| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
On 26 March 2019, at 1530 Eastern Standard Time, a Piper PA-32 with a pilot and three passengers on board departed Scone, New South Wales for Caloundra, Queensland. The flight was operating under visual flight rules (VFR).[1] As the aircraft was in cruise, the pilot, who was IFR[2] rated, detected a vacuum pump[3] failure, which prevented all vacuum gyroscopes from providing accurate readings.
Due to the high amount of cloud in the area, the pilot contacted air traffic control (ATC) and requested a lower altitude in order for the flight to continue in visual conditions. ATC granted a descent clearance to 4,500 ft, however due to the descent rate and approaching cloud, the aircraft inadvertently entered IMC.[4] The pilot contacted ATC and requested a further descent clearance, which was granted. The rest of the flight continued in visual conditions and the aircraft landed in Caloundra without further incident.
Safety message
This incident highlights the importance of pilots being prepared for high workload situations that may arise, such as managing an equipment failure. In this instance, the pilot recognised the risk of entering into IMC with a faulty vacuum pump and effectively communicated with ATC for a safe outcome.
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.
__________
- Visual flight rules (VFR): a set of regulations that permit a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going.
- Instrument flight rules (IFR): a set of regulations that permit the pilot to operate an aircraft in instrument meteorological conditions (IMC), which have much lower weather minimums than visual flight rules (VFR). Procedures and training are significantly more complex as a pilot must demonstrate competency in IMC while controlling the aircraft solely by reference to instruments. IFR-capable aircraft have greater equipment and maintenance requirements.
- The vacuum pump works by drawing air through a fine air filter as it enters the instruments to drive the gyro rotor. The vacuum pump has a limited life span and if it fails a slow drop in suction and gyros will slowly start to tumble in the instruments. This effect is especially noticeable in the attitude indicator.
- Instrument meteorological conditions (IMC): weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules (IFR), rather than by outside visual reference. Typically, this means flying in cloud or limited visibility.