Serious incident Boeing 737-4Q8 N771AS,
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ASN Wikibase Occurrence # 370194
 
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Date:Saturday 20 December 2008
Time:08:47 LT
Type:Silhouette image of generic B734 model; specific model in this crash may look slightly different    
Boeing 737-4Q8
Owner/operator:Alaska Airlines
Registration: N771AS
MSN: 25104/2476
Year of manufacture:1993
Engine model:CFM INTL. CFM56 SERIES
Fatalities:Fatalities: 0 / Occupants: 88
Aircraft damage: None
Category:Serious incident
Location:Sitka, AK -   United States of America
Phase: Standing
Nature:Passenger - Scheduled
Departure airport:Sitka Airport, AK (SIT/PASI)
Destination airport:Juneau International Airport, AK (JNU/PAJN)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
After departure the cabin crew reported to the captain that they were becoming nauseated. The captain noted that the departure was the first flight of the day and that the airplane had been sitting on the ramp overnight connected to an external heating unit. He said that prior to flight the first officer and cabin crew went to prepare the airplane while he remained in the operations center with paperwork. He said the first officer requested the ground crew shutdown the external heater because of exhaust fumes in the airplane's cabin. The first officer started the airplane's auxiliary power unit to provide power and heat to the airplane. The captain said that about 15 minutes later he did not detect any unusual smells or odors, and wiped his hand across seats and surfaces to detect contamination. Finding none, he felt it was safe to continue boarding. He reported that the boarding process was normal, and none of the crew or passengers reported any unusual smells or odors. When the cabin crew reported feeling nauseated, the captain determined that they were 20 minutes from their destination and decided to continue the flight rather than turn back. The captain reported that he and the first officer were symptom free, and that the first officer remained on oxygen for the remainder of the flight as a precaution. Upon arrival the flight crew all tested positive for elevated levels of carbon monoxide. The cabin of the airplane was examined and no traces of carbon monoxide were found. Tests of the ground heating unit found no anomalies, and the heat output hose was tested for CO with negative results. According to the director of safety for the operator, the contamination probably occurred when the morning ground crew started the push-back unit in the proximity of the heater's fresh air intake. As a result, the heating unit has been repositioned away from other operating equipment, and a 20-foot exhaust hose attached. Carbon monoxide detectors are now placed in the operator's aircraft during extended external heater usage.

Probable Cause: The placement of operating equipment in close proximity to an external heating unit's intake by ground personnel, resulting in the contamination of the airplane's cabin with carbon monoxide.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: ANC09IA015
Status: Investigation completed
Duration: 1 year and 3 months
Download report: Final report

Sources:

NTSB ANC09IA015

Location

Revision history:

Date/timeContributorUpdates
25-Mar-2024 08:04 ASN Update Bot Added

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