Incident Cessna 208B Super Cargomaster N781FE,
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ASN Wikibase Occurrence # 219038
 
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Date:Friday 23 November 2018
Time:17:33
Type:Silhouette image of generic C208 model; specific model in this crash may look slightly different    
Cessna 208B Super Cargomaster
Owner/operator:West Air Inc opf FedEx Corporation
Registration: N781FE
MSN: 208B0278
Year of manufacture:1991
Total airframe hrs:12600 hours
Engine model:Pratt & Whitney PT6A-114A
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: None
Category:Incident
Location:Meadows Field Airport (KBFL), Bakersfield, CA -   United States of America
Phase: Taxi
Nature:Cargo
Departure airport:Bakersfield-Meadows Field, CA (BFL/KBFL)
Destination airport:Ontario International Airport, CA (ONT/KONT)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot loaded the cargo onboard the airplane, closed the door, and started the engine with the cabin air vents closed, as it was cold outside. While taxiing the airplane to the run-up area, the pilot became sleepy, had difficulty breathing, and subsequently became unconscious and unresponsive to tower controllers. About 37 minutes after the pilot closed the door of the unvented cockpit, a firefighter responded to the airplane, which was still parked in the run-up area, opened the airplane door, and the pilot regained consciousness. The airplane was not damaged.

The shipper of the boxes had grossly underreported the amount of dry ice contained in the boxes due to an improperly trained employee who had deposited nearly twice the amount of dry ice in each box. Dry ice sublimates into carbon dioxide (CO2), which can lead to loss of consciousness and death at certain exposure levels. Within 5 minutes, the airplane's unvented configuration led to a CO2 concentration that was twice the Federal Aviation Administration and Occupational Safety and Health Administration standards and, within 30 minutes, the concentration reached a level consistent with loss of consciousness.

Based on the CO2 concentrations at the time of the incident, the cause of the pilot's loss of consciousness was CO2 poisoning from the sublimation of dry ice in an unventilated space.

The pilot may still have suffered symptoms from CO2 poisoning and possibly incapacitation had the unventilated cabin been loaded with the dry ice weight that was reported on the label; however, proper ventilation would have decreased the CO2 concentration in the cabin and may have prevented the pilot's loss of consciousness altogether. At the time of the incident, publicly available literature included an advisory circular to pilots flying cargo loads of dry ice to maintain an adequate circulation of fresh air. Despite the availability of this information, the pilot chose to fly the airplane in an unventilated configuration, and the operator did not have any guidance to encourage ventilation, as its policy permitted operation with both the overhead and side vents closed.

Probable Cause: The pilot's loss of consciousness while taxiing due to an accumulation of toxic levels of carbon dioxide gas inside the airplane as a result of dry ice sublimation. Also causal was [sic] the pilot's decision to fly the airplane in an unventilated configuration, the operator's policy that allowed this configuration, and the shipping company's inadvertent loading of excess dry ice, which exacerbated the concentration of carbon dioxide.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: WPR19IA030
Status: Investigation completed
Duration: 3 years and 4 months
Download report: Final report

Sources:

NTSB : https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20181124X14130&AKey=1&RType=Prelim&IType=IA
FAA : https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N781FE
http://aerossurance.com/safety-management/dangerous-goods-error-co2/
Docket: https://data.ntsb.gov/Docket?ProjectID=98675

History of this aircraft

Other occurrences involving this aircraft
28 August 1993 N781FE Westair Industries 0 Los Angeles, CA sub

Location

Media:

Revision history:

Date/timeContributorUpdates
05-Dec-2018 18:33 Captain Adam Added
23-Mar-2022 18:58 Aerossurance Updated [Destination airport, Source]
26-Mar-2022 16:36 Aerossurance Updated [Operator, Phase, Source]
28-Mar-2022 06:29 Aerossurance Updated [Location, Departure airport, Destination airport, Source, Embed code]
02-Apr-2022 10:05 Aerossurance Updated [Embed code, Narrative]
03-Apr-2022 13:14 Captain Adam Updated [Location, Destination airport, Narrative, Category, Accident report]

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