatter" and the bucket operator began deicing operations "after we received no objections" from the flight crew. Company deicing procedures state, in part, "prior to fluid application, Ground Deicing Crew member shall confirm with Flight Crew that the aircraft is configured for deicing." The flight crew gate deicing checklist states that the APU and engine bleed air switches are to be turned off prior to deicing. At the time, the APU and engine bleed air switches were still in the ON position when deicing fluid was sprayed on the airplane. This allowed the fluid to be introduced into the air supply lines leading to the cabin and cockpit.

Analysis

Primary failure mode

Human factors

First missed decision gate

Flight crew did not confirm deicing configuration with ground crew before operations began.

NTSB coding

• Ground handling event · Pushback/tow-engine not oper

Evidence available

• 13 docket documents

Docket documents13

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Captain Statementinterview
• First Officer Statementinterview
• Primary Deicing Truck - Bucket Operator Interviewinterview
• Primary Deicing Truck Driver Statement / Questionsinterview
• Push Back Tug Operator Statementinterview
• Secondary Deicing Truck Bucket Operator Interviewinterview
• Secondary Deicing Truck Bucket Operator Statementinterview
• Secondary Deicing Truck Driver Interviewinterview
• Secondary Deicing Truck Driver Statementinterview
• Alaska Airlines Boeing 737-400/NG Deicing Cardother
• Portion of Alaska Airlines Cold Weather / Deicing Procedures Manualother
• Portion of Alaska Airlines Flight Operations Manualother

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