| 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 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.