Depressurisation

What happened

On 23 July 2025, a Raytheon B200 was being used to conduct a positioning flight from Darwin Airport to Gove Airport, Northern Territory with a single pilot on board. At 0217 local time, the aircraft was cruising at flight level 250^[1] approximately 192 km from Darwin. The pilot reported that, at about this time, they momentarily placed their knee board on the centre console before picking it back up. While lifting it from the console, it caught on the cabin pressure switch, inadvertently moving it upwards from the centre PRESS position to the DUMP position (Figure 1).

Figure 1: Cabin pressure switch

Source: Supplied

Immediately the pilot felt a pressure change and a sudden drop in temperature consistent with a depressurisation. Additionally, the cockpit cabin altitude warning indicator illuminated, and the passenger oxygen masks deployed throughout the cabin. In response, the pilot donned their emergency oxygen mask. Suspecting the likely reason for the sudden depressurisation, they checked the cabin pressure switch and returned it to the PRESS position. Not sensing that cabin pressure was returning, the pilot conducted a descent to 10,000 ft. By the completion of the descent the cabin had repressurised.

Following the descent, the pilot determined that the passenger oxygen masks would need to be reset, and they elected to return to Darwin where engineering services were available. During the return flight at FL 240, the aircraft’s pressurisation system functioned normally, and the aircraft landed without further incident.

Safety action

The operator issued a safety notice to all flight crew outlining the event and highlighting the dangers of loose objects in the cockpit.

Safety message

Loose items in an aircraft can be a significant hazard, potentially interfering with flight controls, cabin switches or aircraft systems. Pilots should carefully consider the surrounding cockpit environment when moving or stowing loose objects in flight, particularly at night in a dark cockpit. 

These items can also become dangerous projectiles causing serious injuries during an abrupt stop, turbulence or an accident sequence. Therefore, all loose items should be securely stowed for take-off and landing.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.