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On 29 June 2006, Bombardier DHC-8-402 (Dash 8-400) was being operated on a scheduled passenger service from Brisbane to Mackay, Qld. As the aircraft passed through FL220, the cabin altitude warning light illuminated, accompanied by the associated aural warning.

Initial checks by the crew indicated that the cabin differential pressure and cabin air flow appeared to be normal. The aircraft's bleed air switches also appeared to the crew to be correctly selected to the ON position.

An attempt by the crew to manually confirm the position of the bleed air switches revealed that both switches were in the OFF position. The subsequent selection of the switches to the ON position extinguished the cabin altitude warning light and the associated indications, and the aircraft's pressurisation system commenced normal operation.

In response to this incident, the operator developed an amendment to the Flight Crew Operating Manual for application in the company's turboprop operation, including affecting the Dash 8-400 checklist. The amendments to the aircraft checklist included:

  • revised responses to the pressurisation-related checklist items
  • an additional Pressurisation checklist requirement to be conducted at Transition
  • the addition of the requirement for the tactile confirmation of some checklist responses, including when one pilot has responsibility for both the 'challenge' and 'response' actions.
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