Warning devices

On 11 October 2006, at approximately 1420 Central Standard Time, a Boeing Co 767-336 was departing from bay 3 at Darwin Airport, NT for Brisbane Airport, Qld. Just prior to taxi, an auxiliary power unit (APU) fire warning activated with associated indications. The crew carried out the APU FIRE checklist items and the APU fire warning message extinguished, and the aural APU fire warning ceased.

Company engineering and Aviation Rescue and Fire Fighting (ARFF) personnel performed an external visual inspection of the APU area and advised the crew that there were no signs of a fire from the APU. The aircraft was returned to the departure gate.

The aircraft was returned to service under the provision of the B767 minimum equipment list item applicable for the operation of the aircraft with an inoperative APU.

During overnight maintenance in Sydney, company engineering staff found the remnants of a significantly charred cloth rag located on top of the aircraft's APU.

A number of safety actions were carried out or proposed by the operator as a result of this incident, including:

• amendments to the maintenance documentation for clearance closure inspections
• action to reinforce the responsibility and importance of the clearance closure inspections and to remind maintenance staff of the company's 'Safety over Schedule' principles
• the review of the suitability of equipment to gain access to all areas of the APU compartment
• a review of relevant licensed aircraft maintenance engineer training.

In addition, as a result of this incident, the ARFF changed its procedures to include that, until an ARFF response was called to a 'STOP', either an aircraft engineer or ARFF member was required to inspect the relevant aircraft compartment or area where a fire had occurred, an aircraft's fire warning system had activated, or an onboard fire extinguisher had been activated.

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.

On 21 January 2006, at 1155 Eastern Daylight-saving Time, a Saab AB SF340B aircraft, registered VH-ORX, departed Lismore Aerodrome, NSW, on a scheduled regular public transport flight to Sydney, NSW. On board were 3 crew and 21 passengers. Shortly after passing 8,000 ft on climb, the crew received a master caution warning indicating that there had been numerous system failures. After conducting failure management procedures, the crew elected to return to the departure aerodrome. while en-route to the departure aerodrome they received another master caution indicating a hydraulic failure. The crew then diverted to Coolangatta Aerodrome.

Subsequent investigation revealed that the K9 circuit breaker had been tripped. The investigation by the operator revealed that it was possible to inadvertently trip the circuit breaker when moving a navigation folder for use

As a result of the occurrence the operator issued an Operations Notice to flight crew advising that items are not to be stored on the circuit breaker panel and that all circuit breakers are to be checked correctly during failure management procedures.

Discontinued Investigation

Statement of Reasons

Occurrence investigations commenced from 1 July 2003 are initially categorised as category 4 unless agreed by the ATSB Executive to be above this level at the outset. As detailed in Section 21 (2) of the TSI Act 2003, the Executive Director in empowered to discontinue an investigation at any time. Section 21 (3) of the TSI Act 2003 requires the Executive Director to publish a statement setting out the reasons for discontinuing an investigation (commenced from 1 July 2003) within 28 days of discontinuing the investigation. To obtain a copy of the Brief Print Public for Discontinued Investigations prior to 1 July 2003.