VH-SKC Ground track, from Investigation Report, figure 1.

Eddie Sez:

One of the problems with a mishap involving an aircraft without a full suite of flight data recorders is that much of the evidence is destroyed by the impact of the crash and the fire that follows. That is the case with this mishap. Regardless, there are many lessons to be learned:

  • Fuselage pressure leaks should be addressed immediately and repaired.

  • Oxygen supply and delivery equipment must be pre-flighted.

  • During every climb, part of your 10,000 foot check must be a check of cabin altitude. Most airplanes have a maximum cabin altitude between 6,000 and 8,000 feet. You certainly should not be above that at 10,000 feet aircraft altitude. You should know your normal cabin climb rate, typically around 300 fpm. Even if it takes you ten minutes to get to 10,000 feet aircraft altitude, you should not see more than 3,000 feet cabin altitude at that point. In any case, if it isn't where it should be, level off and investigate.

  • When troubleshooting a pressurization problem, donning oxygen quickly will not only improve your mental capabilities, it can keep you in the game if things go south quickly or insidiously.

  • When in doubt, descend.

What follows are quotes from the sources listed below, as well as my comments in blue.


Accident Report


Narrative

[Investigation Report, ¶1.1]


Analysis

[Investigation Report, ¶1.6]

[Investigation Report, ¶1.12]

[Investigation Report, ¶2.3] The lack of evidence supporting the presence of toxic fumes and the speech and breathing symptoms displayed by the pilot during the radio transmissions associated with the observed lack of movement within the aircraft, indicated that the occupants were probably incapacitated by hypoxia. The occupants were probably incapacitated by hypobaric hypoxia as a result of inadequate cabin pressurisation.

[Investigation Report, ¶2.4]

[Investigation Report, ¶2.6] As hypobaric hypoxia took effect, the pilot’s visual acuity and colour discrimination would have reduced, making the red warning lights even less likely to be noticed by the pilot. An aural warning was more likely to have been detected and acted upon by the pilot than a visual warning alone. An aural warning for high cabin altitude may also have gained the pilot’s attention when the cabin altitude exceeded 10,000 ft, well before he may have experienced significant effects of hypoxia. Had the visual warning system been set to provide the warning when the cabin pressure altitude exceeded 10,000 feet rather than 12,500 feet, and functioned normally, the pilot would have had more time to observe and react to the warning.


Probable Cause

[Investigation Report, ¶3]


See Also:

Abnormal Procedures & Techniques / Hypoxia

Abnormal Procedures & Techniques / Slow Onset Hypoxia

Technical / Oxygen


References

Pilot and Passenger Incapacitation, Beech Super King Air 200 VH-SKC, Wernadinga Station, Qld, 4 September 2000, Department of Transportation and Regional Services, Australian Transport Safety Bureau, Investigation Report, 200003771