Avionics/flight instruments

What happened

On 14 August 2019 at approximately 1500 Eastern Standard Time, an Aeroprakt 32 was conducting a training flight from Moorabbin Airport, Victoria, with an instructor and a student on board.

During the take-off run, the crew detected that the airspeed indicator (ASI) was indicating zero and subsequently rejected the take-off. The aircraft then taxied off the runway.

Following the incident, an engineering inspection was carried out. It was determined that the pitot tube was blocked, likely from water. A blocked pitot tube affected the accuracy of the ASI, resulting in fluctuating or zero speed indications.

A test flight was subsequently conducted, and the aircraft was returned to service.

Safety action

As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:

• ensuring all aircraft are allocated pitot tube covers
• issuing a safety reminder to all pilots to fit pitot tube covers after all flights and report if a pitot tube cover is missing.

Safety message

This occurrence highlights the importance of pre-flight checks, as well as the use of pitot tube covers to minimise the risk of the aircraft departing with an unserviceability. Pitot tube covers are designed to prevent foreign objects from entering the pitot tube while the aircraft is stationary.

It also serves as a reminder to be aware of unreliable or erroneous airspeed indications during the take-off run. If detected and it is safe to do so, abort the take-off.

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.

What happened

On 26 March 2018, a Raytheon Aircraft Company B200 aircraft was flying from Kowanyama, Queensland (Qld) to Cairns, Qld. At 2000 Eastern Standard Time, passing 3,700 ft on approach to runway 15 using the instrument landing system (ILS), the pilot reported that the ILS flagged intermittently and then permanently. The co-pilot side had a glideslope flag. The pilot subsequently elected to conduct a missed approach.

The pilot turned left onto the missed approach heading of 030 earlier than detailed in the published missed approach procedure. The air traffic control tower expected the aircraft to continue to overhead the middle marker before making the turn. The pilot reported that he chose to turn early to remain well clear of the hills on his right side and because of the lack of lateral guidance. He also took into consideration that there was a 28 kt westerly wind.

During the missed approach circuit, the pilot hand flew the aircraft on the co-pilot’s instruments. He communicated further with the air traffic control tower, who confirmed the correct operation of the ILS. The aircraft landed without further incident.

Figure 1: ILS Approach for Cairns 

Source: Airservices Australia, annotated by the ATSB

Safety action

As a result of this occurrence, the aircraft operator has advised the ATSB that they contacted the equipment vendor who advised a range of tests to carry out. The operator conducted the tests and narrowed the problem down to small green particles on the cannon plugs on the rear of the instrument. These plugs were replaced, and no further fault could be found with the instrument. The aircraft has subsequently flown the ILS into Cairns several times without fault.

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.