In 1991 ATSB's predecessor (BASI) published a research report titled Limitations of the See-and-Avoid Principle. This report concluded that 'the see-and-avoid principle in the absence of traffic alerts is subject to serious limitations'. Unalerted see and avoid has a 'limited place as a last resort means of traffic separation at low closing speeds', and is 'completely unsuitable as a primary traffic separation method for scheduled services'.
Nevertheless, operations in a number of types of airspace currently require the application of see-and-avoid techniques by the pilots of both visual flight rules and instrument flight rules aircraft operations. In areas such as mandatory broadcast zones, pilots should be assisted by radio calls from all other aircraft to provide an 'alerted' see-and-avoid environment. However, the final level of protection is provided by pilots being able to see potentially dangerous traffic in time to take avoidance action.
The report highlighted the fact that 'many of the limitations of see-and-avoid are associated with physical limits and human perception' and encouraged pilots to be 'made aware of the limitations of the see-and-avoid procedure, particularly the factors which can reduce a pilot's effective visual field'.
Each year ATSB investigates incidents where aircraft have come perilously close whilst operating in weather conditions well above the visual meteorological conditions minima. Some of these incidents occur in the circuit area, where pilots should have had an acute awareness of the position of all traffic at all times. Incidents also occur where aircraft were established in an en-route cruise. Given that there indeed is a lot of sky out there, there is often an understandable tendency during the cruise to be less assiduous in maintaining a lookout. The following paragraphs address the issue of detecting other aircraft during an en-route cruise by examining some of the problems of lookout or visual
|Type:||Educational Fact Sheet|
|Publication date:||8 October 1999|