Aviation safety investigations & reports

Air system event - Beechcraft King Air C90 aircraft, VH-TAM, 74 km NE of Perth Airport, WA, 16 July 2009

Investigation number:
Status: Completed
Investigation completed


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On 16 July 2009 the pilot of a Beechcraft King Air C90 aircraft, registered VH-TAM, departed Perth Airport on a flight to Wiluna, Western Australia with one passenger on board.

Sometime after becoming established at flight level (FL) 210, the pilot became affected by hypoxia, which resulted in him becoming fixated on the 'distance-to-run' figures on the aircraft's Global Positioning System equipment display and incorrectly interpreting those figures as the aircraft's 'groundspeed'. That confusion resulted in the pilot interpreting the lower-than-expected figures as a significant headwind and in him descending the aircraft to escape the winds. Once established at FL150 for a significant period of time, he realised that that he had been affected by hypoxia. The pilot descended further before landing at his destination.

The investigation identified problems with the aircraft's left landing gear squat switch that prevented the aircraft from pressurising in flight. In addition, the cabin altitude warning system was non‑operational due to the incorrect connection of the switch wiring during previous maintenance.

Following this occurrence, the aircraft manufacturer changed the aircraft type's maintenance manuals and documentation and the Civil Aviation Safety Authority (CASA) issued a letter to owners and operators of Australian-registered pressurised aircraft that proposed mandating the fitment of aural cabin pressure warning systems in those aircraft. As a result of that industry consultation, CASA determined that a uniquely Australian installation requirement could not be justified.

Notwithstanding, as a result of the ongoing risk of serious incidents and fatal accidents in which the occupants of single-pilot, turbine‑powered, pressurised aircraft have been affected by, or have succumbed to unrecognised hypoxia in an unpressurised cabin, the Australian Transport Safety Bureau has issued a safety advisory notice. That notice encourages all operators of such aircraft to consider the installation of an aural cabin altitude pressure warning system that operates separately to their aircraft's visual warning system.

Download Final Report
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Alternate: [Download  DOC: 4.1MB]

Safety Issues

Go to AO-2009-044-SI-01 - Go to AO-2009-044-SI-02 -

Cabin Altitude Warning switc wiring diagram

The cabin altitude warning pressure switch maintenance manual wiring diagram did not provide a clear indication of the wiring connections for the superseded switch.

Safety issue details
Issue number: AO-2009-044-SI-01
Who it affects: Owners, operators and maintenance venues for Beech King Air 90 aircraft
Status: Adequately addressed

Replacement of cabin altitude warning switch

The aircraft maintenance manuals did not include the operating specifications of the replacement cabin altitude warning pressure switch hampering the required verification of switch serviceabilty.

Safety issue details
Issue number: AO-2009-044-SI-02
Who it affects: Owners, operators and maintenance venues for Beech King Air 90 aircraft
Status: Adequately addressed
General details
Date: 16 July 2009   Investigation status: Completed  
Time: 10:30 WST   Investigation level: Systemic - click for an explanation of investigation levels  
Location   (show map): 74 km NE of Perth Airport    
State: Western Australia   Occurrence type: Landing gear/indication  
Release date: 21 September 2011   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Beech Aircraft Corp  
Aircraft model 90  
Aircraft registration VH-TAM  
Serial number LJ-919  
Type of operation Charter  
Damage to aircraft Nil  
Departure point Perth, WA  
Destination Wiluna, WA  
Last update 03 April 2020